Electromagnetic Radiation and Human Health

How To Beat Electrical Sensitivity

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Epidemiology of Thyroid Cancer Induced by Ionizing Radiation

The association between ionizing radiation and thyroid cancer was first suggested in 1950 in children who received X-ray therapy in infancy for an enlarged thymus 1 . More conclusive evidence for a causal relationship between external radiation exposure in childhood and thyroid cancer was obtained from pooling the data from several large studies following radiation treatment to the thymus, tonsils, or scalp, and showing a dose-dependent increase in relative risk for development of thyroid cancer 2 .Since the early 1960s, when the use of radiotherapy for benign conditions was abandoned, the incidence of radiation-associated thyroid malignancy in children has gradually decreased 3 . Currently, radiation therapy for other malignancies continues to be a source of radiation-associated thyroid cancer 4,5 . However, this association has been more difficult to establish, in part because radiation is used more often for adults where the thyroid is less sensitive to its effects 6 .

Direct Ionizing Radiations

A high-speed particle can also be sharply decelerated and deflected by an atomic nucleus, causing it to emit the energy lost as electromagnetic radiation in a process called bremsstrahlung (braking radiation). The rate of energy loss by this process is proportional with z2Z2 m2, where z and Z are the charge of the particle and the atomic number of the nucleus, and m the mass of the particle. For particles with a heavier mass than electrons bremsstrahlung production is negligible at the energies used for the irradiation of biological samples. For electrons bremsstrahlung production is a second-order effect in the radiolysis of biological materials, because they are low-Z materials. The bremsstrahlung process is in this context only relevant for the production of X-rays with electron accelerators (see next chapter).

Electromagnetic Radiation

Electromagnetic radiation is pure energy. The amount of energy associated with each bundle , or quantum, of energy is determined by the wavelength (A) of the radiation. Human senses are capable of detecting some forms of electromagnetic radiation, for example, thermal radiation, or heat, (A 10-5m), and visible light (A 10-7m). The energy of the radiation can be absorbed to differing degrees by different materials light can be stopped (absorbed) by paper, whereas radiation with longer wavelength (e.g., radio waves) or higher energy (y rays) can penetrate the same paper. We commenced our discussion at the beginning of this chapter with the comment that we are dealing with models of reality, rather than an accurate description of the reality itself we likened this to dealing with paintings of landscapes rather than viewing the landscapes themselves. This is certainly the case when we discuss electromagnetic and particulate radiation. It had long been known that light acted like a wave,...

Stem cell transplantation

Bone marrow and stem cell transplantation is the most obvious application of stem cell research. It originated in early studies of the haematological reconstitution of mice whose bone marrow had been ablated by ionizing radiation. It soon became apparent that haematological rescue of these animals required infusion of syngeneic marrow because transplantation of cells from a different strain resulted in a wasting condition called 'secondary disease', which is now known as graft-versus-host disease (GvHD). Both the transplantation of stem cells into mice and the recognition of the importance of histocompatibility in the murine system were important contributions to modern clinical transplantation. The identification of the stem cell immuno-phenotype and the development of cell separation technologies facilitated the development of graft engineering to improve the results of clinical transplantation. One application of cell separation was to deplete the graft of T lymphocytes, either by...

Esophageal Toxicity

The radiotherapeutic management ofthoracic malignancies often exposes the esophagus to high levels of ionizing radiation. After 2 3 weeks of conventionally fractionated radiotherapy, patients often complain of dysphagia and or odynophagia. This acute reaction to radiation can cause significant morbidity from dehydration and weight loss that can lead to treatment interruptions. In rare instances, patients may experience perforation or obstruction. The late reactions of the esophagus to radiation usually involve fibrosis of the organ, which can lead to strictures. Patients may experience various degrees of dysphagia and may require endoscopic dilatation. As with the acute reaction, rare cases may involve perforation or fistula formation. Tables 5 and 6 define the grading of acute and late esophageal toxicity, respectively.

D4 Preventive Strategies

Recently, several randomized trials have studied the role of amifostine, a radiopro-tector, in the setting of lung cancer. Amifostine (Ethyol WR-2721) is an organic thio-phosphate selected from over 4400 compounds screened by the US Army as the best radioprotective compound. Amifostine is dephosphorylated at the tissue site to its active metabolite (WR-1065) by alkaline phosphatase.51 Once inside the cell, WR-1065, the free thiol, acts as a potent scavenger of oxygen free radicals induced by ionizing radiation.52

Mechanisms of Genetic Dominance

When normal protein function requires assembly of several polypeptides, the presence of a population of mutant polypeptides may disrupt normal assembly of a disproportionate fraction of protein complexes. This deleterious effect of mutation of just one polypeptide on the function of such proteins is known as a dominant negative effect. As an example, certain p53 mutations are commonly found in cancer (see Chap. 7). p53 functions as a transcriptional activator requiring assembly of a tetramer in order to bind to DNA and stimulate transcription of genes that p53 activates in response to certain cell injuries such as ionizing radiation. Mutations that abolish the ability of p53 to form tetramers prevent this response (Fig. 7). Because of the requirement for formation of tetramers, the presence of a mutant p53 can disrupt the function of wild-type p53 polypeptides. Such mutations are therefore regarded as dominant negative mutations (10).

Scattering In Other Fields

No account of theories of ultrasonic scattering is complete without an acknowledgement of the vast amount of work from other fields. Scattering is a phenomenon common to all waves, including electromagnetic radiation, seismic waves, sonar and nuclear particles. Much of the scattering theory of these modalities is similar, with different terms inserted into the relevant wave equation. Much of the theory relevant to pulse-echo ultrasound was initially developed for radar, and many examples of this are contained in Ishimaru's book. Scattering of acoustic fields has been used in sonar interrogation of fish shoals, examination of the ocean bed and non-destructive testing of metals (Hill et al. 1978).

Cramer Rao Minimum Variance Bound

Water has another particular disadvantage when used in large volumes. Its high dielectric constant (e 80) leads to the presence of radiofrequency standing waves (dielectric resonance), where Bi is enhanced, giving an artificially high flip angle and signal (see Figure 3.8). The high dielectric constant reduces the wavelength of electromagnetic radiation, compared with its value in free space, by a factor e at 1.5 T the wavelength is 0.52 m, comparable with the dimensions of the subject (Glover et al., 1985 Tofts, 1994 Hoult, 2000). Standing waves are also present in the head, particularly at high field (see Figure 3.9), but to a much less extent, because electrical conductivity in the brain tissues damps the resonance. Even at 1.5T this effect is significant, and early attempts to measure head coil nonunifor-mity using large aqueous phantoms are now seen as fatally flawed (Table 3.4).

Inevitable aplastic anaemia

Most cytotoxic drugs, penetrating ionizing radiation and radioactive substances concentrated in the marrow are capable of producing aplastic anaemia through their effects on actively dividing cells. The timing and duration of the aplasia and the order in which cell lines recover depend to some extent on the nature of the cytotoxic agent and the dose. Recovery is usual, with the exception of marrow rendered aplastic by whole-body irradiation given in a critical dose that destroys the haemopoietic system without killing the patient from additional toxicity. Although, in general, the development and recovery of aplasia following exposure to cytotoxic drugs are predictable, there are exceptions. Repeated or prolonged exposure to small doses of alkylating agents, particularly busulphan, may lead to a prolonged and unpredictable aplasia, even when given for myeloproliferative disorders such as chronic myeloid leukaemia, essential thrombocythaemia or myelofibrosis.

Root Stem Cells Generate Longitudinal Files of Cells

Cells are more sensitive to ionizing radiation when they are dividing. This is the basis of the use of radiation as a treatment for cancer in humans. As a result, the rapidly dividing cells of the meristem can be killed by doses of radiation that nondividing and slowly dividing cells, such as those of the quiescent center, can survive. If the rapidly dividing cells of the root are killed by ionizing radiation, in many cases the root can regenerate from the cells of the quiescent center. This ability suggests that quiescent-center cells are important for the patterning involved in forming a root.

Cellular Mechanisms of Toxicity

Within the cell, the macromolecules described above must work in concert to allow the cell to survive and carry out its particular function. A contaminant may either damage critical macromolecules directly or may damage them indirectly by forming free radicals. Examples of cellular malfunction induced by direct interference with macromolecules are the binding of carbon monoxide to the iron in hemoglobin, thus impairing the ability of the blood to deliver oxygen to tissues, and ionizing radiation damage to DNA as a result of ionization of an atom in the DNA molecule. Indirect damage accounts for a wide array of toxic effects. For example, in addition to its direct effects, ionizing radiation can also damage DNA indirectly by the formation of free radicals, which subsequently react with and damage the DNA. Chemical contaminants are also suspected of exerting toxic or carcinogenic effects by the generation of highly reactive species. Other forms of DNA damage include strand breaks and...

The Place Of Ultrasound In Medical Imaging

One of the reasons most commonly put forward in favour of ultrasound methods of imaging in medicine is their relative 'safety'. Some of the evidence on this issue is given in Chapter 14 but at this point we might rephrase the statement in the form that 'for levels of radiation exposure of patients that are associated with a given level of risk, ultrasound will generally be capable of providing a significantly higher image signal-to-noise ratio than will be available from imaging systems based on the use of ionising radiation'. Although such a statement, of course, begs some questions about comparative hazards and risks, it makes the point that, in practice, it is signal-to-noise considerations and their influence on such factors as contrast resolution that ultimately determine the minimum radiation dose levels that are attainable in X-ray and radioisotope imaging. With ultrasound, by contrast, although signal-to-noise ratio

Mechanisms And Effects Of Toxicity

Hereditary effects are adverse effects observed in offspring or in future generations as a result of parental exposure prior to conception. Teratogenic effects are developmental abnormalities induced between conception and birth as a result of direct exposure of the developing organism. The relationship between deterministic or stochastic effects (discussed in Chapters 1 and 11) and the clinical taxonomy used in this chapter is illustrated in Figure 10.7. Contaminants may trigger more than one type of effect for example, ionizing radiation can result in both systemic effects (at high doses and dose rates) and carcinogenic effects. Other classification schemes for clinical effects of toxic substances exist (e.g., EPA 2006a), but this scheme has the advantage of being able to accommodate both chemical and radioactive contaminants.

Interaction Of Objects With Light

When electromagnetic radiation strikes an object, the resulting interaction is affected by the properties of an object such as color, physical damage, and presence of foreign material on the surface. Different types of electromagnetic radiation can be used for quality control of foods. For example, near-infrared radiation can be used for measuring moisture content, and internal defects can be detected by X-rays. Electromagnetic radiation is transmitted in the form of waves and it can be classified according to wavelength and frequency. The electromagnetic spectrum is shown in Fig. 4.1. Figure 4.1 Electromagnetic spectrum. Electromagnetic waves travel at the speed of light and are characterized by their frequency (f) and wavelength (X). In a medium, these two properties are related by

Anatomic Considerations

The goal of radiotherapy is the accurate delivery of a therapeutic dose of ionizing radiation to the tumor while minimizing the dose received by normal surrounding tissues.10 The prostate gland is a midline pelvic structure that lies in close proximity to the rectum and bladder. Treatment planning for the radiotherapeutic management of prostate cancer must take into account the volume and distribution of both tumor tissue and these normal structures.11 The major sequelae following radiotherapy involve the gastrointestinal (GI) and genitourinary (GU) tract.

Jwm Bulteand Lh Bryant Jr

Image contrast in MR imaging is largely determined by the magnetic relaxation times of tissues. Following a radiofrequency (RF) pulse at the resonance frequency (42.57 MHz Tesla), protons absorb the electromagnetic radiation, and return or relax to the lowest energy state of alignment with the applied magnetic field. This magnetic relaxation is described by the time constant T1, which represents the time for 63 of the relaxation to take place. The RF pulse also creates a transverse magnetisation that precesses about the applied magnetic field. The time constant T2 refers to the time it takes for 63 of the transverse magnetisation to decay following multiple spin echoes. MR contrast agents alter the magnetic relaxation times and may affect both T1 and T2 by dipole-dipole interactions. Their efficiency is usually expressed as relaxivity (R), which represents the reciprocal of the relaxation time per unit concentration of metal, with units mM-1s-1. Because of dephasing effects, one can...

Stochastic Nonthreshold Endpoints

Approximation for exposure to both carcinogenic chemicals and ionizing radiation. The functional form of this relationship was given in Eq. 11.6. The key parameter in the equation is the cancer slope factor or the radiation risk factor. For ionizing radiation, a unified framework for estimating the risk of stochastic effects has been developed by a variety of national and international agencies. This framework is based on the radiological effective dose introduced in Section 9.2.2. The effective dose is a single measure of dose that is comparable across a broad range of exposure scenarios. Current estimates of the risk of fatal cancer following exposure to ionizing radiation rely heavily on observations of cancer fatalities from survivors of the atomic bombings of Hiroshima and Nagasaki. The current recommended values for the risk coefficient are 0.04 Sv-1 for workers and 0.05 Sv-1 for the general public (ICRP 1991).

Gastrointestinal imaging findings

Radiation exposure is between 3 and 5 cGy per examination and should not preclude use of the technique during pregnancy if otherwise indicated in an equivalent setting outside of pregnancy. Complications related to CT are uncommon and are associated with the use of IV contrast agents, primarily as nephrotoxicity (defined as an increase in serum creatinine by more than 1 mg in the ensuing 48 h) or anaphylactoid reactions (-1 2500).

Dosimetric Logistic and Computing Considerations

There have been few dose estimates reported in the literature on transmission scanning in emission tomography. Unfortunately, many studies were very superficial and reported very approximate estimates of the maximum absorbed dose at the skin surface using survey meters rather than effective dose equivalent (EDE) values (a quantity, which is suitable for comparing risks of different procedures in nuclear medicine, radiology, and other applications involving ionizing radiation) using anthropomorphic phantoms and suitable dosimeters. , , It is worth noting the discrepancy between results reported in the literature even when using the same experimental set-up, scanning source geometries, and dosimeters. The discrepancies may be explained by differences in thermoluminescent dosimeters (TLDs) positioning and other uncontrolled factors. In SPECT, the use of sliding collimated line sources and parallel collimation allows a significant dose reduction when compared with the use of a static...

Clinical Characteristics of Radiation Induced Thyroid Cancers from Chernobyl

The average latency between radiation exposure and cancer diagnosis was 6.9 years in a series of 472 patients from Belarus reported by Pacini et al. 11 . Prior to Chernobyl, the latency period for radiation-induced thyroid cancer was considered to be at least 5 years,typically 5-10 years. However, the Chernobyl experience has clearly demonstrated that it can be as short as 4 years. The clinical characteristics of thyroid cancers arising in children exposed to radiation after Chernobyl differed in significant respects from those arising in children without known radiation exposure treated in Italian and French centers 11 . The vast majority of post-Chernobyl pediatric thyroid cancers were papillary carcinomas (94 ) 11 , which is consistent with what was found in other populations exposed to ionizing radiation. Although papil

Infrared Thermometers

In Chapter 23, we defined black body and emissivity. Here we define other terms that are used in association with radiation and in the literature dealing with infrared thermometers. We shall use the definitions provided by van Wijk and Scholte Ubing (1966, pp. 62-63). Radiant energy is the energy traveling in the form of electromagnetic waves. It has the dimension of energy so that it is measured in joule, erg, calorie, or an equivalent quantity. The amount of radiant energy emitted, transferred, or received per unit time is called radiant flux F (Greek letter, capital phi). It has the dimension of energy per unit time. In physical literature, the watt (W) (1 watt 1 joule s-1) or the erg s-1 are commonly used as units in meteorology, the unit cal min-1 is frequently employed. Radiant flux density H dF dA is the flux per unit of surface it is expressed as W m-2, erg cm-2 s-1, cal cm-2 min-1 ( langley min-1) (one langley 1 cal cm-2), or equivalent units. The units of radiant flux...

Summary and Recommendations

Any patient with an incidental, occult, or non-incidental PMCT who has a history of significant prior radiation exposure, no matter when, or a documented history of familial papillary carcinoma, should probably have a near-total thyroidectomy rather than a more conservative operation. The latter applies especially to children and adolescents as age alone in this group constitutes a risk factor for recurrence and distant metastases. These individuals require RAI ablation and very close follow-up.

Other Emerging Therapies for Thyroid Cancer

Chemoprevention is another alternative for thyroid cancer that remains relatively unexplored other than the use of iodide after accidental exposure to iodine isotopes. Chemo-preventive strategies could include administration of apoptotic-promoting agents after radiation exposure, to induce cell death and subsequent hypothyroidism. Or low doses of other agents that are shown to be radiation sensitizers. Finally, cyclooxygenase-2 inhibitors have been utilized as chemopreventive agents for malignancies such as colon cancer with high levels of cyclooxygenase-2 activity. Thyroid cancers also have been shown to have high levels of cyclooxygenase-2 expression and activity 60-63 .

Experimental And Theoretical Methods For Detecting And Studying Radicals

The transition from the lower to the higher energy state is made most efficiently when the energy-level separation equals hv, where h is Planck's constant and v is the frequency of a microwave electromagnetic field. Then the sample and the electromagnetic field are in resonance. Thus an EPR spectrometer will basically consist of a source of microwaves (most frequently a klystron), a magnet capable of providing a tuneable but stable and homogeneous magnetic field and a device to detect the absorption.

Human Applications of Imaging Gene Therapy

Undergoing HSV1-ffc suicide gene therapy or therapy where a therapeutic gene is linked to HSV1-fft (Fig. 18.9). This study showed that FHBG cleared rapidly via the renal and hepatobiliary systems, and that relatively low signal throughout the whole body was achieved within 60 minutes of injection of tracer. Furthermore, FHBG is stable in blood, and results in sufficiently low radiation exposure to allow multiple FHBG PET scans per year. There are no other safety issues, since FHBG is injected in trace amounts. Using FHBG to image HSV1-ffc reporter gene expression at sites near the gall bladder, kidneys, or bladder would be difficult due to tracer concentration in these regions. Furthermore, imaging in the brain would be limited by the failure of FHBG to cross the blood-brain barrier.

Reproductive Endocrinology Diagnostic Imaging

Normal Follicular Ultrasound Chart

The last few decades have witnessed rapid advances in diagnostic and therapeutic options in modern medicine. While the field of reproductive endocrinology has stayed away from many diagnostic modalities using ionizing radiation, the field has benefited from advances in imaging modalities such as ultrasound and magnetic resonance. In this chapter, we will review the general principles of these techniques and offer examples from reproductive endocrinology where imaging has proved helpful. Although some have attempted to use 3-D dynamic MR-hysterosalpingography to visualize both the endometrial cavity and tubes with decreased exposure to ionizing radiation from HSG imaging, we do not feel that the high costs and technical difficulties are not outweighed by any potential benefits of this modality. This is an expensive study that does not improve on sensitivity, specificity or patient comfort. Diminished ovarian reserve is a term used to identify women who are nearing the end of their...

Interaction of Photons with Matter

Compton Scattering Angular Distribution

High-energy photons interact with matter by three main mechanisms, depending on the energy of the electromagnetic radiation. These are (i) the photoelectric effect, (ii) the Compton effect, and (iii) pair production. In addition, there are other mechanisms such as coherent (Rayleigh) scattering, an interaction between a photon and a whole atom which predominates at energies less than 50 keV triplet production and photonuclear reactions, where high energy gamma The photoelectric effect occupies a special place in the development of the theory of radiation. During the course of experiments which demonstrated that light acted as a wave, Hertz and his student Hallwachs showed that the effect of an electric spark being induced in a circuit due to changes in a nearby circuit could be enhanced if light was shone upon the gap between the two coil ends. They went on to show that a negatively charged sheet of zinc could eject negative charges if light was shone upon the plate. Philipp Lenard...

Radioactive Iodine 131I Therapy Thyroid Remnant Ablation

A second approach is to use quantitative dosimetry to predict radiation doses to the target tissues, namely thyroid remnant or metastases, and to radiosensitive tissues to which the radiation dose must be limited, including the bone marrow and lungs in those with diffuse pulmonary metastases, and the whole-body radiation dose. This is favored by some because radiation exposure from arbitrarily fixed doses of 131I can vary considerably 137 . If the lesional dose is less than 35Gy (3500 rads), it is unlikely that the tumor will respond to 131I therapy 137 138 . Conversely, 131I activities that deliver 80 to 120Gy (8000 to 12 000 rads) to the thyroid remnant or deliver 300Gy (30000rads) to metastatic foci are likely to be effective. To make these calculations it is necessary to estimate tumor size, which in some situations is not possible.

A12 Surface Plasmon Resonance

Light that is coupled into the prism is totally internally reflected at the metal-coated surface. When the angle of the incident light meets the resonant condition, surface plasmons, oscillating electromagnetic waves on the surface of the metal layer, are excited causing a reduction in the (energy) intensity of the reflected light. The surface plasmons have an associated electromagnetic field (evanescent field) that decays exponentially normal to the layer surface, which extends a few hundred nanometres from the metal surface. Changes in the refractive index (dielectric constant) within this region leads to changes in the observed resonance angle. Therefore, when macromolecules are adsorbed or desorbed in the immediate vicinity of the metallic sensor surface, the refractive index changes, leading to a commensurate change in the measured resonant angle. Commercially

Etiology And Pathogenesis

Unlike that associated with chemotherapy, radiation damage is anatomically site-specific toxicity is localized to irradiated tissue volumes. The degree of damage is dependent on the treatment regimen-related factors including type of radiation used, total dose administered, and field size fractionation. Compared with chemotherapy-related effects, an important clinical feature characterizing radiation-induced tissue damage deserves mention. Irradiated tissues tend to manifest permanent damage that places the patient at continual risk for oral sequelae. The oral tissues are thus more easily damaged by subsequent toxic drug or radiation exposure, and normal physiologic repair mechanisms are compromised as a result of permanent cellular damage.

Radical Reactions With Biomolecules

The study of the chemistry of bioradicals is important for the understanding of later biological effects. As we will discuss further damage to the genetic material DNA is the most critical event in radiation exposure of biological systems. Radiation exposure of cells in living organisms may result in cell replication failure or in chromosome aberrations, leading to mutagenesis and carcinogenesis. Radiation damage to proteins, lipids and carbohydrates is relevant for effects such as enzyme inactivation and also has applications in the radiation treatment of foods and drugs where toxicity of radiation products is a point of major concern. Amino acids arid sugars are important for dosimetric applications. The amino acid L-a-alanine is currently used as a reference dosimeter suitable over a wide dose range (Callens 1996 McLaughlin 1993 Van Laere 1993). The study of radiation-induced effects on various sugars (e.g. glucose, fructose, and sucrose) is relevant for the detection of some...

Complications of Radioiodine Treatment

The radiation dose delivered by 131I to each organ is difficult to estimate from established mathematical models uptake by metastases may modify the dose delivered to a given organ and the hypothyroid status at the time of iodine administration decreases renal clearance of 131I, thereby increasing the body retention of iodine by a factor of 2-4. Liberal fluid intake, frequent micturition, and use of laxatives will promote iodine excretion and reduce radiation exposure.

Alternative Medicine and Female Infertility

Acupuncture is a vital therapeutic modality in traditional Chinese Medicine and its use can be traced back for centuries. The theory behind acupuncture is based upon the premise that there are patterns of energy flow, or Qi, through the body, which are essential for health. When a disease state exists, the flow of Qi is interrupted and its correction will assist in the healing process. Acupuncture can correct imbalances of flow at identifiable points close to the skin. The flow of Qi is based upon a meridian system of vital channels. The meridians consist of 20 channels interconnected by about 400 acupoints. These acupoints correspond to specific areas on the surface of the body, which demonstrate higher electrical conductance, thought to be due to the increased density of gap junctions along cell borders. These gap junctions serve as sinks, or converging points for electromagnetic fields. In addition, a higher metabolic rate, temperature, and calcium ion concentration are also...

Radiation Safety And Regulations

Radiation is frightening to many people. The reality is much less sensational. The potential harm from radiation exposure is proportional to the dose. The harm of greatest concern from occupational exposure to radiation is that the radiation will cause cancer. Although it has been possible to measure small (8 ) increases in cancers in large populations instantaneously exposed to large doses of radiation (e.g., atomic bomb survivors), it has been difficult to measure any increase in cancers in occupationally exposed persons. Since the harm from radiation exposure is proportional to dose, it is helpful to have some examples of the possible magnitudes of radiation doses. A useful benchmark is the amount of radiation we are all exposed to every year due to naturally occurring radioactive materials in our body and in our environment. Natural background radiation exposes every person in the U.S. to about 300 mrem per year. There is considerable variation in the amount of background...

Cell and molecular biology

Activated FANCD2 protein collocalizes and co-purifies with the breast cancer susceptibility protein, BRCA1, a protein that is important in many DNA damage-response pathways. These nuclear foci appear in cells after DNA damage and in those cells undergoing DNA replication. Proteins such as the recombination molecule RAD51, and those in the RAD50-NBS1-MRE11 DNA repair pathway are also present in BRCA1-containing foci (NBS1, complex Nijmegen breakage syndrome 1 MRE11, meiotic recombination 11). In cells from A, C, E, F or G patients, FANCD2 ubiquitination is not observed and it is not targeted to nuclear foci. ATM (ataxia telangiectasia mutated) can phos-phorylate both FANCD2 and BRCA1. The ATM-dependent phosphorylation of FANCD2 (at serine 222) occurs in response to ionizing radiation. Therefore, this puts FANCD2 in a central position in signalling DNA damage double-strand DNA breaks caused by ionizing radiation result in ATM-dependent phos-phorylation of FANCD2 at serine 222, whereas...

Role of the Clinical Psychologist in Thyroid Cancer

A clinical psychologist should be involved in the design and implementation of a program of education for healthcare staff involved with thyroid cancer patients. The education program should include psychological needs of patients, communication skills, and evidence-based information on risks of radiation exposure and relevant precautions. Nuclear medicine technicians as well as doctors and nurses should be included in the educational program. The clinical psychologist could also offer consultation and advice on preparation of patients for treatment and the provision of both oral and written information.

Disorders of Swallowing

Nasopharyngeal Penetration

Maintained sitting in the true lateral position, best accomplished in an infant feeding seat. Participation of the parents and caregivers helps to reassure the child, and recreates some aspect of daily feeding. The child's own speech therapist or feeding therapist should optimally be present during the examination to witness the events. The therapist can observe the optimal food volume and consistency and compensatory maneuvers that assist swallowing (FerNbAcH 1994). Boluses of different consistencies are fed. Young children are given liquids, though the density of various liquids may vary. The examination in older children begins with thin liquid barium, proceeding to feeds with a mixture of barium thickened with pudding or pureed food, and finally with more solid food such as barium-coated crackers. Barium density influences the swallowing mechanism. High-density barium has a slower transit time, causing the upper esophageal sphincter to open later, to remain open for longer and to...

Annihilation Radiation

As this book is primarily concerned with positrons and their applications, we include a further classification for electromagnetic radiation which is neither x nor y Annihilation radiation is the energy produced by the positron-electron annihilation process. The energy of the radiation is equivalent to the rest mass of the electron and positron, as we saw in the section on Mass and Energy, above. The mechanism of positron decay is discussed in depth in the next section.

Magnetic Resonance Imaging

Brain Has Structure Magnet

The NMR phenomenon was first used to examine magnetic resonance spectroscopic (MS) properties of compounds in solution. In the 1960s, superconducting magnets and more efficient computers were developed. When they were combined with the image reconstruction techniques developed by Godfrey Hounsfield for X-ray tomography, the first in vivo magnetic resonance images could be reconstructed, which took place in the early 1970s 13 . Several kinds of MRI data can be acquired without exposing subjects to ionizing radiation or radioactive isotopes. Initially MRI was mainly used for visualizing the structure of the brain. In the early 1990s, functional magnetic resonance imaging (fMRI) was developed for the recording of rapid changes in local cerebral blood flow. The term functional MRI is related to neurovascular coupling, a phenomenon first reported by Roy Sherrington in 1894, who reported that local variations of functional neuronal activity are followed by local changes in blood flow. fMRI...

Specific Brain Imaging Methods Computed Tomography

Aplicaciones Del Fosforo

The major disadvantage is the radiation exposure, which is of the same order as that of an ordinary skull or chest X-ray. This precludes carrying out many repeated investigations. Another disadvantage is that it can only be used to examine structural features of the brain. Compared to MRI it gives rather low resolution and poor tissue differentiation, e.g. with regard to grey and white matter.

Basic Radiation Terminology

Radio Medical Terminology

Ionizing radiation is subdivided into non-particulate and particulate radiation. Non-particulate ionizing radiation (photons) consists of x-rays and gamma rays. Higher energy x-rays and gamma rays penetrate the body, are detectable outside the body and therefore are useful for imaging. X-rays and gamma rays are, by definition, distinguished by the way in which they are formed and are Radioguided Surgery, edited by Eric D. Whitman and Douglas Reintgen. 1999 Landes Bioscience indistinguishable once they have been emitted. X-rays result from transitions in the energy state of an electron. Gamma rays and the particulate forms of ionizing radiation are created when the nucleus undergoes a transition from a high energy state to a lower energy state. Gamma rays generally are of higher energy than x-rays, but there is considerable overlap. The magnitude of the energy content of a photon is expressed in electron volts (eV). Visible light photons (one form of nonionizing radiation) have...

Evaluation of Body Composition

Nome Dos Componentes Microscopio

In infants, the only practical means of measuring body composition is by noninvasive and indirect methods. Several methods have been developed to indirectly measure body composition in vivo (table 1). Unfortunately, these methods have limited application in infants, i.e. they are relatively invasive, may involve significant radiation exposure, and or need active cooperation of the subject. Whole body composition analysis may be based on different models, i.e. 2, 3, or more compartments. The basic 2-compartment model, which assumes that body mass is composed of adipose and non-adipose issue, i.e. fat mass (FM) and fat-free mass (FFM) or lean body mass (LBM), is the widely used. The total body fat (TBF) compartment is the most variable one and most sensitive to changes in nutritional status so most emphasis has been laid on its measurement 5 . The three-compartment model adds a value for skeletal or bone mass, whereas in the multi-component model, body composition is obtained by...

Protein Identification by Mass Spectrometry

Schema Skate Board

Quadrupole mass analysers (Fig. 3.4) consist of four parallel and symmetrically arranged metallic rods. One couple of opposite rods have a positive electrical potential + U + Vcos(rot) , while the other couple of opposite rods have a negative potential - U + Vcos(rot) . Ions oscillate while traversing the field along the central axis of the rods. For each U, V and ro value, only ions of a certain m z enter in resonance and follow a stable trajectory through the quadrupole to the detector. All others are not stabilised and deviate out of the mass analyser. The quadrupole is therefore considered as a mass filter. To obtain a complete spectrum, one continuously varies or scans the electromagnetic field in the quadrupole while the sample passes through the analyser.

Absorption And Emission Spectroscopy

Spectroscopy is the measurement of electromagnetic radiation absorbed, scattered, or emitted by chemical species. Because different chemical species and electromagnetic radiation interact in characteristic ways, it is possible to tailor instrumentation to detect these interactions specifically and quantitatively. A simple absorption spectrophotometer, depicted schematically in Figure 12.2, contains components that are common to many spectroscopic devices and are representative of many of the basic principles of instrumentation found in analytical biochemistry.

Future of Dual Modality Imaging

Magnetic resonance spectroscopy (MRS) to measure the regional biochemical content and to assess metabolic status or the presence of neoplasia and other diseases in specific tissue areas171-173 including the prostate.153,174-176 Finally, MRI does not use any ionizing radiation and therefore can be used in serial studies, for paediatric cases,177 and in other situations where radiation dose should be limited. Radionuclide imaging (specifically PET) records the regional distribution of radiolabeled tracers, but unlike MRS cannot distinguish the specific molecular species to which the radionuclide is attached and unlike MRI provides only little anatomical information.

Transportation Risks Preventative Measures Air Travel

The radiation exposure associated with a long flight from London to Tokyo has been estimated to be the equivalent of one chest radiograph. For the infrequent flyer this is not of much concern. For pregnant travelers who are aircrew or business frequent flyers this may be a consideration and should be discussed with their physician. Airport security machines are magnetometers and are not harmful to the fetus.

Toxictherapeutic disturbances

There may be a definitive history of accidental or deliberate ingestion of therapeutic or toxic substances such as an overdose of tablets or exposure to carbon monoxide. However, even if there is no specific evidence of poisoning, it should be considered as the cause of cardiac arrest in every collapsed patient. The hospital team should ensure that they are not put at risk if chemical or radiation exposure from the patient is a possibility.

Well Differentiated Thyroid Carcinoma

One cause of TC is the external beam radiotherapy widely used from 1920 to 1960 in children for treating benign conditions of the head, neck, and upper chest, such as tinea capitis, acne, tonsillar hypertrophy, and thymic enlargement. In 1949, Quimby and Werner 5 suggested a relationship between neck irradiation and the development of TC later in life. The thyroid gland in childhood is highly sensitive to radiation.After 1950,the use of radiotherapy for benign conditions gradually diminished. Currently, certain diagnostic techniques, especially fluoroscopy, can also involve radiation exposure in the range implicated in the pathogenesis of thyroid tumors 6 . Moreover, medically indicated radiation therapy for the treatment of assorted malignancies,especially acute lymphocytic leukemia and Hodgkin's disease, continues to be administered. Scattered radiation from the primary fields of therapy, which transverses thyroid tissue, results in sublethal thyroid irradiation in such patients....

Technique and Normal Appearances

MRI and CT are powerful imaging tools and the choice of which modality to use is not always straightforward. MRI shows exquisite soft-tissue contrast 8 and will therefore better demonstrate tumor invasion of structures such as strap muscle, larynx, and esophagus. It does not involve ionizing radiation and this may

Mass and Energy

In 1900 Max Planck demonstrated that the energy (E) of electromagnetic radiation was simply related to the In addition, experiments indicated that the radiation was only released in discrete bursts . This was a startling result as it departed from the classical assumption of continuous energy to one in which electromagnetic radiation could only exist in integral multiples of the product of hu. The radiation was said to be quantized, and the discrete quanta became known as photons. Each photon contained an amount of energy that was an integer multiple of hu. The unit for energy is the joule (J), and we can calculate the energy of the radiation contained in a photon of wavelength of, for example, 450 nm as Figure 2.2. The electromagnetic spectrum showing the relationship between wavelength, frequency, and energy measured in electron volts (eV).

Apoptosis

Death may be signaled through ligand enforced clustering of receptors at the cell surface via the extrinsic pathway, which leads to the activation of apical caspase-8.54 This caspase then directly activates the executioner caspase-3 and caspase-7 (and possibly 6), which are primarily responsible for the limited proteolysis that defines apoptotic dismantling of the cell. Irreparable damage to the genome caused by mutagens, pharmaceuticals that inhibit DNA repair, or ionizing radiation - transmitted by a mechanism thought to involve the release of cytochrome C from mitochondria via the intrinsic pathway - engages the same executioner caspases.55 The latter events progress through the apical caspase-9 and its cofactor Apaf-1.26 Activation of the extrinsic pathway is regulated by FLIP, which modulates the recruitment of caspase-8 to its adapters.56 The execution phase is regulated through direct caspase inhibition by XIAP, which can also regulate the...

Definitions

The Glossary of Soil Science Terms (Soil Science Society of America, 1997) defines flux as follows The time rate of transport of a quantity (e.g., mass or volume of fluid, electromagnetic energy, number of particles, or energy) across a given area. See also flux density. The Glossary defines flux density as follows The time rate of transport of a quantity (e.g., mass or volume of fluid, electromagnetic energy, number of particles, or energy) per unit area perpendicular to the direction of flow. Flux and flux density often are used interchangeably.

Cellular Senescence

Cells arrest growth with a phenotype essentially indistinguishable from replicatively senescent cells when they experience moderately high levels of DNA damage, caused, for example, by ionizing radiation or oxidants (46,47) (Chapter 5). Likewise, they become senescent when treated with agents, or suffer mutations, that disturb normal chromatin organization (48-52). Cells also become senescent when they experience strong mitogenic or stress signals, especially those delivered by certain oncogenes. Examples include the overexpression or activation of growth factor-signaling molecules such as RAS or RAF or growth-promoting transcription factors such as E2F (53-56).

Damage Signals

Endogenous sources (e.g., reactive oxygen species produced by mitochondria), or exogenous sources (e.g., ionizing radiation or chemicals). Upon damage, cells mount an appropriate damage response, which entails four options What determines which options a cell chooses Important considerations are the cell type and physiological context, as well as the level and type of damage. Thus, a given dose of ionizing radiation typically causes senescence in human fibroblasts, but apoptosis in T-lymphocytes. Likewise, a higher dose of radiation may cause human fibroblasts to undergo apoptosis, and an even higher dose may cause the same cells to die by necrosis.

Radiological Dose

Biological damage due to radiation exposure depends primarily on the amount of energy deposited per unit mass of tissue and the type of radiation. Four primary types of nuclear radiation are encountered in risk assessments alpha, beta, gamma, and neutron radiation. Environmental contaminants emit primarily the first three types of radiation. Alpha radiation consists of energetic helium nuclei (two protons and two neutrons) and is highly damaging, although it has a limited ability to penetrate matter and only poses a significant risk if a -emitting radioactive contaminants are taken into the body. Beta radiation consists of energetic electrons and can pose a risk due to doses to the skin or by -emitting radioactive contaminants taken into the body. Gamma radiation is highly penetrating and thus poses a risk from radioactivity located either inside or outside the body. Neutron radiation does not typically arise from environmental contamination, since most radiation from environmental...

Free Radicals

A free radical is a highly reactive chemical species containing an unpaired electron in its outer electron shell. Some free radicals occur naturally in the body however, additional free radicals may be derived from interactions of normal body compounds with chemical contaminants in the body or with ionizing radiation. Radiolysis is the process by which ionizing radiation breaks water, inorganic, or organic molecules into highly reactive species. For example, radiolysis of water can result in the formation of the hydroxyl (OH) and hydrogen (H-) free radicals. These free radicals can then react with other aqueous species to form other highly reactive species. Although DNA is one of the target macromolecules for these reactive species, other macromolecules can also be damaged by them. For example,

Example 105

Methyl mercury has been implicated in developmental neurotoxicity, primarily on the basis of animal studies consistent with epidemiological data on a variety of populations (NAS-NRC 2000). Methyl mercury has been shown to interact with critical molecules (DNA and RNA) in the cells of the central nervous system, causing interference with RNA synthesis. As the cells divide, the altered cells are no longer able to reproduce properly, leading to abnormal growth and development of the brain cells. Among its other effects, ionizing radiation can exert teratogenic effects. An increase in mental retardation was observed in Japanese children irradiated in utero at Hiroshima and Nagasaki. Those exposed during the period from 8 to 15 weeks after conception showed the clearest effects, with the effects increasing with increasing dose.

Gammaemitters

A large group of radioisotopes emits g-rays during decay. Gamma rays represent excess energy that is given off as the unstable nucleus breaks up and decays in its efforts to reach a stable form. The energy is emitted in the form of electromagnetic radiation (photons), with a radioisotope-characteristic photon energy typically expressed in kilo-electronvolt (keV). Photons are absorbed in biological material by both the photoelectric and Compton process, and then indirectly ionise the surrounding atoms, producing chemical and biological changes. Most g-emitters are used primarily for diagnostic purposes and those used in nuclear medicine (Table 4) were chosen so that a) their g-ray energy is not too high (radiation safety concerns) and matches the g-camera, b) their half-life is practical and logistically feasible, c) they are easily available and inexpensive, and d) they can be bound to microspheres in an easy (kit) and stable fashion.

Brachytherapy

The etiology of impotence after brachytherapy is thought to arise from either excessive radiation exposure to the neuro-vascular bundles92,93 or vascular etiologies.90 DiBiase et al. reported that the patients who developed early postimplant impotence had doses to the neurovascular bundles that far exceeded the average values.93

DNA changes

If only one of the cells in any given organ fails the checkpoint mechanisms and divides with faulty DNA, the birth of cancer may ensue. One major way DNA is damaged is by reactive oxygen species, such as superoxide, hydrogen peroxide and hydroxyl radicals. These are formed as byproducts of mito-chondrial aerobic oxidation incompletely reducing oxygen to water, as well as by carcinogens, ionizing radiation and ultraviolet light. These byproducts are termed free radicals because they lack the ability to be paired they have the propensity to attack proteins, lipids and DNA within the cell. Specifically, the nucleotide guanine is converted to 8-oxoguanine, which leads to mutations in the DNA as 8-oxoguanine preferentially mispairs with adenine. Cells attempt to repair this error by excising the 8-oxoguanine and replacing it with the proper guanine, excreting 8-oxoguanine in the urine. Since reactive oxygen species are always being created, the cell has a number of enzymes that protect...

Models of the Atom

Fluorine Protons Neutrons Electrons

By the nineteenth century it was clear that chemicals combined in set proportions, thus supporting a corpuscular, or discrete, model of matter. At the turn of the twentieth century evidence was mounting that there were basic building blocks of matter called atoms (Greek indivisible), but the question remained as to what, if anything, the atoms themselves were composed of. It was shown by JJ Thomson and, later, Ernest (Lord) Rutherford, that atoms could be broken down into smaller units in experiments using cathode ray tubes. Thomson proposed a model of the atom that was composed of a large, uniform and positively charged sphere with smaller negative charges embedded in it to form an electrostatically neutral mixture. His model of the atom is known as the plum pudding atom. Rutherford showed, however, that alpha particles (doubly ionized helium nuclei emitted from some unstable atoms such as radium) could pass through sheets of aluminum, and that this was at odds with the...

Thyroid Lymphoma

Primary thyroid non-Hodgkin's lymphoma (NHL) is uncommon, representing 4 of all thyroid cancers 1 . Only 2 of extranodal lymphomas arise within the thyroid. Secondary involvement is more frequent as a manifestation of generalized disease, which occurs in 10 of all lymphomas and leukemias 2 . The mean age at presentation is 60-70 years with a female male predominance of 3 1. Presentation before age 40 is rare. Preexisting Hashimoto's thyroiditis is a significant risk factor 3 and may be the result of chronic antigen stimulation. Radiation exposure is not associated with an increased risk.

Acute Pancreatitis

Reading Week Ultrasound

Erogeneous attenuation, a poorly defined pancreatic contour, and peripancreatic fluid collections, which are most commonly found in the anterior pararenal space and lesser sac (Baltazhar 2002). More than one third of patients with acute pancreatitis have an initially normal CT. MRI should be preferred to CT when available because of the lack of ionizing radiation. Pseudocyst formation is the most common complication of the acute pancreatitis and

Carcinogenic Effects

In 2005, 22 of deaths in the United States were from cancer. Along with heart attacks and strokes, it is one of the three leading causes of death. Although life-style choices such as the use of tobacco products, alcohol consumption, and diet are thought to be responsible for a majority of cancers, it is also known that cancer can result from exposure to ionizing radiation and to some chemicals in the environment. In fact, cancer is often the primary stochastic effect analyzed in risk assessments. Cancer is of particular concern because it can be induced at doses far below the level required to induce an observable systemic effect (and possibly, at any nonzero dose). Thus, controlling exposures to prevent systemic effects may be ineffective in providing an acceptable level of protection against cancer.

Positron Decay

When the positron and electron eventually combine and annihilate electromagnetic radiation is given off. The most probable form that this radiation takes is of two photons of 0.511 MeV (the rest-mass equivalent of each particle) emitted at 180 to each other, however, three photons can be emitted (

Etiology

Ionizing Radiation That radiation exposure favors the development of thyroid carcinoma including the papillary variety, and that the very young are especially vulnerable, is unquestioned. Duffy and Fitzgerald called attention to this as far back as 1950 in their study from Memorial Hospital in New York of 28 cases ranging in age from 4 to 18 years The atomic bombs that exploded in Hiroshima and Nagasaki, resulting in mainly neutron and gamma irradiation in 1945 and the subsequent testing of nuclear weapons, exposing unprotected populations from radiation and fallout, afforded the opportunity to study the issue of ionizing radiation and thyroid cancer. Sampson et al. 32 examined the thyroid glands at autopsy of 3067 Japanese survivors who had lived in proximity to the atomic detonations. They discovered 536 thyroid carcinomas, a combined incidence rate of 17.5 for both men and women. Ninety-seven percent of the tumors were PMCTs although tumors as large as 1.5 cm were included in the...

Death Receptors

Ceramide Signaling

And TNFR1 can both activate acidic and neutral sphingomyelinases, studies using various inhibitors of ceramide signaling suggest that they play no role in apoptosis induced by these receptors. Supporting this conclusion are experiments performed with cells from patients with Neimann-Pick disease, which lack functional acidic sphingomyelinase. These cells are resistant to apoptosis induced by ionizing radiation, but not to apoptosis induced by Fas ligand or TNF-a. Thus, it appears that ceramide may be important in some apoptotic signal transduction pathways but not others, or perhaps only in certain cell types or in combination with other modulatory signals.

Radiation

Radiation can be classified into electromagnetic or particulate. Ionising radiation is radiation that has sufficient energy associated with it to remove electrons from atoms, thus causing ionisation. This is restricted to high-energy electromagnetic radiation (x and y radiation) and charged particles (a, P-, P+). Examples of non-ionising electromagnetic radiation include light, radio, and microwaves. We will concern ourselves specifically with ionising radiation as this is of most interest in nuclear medicine and radiological imaging.

Dosimetry

Fixed activities of 1.1-3.7GBq for remnant ablation and 3.7-7.4GBq for therapy are based on experience. They are known to be safe and this is the most widely used system but insufficient 131I may be delivered to eradicate tumor 22 . To overcome this problem some centers administer up to 11.1GBq (300mCi) in patients with distant metastases 79 . This may be associated with greater toxicity and unnecessary whole-body radiation exposure. Quantitative tumor dosimetry is the third alternative 68 . The rationale is that tumors have different biological behavior in different individuals which merits 131I treatment on a calculated patient-specific basis (Figure 15.5). Measurement of the absorbed dose in tumor has several advantages. Firstly, overtreatment and overall radiation exposure is kept to a minimum an absorbed dose can vary widely with fixed activities, from ineffective to excessive. Secondly, it is the best way to determine whether future 131I therapy will be effective, so that...

Umwelt

The eye, the best understood of all the sense organs, consists of a lens which focuses light (a kind of electromagnetic energy) through a small hole (the pupil) onto a sheet of cells (the retina). The retina contains the eye's receptor cells the rods, which are sensitive to all wavelengths of light in the visible spectrum, and three kinds of cones, which are sensitive to those wavelengths that the brain perceives as blue, green, and yellow.

Solar Radiation

All bodies emit radiant energy in the form of electromagnetic waves when they are at a temperature above absolute zero (-273.16 C or -459.69 F hypothetical point at which a substance would have no molecular motion and no heat). The source of this thermal radiation or temperature radiation is the incessant molecular motion. During collisons, or more generally as a result of interactions between molecules, part of their energy is transformed into radiation. Conversely, radiation can be absorbed by the molecules and converted into kinetic and potential energy, thereby raising the temperature of the body (van Wijk and Scholte Ubing, 1966, p. 62). (We ignore radiation from radioactive materials. This is another type of radiation.)

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