bluuebunny/crossref_metadata_2025 huggingface dataset:
Radiation Protection Instrumentation
Authors: Glasgow Glenn P.
Published: April 2006

This article describes common radiation protection instruments used around or with radioactive materials and equipment in medical facilities. This article describes availability of instruments and sources of information about their use; instruments for specific tasks; types and sources of radiation; international definitions of radiation quantities and units; and common features of instruments. The detection principles of ionization chambers, gas proportional counters, Geiger–Müeller detectors, scintillation detectors (solid, liquid, and plastic), solid‐state detectors (semiconductors, thermally, and optically stimulated luminescence phosphors), and photographic detectors are described. Worldwide web Internet addresses are given for some major instrument manufacturers and vendors. The bibliography lists the latest editions of relevant textbooks. Common medical uses of these instruments include equipment surveys; personnel and area monitoring; contamination surveys; locating misplaced radioactive sources; air sampling; responding to emergencies; and spectroscopy. Using recent data (2002) from the Committee on Data for Science and Technology, this article describes electrons, beta particles, alpha particles, protons, neutrons, X rays, γ rays, and some radionuclides commonly used in medicine. Fundamental terms (exposure, kerma, absorbed dose), internationally recommended definitions of terms used for radiation protection (equivalent dose, committed equivalent dose, effective dose, committed effective dose), and units (roentgen, gray, sievert) are described. Currently used personnel radiation monitors are described. Instrument electronic circuitry is discussed only briefly.
Radiation Therapy Simulator
Authors: Low Daniel A. , Mutic Sasa
Published: April 2006

Radiation therapy is a medical specialty for treatment of malignancies (tumors or neoplasms) with high doses of radiation using X rays, γ rays, electrons, protons, and neutrons. This field is rapidly evolving because of recent advances in the technology used for diagnosis, treatment planning, treatment delivery, and verification of patient treatments. One of the cornerstones of modern radiation therapy practice are volumetric patient image datasets from computed tomography (CT), magnetic resonance imaging (MRI), positron emission tomography (PET), and ultrasound (US). Devices that produce the
primary
images for use in radiation therapy treatment planning are called
Radiation Therapy Simulators
. Current devices include (1) Conventional Simulators (based on conventional X‐ray radiography planar imaging); (2) CT‐simulators (based on CT scanners); (3) PET/CT‐simulators (based on PET/CT scanners); (4) MR‐simulators (based on MR scanners).

The radiation therapy simulator has been an integral component of the treatment planning process since the 1960s. Conventional simulators are designed to mimic the linear accelerator geometry while providing a diagnostic‐quality X‐ray beam for anatomic imaging. Because of the increased use of three‐dimensional (3D) imaging for treatment planning, conventional simulators are less popular than in the past. Still, this technology continues to be developed and retains its presence in most radiation oncology departments. Shortly after the introduction of clinical CT scanners in the early 1970s, it was realized that this imaging modality had much to offer in a radiation oncology setting because they provided a volumetric view of the patient’s normal and tumor anatomy with excellent spatial accuracy. In response, CT simulators were developed during the 1980s, and 1990s and today CT simulator is the main imaging device in radiation therapy. The CT simulators have developed to a point where CT scanner manufacturers are designing scanners specifically for CT simulation purposes. PET imaging can also provide valuable information about tumors and PET–CT scanners have been implemented as radiation therapy simulators and can be found in many radiotherapy centers. Finally, MRI scanners have also been implemented and are used for treatment simulation in radiation therapy. The MRI scanners are less commonly found in radiotherapy departments, but because of the imaging advantages that MRI has to offer it is expected that the use of MRI scanner for radiotherapy simulation will experience significant growth.

This article describes the radiation therapy simulation process, design and features of conventional, CT, PET–CT, and MRI simulators, and their use for treatment planning.
Radionuclide Production and Radioactive Decay
Authors: Jurisson Silvia S. , Miller William , Robertson J. David
Published: April 2006

Radionuclide production and radioactive decay are two important factors for the development and use of radiopharmaceuticals for nuclear medicine imaging and radiotherapy applications. Sufficient quantities of the radionuclides used in medicine must be available on a routine basis at a reasonable cost. The radioactive ingredient must be sufficiently pure (both radiochemical and radionuclidic) and have enough activity to provide the therapeutic activity or the image information. The selection of a particular radionuclide for a specific application is determined by the radioactive decay properties (half‐lives, particle emission(s), particle energies, photon emissions, photon energies) and the behavior of the radionuclide in the body. Imaging applications require emission of penetrating radiations (gamma or positron annihilation photons), whereas radiotherapy applications require emission of short‐ range, high linear energy transfer (LET) radiations (alpha, beta, Auger electrons). Therapeutic radionuclides should not have significant emissions of penetrating radiations (gamma or positron annihilation photons), however, low abundance gamma emissions allow tracking of the
in vivo
therapeutic dose and dosimetry calculations. The factors of radioactive decay and radionuclide production are discussed, with examples and emphasis being on those radionuclides with applications to nuclear medicine.
Radiopharmaceutical Dosimetry
Authors: Thierens Hubert M.A.
Published: April 2006

In nuclear medicine, radiopharmaceuticals are administered to patients for diagnosis and therapeutic purposes. In diagnostic nuclear medicine, patient dosimetry aims predominantly to assess the risk for late effects of ionizing radiation (e.g., cancer and leukemia). To this end, the medical internal radiation dose (MIRD) dosimetry protocol is applied adopting standard biokinetics of the radiopharmaceutical and a standard anatomy of the reference male or female for the patient. For treatment purposes high activities of disease‐specific pharmaceuticals labeled with β‐emitters are given, necessitating an accurate patient‐specific dosimetry. In general patient‐specific biokinetics are derived from sequential images after administration of a tracer activity and combined with the MIRD methodology to calculate absorbed doses to target and critical tissues. In a complete patient‐specific dosimetry approach the individual patient anatomy is also taken into account and derived from computed tomography (CT) or magnetic resonance imaging (MRI) imaging. Three‐dimensional (3D) absorbed dose estimates are then determined from single single photon emission computed tomography (SPECT) or positron emission tomography (PET) activity data using dose‐point kernel convolution methods or by direct Monte Carlo calculation. A first part of the paper deals with the principles of the MIRD protocol and microdosimetric considerations, especially applicable to diagnostic nuclear medicine. The second part describes the methodology of dosimetry in metabolic radiotherapy with emphasis on the radioiodine therapy for treatment of benign and malignant thyroid diseases, meta‐iodo benzyl guanidine(131I‐MIBG) therapy for neuroblastoma and radioimmunotherapy. Finally, the dosimetric principles in the risk estimation of volunteers after administration of radiolabeled compounds in the framework of the development of new drugs are discussed.
Radiotherapy: Particle Beams
Authors: Becchetti F. D.
Published: April 2006

An overview, including historical developments, of various types of particle‐beam radiotherapies is given. This overview also includes electron, proton, neutron, and heavy‐ion radiotherapy. The types of particle accelerators and related apparatus for these are described together with the radiological aspects of each type of particle beam. Possible future developments in the field are outlined.
Radiotherapy Treatment Planning, Optimization of
Authors: Wolbarst Anthony B. , Chin Lee , Stavrev Pavel
Published: April 2006

Radiotherapy treatment planning is becoming ever more complex, driven largely by the growing use of intensity modulated radiotherapy (IMRT). There is a corresponding need to improve the computer‐based programs being designed to optimize the process of planning the spatial and temporal distributions of dose for such treatments. This article reviews the general objectives of treatment planning, and also the various physical and biological/statistical criteria that have been explored to serve as the bases for optimization objective functions.
Rehabilitation, Computers in Cognitive
Authors: Abreu Beatriz C. , Seale Gary , Temple Richard O. , Sangole Archana P.
Published: April 2006

This research is supported, in part, by the National Institute on Disability and Rehabilitation Research (NIDRR) grant no. H133P990001. The authors express their sincere gratitude to the Moody Foundation and the Moody Endowment for their support of this work.
Rehabilitation and Muscle Testing
Authors: Durfee W.K. , Iaizzo P.A.
Published: April 2006

Measurement of muscle function and strength is an essential component of many neurological and physical exams. Such evaluation of muscle strength is necessary for differential diagnosis, to determine the presence of disability, to plan potential treatments, and to track the effectiveness of treatments. As outcomes‐based medical practice bocomes more prevalent, the need for quantitative outcomes assessment of muscle strength will become even more critical. Several assessment techniques and tools are currently available. Manual muscle testing is the most widely used method to assess muscle function, however, its reliability and accuracy are questionable. when greater accuracy of results is needed, instruments are available that provide precise readouts of resistive force that muscle works against (i.e., hand dynamometers, pinch grips, and computer‐controlled dynamometers). More advanced muscle asessment methods include mathematical modeling of muscle activity and electromyogram recording of skeletal muscle contractions. Finally, stimulated muscle force assessment is discussed as a versatile approach for quantitative involuntary muscle torque.
Scoliosis, Biomechanics of
Authors: Stokes I.A.F. , Aubin C.E.
Published: April 2006

This article summarizes current understanding of scoliosis and concentrates on the biomechanical aspects of the deformity, its etiology, and its treatment.
Sexual Instrumentation
Authors: Brunswig Newring Kirk A. , Draper Crissa , O’Donohue William
Published: April 2006

The measurement of human sexuality has recently centered on the dysfunctional and disordered, while the early work was directed at understanding and assessing the human sexual response. This article reviews the development of medical devices and instruments for the assessment and treatment of female sexual function and dysfunction; then our attention is turned to the assessment and treatment of male sexual function and dysfunction, and lastly, we review phallometry and other assessments related deviant sexual interest and arousal in the human male.

Tremendous gains have been made in the last 50 years of research and development in the measurement of human sexuality. Unfortunately, these gains have occurred within a context of varied approaches, methodologies, and instruments. Despite several reviews and recommendations, there remain differing instruments, methodologies, and procedures in the physiological assessment of human sexuality. Furthermore, with the advent of more easily administered self‐report questionnaires, many outcome studies now rely on these self‐report measures, often ignoring the physiological aspects of sexual interest, arousal, and functioning.

Further complicating research in this area is the lack of representativeness of human sexuality research volunteers in comparison with “normals”. Thus, we are left with an indeterminate field; what research we have may be based in part on participant variables, a lack of standard instruments in methodologies and procedures, which impedes cross‐study comparisons, and on continuing advances in technology, leading to the promulgation of new devices and instruments. There are several reliable, valid, and useful devices and instruments for the psychophysiological assessment of human sexuality, and there is hope that with advances in technology, some of the concerns sounded by the scholars and pioneers in human sexuality research will be addressed.
Shock, Treatment of
Authors: Decau Sabin , Mackenzie Colin F.
Published: April 2006

Shock is a state of inadequate O2supply. It has many causes that include hypovolemia, maldistribution of perfusion, and cardiac pump failure. The common end‐point of all causes of shock is deficient capillary perfusion that triggers metabolic changes in organs and tissues. Acid–base and blood gas measurements are a common global measure of these metabolic changes. Mean blood pressure, heart rate, sublingual capnometry, capillary refill time, and mental status changes are noninvasive measures that have been used to quantitate shock. Invasive measurements include pulmonary artery or central venous pressure changes in response to fluid challenge, blood sampling, and cardiac output measurement to calculate O2consumption, O2extraction, and O2delivery. Brain function can be monitored continuously by near‐infrared spectroscopy and cerebral oximetry, cardiac function by transesophageal echocardiogram, and renal function by urinary flow and creatinine clearance. But all these measures have drawbacks because of their invasiveness, lack of validation, or sensitivity as markers of shock. The future holds promise of proteomic diagnostic tools and identification of shock factors and mediators that may reverse the multiorgan effects of prolonged shock and reduce mortality and morbidity.
Skin, Biomechanics of
Authors: Chen Yan , Davis Brian L.
Published: April 2006

This article provides a background description of skin and discusses the mechanical properties of skin.
Spinal Cord Stimulation
Authors: Trentman Terrence L. , Weinmeister Kent P.
Published: April 2006

Spinal cord stimulation (formally known as dorsal column stimulation) is a minimally invasive technique of applying an electric current in the vicinity of the spinal cord. It is used primarily to treat refractory neuropathic (nerve injury) pain. Patients typically considered for treatment with this modality include those suffering from the failed back surgery syndrome, chronic regional pain syndrome (RSD and causalgia), phantom limb pain, and other neuropathic pain in the lower extremity. Upper extremity neuropathic pain has also been treated successfully with spinal cord stimulation. After an initial successful trial, permanent spinal cord stimulation is accomplished via either a percutaneously inserted polyurethane lead or a surgically inserted “paddle” lead. To power the lead, an implanted pulse generator or radio frequency receiver is inserted in a subcutaneous pocket in the low abdomen or buttock. The patient then controls the stimulator with a hand‐held device. Animal and human studies have suggested that spinal cord stimulation has multiple effects on the spinal cord and pain transmission. Outcome studies show that long‐term success with this modality is ∼ 50%. In recent years, the potential role of stimulation has expanded to include treatment of peripheral neuropathic pain such as occipital neuralgia, ischemic pain (e.g., angina and lower extremity vascular insufficiency), and stress urinary incontinence.
Sterilization of Biologic Scaffold Materials
Authors: Freytes Donald O. , Badylak Stephen F.
Published: April 2006

Biologic materials are currently used for tissue and organ repair and are typically regulated as medical devices and subjected to established sterilization guidelines. Sterilization of biologic materials involves unique considerations that may have an impact on their performance and clinical utility. This article discusses the advantages, disadvantages, and physical effects upon synthetic and naturally occurring materials of four commonly used methods of sterilization: heat, ethylene oxide, gamma irradiation, and electron beam irradiation. Alternative methods of sterilization and disinfection are briefly discussed, with emphasis on methods typically used for naturally occurring biomaterials. The majority of the biologic materials currently available for clinical use are sterilized by exposure to either ethylene oxide (ETO) or ionizing radiation (IR). Although there are dose‐dependent effects associated with both ETO and IR, effective doses can be used with minimal effects upon the structure and function of naturally occurring biologic materials.
Physiological Systems Modeling
Authors: Smith N. Ty , Starko Kenton R.
Published: April 2006

This article discusses modeling as a device that you might use in research, education, or the practice of medicine or engineering. The purpose of the article is to allow you to explore, examine, and perhaps even use models, just as you would a device. Physiological models are almost unique among equipment, because a major use is education. Through physiological models, one can learn about physiology, pharmacology, scientific concepts, and clinical situations. The main way to use a model is through simulation or a simulator. We distinguish between simulation and simulators, the former being much more common. We usually give enough detail about a model so that the reader can decide whether to make the effort to locate the reference(s), author(s), and/or a simulator.

The article is divided by systems. Each section describes some characteristics and peculiarities of the system, followed by a description of the models available, highlighting some of the ones that can be easily and inexpensively used. We concentrate on the central nervous, cardiovascular and thermal regulatory systems, mainly in the area of classical, or macro, physiology.

The body and its systems depend on control systems, and these are emphasized, including the fascinating phenomenon of autoregulation, which has its own section. Autoregulation can be astoundingly simple or amazingly complex, but never completely independent of other regulatory systems.

The past, present, and future of physiological systems modeling are also explore. The future is particularly exciting. The physiome project is to physiology what the genome project has been to genetics.
Temperature Monitoring
Authors: Frasco Peter
Published: April 2006

This article will focus on the technical aspects of temperature monitoring. This emphasis on basic science of the instrumentation of temperature monitoring will be balanced with a discussion of the clinically important topics of heat loss and heat conservation in the surgical patient.
Thermocouples
Authors: Wren Joakim , Loyd Dan
Published: April 2006

Thermocouples are widely used in various applications in medicine and biomedical engineering. The sensors are accurate, flexible, well documented, and not too expensive. Thus they are considered to have the best cost/performance ratio for many applications.

Thermocouples are based on the thermoelectric Seebeck effect, which gives an electric potential between the junctions of two dissimilar metallic conductors when the junctions are held at different temperatures. Virtually every pair of metallic conductors are possible to use, but for practical reasons standardized thermocouples with determined thermoelectric properties and temperature/potential relation are used.

As all temperature sensor thermocouples are associated with various kinds of measurement errors. Some are specific for thermocouples, but the most important is based on the fact that every contact sensor only measures its own temperature. The sensor should therefore be in good thermal contact with the measuring object in order to obtain an accurate temperature at a reasonable time.

Depending on, for example, the present temperature gradients and the heat flux in the probe compared to its surroundings, significant and even substantial deviations and uncertainties can easily occur. Another important source of measurement errors is electromagnetic (EM) interference, which is particular troublesome in EM induced thermal treatment applications when temperature measurement is carried out in strong fields.
Thermography
Authors: Qi Hairong , Diakides Nicholas A.
Published: April 2006

This article discusses some new developments in medical thermography, including the new‐generation infrared technologies, the smart image processing algorithms, and the pathophysiological‐based understanding of infrared images. These developments have largely advanced the role of thermography in health monitoring and examination, as well as in assisting diagnosis.
Thermometry
Authors: Samaras Theodoros
Published: April 2006

This article details specifications and types of temperature measuring systems.
Integrated Circuit Temperature Sensor
Authors: Togawa Tatsuo
Published: April 2006

Temperature can affect the electronic characteristics of semiconductor devices. Although this is a disadvantage in many applications, especially for analogue devices, it may be turned into an advantage if such a device is used as a temperature sensor. In principle, any parameter in such a device having a temperature coefficient can be used for temperature measurement. For example, a temperature telemetry capsule, in which a blocking oscillator frequency varies with temperature, has been developed for measuring gastrointestinal temperature.
Tooth and Jaw, Biomechanics of
Authors: Müftü Sinan , Müftü Ali
Published: April 2006

The teeth and jaw perform the critical function of initiating the digestion by breaking the food into smaller sizes. Mastication is defined as the action of chewing foods. Biomechanical investigations of tooth and jaw are primarly involved with the mastication system. The masticatory system is composed of the dentition, bones, ligaments, muscles, and the temporomandibular joint (TMJ). The aim of biomechanical investigations of the masticatory system is to understand the fundamental relations between anatomy and function and, thus, either provide guidance to clinicians in existing treatment modes or help design new ones. In this article the functional anatomy, biomechanics of mastication, and the biomechanical aspects of prosthodontic treatments are presented. The fundamental definitions of force, stress, strain, and material properties are defined. The relevant material properties for the components of the masticatory system are reported. Biomechanical models and results related to the jaw open–close motions, TMJ loading, deformations of the mandible, and effect of endosseous implants are presented.
Tracer Kinetics
Authors: Di Bella Edward V. R.
Published: April 2006

Tracer kinetics refers to the changing distribution of a tracer that provides information regarding a biological system. The tracer may be introduced by injection into the bloodstream, or inhaled, or in some cases be native. By definition, the tracer is present in relatively small (trace) amounts so that it has little or no effect on the system being studied.
High Frequency Ventilation
Authors: Bunnell J. Bert
Published: April 2006

High frequency ventilators (HFVs) were developed to lessen the lung injury caused by conventional positive pressure ventilators (CVs). Although HFVs use positive pressure, the magnitude of the pressure that reaches the distal areas of the lungs is much lower, and their tidal volumes are a fraction of those used during normal breathing. Thus, HFVs are inherently gentler than CVs, and their use in the treatment of prematurely born infants would appear to be most desirable. However, after >20 years of clinical use, it is still unclear to many clinicians whether HFVs are safe or effective.

Most clinical trials applying HFVs to neonates have demonstrated decreased chronic lung disease with no increase in adverse side effects. Some trials conducted with children and adults in severe respiratory failure demonstrated increased survival. Other trials have shown no advantages and increased adverse side effects. Application strategies appear to be essential for successful outcomes, but better equipment design is also needed.

Given the skill and training needed to master HFVs, their use may be considered “risky” indefinitely.
X‐Rays: Interaction with Matter
Authors: Sethi Anil
Published: April 2006

A photon in an X‐ray beam that passes through a medium is likely to undergo one of three fates: complete absorption, scatter, or transmission. The first two processes contribute to X‐ray beam attenuation. Five main interactions can cause attenuation of photons: (1) coherent scattering, (2) photoelectric effect, (3) Compton scattering, (4) pair producion, and (5) photodisintegration. How much of the beam gets attenuated depends on which interaction process dominates. This in turn depends on the incident photon energy and the medium compositon. Broadly speaking, coherent scattering is most important at low photon energies and photondisinteration at high energies, whereas the other interactions are likely to occur at intermediate photon energies. The rich physics of interaction processes is presented in this article. We also define various attenuation coefficients, explain their dependence on photon energy and medium composition, and describle how they contribute to many exciting phenomena observed in medical physics.
X‐Ray Equipment Design
Authors: McKinley Randolph L. , Tornai Martin P.
Published: April 2006

This article discusses the functional organization of an X‐ray system, including delivering a controlled X‐ray beam to the patient, positioning the patient relative to the beam, detecting the modulated X‐ray beam passing through the patient, and delivering the image to the radiologist.
X‐Rays, Production of
Authors: Horn Bruce
Published: April 2006

Discovered by Wilhelm Roentgen in 1895, X rays are commonly used for many medical diagnostic imaging procedures—from a simple chest radiograph to a multislice computed tomography exam. X‐ray tube components are contained within an evacuated glass envelope that allows a focused beam of electrons to interact with a metal target to produce X rays by two methods: bremsstrahlung and characteristic X rays. This process is relatively inefficient because most of the electrons’ energy results in heat that must be dissipated to avoid failure of the tube. In addition, the size of the focus of the electron beam impinging on the target directly affects the image quality of clinical procedures. Due to these competing factors, an X‐ray tube design must represent the right balance between imaging quality and heat dissipation for a particular clinical application.
Tissue Ablation
Authors: Haemmerich Dieter
Published: April 2006

Tissue ablation is the destruction of diseased tissue, with the aim to cure a disease. Tissue destruction is achieved by thermal methods, or by application of chemical substances. Thermal methods cause either local heating or cooling of the tissue to lethal temperatures (typically below −40 deg C, or above 50 deg C). A number of different physical principles are employed for heating (radiofrequency electric current, microwaves, laser, ultrasound), and cooling tissue. Current clinical applications include treatment of heart arrhythmia, cancer (liver, lung, brain, kidney, bone, prostate), uterine bleeding, varicose veins, and enlarged prostate, with other emerging applications. During the ablation procedure, an applicator is introduced into the treatment site under imaging guidance. Then the tissue region around the applicator is ablated, destroying the diseased tissue area.
Computed Tomography Screening
Authors: Brenner David J.
Published: April 2006

Computed tomography (CT) has revolutionized much of medical imaging by allowing a three dimensional view of the organ or part of the body of interest. As of 2005, about 60 million CT scans are being performed each year in the USA. The use of CT for mass screening is a more recent innovation, driven in part by much increased availability and convenience of CT scans. Three applications, each of which will be discussed, have been suggested for CT‐based screening, for early stage lung cancer in smokers and ex smokers; for lesions in the colon (virtual colonoscopy); for general screening for many diseases in the whole body (full‐body screening). All these three modalities, as of 2005, are quite new, and a general consensus has not yet been reached about their efficacy. There is an added issue for CT‐based screening modalities, namely the significant x‐ray radiation exposures involved: the potential benefits of any CT‐based screening procedure must, in addition to more general efficacy issues, significantly outweigh any potential harm from repeated low‐dose x‐ray exposures.
Computed Tomography Simulator
Authors: Tang Xiangyang , Wang Ge
Published: April 2006

A computed tomography simulator (CTsimulator) originally referred to the combination of a radiation therapy dedicated (RT‐dedicated) CT scanner and a simulation workstation that is used for treatment planning in three‐dimensional (3D) conformal radiation therapy. Except for a larger gantry aperture and display field of view (DFOV), as well as a flat top patient couch, an RT‐dedicated CT scanner is virtually identical to a diagnostic CT scanner. The simulation workstation consists of a high quality display screen and a simulation software package. Based on the 3D patient data set acquired by an RT‐dedicated CT scanner, a treatment simulation is conducted to make sure an optimized 3D conformal radiation therapy be delivered to all of the targeted cancerous tumor volume while the inevitable radiation dose absorbed by surrounding normal tissues or organs is as little as possible. Although a CT scanner is currently preferable, other modalities, such as magnetic resonance imaging (MRI), positron emission tomography (PET), or ultrasound, can also be utilized to acquire 3D patient data set for treatment simulation (viz., virtual simulator). In a simulation process, numerous modern 3D visualization techniques, such as 3D volume rendering and surface rendering, are utilized to facilitate anatomic structure identification and radiation beam designing, take care of geometrical uncertainty caused by patient organ motion, such as breathing, swallowing, and assure spatial integrity between an RT‐dedicated CT scanner and a treatment machine. In addition to being employed in conventional 3D conformal radiation therapy, a CT simulator can be utilized in advanced 3D conformal radiation therapy, such as intensity modulated radiation therapy, tomotherapy, or radiosurgery. With the development of advanced 3D conformal radiation therapy techniques, more radiation therapy treatment planning systems are including the functionality of a stand‐alone CT simulator as an integrated component to accomplish an optimized radiation therapy via much more complicated 3D conformal beam‐forming techniques.
DNASequencing
Authors: Tsaftaris Sotirios A. , Katsaggelos Aggelos K.
Published: April 2006

Understanding how DNA sequencing works is the objective of this article, which is organized as follows. First, a very short introduction into the chemistry of the DNA molecule is provided. Subsequently, some of the basic principles used by common sequencing techniques are presented. This analysis is followed by a presentation of the most commonly available techniques and equipment. This article concludes with the presention of some of the most promising techniques for DNA sequencing in the future.
Drug Delivery Systems
Authors: Paolino Donatella , Sinha Piyush , Fresta Massimo , Ferrari Mauro
Published: April 2006

To obtain a given therapeutic response, the suitable amount of the active drug must be absorbed and transported to the site of action at the right time and the rate of input can then be adjusted to produce the concentrations required to maintain the level of the effect for as long as necessary. The distribution of the drug to tissues other than the sites of action and organs of elimination is unnecessary, wasteful, and a potential cause of toxicity. The modification of the means of delivering the drug by projecting and preparing new advanced drug delivery devices can improve therapy. The aim of advanced drug delivery devices is to control (1) the drug release rate from formulations or dosage forms, (2) the drug rate to reach absorbing membranes and surfaces, and (3) the site‐specific drug release. The control of drug release and the control of body distribution are the two most important features of the various drug delivery devices. The most important drug delivery devices were taken into consideration and their most usefull and successful applications in disease therapy were discussed. In particular, the attention was focused on the use of microelectro‐mechanical‐systems, cyclodextrins (the most representative of molecular drug delivery systems), microemulsion and organogel (supramolecular aggregates), and colloidal carriers (liposomes, niosomes, ethosomes, ultradeformable vesicles, nanoparticles) for delivery of drugs.
Engineered Tissue
Authors: Rutkowski Gregory E.
Published: April 2006

Engineered tissue is developed using the principles of engineering in combination with the life sciences to create implants that can be used to repair tissue lost to injury or disease. The three main components of engineered tissue are cells to enhance regeneration or replace lost tissue, a biodegradable matrix to hold cells together and promote tissue integration, and chemical factors to stimulate regeneration. Almost every tissue of the human body is currently being investigated as a candidate for engineered tissue repair. With advances in biodegradable polymers, stem cell technology, and immune regulation, engineered tissue has the potential to dramatically change healthcare by improving the quality of life of those for whom it was not previously possible.
Gamma Knife
Authors: Goetsch Steven J.
Published: April 2006

The Leksell Gamma Knife is the largest and costliest medical device ever created. It is designed to treat human patients with brain tumors and other abnormalities. A stereotactic headframe is affixed to the patients skull, a brain imaging study is then obtained, and a specialized computer is used to plan the treatment. The patient is placed on a treatment couch attached to the 22‐ton central body of the device, which contains 201 powerful radioactive cobalt‐60 sources. The patient is transported forward to the treatment position where the 201 sources converge with exquisite precision to irradiate the brain tumor (or lesion) while sparing the adjoining normal brain. This radiosurgery procedure can be used instead of open surgery, which is typically more costly, invasive, and risky. The device has been in use since 1968 and has been used to treat >229,000 patients with primary cancerous brain tumors, metastatic brain tumors, nonmalignant brain tumors, arteriovenous malformations, and functional neurological disorders. It is manufactured exclusively by Elekta Instruments, AB of Stockholm, Sweden. More than 180 units are in use worldwide, about one‐half of them in the United States. The instrument has enjoyed widespread clinical acceptance in the last 10 years by neurosurgeons and radiation oncologists who wish to use minimally invasive techniques to treat brain tumors and other disorders.
Heart Valves, Prosthetic
Authors: More Robert
Published: April 2006

This article discusses the history, evolution, design, and performance of prosthetic heart valves.
Imaging Devices
Authors: Rivard Mark J. , Van den Heuval Frank
Published: April 2006

Electronic portal imaging detectors (EPIDs) are devices that electronically capture the photon energy fluence transmitted through a patient irradiated during treatment, and allow direct digitization of the image. This image is then immediately available for visualization on a computer screen and electronic storage. A variety of technologies have been explored in the past two decades. These include camera based systems, liquid ionization chambers, linear arrays of silicon diode detectors, and flat‐panel displays composed of thin film technology (TFT) integrated circuits. TFT EPIDs permit high imaging resolution, high signal‐to‐noise ratios, and high photon detection efficiencies at reasonable cost. EPIDs permit digital comparisons of the simulated treatment plan with the resultant radiotherapy implementation. EPIDs are quickly replacing radiographic film as an important tool for providing direct confirm treatment delivery. Due to the electronic nature of the system, on‐ and off‐line image analysis is possible for augmenting patient positioning, artifact removal, imaging processing, and evaluation. While increasing the rate of image acquisition, patient throughput is largely unimpeded and improvements in radiotherapy delivery result. EPIDs can reduce the incidence and extent of errors made during radiation treatment delivery. Due to the electronic nature of EPID measurement of the photon energy fluence exiting a patient, one can perform exit dosimetry and quantitative comparisons with treatment planning intentions. EPID quality assurance is described in the 2001 Task Group No. 58 protocol of the American Association of Physicists in Medicine. Daily, monthly, and annual tests are performed to assure the EPID is reliable for clinical use.
Microbioreactors
Authors: Zhu Xiaoyue , Bersano‐Begey Tommaso , Kamotani Yoko , Takayama Shuichi
Published: April 2006

Recent advances in micro‐ and nanotechnologies coupled with the need in biology and medicine to perform cellular scale studies and productions have led to the emergence of a variety of microscale biological reaction systems. These microbioreactors are promising as low cost modules for optimizing bioproduction processes, highly parallel analytical platforms for screening pharmaceutical drugs, therapeutic implements for treating disorders and deficiencies, and examination tools for exploring basic physiological responses and biological reactions. This article summarizes the basic concepts, designs, and applications of microbioreactors with a special focus on medical, pharmaceutical, and cell biological applications. Important concepts include scaling laws and how the small size of the microbioreactors affects fluid flow, mixing, mass transport, heat transfer, and sterilization. Examples of specific microbioreactors for fermentation, drug toxicity screening, drug administration, assisted reproduction, and basic cell biological and physiological studies are also discussed. Microscale phenomena provide both a challenge and an opportunity for the development of microbioreactors.
Micropower for Medical Applications
Authors: Kang Ji Yoon
Published: April 2006

This article reviews the recent development of micropower devices in view of medical applications. Microelectromechanical system technology makes implantable devices smaller and cheaper recently, however, developing micropower source of implant device is still challenging. Micropower is classified into two categories: energy storage or energy generation. Current research on miniaturized batteries like fuel cells, thin‐film battery, and micromachined battery are surveyed and their application for implant devices is discussed. Several microfabricated power generators using vibration and body heat are compared and their applicability to medical devices is considered. In the future, a miniaturized battery with high energy density and high power will be the main power source, and a micropower generator will recharge the consumed energy as an auxiliary device.
Microscopy, Scanning Force
Authors: Wojcikiewicz Ewa P. , Kwak Kwanj Joo , Moy Vincent T.
Published: April 2006

Recent advances in technology have allowed us to study our world at molecular, even subatomic, resolution. One of the devices in the forefront of such studies is the atomic force microscope (AFM), which is a relatively complex device with two major applications. It can be used for imaging of biological samples in near‐physiological conditions at atomic‐level resolution. The AFM can also be used as a force apparatus to measure forces of receptor‐ligand interactions down to the single‐molecule level, acquire information about the mechanical properties of biological materials including cells, as well as to measure forces of protein folding/unfolding.
Microscopy, Scanning Tunneling
Authors: Ayres Virginia M. , Udpa Lalita
Published: April 2006

Scanning tunneling microscopy (STM) has the highest resolution of all scanning probe techniques, routinely producing atomic scale images. With such resolution, it is highly desirable to apply STM to investigations of molecular biology and medicine. The difficulty when considering the application of STM to molecular biology is that biological samples are nonconductive. It may be more accurate to describe biological samples as having both local and varying conductivities. These two issues will addressed in this review, and examples of conditions for the successful use of STM for biomedical imaging will be discussed. Successful applications of STM to significant research problems in biology and medicine will be presented.
Microsurgery
Authors: Rebello Keith J.
Published: April 2006

Microsurgery is a specialized surgical technique whereby a microscope is used to operate on tiny structures within the body. Fine precision microinstruments are used to manipulate tissue with or without robotic or computer control. This technique has allowed for significant advances in surgery especially for operations involving the inner ear, eye, brain, nerves, and small blood vessels.
Optical Tweezers
Authors: Schek Henry , Hunt Alan J.
Published: April 2006

Optical tweezers fill an important niche in the arsenal of single molecule biophysical techniques, combining the ability to manipulate micron scale objects with the ability to measure piconewton forces and nanometer displacements. This article briefly reviews the history and theory of optical trapping, and introduces the basic principals for applying an optical tweezers device to measure force and displacement. Several seminal experiments utilizing optical tweezers are reviewed to illustrate the capabilities and limitations of optical trapping.
Pancreas, Artificial
Authors: Hovorka Roman
Published: April 2006

In the last two decades, the advancements in the field of continuous glucose sensors have stimulated the development of prototypes of a closed‐loop system based on combination of a continuous monitor, a control algorithm, and an insulin pump. This is denoted as an artificial electromechanical endocrine pancreas.

The existing prototypes can be divided according the way they handle meal delivery into “fully closed‐loop” or “closed‐loop with meal announcement” systems. Depending on body interface, three major types of artificial pancreas are recognized, (i) the subcutaneous (sc) sensing and sc delivery (sc–sc) system, (ii) the iv sensing and intraperitoneal (ip) delivery (iv–ip) system, and (iii) the iv glucose sensing and iv insulin delivery (iv–iv) system.

The description of the following prototypes and the work of the following research groups is reviewed: the Biostator, Shichiri’s group, Minimed–Medtronic, Roche Diagnostics, Adicol project, Institute for Diabetes Technology, and EVADIAC group. Human clinical studies are summarized.

It is concluded that the lack of availability of a glucose monitor with adequate properties appears to hinder further progress and the development of a commercially viable system. The existing control algorithms need to be improved and subjected to rigorous clinical testing. The artificial pancreas is most likely to find its wider use in the supervised hospital environment, such as at the intensive care units. The application in home settings will most likely be gradual starting with a supervised system (by the treated subjects) and increasing its autonomous function following on from wider experience.
Radiation Therapy, Quality Assurance in
Authors: Gejerman Glen , Hanley Joseph
Published: April 2006

A prerequiste to a successful radiation oncology prgram is accurate treatment planning and consistent treatment delivery. The Nuclear Regulatory Commission and most state regulatory bodies have published quality assurance guidelines requiring interval testing of the simulation, treatment planning, and treatment delivery process. Recognizing the challenge of ensuring proper maintenance and use of increasingly complicated systems, the American Assiciation of Physicists (AAPM) published a series of comprehensive quality assurance guidelines that can be applied to X‐ray and CT simulators, treatment planning systems, and linear accelerators. Comprehensive quality assurance must encompass both systematic and random uncertainity in treatment planning and delivery to minimize their occurrence. The many factors that contribute to target dilineation uncertanity including acquisition parameters, organ motion, imaging modality, image fusion, and intra‐observer variablity should all be examined closely for their contributions to treatment uncertainities. To minimize treatment inaccuracies, it is essential that each radiation oncology department establishes a “quality system” or quality assurance program to provide the organizational structure, responsibilities, procedures, processes, and resources for assuring the quality of patient management.
Radiation Therapy Treatment Planning, Monte Carlo Calculations in
Authors: Chui Chen‐Shou , Yorke Ellen , Sheu Ren‐Dih
Published: April 2006

The distribution of radiation in three‐dimensional (3D) heterogeneous geometry is governed by the Boltzmann transport equation. In general, it does not have analytic solutions, and therefore one has to rely on numerical methods.

Monte Carlo simulation is probably the most accurate numerical method for such problems. It uses random sampling techniques to simulate various physical events. In radiation therapy, the most commonly used radiations are photons and electrons with energies up to 20 MeV. The geometry can be the machine that produces the radiation or the 3D images of the patient under treatment. In a Monte Carlo calculation for radiation therapy treatment planning, radiation particles are generated and tracked through various components in the machine head and followed into the patient body, inside of which the relevant physical events are simulated and energy deposited.

Several examples are given to illustrate the application of Monte Carlo calculations in radiation therapy treatment planning. These include the calculation of beam characteristics by simulating the machine head, and dose calculations in patient for photon and electron beams.