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From first principles to current computer applications, Monte Carlo Calculations in Nuclear Medicine, Second Edition: Applications in Diagnostic Imaging covers the applications of Monte Carlo calculations in nuclear medicine and critically reviews them from a diagnostic perspective. Like the first edition, this book explains the Monte Carlo method and the principles behind SPECT and PET imaging, introduces the reader to some Monte Carlo software currently in use, and gives the reader a detailed idea of some possible applications of Monte Carlo in current research in SPECT and PET. New chapters in this edition cover codes and applications in pre-clinical PET and SPECT. The book explains how Monte Carlo methods and software packages can be applied to evaluate scatter in SPECT and PET imaging, collimation, and image deterioration. A guide for researchers and students developing methods to improve image resolution, it also demonstrates how Monte Carlo techniques can be used to simulate complex imaging systems.
Computed tomography (CT) is a powerful technique providing precise and confident diagnoses. The burgeoning use of CT has resulted in an exponential increase in collective radiation dose to the population. Despite investigations supporting the use of lower radiation doses, surveys highlight the lack of proper understanding of CT parameters that affect radiation dose. Dynamic advances in CT technology also make it important to explain the latest dose-saving strategies in an easy-to-comprehend manner. This book aims to review all aspects of the radiation dose from CT and to provide simple rules and tricks for radiologists and radiographers that will assist in the appropriate use of CT technique. The second edition includes a number of new chapters on the most up-to-date strategies and technologies for radiation dose reduction while updating the outstanding contents of the first edition. Vendor perspectives are included, and an online image gallery will also be available to readers.
Computed Tomography (CT) has been one of the leading imaging modalities in today's practice of Radiology. Since its introduction in 1970s, its unique tomographic capability has not only prevented countless number of unnecessary surgeries but also saved lives by early detection of disease. Radiation dose from CT has been estimated to contribute to almost 50% of all medical radiation exposures. Concerns about radiation-induced carcinogenesis have resulted in efforts that encourage monitoring and reporting radiation dose from CT examinations. It has been suggested that the most appropriate quantity for assessing risk of carcinogenesis from x-ray imaging procedures is the radiation dose to individual patients. Currently employed dose metrics used to report patient dose are CTDIvol and DLP, neither of which is patient-specific dose, let alone dose to individual organs. CTDIvol is dose to a homogenous cylindrical phantom, which is defined for fixed tube current CT exams. With the implementation of Tube Current Modulation (TCM) feature in almost all clinical CT protocols as an intended means for dose reduction, while maintaining an appropriate diagnostic image quality, CTDIvol definition was standardized across scanners to reflect dose to CTDI phantom based on the average tube current across the entire scan length. Depending on the type of CT exam, the average tube current used to report a CTDIvol value may or may not represent the actual tube current at a specific table location. In addition to not taking into account variation of the tube current across a single exam, CTDIvol is size-independent, i.e. patients with different sizes have the same CTDIvol value if scanned using the same imaging parameters. To adjust CTDIvol for size, AAPM Task Group 204 was established and subsequently published a report containing conversions as a function of effective diameter which can be applied to scanner-reported CTDIvol to adjust for patient size. However, the generated conversion factors were based on fixe tube current measurements and Monte Carlo simulations and failed to take into account TCM. Additionally, the size metric used in TG 204 was entirely based on patients' physical dimensions and does not take into account variations in composition and density among patients, let alone within a single patient; i.e. differences between chest and abdomen in terms of attenuation properties could not be explained with a simple measure of dimension such as effective diameter. Instead attenuation-based metrics need to be implemented to explain these differences. The overall purpose of this dissertation was to improve organ dose estimation from Computed Tomography exams by: (a) taking into account the commonly used feature in CT protocols, Tube Current Modulation (TCM), (b) employing a more appropriate way of reporting CTDI for TCM exams and (c) using a patient size descriptor capable of describing the attenuation properties of individual patients. For this dissertation a validated Monte Carlo based MDCT model capable of simulating organ dose was utilized to estimate organ dose to voxelized patient models undergoing tube current modulated CT examinations. Both detailed TCM and z-axis-only modulation information were used in the simulations in case raw projection data was not accessible. In addition to simulated organ doses different CTDIvol values based on the type of patient model, abdomen versus chest, were calculated. These CTDIvol values included regional CTDIvolregional and organ-specific CTDIvolorgan along with scanner-reported CTDIvol, referred to as global CTDIvol. Furthermore different size metrics, such as effective diameter and attenuation-based metrics, were calculated for every axial CT image within a series and averaged corresponding to the same regions and images used to calculated the above mentioned regional and organ-specific CTDIvol values. Using an approach similar to previous efforts and AAPM Task Group 204, the estimated organ doses were normalized by CT Dose Index (CTDIvol) values. However, for TCM scans normalized organ doses by CTDIvol, global were observed to not have a strong correlation with patient size. This result was quite different from that observed previously for fixed tube current exams. In contrast, when regional descriptors of scanner output (CTDIvol, regional and CTDIvol, organ were used as a modified normalization factor, the results demonstrated significantly improved correlations with patient size. Additionally, an attenuation-based patient size metric, the water equivalent diameter (WED), was investigated in terms of its ability to describe the effects of patient size on organ dose. WED was compared to the size metric introduced in TG204, effective diameter, which is based only on patient morphology (e.g. perimeter) and not on attenuation. Results of the comparisons demonstrated no statistically significant improvements of correlation between normalized organ doses and size metric once WED was utilized, except for normalized lung dose. Although there were no statistically significant improvements, the correlation of determination, R2, increased for almost all organs once WED was employed. Similarly, there was no statistically significant difference between differently averaged size metrics, i.e. global average of size metrics versus regional average of size metrics, except for normalized lung dose, which showed a statistically significant improvement in R2 once a regional WED was employed as a size metric compared to global WED. Using improved normalization quantity and patient size metric for tube current modulated CT examinations, Generalized Linear Models were used to generate a predictive model capable of estimating dose from TCM exams using regional CTDIvol and WED. Different models based on scanners and organs were generated to establish the level of accuracy of each model and to determine the level of specification needed to achieve best organ dose estimates. Additionally, models with different response variables, normalized organ dose versus actual organ dose, were explored and compared. When tested using a separate test set, investigated models with regional CTDIvol either as a predictor or normalization factor resulted in very similar results while models created with global CTDIvol as a predictor resulted in underestimation of organ dose across all organs. Additionally, it was shown that a model based on pooled data was not significantly different than scanner and organ-specific models since the pooled-data model resulted in employing significant categorical predictors such as scanners and organs. This observation confirms the fact that TCM algorithms are different across scanners and regional CTDIvol is not capable of eliminating these differences, but it can eliminate differences among TCM functions across a single CT scanner. Predictive organ dose estimates using generated models resulted in a mean percent difference of less than 10% when compared to actual Monte Carlo simulated organ doses. The improvement of the newly generated model was also compared against currently used dose metrics, CTDIvol, SSDE, and ImPACT. While comparisons with actual Monte Carlo simulated organ doses resulted in statistically significant differences between conventional dose metrics and simulated organ doses, comparisons with organ estimates from the newly developed model resulted in no difference from Monte Carlo simulated organ doses. This work demonstrated the feasibility of estimating organ dose from tube current modulated scans from three major CT manufacturers using an improved descriptor of tube current modulated scans as normalization quantity or predictor and a patient size metric based on patients attenuation properties.
The book provides a comprehensive description of the fundamental operational principles, technical details of acquiring and specific clinical applications of dental and maxillofacial cone beam computed tomography (CBCT). It covers all clinical considerations necessary for optimal performance in a dental setting. In addition overall and region specific correlative imaging anatomy of the maxillofacial region is described in detail with emphasis on relevant disease. Finally imaging interpretation of CBCT images is presented related to specific clinical applications. This book is the definitive resource for all who refer, perform, interpret or use dental and maxillofacial CBCT including dental clinicians and specialists, radiographers, ENT physicians, head and neck, and oral and maxillofacial radiologists.
The actual radiation dose absorbed in the body is calculated using three-dimensional Monte Carlo transport. Neutrons, protons, deuterons, tritons, helium-3, alpha particles, photons, electrons, and positrons are transported in a completely coupled manner, using this Monte Carlo All-Particle Method (MCAPM). The major elements of the invention include: computer hardware, user description of the patient, description of the radiation source, physical databases, Monte Carlo transport, and output of dose distributions. This facilitated the estimation of dose distributions on a Cartesian grid for neutrons, photons, electrons, positrons, and heavy charged-particles incident on any biological target, with resolutions ranging from microns to centimeters. Calculations can be extended to estimate dose distributions on general-geometry (non-Cartesian) grids for biological and/or non-biological media.
Written by practitioners experienced in the field, 'Practical Radiation Protection in Healthcare' provides a practical guide for medical physicists and others involved with radiation protection in the healthcare environment.
This publication provides guidelines for the implementation of quality assurance and control programs concerning the combined medical diagnostic modality of positron emission tomography (PET) and computed tomography (CT). These independent, but complementary, imaging techniques are in frequent and increasing use within the fields of diagnostic imaging, oncology, cardiology and neurology, where they allow physicians to locate and diagnose malignant diseases accurately. This publication establishes guidelines for acceptance testing and routine quality control as necessary for optimal clinical performance. Specific topics of discussion include frameworks for reference values, tolerances and action levels, minimal required configurations with corresponding performances characteristics, and the management of ancillary equipment.