|Year : 2012 | Volume
| Issue : 3 | Page : 163-165
Medical Radiological Physics
Ex-DRDO, Ministry of Defence. Jodhpur, India
|Date of Web Publication||1-Aug-2012|
A R Reddy
162 Sector A, AWHO Colony, Secunderabad - 500 009
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Reddy A R. Medical Radiological Physics. J Med Phys 2012;37:163-5
By A Almén, J.H. Bernhardt, L. Johansson, K.-U. Kasch, A. Kaul, H.-M. Kramer, S. Mattsson, B.M. Moores, D. Noßke, H.-J. Selbach, F.-E. Stieve, J. Valentin, S. Vatnitsky
Edited by A. Kaul
(Sub volume A of Volume 7 under Group VIII: Advanced Materials and Technologies in Landolt-Börnstein New Series Numerical Data and Functional Relationships in Science and Technology, on Fundamentals and Data in Radiobiology, Radiation Biophysics, Dosimetry and Medical Radiological Protection)
(Springer, Haberstrasse 7, 69126 Heidelberg, Germany, 2012, 335 pages, Euro 2,450, 30 ISBN 978-3-642-23683-9 Springer Berlin Heidelberg New York)
Medical physics education is generally focused on the topics concerned with the physics aspects of correct patient diagnosis and treatment with different types of radiation. In our country, it is heavily restricted to the requirements of radiotherapy with ionizing radiation and cursory treatment of radiological safety. An Approved Radiological Safety Officer (RSO) is a mandatory regulatory requirement for the practice of radiotherapy. However, in diagnostic radiology departments, lot more is to be done to strengthen radiological safety and appointment of competent RSOs. Study material for passing of the mandatory examination and viva for RSO is scantily available. The present book under review, Medical Radiological Physics, is a comprehensive treatise on the subject encompassing the radiological safety of not only the ionizing radiation but also the radiological safety of non-ionizing radiation, inclusive of ultrasonic and infrasonic waves, electromagnetic fields, optical radiation, etc., when they are applied to medicine for diagnosis and therapy.
About 10 years before the discovery of X-rays and natural radioactivity by W. C. Rontgen and H. Becquerel, more precisely in 1883, Hans Landolt, Richard Börnstein and Julius Springer had started a series of selected and easily retrievable physical data, which became a successful tool for natural scientists working or practising a profession in the fields of chemistry, physics or technology.
Now, i.e. about 120 years after the start of this unique data collection and consequently about 100 years after the introduction of ionizing radiations and radionuclides in natural sciences, medicine and technology, the Landolt-Börnstein New Series is submitting to the reader, which is a full volume on protection of man against ionizing radiations and radionuclides, i.e. Radiological Protection. The 6th edition of the Landolt-Börnstein Series contained a chapter on "Strahlenschutz" of merely six pages. In comparison, many rapid developments specifically in medical radiological protection, within the last five decades, necessitated the above full volume on the subject.
The Landolt-Börnstein New Series Group VIII Advanced Materials and Technologies six volumes on Laser Physics and Applications, Energy Technologies, Radiological Protection, Liquid Crystals, Polymers have been published with world-renowned authorities contributing treatises like articles for the volumes. Radiological Protection, a volume in this series, is of specific interest to the radiation and radioisotopic applications community. The volume, ably edited by Prof Alexander Kaul, former Chairman, Committee 2 of International Commission on Radiation Protection (ICRP) and Dr D. Becker, and published in 2005, is a landmark treatise that contains chapters on the conceptual basis of Radiological Protection, Biological effects of ionising radiation, Physical fundamentals, Radiological quantities and units, Shielding against ionizing radiation, External dosimetry, Internal dosimetry of radionuclides, Decontamination, Decorporation of radionuclides, Measuring techniques and Exposures from natural and man-made radiation sources. This volume presents scientific basis and required data for dealing with tasks of practical radiological protection, specifically in the field of lower energies of ionizing radiation. It emphasizes the philosophy of the ICRP or of the International Commission on Radiation Units and Measurements (ICRU), and includes summarized information of many relevant ICRP and ICRU publications.
Medical Radiological Physics, the sub volume A of Volume 7 of Landolt-Bornstein New Series of Group VIII on Advanced Materials and Technologies (sub volume VIII/A) expertly edited by Prof Dr Alexander Kaul (e-mail: [email protected]) has comprehensive chapters on radiation physics and biophysics, radiobiology, dosimetry and medical radiological protection, and is authored by internationally outstanding experts in the field. Each chapter not only gives a detailed scientific input on the subject to the clinical physicists, engineers and physicians working or intending to work in radiological diagnostics and therapy but also comprehensive data sets required for practical purposes while pursuing their professional activity in the field of medical radiology. An exhaustive list of references to original articles/reports for more detailed study are provided for each chapter. At the end of sub volume VIII/7A, a Glossary of about 420 radiological quantities, units and biophysical/biomedical terms is provided with index to the terms where they occurred first in the text.
The first chapter, an Introduction to the sub volume VIII/7A, summarizes the required fundamentals and data sets of the subjects dealt in the next four chapters in the volume. The sub volume VIII/7A, as against other text books on medical physics and radiation protection, deals extensively with the subject of non-ionizing radiation, covering their fundamental aspects with extensive data sets, their biological effects, medical applications and radiological safety. The chapter also mentions about the forthcoming sub volume VIII/7B, in which important information of the biophysical, biological, dosimetric fundamentals and knowledge in radiological protection as the basis for a better understanding of the imaging and treatment planning in radiation oncology is being incorporated.
Description of the physical characteristics of ionizing radiation, including photons and charged particles of energies of interest in the diagnosis and therapy, their biophysical interaction mechanisms with biological tissues and the possible induction of adverse health effects, are dealt with in detail in Chapter 2. It also deals with the physical and biophysical properties and possible adverse effects of non-ionizing radiation (NIR). NIR in the context of health protection and medical applications, dealt with in this sub volume 7A, is a general term for both radiations and fields that form part of the electromagnetic spectrum, having insufficient radiated energy to produce ionization in the medium through which it passes. NIR includes optical radiations of wavelengths between 100 nm and 10 6 nm (ultraviolet, visible, infrared and laser radiation); radiofrequency radiation including microwaves of wavelengths between 1 mm and 3000 m (corresponding to frequencies of 300 GHz and 100 kHz); and time varying electric and magnetic fields of frequencies less than 100 kHz. Static magnetic fields of strength 0.2-3 T that are encountered in the use of magnetic resonance imaging (MRI) scanners are also included in the NIR. Physical interactions of static magnetic fields with biological systems, electrodynamic interactions with ionic conduction currents, magnetomechanical effects and effects on electronic spin states of reaction intermediates are dealt with in Chapter 2. In case of time varying electric and magnetic fields of frequencies 100 kHz and above encountered while working with MRI scanners, the clinicians and maintenance engineers are exposed to gradient magnetic fields up to 10 mT at an equivalent frequency of around 500 Hz. Cancer-related effects of RF radiation, like microwaves, are unlikely at specific absorption rates, up to 4 W/kg.
The pressure waves such as ultrasound and infrasound, i.e. waves on either side of the audible frequency range (20-20 kHz) are also included under NIR. Medical diagnostic application of ultrasound, both in pulsed and in continuous modes, is mostly in the frequency range of 2-10 MHz. Thermal and non-thermal interaction mechanisms of ultrasound waves are described in Chapter 2.
The current International Commission on Non-Ionizing Radiation Protection (ICNIRP) guidelines of exposure to electromagnetic fields pertaining to occupational exposures and exposures to members of public can be downloaded free at www.icnirp.org/pubEMF.htm. Fact sheets summarizing the potential health effects and prescribed guidelines to the electromagnetic fields and optical radiations can also be downloaded free from the same site.
Measurement of Dose in Diagnostic Radiology, Radiotherapy and Brachytherapy is the subject matter of Chapter 3. In the first section of Chapter 3, quantities for measurement of dose in diagnostic radiology, in all forms of projection radiography, are described in terms of the incident air kerma, entrance surface air kerma, kerma area product or dose area product. It is the kerma area product that is used for providing diagnostic reference level in projection diagnostic radiology examinations. Because the geometry of exposure in computed tomography (CT) is different from the projection radiography, a group of dose quantities that fall under the general heading of the dose-length product, which is the line integral of the air kerma along a linear section either on the system axis or parallel to the system axis, have been specifically defined for CT. Based on this concept, a group of Computed Tomography Dose Indices (CTDI), such as the CTDI in free air, CTDI for the CT head phantom, CTDI for the CT body phantom, weighted CTDI for body or head, CT pitch factor and volume CTDI are used in quantifying the exposures in CT. Dosimetric equipment such as ionization chambers (both gas filled and solid state), scintillation dosimeters, thermoluminescent dosimeters, kerma area product dosimeters and dose length product dosimeters are briefly mentioned in this Chapter for quantifying the radiation dose in diagnostic radiology.
The main task in radiotherapy is to deliver correctly the prescribed dose to the tumor while minimizing the dose to the neighbouring normal tissue. The uncertainty in tumor dose should be less than 2.5% as per ICRU. The dosimetric quantity of interest in radiotherapy is the absorbed dose to water, and is based on calibration of reference dosimeters in national metrology laboratories. After briefly describing the parameters of relevance in radiotherapy, such as absorbed dose in water and percentage depth dose in water phantom, different dosimetric systems used for their measurements, uncertainties to be considered and corrections needed in their measurements have been described in Chapter 3 for photon and charged particle beams, including for hadron beams used in external beam radiotherapy. Similar considerations for brachytherapy have also been presented. Extensive listing of references to protocols from a number of national and international organizations on teleradiotherapy and brachytherapy are included.
Chapter 4 of sub volume VIII/7A deals comprehensively with the dosimetry in diagnostic and therapeutic nuclear medicine. Medical Internal Radiation Dose (MIRD), International Commission on Radiological Protection (ICRP) and joint MIRD-ICRP dose formalisms are presented in detail. Computational methods to obtain physical data in the form of S-values for different radionuclides using different mathematical anthropomorphic/voxel phantoms as well as the biological data in the form of cumulated activity, Ǎ, using respiratory tract model and Human Alimentary Tract Model are described in methods for measurement and collection of radiopharmaceutical biokinetic data. Reference levels of different nuclear medicine diagnostic investigations are provided that could be used as guidance values. Dose estimates to embryo/fetus using the pregnant woman model as well as doses to breast fed infants are also given.
Patient-specific dose estimation in therapeutic nuclear medicine is dealt with in some detail in Chapter 4, bringing out the importance of patient-specific radiopharmaceutical kinetic data for obtaining the cumulated activity, Ǎ, as well as patient-specific voxel information for S-value computations. Different therapy applications of radiopharmaceuticals for palliative and curative therapy are briefly presented. Current trends and future developments for better patient-specific dosimetry of tumor as well as normal tissues in radionuclide therapy, application of concepts of local dosimetry and microdosimetry with Auger electron emitters, alfa particles as well as with beta particles and estimating biologically effective dose from the heterogeneously distributed tumor dose have also been mentioned at the end.
Chapter 5 presents a summary of the current concepts and recommendations in protection against ionising radiation, and their application to the protection of patients and staff as well as members of the public in terms of clinical management in diagnostic radiology and radiotherapy and in diagnostic and therapeutic nuclear medicine. Protection against non-ionising radiation as used for diagnostic purposes is also discussed, focusing on MRI and diagnostic ultrasound. Guideline limits for occupational exposures and exposures to members of public as per recommendations of the International Commission of Non-Ionizing Radiation Protection are also given.
The volume VIII/4 on Radiological Protection and the sub volume VIII/7A on Medical Radiological Physics will be of immense use to have at one place not only the scientific background but also the required comprehensive data sets for addressing practical tasks in the clinics by physicians, physicists and engineers in medical radiology; for students of medical physics; and for enhancing competence by young physicists and physicians as newcomers to the field of medical radiological physics. It may be pretty expensive for individuals to own the volumes, but the institutions that train, do research and pursue developments in Medical Physics should certainly have them in their libraries.
I consider it a privilege to review this sub volume VIII/7A ably edited by my mentor during my tenure in Germany, Prof. A. Kaul, and authored by some of my colleagues in Germany who authored different chapters in the sub volume.