Estimation of Radiation Dosimetry for some Common SPECT-CT Exams (original) (raw)
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Clinical and Translational Imaging, 2014
Single-photon emission computed tomography combined with X-ray computed tomography (SPECT/CT) improves diagnostic accuracy by allowing better localization and definition of scintigraphic findings. However, the combined acquisition of functional and anatomical images can substantially increase radiation exposure to patients, particularly when using a hybrid system with diagnostic CT capabilities. At the same time, the introduction of new SPECT and CT reconstruction techniques (based on the use of iterative algorithms), and of CT automatic dose modulation techniques, has opened the way for possible reductions in patient dose and/or improvements of image quality. It is, therefore, essential to carefully balance the diagnostic needs and the radiation protection requirements, optimizing the choice of radiopharmaceutical and administered activity, and the image acquisition and processing modalities both in SPECT and in CT. This is particularly important in the case of pediatric examinations. In short, to maximize benefit to patients, SPECT/CT studies have to be optimized, adopting dose-reduction measures both from CT and SPECT practices. In SPECT, shorter lived gamma emitters should be preferred and the amount of activity administered must be carefully adjusted to the patient's size. In CT, scanning parameters (scanning length, tube current, tube voltage, filtration, collimation, slice thickness, pitch, automatic dose modulation method, reconstruction technique, and image processing) must be chosen carefully, remembering that normally the scanned images are used only for the purposes of attenuation correction and/or a more precise localization of scintigraphic findings, which require lower quality and consequently entail a lower dose to the patient. On the other hand, good quality diagnostic CT images, obtained at higher dose levels, are necessary if a diagnostic CT examination must still be planned for the patient. The purpose of this review on SPECT/CT radiation dosimetry is to provide updated information on the total effective dose and total equivalent doses to critical organs due to both radiopharmaceutical administration and CT scan modality for both adults and pediatric patients. The use of new solid-state detectors (cadmium zinc telluride) for SPECT cameras will also be considered. Finally, the means of easily determining SPECT/CT dose to patients will be provided.
Annals of Nuclear Medicine, 2013
Hybrid imaging, such as SPECT/CT, is used in routine clinical practice, allowing coregistered images of the functional and structural information provided by the two imaging modalities. However, this multimodality imaging may mean that patients are exposed to a higher radiation dose than those receiving SPECT alone. Objectives The study aimed to determine the radiation exposure of patients who had undergone SPECT/CT examinations and to relate this to the Background Equivalent Radiation Time (BERT). Methods 145 SPECT/CT studies were used to estimate the total effective dose to patients due to both radiopharmaceutical administrations and low-dose CT scans. The CT contribution was estimated by the Dose-Length Product method. Specific conversion coefficients were calculated for SPECT explorations. Results The radiation dose from low-dose CTs ranged between 0.6 mSv for head and neck CT and 2.6 mSv for whole body CT scan, representing a maximum of 1 year of background radiation exposure. These values represent a decrease of 80-85 % with respect to the radiation dose from diagnostic CT. The radiation exposure from radiopharmaceutical administration varied from 2.1 mSv for stress myocardial perfusion SPECT to 26 mSv for gallium SPECT in patients with lymphoma. The BERT ranged from 1 to 11 years. Conclusions The contribution of low-dose CT scans to the total radiation dose to patients undergoing SPECT/CT examinations is relatively low compared with the effective dose from radiopharmaceutical administration. When a CT scan is only acquired for anatomical localization and attenuation correction, low-dose CT scan is justified on the basis of its lower dose. Keywords SPECT/CT Á Effective dose Á Background Equivalent Radiation Time Á Radiopharmaceutical C. Montes and P. Tamayo contributed equally to this work.
SPECT-CT in routine clinical practice
Nuclear Medicine Communications, 2012
Objective To assess the patient radiation dose during routine clinical single-photon emission computed tomography-computed tomography (SPECT-CT) and measure the increase as compared with SPECT alone. Materials and methods Data pertaining to 357 consecutive patients who had undergone radioisotope imaging along with SPECT-CT of a selected volume were retrospectively evaluated. Dose of the injected radiopharmaceutical (MBq) was noted, and the effective dose (mSv) was calculated as per International Commission on Radiological Protection (ICRP) guidelines. The volume-weighted computed tomography dose index (CTDIvol) and dose length product of the CT were also assessed using standard phantoms. The effective dose (mSv) due to CT was calculated as the product of dose length product and a conversion factor depending on the region of investigation, using ICRP guidelines. The dose due to CT was compared among different investigations. The increase in effective dose was calculated as CT dose expressed as a percentage of radiopharmaceutical dose. Results The per-patient CT effective dose for different studies varied between 0.06 and 11.9 mSv. The mean CT effective dose was lowest for 99m Tc-ethylene cysteine dimer brain SPECT-CT (0.9±0.7) and highest for 99m Tc-methylene diphosphonate bone SPECT-CT (4.2±2.8). The increase in radiation dose (SPECT-CT vs. SPECT) varied widely (2.3-666.4% for 99m Tc-tracers and 0.02-96.2% for 131 I-tracers). However, the effective dose of CT in SPECT-CT was less than the values reported for conventional CT examinations of the same regions. Conclusion Addition of CT to nuclear medicine imaging in the form of SPECT-CT increases the radiation dose to the patient, with the effective dose due to CT exceeding the effective dose of RP in many instances. Hence, appropriate utilization and optimization of the protocols of SPECT-CT is needed to maximize benefit to patients. Nucl Med Commun 33:926-932
Patient dose considerations in computed tomography examinations
World Journal of Radiology, 2010
Ionizing radiation is extensively used in medicine and its contribution to both diagnosis and therapy is undisputable. However, the use of ionizing radiation also involves a certain risk since it may cause damage to tissues and organs and trigger carcinogenesis. Computed tomography (CT) is currently one of the major contributors to the collective population radiation dose both because it is a relatively high dose examination and an increasing number of people are subjected to CT examinations many times during their lifetime. The evolution of CT scanner technology has greatly increased the clinical applications of CT and its availability throughout the world and made it a routine rather than a specialized examination. With the modern multislice CT scanners, fast volume scanning of the whole human body within less than 1 min is now feasible. Two dimensional images of superb quality can be reconstructed in every possible plane with respect to the patient axis (e.g. axial, sagital and coronal). Furthermore, three-dimensional images of all anatomic structures and organs can be produced with only minimal additional effort (e.g. skeleton, tracheobronchial tree, gastrointestinal system and cardio-vascular system). All these applications, which are diagnostically valuable, also involve a significant radiation risk. Therefore, all medical professionals involved with CT, either as referring or examining medical doctors must be aware of the risks involved before they decide to prescribe or perform CT examinations. Ultimately, the final decision concerning justification for a prescribed CT examination lies upon the radiologist. In this paper, we summarize the basic information concerning the detrimental effects of ionizing radiation, as well as the CT dosimetry background. Furthermore, after a brief summary of the evolution of CT scanning, the current CT scanner technology and its special features with respect to patient doses are given in detail. Some numerical data is also given in order to comprehend the magnitude of the potential radiation risk involved in comparison with risk from exposure to natural background radiation levels.
Effective Doses in Radiology and Diagnostic Nuclear Medicine: A Catalog
Radiology, 2008
Medical uses of radiation have grown very rapidly over the past decade, and, as of 2007, medical uses represent the largest source of exposure to the U.S. population. Most physicians have difficulty assessing the magnitude of exposure or potential risk. Effective dose provides an approximate indicator of potential detriment from ionizing radiation and should be used as one parameter in evaluating the appropriateness of examinations involving ionizing radiation. The purpose of this review is to provide a compilation of effective doses for radiologic and nuclear medicine procedures. Standard radiographic examinations have average effective doses that vary by over a factor of 1000 (0.01-10 mSv). Computed tomographic examinations tend to be in a more narrow range but have relatively high average effective doses (approximately 2-20 mSv), and average effective doses for interventional procedures usually range from 5-70 mSv. Average effective dose for most nuclear medicine procedures varies between 0.3 and 20 mSv. These doses can be compared with the average annual effective dose from background radiation of about 3 mSv.
International Journal of Scientific Research in Science and Technology, 2017
The study discussed two parameters these include; administered activity (patients dose) and image quality. The aim is to determine the relationship between administered activity with resultant patient radiation dose and the quality of images produced. This will help make appropriate recommendation to the technologist and the nuclear medicine physician to produce images that would answer clinical question and at the same time maintain a balance with patient's radiation dose and its prognostic consequences. The study include both quadrant bar phantom study and patient image study in the form of static and dynamic studies. To determine image quality both the quadrant bar phantom and the patients images were assess by using SNR. The quadrant bar phantom was imaged by placing it on flood field uniform phantom which contained the radionuclide. The flood field uniformity phantom was filled with water and then an injected activity, which varied between 5 to 45 mCi of Tc-99 m were added ...
© 2017 IJSRST | Volume 3 | Issue 1 | Print ABSTRACT The study discussed two parameters these include; administered activity (patients dose) and image quality. The aim is to determine the relationship between administered activity with resultant patient radiation dose and the quality of images produced. This will help make appropriate recommendation to the technologist and the nuclear medicine physician to produce images that would answer clinical question and at the same time maintain a balance with patient's radiation dose and its prognostic consequences. The study include both quadrant bar phantom study and patient image study in the form of static and dynamic studies. To determine image quality both the quadrant bar phantom and the patients images were assess by using SNR. The quadrant bar phantom was imaged by placing it on flood field uniform phantom which contained the radionuclide. The flood field uniformity phantom was filled with water and then an injected activity, whi...
International Journal of Cancer Therapy and Oncology, 2014
Purpose: Computed tomography (CT), is an X-ray procedure that generates high quality cross-sectional images of the body, and by comparison to other radiological diagnosis, is responsible for higher doses to patients. This work studies the doses and image qualities produced from the default primary scanning factors of a Siemens CT machine and afterwards came up with scanning protocols that allow radiologists to obtain the necessary diagnostic information while reducing radiation doses to as low as reasonably achievable. Methods: Approximately 1000 CT scans from mostly common examinations; head, thorax, abdomen and pelvis routines were selected and analyzed for their image quality and radiation doses over a two year interval. Dose measurements were performed for the same routines using Computed Tomography Dose Index (CTDI) phantoms, RTI barracuda system with electrometer, and CT dose Profiler detector to evaluate the doses delivered during these CT procedures. Subsequently, image quality checks were performed using the CT Catphan 600 and anthropomorphic phantoms. CTDI and Dose Length Product (DLP) values were calculated for each scan. From analyzing these measurements, the appropriate machine scanning parameters were adjusted to reduce radiation does while at the same time providing good image quality. Results: Doses to patients using the default head sequence protocol had an average CTDIvol value of 65.45 mGy and a range of 7.10-16.80 mGy for thorax, abdomen and pelvis examinations whiles the new protocol had an average CTDIvol of 58.32 mGy for the head and a range of 3.83-15.24 mGy for the truck region. The DLP value for default head scans decreased from an average of 2279.85 mGy.cm to 874.53 mGy.cm with the new protocol. Tube potentials (KV) and tube current-time (mAs) had an effect on spatial resolution and low contrast detectability as well as doses. Conclusion: From the new protocols, lower values of KV and mAs together with other factors were enough to produce acceptable level of image quality which leads to adequate diagnosis without unnecessary doses to patients.