ESTIMATION OF THE ORGAN AND EFFECTIVE DOSE TO PATIENTS UNDERGOING MEDICAL DIAGNOSTIC X-RAY EXAMINATIONS IN SAUDI ARABIA.

Quantifying the radiological risk from diagnostic radiography is essential for patients' safety. Effective dose is considered the best quantity to determine the stochastic risk associated with the radiological examinations. Therefore, the present work investigated organ and effective dose for adult patients in the most common type of X-ray examinations, such as the chest (PA/LAT), abdomen (AP) and lumbar spine (AP/LAT) projections. The PCXMC version 2 Monte Carlo program was used to estimate the organ and effective dose for 547 patients who underwent a radiographic examination at the King Abdulaziz Hospital, Saudi Arabia. The results showed wide variation in organ doses. The largest organ dose in each X-ray examination were 2.72 mGy for the spleen in the lumbar spine (LAT), 1.98 mGy for the urinary bladder in the lumbar spine (AP), 0.40 mGy for the spleen in the chest (PA), 0.11 mGy for the kidney in the chest (LAT) and 1.78 mGy for the testicles in the abdomen (AP) examinations. Values for the effective dose were estimated for each investigated X-ray examination, and the results were compared with the published values available in the literature. The obtained values for effective dose were relatively lower than those reported by the European Commission and the United Nations Scientific Committee on the Effects of Atomic Radiation for the same examinations. The results presented here will help establish a database that will be useful for future comparisons and monitoring in radiographic procedures.

Assessment of Patient Radiation Dose during Conventional Diagnostic X-ray Examinations in Three Public Hospitals in Northern Jordan using TLDs.

This study aims to measure entrance surface doses during routine chest and abdomen x-ray examinations of adult and child patients. Radiation dose measurements were performed using thermoluminescent dosimeters TLD-100s in three major public hospitals in northern Jordan on a total of 100 patients. Wide variations in entrance surface doses were observed within and between hospitals, which might be attributed to significant variations of the selected exposure parameters. For adult patients, the results have shown that the majority of entrance surface dose values from both chest and abdomen examinations were within recommended values of diagnostic reference levels. For child patients, the mean entrance surface dose from chest examinations in three age groups were 0.131 mGy (0-1 y), 0.136 mGy (1-5 y), and 0.191 mGy (5-10 y). These values were considered relatively high compared to the European reference levels and published results in the literature. However, for abdomen examinations, entrance surface dose values were relatively lower than European reference levels. Patient effective doses were estimated using a PCXMC 2.0 Monte Carlo program. The results for both adults and children were found to be relatively lower than the values reported by international publications. Due to the wide variations of entrance surface dose and the higher radiation doses delivered to child patients, this study recommends implementing a quality assurance program in such hospitals to achieve optimization between good image quality and minimum dose according to the as low as reasonably achievable principle. Moreover, the results of this work will provide a useful base for establishing local diagnostic reference levels for chest and abdomen examinations in Jordan.

Assessment of the committed effective dose due to the 210Po intake from fish consumption for the Arabian Gulf population.

This study aims to assess the committed effective dose due to the intake of 210Po from the consumption of fish in Arabian Gulf countries. Twenty different kinds of fish, which represent the most common fish species consumed in the Arabian Gulf countries, were analyzed using alpha spectrometer technique. 210Po activity concentrations in fish samples were found to vary over a wide range from 0.1 to 14.7 Bq kg-1 fresh weight. This variation of 210Po concentrations between various type of fish samples might be attributed to the feeding type pattern and the size of fish. The annual committed effective dose due to ingestion of 210Po in fish species for adults in the Arabian Gulf countries was estimated and found to vary from 38 µSv in Bahrain to 85 µSv in Oman with an average value of 59 µSv. These values are considered relatively high compared to those reported in some other regions. However, it is still much lower than the world average ingestion dose due to natural radiation sources.

Measurement of natural and artificial radioactivity in powdered milk consumed in Jordan and estimates of the corresponding annual effective dose.

The activity concentrations of (40)K, (226)Ra, (228)Ra and (137)Cs were measured for 14 brands of the powdered milk consumed in Jordan, which are imported from various regions around the world. The activity concentrations of (40)K were found not to vary greatly from one brand to the other with an average of 348 +/- 26 Bq kg(-1). However, the activity concentrations of (137)Cs revealed a geographical distribution being: (i) undetected in any of the samples from Argentina, (ii) uniformly distributed in samples from Europe with an average of 0.43 +/- 0.05 Bq kg(-1), and (iii) widely varying in samples from New Zealand (from being not detected (ND) to 1.55 Bq kg(-1)). (226)Ra and (228)Ra were measured above the detection limits in five brands only and displayed relatively low activity concentrations of 0.50-2.14 and 0.78-1.28 Bq kg(-1) for (226)Ra and (228)Ra, respectively. The total average annual effective doses due to intake of (40)K, (226)Ra, (228)Ra and (137)Cs from the ingestion of the powdered milk for infants, children and adults were estimated to be (in microSv): 332, 138 and 43, respectively. These results indicate no significant radiation dose to the public.

A software tool for 2D/3D visualization and analysis of phase-space data generated by Monte Carlo modelling of medical linear accelerators.

A computer program has been developed for novel 2D/3D visualization and analysis of the phase-space parameters of Monte Carlo simulations of medical accelerator radiation beams. The software is written in the IDL language and reads the phase-space data generated in the BEAMnrc/BEAM Monte Carlo code format. Contour and colour-wash plots of the fluence, mean energy, energy fluence, mean angle, spectra distribution, energy fluence distribution, angular distribution, and slices and projections of the 3D ZLAST distribution can be calculated and displayed. Based on our experience of using it at Massachusetts General Hospital, the software has proven to be a useful tool for analysis and verification of the Monte Carlo generated phase-space files. The software is in the public domain.

Internal target volume determined with expansion margins beyond composite gross tumor volume in three-dimensional conformal radiotherapy for lung cancer.

PURPOSE: Gross tumor volume (GTV) of lung cancer defined by fast helical CT scan represents an image of moving tumor captured at a point in active respiratory movement. However, the method for defining internal margins beyond GTV to account for its expected physiologic movement and all variations in size and shape during the administration of radiation has not been established. The goal of this study was to determine the internal margins with expansion margins beyond individual GTVs defined with (1) fast scan at shallow free breathing, (2) breath-hold scans at the end of tidal volume inspiration and expiration, and (3) 4-s slow scan to approximate the composite GTV of all scans. METHODS AND MATERIALS: A series of sequential CT scans were acquired with (1) a fast helical scan at shallow free breathing and (2) breath-hold scans at the end of tidal volume expiration and inspiration for the first 6 patients, and (3) a 4-s slow scan at quiet free breathing, which was added for the latter 7 patients. We fused breath-hold scans and the 4-s slow scan to the fast scan at shallow free breathing to generate the composite GTV. Margins necessary to encompass the composite GTV beyond individual GTVs defined by either fast scan at quiet free breathing, breath-hold scans, or the 4-s slow scan at quiet free breathing were defined as expansion or internal margins and termed the internal target volumes. The centroid of the tumor volume was also used as another reference for tumor movement. RESULTS: Thirteen patients with 14 tumors were enrolled into the study. Substantial tumor movement was noted by either the extent of internal margins beyond each GTV or the movement of the centroid. Internal margins varied significantly according to the method of CT scanning for determination of GTV. Even for tumors in the same lobe of the lung, a wide range of internal margins and significant variation in the centroid movement in all directions (x, y, and z) were observed. The GTV of a single fast helical scan at free breathing (n = 14) required the largest internal margin (mean, 3.5 mm; maximum, 18 mm; standard deviation [SD], 4.2 mm) to match the composite GTV, compared with those of the 4-s slow scan (mean 2.7 mm, maximum 14 mm, SD 3.5 mm) or combined breath-hold scans (mean 1.1 mm, maximum 9 mm, SD 1.9 mm). Internal margins (expansion margins) required to approximate the composite GTV in 95% of cases were 13 mm, 10 mm, and 5 mm for the GTVs of a single fast scan, 4-s slow scan, and breath-hold scans at the end of tidal volume inspiration and expiration, respectively. CONCLUSIONS: The internal margins required to account for the internal tumor motion in three-dimensional conformal radiotherapy are substantial. For the use of symmetric and population-based margins to account for internal tumor motion, GTV defined with breath-hold scans at the end of tidal volume inspiration and expiration has a narrower range of internal margins in all directions than that of either a single fast scan or 4-s slow scan.