Patient Doses For Examinations Research Articles

Patient and staff doses for some complex x-ray examinations

The aim of this study was to measure patient and staff doses simultaneously for somecomplex x-ray examinations. Measurements of dose–area product (DAP) and entrance skindose (ESD) were carried out in a sample of 107 adult patients who underwent differentx-ray examinations such as double contrast barium enema (DCBE), single contrast bariumenema (SCBE), barium swallow, endoscopic retrograde cholangiopancreatography(ERCP) and percutaneous transhepatic cholangiography (PTC), and variousorthopaedic surgical procedures. Dose measurements were made separately foreach projection, and DAP, thermoluminescent dosimetry (TLD), film dosimetryand tube output measurement techniques were used. Staff doses were measuredsimultaneously with patient doses for these examinations, with the exception ofbarium procedures. The measured mean DAP values were found to be 8.33, 90.24,79.96 Gy cm2 for barium swallow, SCBE and DCBE procedures with the fluoroscopy timesof 3.1, 4.43 and 5.86 min, respectively. The calculated mean DAP was26.33 Gy cm2 for diagnosticand 89.76 Gy cm2 therapeutic ERCP examinations with the average fluoroscopy times of1.9 and 5.06 min respectively. Similarly, the calculated mean DAP was97.53 Gy cm2 with a corresponding fluoroscopy time of 6.1 min for PTC studies. The calculatedmean entrance skin dose (ESD) was 172 mGy for the orthopaedic surgical studies.Maximum skin doses were measured as 324, 891, 1218, 750, 819 and 1397 mGy forbarium swallow, SCBE, DCBE, ERCP, PTC and orthopaedic surgical procedures,respectively. The high number of radiographs taken during barium enema examinations,and the high x-ray outputs of the fluoroscopic units used in ERCP, were themain reasons for high doses, and some corrective actions were immediately taken.

Monte Carlo study of grid performance in diagnostic radiology: factors which affect the selection of tube potential and grid ratio

A Monte Carlo computational model has been developed for the study of the performance of anti-scatter grids in diagnostic radiology. It is used here to estimate the scatter in the image plane from soft tissue phantoms (representing the patient) and to calculate image contrast and the mean absorbed dose in the phantom. Different scattering conditions, representative of various examinations, have been investigated: adult lumbar spine; small field radiography and fluoroscopy; adult chest and paediatric pelvis and chest. For each scattering condition, the combinations of tube potential and grid ratio have been found which, for a well designed grid, result in the lowest mean absorbed dose in the phantom for a fixed contrast level. In examinations which generate large amounts of scatter, the use of high grid ratios in combination with high tube potentials is favourable with regard to both mean absorbed dose in the phantom and tube charge. When less scatter is generated, either the grid ratio or the tube potential can be varied to achieve the desired contrast level. High grid ratios require shorter exposure times, but need careful alignment in the beam to prevent primary radiation cut-off. It is shown that the air gap technique can be used to reduce patient dose in examinations with small amounts of scatter, but in combinations with a lower tube potential than when a grid is used.