Exposure pattern, surface, bone marrow integral and gonadal dose from fluoroscopy

Suitability of laser stimulated TLD arrays as patient dose monitors in high dose x-ray imaging

Skin entrance doses of patients undergoing interventional x-ray procedures are capable of causing skin damage and should be monitored routinely. Single TLD chips are not suitable because the location of maximum skin exposure cannot be predicted. Most photographic films are too sensitive at diagnostic x-ray energies for dosimetry, exhibit temporal changes in response, and require special packaging by the user. We have investigated the suitability of laser heated MgB4O7 TLDs in a polyimide binder in the range of 0.2-20 Gy. These are available in radioluscent arrays up to 30 x 30 cm for direct measurement of patient skin dose. Dose response was compared with a calibrated ion chamber dosimeter. Exposures were made at 60, 90, and 120 kVp, at low (fluoroscopy) and high (DSA) dose rates, and at different beam incidence angles. Longitudinal reproducibility and response to temperature changes during exposure were also checked. The dose response is linear below approximately 6 Gy where the slope starts to increase 2% per Gy. Errors were less than +/- 2% over a 0-80 degrees range of beam incidence angles; less than +/- 3% for both dose rate variations and kVp differences between 70 and 120 kVp. The response was unaffected by temperature changes between 20 and 37 degrees C. Reproducibility is current +/- 7%. MgB4O7 TLD arrays are suitable for patient dosimetry in high dose fluoroscopy procedures if appropriate calibrations are used. Uncertainty in skin dose measurement is less than 10%, which is substantially better than film dosimetry.

The distribution of medical X-ray doses amongst individuals in the British population

This study has estimated the distribution of diagnostic X-ray doses amongst individuals in the British population by sampling the records kept by general practitioners (GPs) on their patients and the records held by the radiology department of a district general hospital. Deceased patients were chosen in the former case in order to evaluate the dose acquired over a complete lifetime. In each case, several hundred records were sampled. The GP data obtained have enabled an estimate to be made of the likelihood of reaching various dose levels in a lifetime. It is estimated that about 1% of the population has received a lifetime effective dose-equivalent of more than 100 mSv. The largest cumulative dose revealed by the samples of GP and radiology department records was about 200 mSv. The GP data have also shown that the last year of life sees a four-fold increase in the number of X-ray examinations experienced compared with the previous 9 years. The hospital data have allowed an estimate to be made of current rates of dose acquisition amongst the population of a District Health Authority.

Organ doses to atomic bomb survivors during photofluorography, fluoroscopy and computed tomography

Doses to the salivary glands, thyroid gland, breast, lung, stomach and colon during mass radiological gastric screening, mass radiographic chest screening, upper gastrointestinal series and computed tomography were determined by exposing a female human phantom to simulated radiological X-ray examinations as performed in community hospitals. The doses were measured using thermoluminescent dosimeters, and the results will be used to document organ doses received by participants in the Atomic Bomb Casualty Commission/Radiation Effects Research Foundation Adult Health Study.

An assessment of the radiation dose received by staff using fluoroscopic equipment

Measurements of scattered radiation were made on two fluoroscopic installations, one with an overcouch tube and one with an undercouch tube. The annual doses to staff involved in a fluoroscopic procedure undertaken on both types of unit were estimated using measured dose rates and weighting factors referred to in ICRP 26. Environmental monitoring at the protective barrier was performed for various room layouts to determine the effect of both equipment and room design on the annual dose received by staff at the control panel. In all circumstances the annual dose to staff inside the control cubicle was negligible.

Determination of the active marrow dose distribution within the paediatric pelvis and spine

The active marrow dose distributions have been determined inside the pelvis and the spine of two heterogeneous phantoms representing children aged one and five years. Both theoretical calculation and experimental measurement were used to simulate radiographic examinations typical for those ages. Twelve typical radiographic examinations were performed on these phantoms to represent common paediatric diagnostic procedures. The calculated and measured tissue-air ratios were compared for the pelvis and the spine. Uncertainty associated with the measured dose was estimated to be +/- 7%. The results show that most calculated absorbed doses agreed with those measured within twice the coefficient of variation of the calculated value.