Evolution of diagnostic radiology in a big hospital during a 5 year period, and the derived collective dose

Radiation protection in diagnostic radiology

INTRODUCTION

The use of ionizing radiation is regulated by legislative bodies to limit both individuals' and the population's exposure to radiation. Germany has implemented the European 97/43/EURATOM directive in national law by updating the existing radiation protection regulations. The German Commission on Radiological Protection regularly publishes statements and recommendations on radiation protection in medicine and diagnostic radiology, such as the introduction of diagnostic reference levels and referral guidelines for radiological and nuclear medicine imaging.

METHODS

Review of selected literature, national and international recommendations and legal texts.

RESULTS

From a radiological protection perspective, clear justification for radiological examinations and techniques aimed at minimizing radiation dose while providing the required diagnostic information, are essential.

DISCUSSION

Referring doctors should be sure to use existing guidelines for medical imaging, and liaise with radiologists and nuclear medicine specialists, with whom they share the responsibility for choosing appropriate imaging modalities.

Pratique du scanner en Suisse : fréquence et évolution temporelle

PURPOSE

This study analyzes CT examinations in Switzerland.

MATERIALS AND METHODS

Using different sources (administrative data on the equipment, a 1998 nationwide inquiry into practices, and data provided by the Swiss University Hospitals of Basel, Zurich, and Lausanne), we determined the frequency of CT examinations (hospitals and private radiologists) in 1998 according to different descriptive variables and studied the progression in CT use over time.

RESULTS

CT scanners increased by 7% between 1998 and 2004. The average annual number of CT examinations in 1998 was 46.3/1000 population, 3.4% of all radiological examinations in Switzerland in 1997-1998. The most frequent examination was CT of the skull (24%), while private radiology institutes perform more CTs of the spine. More CT examinations were performed for men than for women (sex ratio M/F=1.17). The average annual increase in CT in Swiss hospitals varied from 8% for Basel to 18% for Lausanne. Finally, the proportion of pediatric examinations was 5%; their numbers appear to be stabilizing.

CONCLUSION

There is a significant increase in CT examinations. It is hoped that our study will heighten awareness among doctors of CT examinations in order to optimize their use.

UK population dose from medical X-ray examinations

OBJECTIVE

To assess the annual per caput and collective effective dose to the United Kingdom population from medical and dental X-ray examinations.

METHOD

The results of a detailed survey of the frequency of X-ray examinations during the financial year 1997/1998 were combined with contemporary data on the effective doses typically received by patients. The resulting per caput and collective dose for 1997/1998 was updated to 2001/2002 by using annual statistics on the total numbers of computed tomography (CT), interventional and conventional examinations collected by the English Department of Health.

RESULTS

The annual per caput effective dose for the UK in 2001/2002 was estimated at 0.38 mSv. Over the last 10 years CT has more than doubled its contribution and is now responsible for 47% of the collective dose from medical X-rays. The contribution from conventional radiographic and fluoroscopic examinations has nearly halved to about 34%. Interventional and angiographic procedures together contribute the remaining 19%.

CONCLUSIONS

The annual per caput effective dose of 0.38 mSv is low in comparison with other countries having similarly developed systems of health-care. This is due to both a lower frequency of X-ray examinations per head of population and generally lower doses in the UK than in other developed countries.

Influence of radiologists' sex and training on fluoroscopy doses during barium enema

Variables influencing radiation exposure were studied using analysis of covariance in 523 double contrast barium enemas performed by 21 radiology residents (12 female, 9 male). Dose-area products (DAPs) (ns), number of exposures per patient (p < 0.05) and screening times (p < 0.05) were higher for female residents (mean 52.0 Gy cm2, 9.55 exposures and 4.02 min, respectively) than for male residents (mean 41.7 Gy cm2, 8.26 exposures and 3.20 min, respectively). The number of lectures on radiation protection attended by the resident (range 0-20) had no significant effect on these radiation-related variables. Other factors explaining these variables were patient age, diagnosis and anteroposterior thickness. Radiologists' use of ionizing radiation during fluoroscopy may be sex-related. Traditional lecture-based education on radiation protection was not effective with this group; thus, improved methods should be developed to control doses.

Patient dose from barium procedures

The objective of this work was to estimate patient doses (dose-area product, organ dose, effective dose and entrance surface dose) for barium procedures. A total of 175 procedures, in 175 patients, for five different examination categories was analysed. Dose-area product was determined using a transmission ionization chamber. Organ dose and effective dose were assessed using a knowledge of the examination and the software. For all patients, the contribution of fluoroscopy to the total dose was greater than that from radiography. Dose-area product from double contrast barium enema, enteroclysis and intestinal tract procedures was higher than that obtained for the other procedures. The average effective dose was 1.04 mSv and 13.99 mSv for oesophageal tract and enteroclysis examinations, respectively. Entrance surface dose in the oesophageal tract was 16 mGy, 10 times lower than for the other four procedures. Patient dose reduction in barium procedures may be achieved by improved training of resident radiologists, senior radiologists and other specialists in radiation protection.

Stochastic risk estimate for barium radiological examinations in Malaga (Spain)

The aim of this research work has been the estimation of the stochastic risk for five barium examinations. The sample was the population attending the Radiological Service of the 'Nuestra Señora de la Victoria' University Hospital, who had been treated with some barium examinations, set in five different groups: oesophagus tract, oesophagus-gastric-duodenal tract, intestinal tract, enteroclysis and double enema. To estimate the stochastic risk, it is necessary to know the organ dose. This can be calculated from the dose-area product which allows us to determine the effective dose using software. The dose-area product is the most suitable quantity to measure in these types of examination. We have evaluated the contribution that each procedure provides to the genetically significant dose, somatically significant dose, collective effective dose, annual effective dose 'per capita' and detriment, which are useful for assessing the population risk of cancer or hereditary effects after x-ray exposure. The contribution to the genetically significant dose is 6.7 microGy, to the somatically significant dose 8.82 mSv-yr, 16.07 person-Sv for the collective effective dose, 0.03 mSv for the 'per capita' annual effective dose and the annual aggregated detriment is 0.33.

A comparison of patient dose for examinations of the upper gastrointestinal tract at 11 conventional and digital X-ray units in The Netherlands

The objective of this study was to derive the effective dose to patients from examinations of the upper gastrointestinal (GI) tract at 11 X-ray units in 10 Dutch hospitals. Entrance dose and entrance dose rate were measured at the surface of a homogeneous PMMA phantom and at the entrance surface of the image intensifier. Dose-area products (DAPs) were assessed during examinations of patients. The patients (334 females and 256 males) ages were 18-95 years (average 52 years). Effective dose was assessed from DAP using Monte Carlo computer calculations for male and female mathematical anthropomorphic phantoms. The DAPs measured during the survey showed substantial variations, i.e. an overall average value of 21 Gy cm2 and a range of average DAP per X-ray unit varying from 7 to 56 Gy cm2. Variations in the number of images (8-28) and the fluoroscopy time (1.7 min-7.0 min) were also large. A DAP to effective dose conversion factor of 0.32 mSv Gy cm-2 was derived for upper GI studies. The dose survey yielded an overall average effective dose of 6.7 mSv. At one location an examination involving as many as 28 projections was performed, whilst maintaining a DAP well below 15 Gy cm2 and an effective dose below 6 mSv. This was achieved using modern equipment (i.e. high frequency generator, digital spot films) with 0.2 mm additional copper filtration and a relatively high tube voltage. For examinations of the upper GI tract, the application of a reference value of 30 Gy cm2 for the DAP will ensure that, in general, the effective dose to individual patients will not exceed 15 mSv.

Patient doses in hysterosalpingography

The results of a survey of doses imparted on 41 patients undergoing hysterosalpingography is presented. Dosimetric evaluations were carried out by measuring both the dose-area product using a transmission ionization type chamber, and the entrance surface dose using thermoluminiscent dosimeters. As a result, a local reference dose value was obtained for this examination. Correlations between the dose-area product and the entrance surface dose data were analysed and compared in order to find the most appropriate dosimetric procedure. The median dose-area product obtained was 713 cGy cm2 (range 247 cGy cm2-1623 cGy cm2). Ovarian doses were also calculated, and a median value of 4.6 mGy was obtained for the whole examination. Effective doses were estimated with a median value of 3.1 mSv, and a range of 1.0 mSv-8.1 mSv.