Patient radiation doses in the most common interventional cardiology procedures in Croatia: first results.

Apart from its benefits, the interventional cardiology (IC) is known to generate high radiation doses to patients and medical staff involved. The European Union Medical Exposures Directive 97/43/Euroatom strongly recommend patient dosimetry in interventional radiology, including IC. IC patient radiation doses in four representative IC rooms in Croatia were investigated. Setting reference levels for these procedures have difficulties due to the large difference in procedure complexity. Nevertheless, it is important that some guideline values are available as a benchmark to guide the operators during these potentially high-dose procedures. Local and national diagnostic reference levels (DRLs) were proposed as a guidance. A total of 138 diagnostic (coronary angiography, CA) and 151 therapeutic (PTCA, stenting) procedures were included. Patient irradiation was measured in terms of kerma-area product (KAP), fluoroscopy time (FT) and number of cine-frames (F). KAP was recorded using calibrated KAP-meters. DRLs of KAP, FT and F were calculated as third quartile values rounded up to the integer. Skin doses were assessed on a selected sample of high skin dose procedures, using radiochromic films, and peak skin doses (PSD) were presented. A relative large range of doses in IC was detected. National DRLs were proposed as follows: 32 Gy cm(2), 6.6 min and 610 frames for CA and 72 Gy cm(2), 19 min and 1270 frames for PTCA. PSD <1 Gy were measured in 72 % and PSD >2 Gy in 8 % of selected patients. Measuring the patient doses in radiological procedures is required by law, but rarely implemented in Croatia. The doses recorded in the study are acceptable when compared with the literature, but optimisation is possible. The preliminary DRL values proposed may be used as a guideline for local departments, and should be a basis for radiation reduction measures and quality assurance programmes in IC in Croatia.

Efficacy of breast shielding during CT of the head.

In light of increasing frequency of CT examinations in the past decades, the aims of this prospective study were to investigate scatter radiation breast exposure in head CT and its dependence upon body constitution, and to assess the efficacy of lead shielding as a means of breast dose reduction. In 49 women referred to head CT for objective medical reasons one breast was covered with lead apron during CT scanning. Radiation doses were measured by use of thermoluminescent dosimeters, at skin of both breasts and over the apron. The doses were then compared as well as correlated to body mass index and meatus acusticus externus-to-dosimeter distance, respectively. Average exposure at the skin of the unshielded breast was 0.28 mGy (range 0.15-0.41 mGy), compared with 0.13 mGy (range 0.05-0.29 mGy) at the shielded breast. The doses showed a mean reduction by 57% due to lead shielding. At least half of breast exposure was imparted to the breast from outside, whereas the remainder results from internal scatter. The higher the body mass index, the higher the percentage of internal scatter in total breast dose. Although the level of scatter radiation to the breast is generally low during head CT examination, the use of lead cover enables recognizable further reduction of the exposure, and is recommended as a feasible and effective procedure of breast protection during CT of the head.

Breast compression and radiation dose in two different mammographic oblique projections: 45 and 60 degrees.

INTRODUCTION: Standard mammography includes two views, craniocaudal and medio-lateral oblique. Depending on patient's body constitution, central beam angle in mediolateral oblique projection may vary, with 45 degrees being suitable for the majority of patients in routine daily practice. With continuous improvement in X-ray technology and radiographers' training, the risk of radiation induced cancerogenesis is considerably reduced and acceptable when compared to benefit. However, the risk still exists, being cumulative and directly related to absorbed glandular dose. There is no minimal dose of radiation which is absolutely harmless, and every effort to reduce the dose is welcome. In this retrospective study two different angles (45 vs. 60 degrees) of mediolateral oblique view were compared according to radiation dose and efficacy of breast compression. PATIENTS AND METHODS: In 52 women, additional 60 degrees oblique films were done after craniocaudal and mediolateral oblique 45 degrees-films, with the same kVp and positioning technique. Breast thickness, time-current products (mA s) and absorbed doses were compared between 45 degrees- and 60 degrees-films. Subgroups of women with large, small, prominent and pendulous breasts were analyzed separately, following the same methodology as for the whole group. RESULTS: mA s were 11.5% lower and compression 7% better with an angle of 60 degrees than with 45 degrees. In the subgroup of women with small breasts, mA s values were 13% lower and compression 9% better with 60 degrees than with 45 degrees, while in the subgroup with large breasts, mA s were 9% lower and compression 5% better. In the subgroup of patients with pendulous breasts, mA s values were 12% lower and compression 10% better with 60 degrees than with 45 degrees, while in the subgroup with prominent breasts, mA s values were 4% lower and compression 3% better. Absorbed glandular dose was estimated to be approximately 20% lower when an oblique mammogram was done with 60 degrees instead of 45 degrees. The compression with 15 kp was well tolerated by the majority of patients. DISCUSSION AND CONCLUSION: Mammograms of excellent quality should be done with as low a radiation dose as possible. Adequate breast compression is fundamental in mammography due to immobilization of the breast, shortening of the exposure times, reduction of motion and geometric blur and prevention of overpenetration by means of equalizing breast thickness. As the absorbed glandular dose cannot be accurately measured, it is convenient to estimate the dose approximately, on the basis of its linear proportionality with exposure dose. With constant technical properties of X-ray machines, exposure dose is determined only by mA s. Hence, the absorbed glandular dose in our study was influenced only by changes of mA s and breast thickness. As the absorbed dose reduction is proportional to the product of the reduction of mA s and thickness, we estimated that absorbed dose was 7-22% lower if 60 degrees is applied instead of 45 degrees. Breast compression and mA s were more favourable in women with pendulous breasts, possibly because of elongation of the glandular disc in the lateroascending direction, with its longer axis directed more perpendicularly. Fibroglandular tissue in the 60 degrees-view is thus projected onto a larger film area, with less effect of superimposition. In conclusion, because of lower mA s values and better compression, which finally result in a 25% lower absorbed dose, we recommend the oblique view be done with an angle of 60 degrees, especially for small and pendulous breasts.