A retrospective survey to establish institutional diagnostic reference levels for CT urography examinations based on clinical indications: preliminary results.

Objective. To establish institutional diagnostic reference levels (IDRLs) based on clinical indications (CIs) for three- and four-phase computed tomography urography (CTU).Methods. Volumetric computed tomography dose index (CTDIvol), dose-length product (DLP), patients' demographics, selected CIs like lithiasis, cancer, and other diseases, and protocols' parameters were retrospectively recorded for 198 CTUs conducted on a Toshiba Aquilion Prime 80 scanner. Patients were categorised based on CIs and number of phases. These groups' 75th percentiles of CTDIvoland DLP were proposed as IDRLs. The mean, median and IDRLs were compared with previously published values.Results. For the three-phase protocol, the CTDIvol(mGy) and DLP (mGy.cm) were 22.7/992 for the whole group, 23.4/992 for lithiasis, 22.8/1037 for cancer, and 21.2/981 for other diseases. The corresponding CTDIvol(mGy) and DLP (mGy.cm) values for the four-phase protocol were 28.6/1172, 30.6/1203, 27.3/1077, and 28.7/1252, respectively. A significant difference was found in CTDIvoland DLP between the two protocols, among the phases of three-phase (except cancer) and four-phase protocols (except DLP for other diseases), and in DLP between the second and third phases (except for cancer group). The results are comparable or lower than most studies published in the last decade.Conclusions. The CT technologist must be aware of the critical dose dependence on the scan length and the applied exposure parameters for each phase, according to the patient's clinical background and the corresponding imaging anatomy, which must have been properly targeted by the competent radiologist. When clinically feasible, restricting the number of phases to three instead of four could remarkably reduce the patient's radiation dose. CI-based IDRLs will serve as a baseline for comparison with CTU practice in other hospitals and could contribute to national DRL establishment. The awareness and knowledge of dose levels during CTU will prompt optimisation strategies in CT facilities.

99mTc Tetrofosmin imaging in breast tumours.

Eighty-five women, 18 to 80 years of age, with palpable breast lumps were studied 1-4 days before surgery in order to evaluate 99mTc Tetrofosmin imaging for the detection of malignant breast tumours. Intravenous injection of 99mTc Tetrofosmin was followed by 3 min planar images at 5-60 min postinjection. In the latter 57 patients, planar imaging was preceded by a dynamic study of 20x5 sec images. The myocardium was always included in the field of the left breast. Count rates in suspicious areas were compared with normal tissue areas in the same and the opposite breast and with myocardial counts. Data analysis showed that 77 of the 85 scan results were in agreement with the histological findings; six scans were false negative and two false positive for malignancy. The sensitivity of the method was 90.32% and the specificity 91.30%, with a positive predictive value of 96.55%. We conclude that breast scanning with 99mTc Tetrofosmin may play an important role in the detection of breast malignancies.