Breast thickness is the most important parameter in selection of an anode-filter-tube voltage combination. Compared with Mo-Mo, both Mo-Rh and W-Rh gave good image quality of the mammary gland and a considerably lower absorbed dose. Mo-Rh-27 kVp is recommended for breast thicknesses of 60 mm or less; W-Rh-26 kVp, for breast thicknesses of greater than 60 mm.

The purpose of this study was to investigate if the glandular dose to the breast in mammography can significantly be reduced without compromising image quality, when using photon counting technology, in a multi-slit scanning photon counting detector, compared to a conventional film mammography system and commercial available digital mammography systems with TFT-array detectors. A CDMAM phantom study, with two different thicknesses of additional PMMA absorber, 4 cm and 7 cm respectively, has shown that multi-slit scanning photon counting detector technology can reduce the dose, without reducing the image quality. This comparison was made to two commercial available digital mammography systems Senographe 2000D (from GEMS) and Selenia (from Lorad). The results show that dose can be reduced with 63% to 77%, depending on object thickness, when using XCT for mammography. This dose reduction has also been verified clinically through a small pilot study with patients and specimen, where the comparison was made between XCT and film.

The most natural way of digital X-ray imaging is photon counting as the photon flux in itself is digital. In photon counting, the information in the X-ray flux is used more efficiently as the information carrying low-energy photons are given the same weight as higher energy photons carrying less image information. This is in contrast to all existing X-ray instruments, which are energy-integrating systems where the highest energy photons are given the highest weight. A novel technique for high resolution digital X-ray imaging, using gaseous avalanche detectors for photon counting with high signal-to-noise ratios for single X-ray photons, has been developed. The performance of this detector has been studied and compared to analogue film-screen system by imaging phantoms. Our results show that this technology can improve image quality while decreasing the glandular dose to the patient.

99mTc-DTPA clearance was studied in ten healthy non smokers, five asymptomatic smokers and nine non smoking patients with sarcoidosis in the supine position with a dual head gamma camera allowing simultaneous information of regional clearance rates in frontal and dorsal projections. In the patients with sarcoidosis, a bronchoalveolar lavage was performed prior to the clearance study. DTPA clearance rate was measured during 60-90 min and data were corrected for recirculating radioactivity. The coefficients of variation for measurements on 2 consecutive days in the 10 healthy non smokers were 9%-11% for the right and left lung, anterior and posterior projections. The T1/2 calculated from total lung projections were 90-92 min for the anterior view and 84-85 min for the posterior view. Regional measurements did not add further information. No apico-basal difference was found but there was a significant fronto-dorsal gradient in 99mTc-DTPA clearance in the supine position. Smokers had significantly (P less than 0.01) faster clearance rates (T1/2 28 +/- 10 min) than healthy controls. In the sarcoidosis group clearance rates were increased in four patients and no relationships were found between DTPA clearance rates and inflammatory markers (lymphocytes, albumin, ACE) in the bronchoalveolar lavage fluid.

No abstract