First application of computed radiology to mammography with synchrotron radiation.

OBJECTIVE: The aim of this study was to evaluate the feasibility of phase-contrast mammography with synchrotron radiation using a high-resolution computed radiology (CR) system devoted to mammography. MATERIALS AND METHODS: The study was performed at the Synchrotron Radiation for Medical Physics (SYRMEP) beamline of the Elettra synchrotron radiation (SR) facility in Trieste (Italy); X-ray beams were in the range 16-22 keV with a high degree of monochromaticity and spatial coherence. The CR system evaluated is the FCR Profect CS by Fujifilm Global. The first images were obtained from test objects and surgical breast specimens. Images obtained using SR and both screen-film and the CR system were compared with images of the same samples acquired with digital mammography equipment. In view of the good quality of the results obtained, the CR system was used in two mammographic examinations with SR. RESULTS: Images acquired using SR and both screen-film and CR were obtained with the same level of delivered dose. Image quality obtained with CR was similar or superior to that of screen-film images. Moreover, the digital images obtained with SR were always better than those acquired using the digital mammography system. CONCLUSIONS: Phase-contrast mammography with SR using the studied CR system is a feasible option.

The mammography project at the SYRMEP beamline.

A clinical program for X-ray phase contrast (PhC) mammography with synchrotron radiation (SR) has been started in March 2006 at the SYRMEP beamline of Elettra, the SR facility in Trieste, Italy. The original beamline layout has been modified substantially and a clinical facility has been realized. In order to fulfill all security requirements, dedicated systems have been designed and implemented, following redundancy criteria and "fail safe" philosophy. Planar radiographic images are obtained by scanning simultaneously the patient and the detector through the stationary and laminar SR beam. In this first phase of the project a commercial screen-film system has been used as image receptor. Upon approval by the respective authorities, the mammography program is about half way to conclusion. Up to now about 50 patients have been examined. The patients are volunteers recruited by the radiologist after conventional examinations at the hospital resulted in an uncertain diagnosis. As an example one case of PhC SR mammography is shown and compared to conventional digital mammography. Preliminary analysis shows the high diagnostic quality of the PhC SR images that were acquired with equal or less delivered dose compared to the conventional ones.

Retrospective evaluation of occurrence of skin injuries in interventional cardiac procedures.

Interventional cardiology procedures can involve high doses to patients and, in particular, to patients' skin, the tissue at greatest risk of deterministic injuries. The evaluation of skin dose from interventional procedures is recommended, but difficult because of the amount of different X-ray fields and projections used in a procedure. For this reason, a retrospective follow-up study has been developed to identify skin injuries in patients submitted to one or more cardiac interventions in the Udine hospital between 1998 and 2002. Seventy-eight patients with a cumulative dose-area product >300 Gy cm2 were selected from 3332 patients, who underwent 5039 procedures. In this group the maximum skin dose was 6.7 Gy. The clinical follow-up, performed using the LENT-SOMA methodology, has not detected skin injuries and this result allows a frequency to be estimated for skin injuries in patients undergoing repeated cardiac procedures of <3 x 10(-4) in our centre.

Patient skin dosimetry in haemodynamic and electrophysiology interventional cardiology.

With the increase in number and complexity of interventional cardiology (IC) procedures, it is important to monitor skin dose in order to decrease skin injuries. This study investigated radiation doses for patients undergoing IC procedures, compare results with the literature and define a local dose-area product trigger level for operators to identify situations likely to exceed the threshold for transient skin erythema of 2 Gy. Dosimetric data were collected for 77 haemodynamic and 90 electrophysiological procedures. Mean maximum local skin doses (MSDs) were 0.28 Gy for coronary angiography, 1.03 Gy for percutaneous transluminal coronary angioplasty (PTCA), 0.03 Gy for pacemaker insertion, 0.17 Gy for radiofrequency ablation for nodal tachycardia, 0.10 Gy for WPW and 0.22 Gy for atrial flutter. Since MSD values for the other procedures were well below the deterministic effect limit, a trigger level of 140 Gy cm2 was derived for PTCA procedures alone.

Patient dosimetry approaches in interventional cardiology and literature dose data review.

Interventional radiology contributes a significant proportion of the collective dose of the population from medical exposures. Interventional radiology procedures are usually fluoroscopy-guided diagnostic and therapeutic interventions. When complex procedures are performed or procedures are repeated for the same patient, high-radiation dose levels can occur because procedures often require long fluoroscopy times and require high-quality images. For all of these reasons, dosimetric evaluations in interventional radiology are widely increasing. Patient dosimetry methods currently used in interventional radiology may be divided into three categories according to dosimetry purpose: (I) dosimetry for stochastic risk evaluation, (II) dosimetry for quality assurance and (III) dosimetry to prevent the deterministic effects of radiation. A short description of dosimetric methods used in interventional cardiology practice and relevant published dosimetric data are reported.

Reference levels in PTCA as a function of procedure complexity.

The multicentre assessment of a procedure complexity index (CI) for the introduction of reference levels (RLs) in percutaneous transluminal coronary angioplasties (PTCA) is presented here. PTCAs were investigated based on methodology proposed by Bernardi et al. Multiple linear stepwise regression analysis, including clinical, anatomical and technical factors, was performed to obtain fluoroscopy time predictors. Based on these regression coefficients, a scoring system was defined and CI obtained. CI was used to classify dose values into three groups: low, medium and high complexity procedures, since there was good correlation (r = 0.41; P < 0.001) between dose-area product (DAP) and CI. CI groups were determined by an ANOVA test, and the resulting DAP and fluoroscopy time third quartiles suggested as preliminary RLs in PTCA, as a function of procedure complexity. PTCA preliminary RLs for DAP are 54, 76 and 127 Gy cm2, and 12, 20 and 27 min for fluoroscopy time, for the three CI groups.

The application of image quality measurements for digital angiography.

The image quality (IQ) evaluation of a charge-coupled device (CCD)-based digital angiography system was assessed with respect to modulation transfer function and noise power spectrum. These values were used to calculate the system's frequency-dependent detective quantum efficiency (DQE). The X-ray image detector was an image intensifier (II) lens coupled to a CCD camera. Two measurement setups were used. Setup A is standard IQ assessment, while Setup B more closely represented clinical conditions (polymethyl methacrylate (PMMA) of varying thickness placed between the X-ray tube and II, with test object positioned between PMMA slices 30 cm from the II). Exposure parameters varied according to automatic brightness control settings. Setup B included X-ray radiation scattered by the patient-PMMA. A clinical DQE, describing the transmission of the input signal-to-noise ratio associated with both primary and secondary X-ray spectra, was defined.