What are the clinical and technical factors that influence the kerma-area product in percutaneous coronary intervention?

The purpose of the paper is to define predictors of the kerma-area product (KAP) in percutaneous coronary intervention (PCI). Two new digital X-ray interventional cardiology systems recently installed were included. A total of 398 PCI procedures were carried out by 6 board-certified senior interventional cardiologists with more than 15 years' experience and good knowledge of radiation protection measures. Clinical, radiation and procedural data were collected based on a detailed protocol developed by the SENTINEL cardiology subgroup. Correlation with clinical and procedure factors was then investigated. A significant correlation was found between fluoroscopy time and (i) lesion classification, (ii) the level of tortuosity and (iii) the number of vessels treated. No statistically significant differences were observed in the complexity of the case between operators. However, large differences were found in the KAP among operators, which were mostly attributed to the different number of frames taken by each operator. There was no statistically significant correlation between complexity and the total number of frames. The study showed that, in certain circumstances, the clinical need to successfully perform PCI takes precedence over radiation safety concerns.

Optical density variations in CT films and their effect on image quality.

It was recently reported that optical density (OD) variations were observed in CT films printed with a laser camera, depending on the printing format and the frame position within the film. The purpose of the present study was to investigate if these variations are common to both laser and dry-film printers and if the different OD settings along with day-to-day and frame-to-frame variations may affect the image quality. Eight laser and five dry-film printers installed at 12 different CT facilities were tested. For each one, the SMPTE test pattern was printed on all frames of a film using the same printing format. The ODs of the 0%, 10%, 40% and 70% patches of the 11-step greyscale of the SMPTE patterns were measured with a densitometer in all frames, while all films were examined on a viewing box to assess subjectively the image quality by visual inspection of the test pattern. A wide range of OD settings and variations were recorded. Frame-to-frame variations in the same film of up to 0.19, 0.15 and 0.21 OD, were observed for contrast index (CI, the OD difference of patches 10% and 70%), speed index (SI, the OD of patch 40%) and maximum OD (OD(max), the OD of patch 0%), respectively. The variations were not always of the same magnitude, nor always followed the same pattern, even for printers of the same model. Considering all films and frames, the CI ranged from 1.26 to 1.74, the SI from 0.68 to 1.43 and the OD(max) from 2.5 to 3.11 OD, well beyond the proposed settings and tolerances of 1.55+/-0.15, 1.15+/-0.1 and 2.45+/-0.1 given in the literature for CI, SI and OD(max), respectively. Despite these large differences, the various problems that were identified in image quality from the visual inspection of the films could not be directly attributed to OD settings, as films with similar CI, SI and OD(max) presented quite different image quality levels. Therefore, for routine quality control, thorough visual inspection of the SMPTE test pattern provides all the necessary information about the imaging chain status.

Virtual bronchoscopy versus thin section computed tomography in evaluation of moderate and low grade stenoses: receiver operating characteristic curve analysis.

PURPOSE: To evaluate the impact of virtual bronchoscopy, under proper threshold settings, on observer level of confidence in the assessment of bronchial abnormalities producing stenoses < or = 75% compared to interpretation of thin section computed tomography (CT) images. MATERIAL AND METHODS: Sixty-five patients with fiberoptic bronchoscopy positive for tracheobronchial abnormalities were evaluated in a blinded observer study using a commercially available virtual endoscopy software package. The findings of virtual endoscopy were compared with those of fiberoptic bronchoscopy using receiver operating characteristic curves (ROCs) and other statistical tools. RESULTS: A total of 102 lesions were identified by fiberoptic bronchoscopy, with 44 of these producing bronchial stenoses < or = 75%. Concerning the latter lesions, for virtual bronchoscopy the areas under the ROCs were 0.93 and 0.96 for the two observers, respectively, while for thin section CT the corresponding values were 0.86 and 0.88; the differences observed were statistically significant. Contrary to thin section CT, virtual bronchoscopy did not show statistically significant differences from fiberoptic bronchoscopy regarding estimation of degree of stenosis. CONCLUSION: Virtual bronchoscopy under proper threshold settings has a statistically significant impact on observer performance where moderate and low-grade bronchial stenoses are concerned and gives an estimate of the degree of stenosis more precisely than thin section CT.

Radiation doses to patients from enteroclysis.

The purpose of this study was to determine the patient doses during enteroclysis and compare them with the available bibliographical data. For 14 enteroclysis examinations, the dose-area product (DAP) meter readings, fluoroscopy time, number of radiographs and exposure data were recorded. From these data, the fluoroscopy and radiography contributions to DAP, the entrance surface dose (ESD) and the effective dose (E) for each examination were estimated. The mean DAP was 81 Gy cm(2) and the mean fluoroscopy time was 19.5 min. The fluoroscopy contribution to DAP was 77% and 8.7 films were acquired in each examination on average. The mean ESD and E were estimated to be 428 mGy and 21 mSv, respectively. The mean DAP and fluoroscopy time calculated in this study are quite high when compared with those reported in the literature, suggesting that the examination technique should be reviewed and the ways to reduce patient exposure without compromising the diagnostic quality should be acquired.

Threshold selection in virtual bronchoscopy: phantom study and clinical implications.

PURPOSE: To investigate the effect of the threshold selection on the apparent diameter of a virtual bronchus and the virtual wall morphology and to examine the parameters that can affect the selection of the appropriate threshold for virtual bronchoscopy with single slice computed tomography. MATERIAL AND METHODS: A bronchial phantom containing plastic tubes simulating the airways of the tracheobronchial tree was constructed. The diameters of the virtual images of these tubes were measured using various thresholds for two different materials surrounding the tubes: air and water. These measurements were correlated with the density in HU of the walls. Furthermore, data from 20 virtual bronchoscopies in patients were retrospectively analyzed in the same way. RESULTS: The diameter of a virtual bronchus is strongly affected by the selected threshold. The appropriate threshold for accurate diameter representation depends on the density of the bronchial wall. CONCLUSION: Our results suggest that in clinical practice a single threshold value cannot be used for imaging all segments of the tracheobronchial tree. While a value of -520 is appropriate for the trachea and lobar segments, values down to -720 could be needed on the level of segmental and subsegmental bronchi. At these levels, a threshold value about 65 HU more negative than the value where the artificial holes appear on the virtual bronchial walls could be used.

Radiation doses to patients from endoscopic retrograde cholangiopancreatography examinations and image quality considerations.

The purpose of this investigation was to measure the dose-area product (DAP) and the other relevant dosimetric quantities in diagnostic and therapeutic endoscopic retrograde cholangiopancreatography (ERCP). Furthermore, the dependence of patient dose and image quality on the tube potential was investigated. A DAP meter was used for dose monitoring in seven diagnostic and 21 therapeutic ERCPs. For each ERCP the DAP meter readings, fluoroscopy time, number of radiographs and exposure data were recorded. From these data the fluoroscopy and radiography contributions to DAP, the entrance skin dose and the effective dose for each examination were estimated. For the investigation of the effect of tube potential on patient dose and image quality, a water phantom containing syringes filled with diluted contrast media was used. The average DAP was 13.7 Gy cm2 in diagnostic and 41.8 Gy cm2 in therapeutic ERCP whereas the average fluoroscopy times were 3.1 and 6.0 min respectively. DAP was strongly correlated to the fluoroscopy time. Measurements in the phantom showed that a good compromise between image quality and patient dose is obtained for tube potentials around 80 kV. Therapeutic ERCPs deliver on average higher doses to patients than diagnostic ERCPs. However, for a difficult diagnostic ERCP more patient exposure may be required than for a simple therapeutic ERCP.