Image quality and breast dose of 24 screen-film combinations for mammography.

In this study the effect of different mammographic screen-film combinations on image quality and breast dose, and the correlation between the various image quality parameters, breast dose and the sensitometric parameters of a film were investigated. Three Agfa (MR5-II, HDR, HT), two Kodak (Min-R M, Min-R 2000), one Fuji (AD-M), one Konica (CM-H) and one Ferrania (HM plus) single emulsion mammographic films were combined with three intensifying screens (Agfa HDS, Kodak Min-R 2190 and Fuji AD-MA). The film characteristics were determined by sensitometry, while the image quality and the dose to the breast of the resulting 24 screen-film combinations were assessed using a mammography quality control phantom. For each combination, three images of the phantom were acquired with optical density within three different ranges. Two observers assessed the quality of the 72 phantom images obtained, while the breast dose was calculated from the exposure data required for each image. Large differences among screen-film combinations in terms of image quality and breast dose were identified however, that, could not be correlated with the film's sensitometric characteristics. All films presented the best resolution when combined with the HDS screen at the expense of speed, and the largest speed when combined with the AD-MA screen, without degradation of the overall image quality. However, an ideal screen-film combination presenting the best image quality with the least dose was not identified. It is also worth mentioning that the best performance for a film was not necessarily obtained when this was combined with the screen provided by the same manufacturer. The results of this study clearly demonstrate that comparison of films based on their sensitometric characteristics are of limited value for clinical practice, as their performance is strongly affected by the screens with which they are combined.

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.

Radiation doses to patients from digital subtraction angiography.

This investigation determined patient doses during digital subtraction angiography (DSA). Fluoroscopy time, dose-area product (DAP) and entrance surface air kerma (ESAK) were analysed from 263 DSA examinations, classified into seven categories: (1) abdominal aorta, iliac, femoral, popliteal and leg arteries; (2) abdominal aorta and superselective DSA of renal arteries; (3) combination of (1) and (2); (4) superselective DSA of common carotid and vertebral arteries, intracranial branches in face and profile projections; (5) superselective DSA of hepatic, splenic, superior and inferior mesenteric arteries; (6) combination of (1) and (4); and (7) celiac trunk and branches. Median DAP values were 67.7, 92.9, 76.6, 53.6, 105.7, 76.1 and 2.6 Gy cm2, respectively. With the exception of one examination, ESAK values were below 2 Gy: the limit for erythema. Compared with published data, DAP values were within the range reported for (1) and (4), slightly larger for (2) and (5), whereas no references were identified for the remaining three categories.

Variation of the sensitometric characteristics of seven mammographic films with processing conditions.

The effect of different processing conditions on the sensitometric characteristics of mammographic films was investigated and the implications of this effect on clinical practice are discussed. Three Agfa (MR5-II, HDR and HT), two Kodak (MinR-M, MinR-2000), one Fuji (AD-M) and one Konica (CM-H) single emulsion mammographic films were used. For each film type a 21-step sensitometric strip was developed in seven different processing conditions involving the use of four processors, five developing times and four chemistries. The different processing conditions produced a variable effect on the sensitometric characteristics of the mammographic films. While some films seemed relatively insensitive, others were greatly affected. Furthermore, not all the sensitometric parameters of a film were affected in the same way. For example, a change of processing conditions in some cases increased speed and decreased contrast but in some other cases increased both speed and contrast. Different mammographic films present different sensitometric characteristics that can be altered by processing conditions. Thus, in a mammographic facility any change in film processor/processing cycle or chemistry should be carefully investigated before mammograms of patients are acquired. Furthermore, the results of film comparisons under certain processing conditions should not be generalized to other processing conditions.

Image quality assessment and radiation doses in intraoral radiography.

OBJECTIVE: The purpose of this study was to investigate 2 very important aspects of dental radiographic image quality, exposure time settings and film processing, and to assess their relation to radiation dose. STUDY DESIGN: Radiographic images of a dental image quality test tool were obtained in 108 dental practices. Image quality and film processing were evaluated both subjectively and objectively by comparing films developed by the dentists with films developed under optimum conditions. The data consisted of measured values of optical density, which were used to obtain image contrast, and scores of image quality and film processing, which were based on criteria set by 2 independent oral radiologists. Entrance surface dose was also measured for the technique used at each dental practice. RESULTS: The results indicate a great variability of exposure time settings used by the dentists for imaging the phantom. Film processing was inadequate in most of the practices, which resulted in poor image quality and increased patient radiation doses. The mean entrance surface dose for imaging the phantom was 3.8 mGy. CONCLUSION: Intraoral imaging techniques and film processing must be standardized to improve image quality and further reduce patient radiation doses.

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.

Estimation of children's radiation dose from cardiac catheterisations, performed for the diagnosis or the treatment of a congenital heart disease using TLD dosimetry and Monte Carlo simulation.

Entrance surface radiation doses were measured with thermoluminescent dosimeters for 98 children who were referred to a cardiology department for the diagnosis or the treatment of a congenital heart disease. Additionally, all the radiographic parameters were recorded and Monte Carlo simulations were performed for the estimation of entrance surface dose to effective dose conversion factors, in order to further calculate the effective dose for each child. For diagnostic catheterisations the values ranged from 0.16 to 14.44 mSv, with average 3.71 mSv, and for therapeutic catheterisations the values ranged from 0.38 to 25.01 mSv, with average value 5 mSv. Effective doses were estimated for diagnostic procedures and interventional procedures performed for the treatment of five different heart diseases: (a) atrial septal defect (ASD), (b) ventricular septal defect (VSD), (c) patent ductus arteriosus (PDA), (d) aorta coarctation and (e) pulmonary stenosis. The high levels of radiation exposure are, however, balanced with the advantages of cardiac catheterisations such as the avoidance of surgical closure and the necessity of shorter or even no hospitalisation.

Radiation doses to patients undergoing standard radiographic examinations: a comparison between two methods.

The objective of the study was to derive a mathematical method for calculating the entrance surface dose (ESD) from exposure factors for all tube potentials used in clinical practice and to compare the calculated ESDs (ESD(C)) with those measured (ESD(TLD)) using thermoluminescent dosemeters (TLDs). The exposure parameters of 43 patients who underwent (a) posteroanterior (PA) and lateral (LAT) chest examination (13 patients), (b) supine abdomen (10 patients), (c) erectus abdomen (10 patients), or (d) urinary tract examination (10 patients) were recorded. Patient ESD was directly measured by TLDs and calculated from exposure factors. The differences between ESD(C) and ESD(TLD) were quite small and could be explained by the uncertainties involved in both methods, in all but the PA chest examination where the ESD(C) was about 50% larger than ESD(TLD). However, in PA chest the ESD(TLD) was close to the minimum detectable dose of TLDs, questioning the accuracy of ESD(TLD). Further investigation showed that using the high tube potential technique (130 kV) in the PA chest examination resulted in very short exposure times, in the region of 4 ms. In such short exposure times, the X-ray generator operation presented stability problems that led to loss of output linearity and consequently to false calculation of ESD. The calculation method offers a reliable and cheap alternative to the measurement of ESD by TLD, provided that the exposure times are not as short as in the PA chest examinations recorded in this study, so that the output linearity with tube current-time product (mAs) is maintained.