Search

Purpose: The purpose of this study was to compare exposure of patient and operator to ionising radiation during percutaneous vertebroplasty performed under combined computed tomography (CT) and fluoroscopic guidance or fluoroscopic guidance alone., Materials and Methods: With the collaboration of our physics department, we measured exposure on ten patients undergoing vertebroplasty with combined CT and fluoroscopic guidance and on ten undergoing vertebroplasty with fluoroscopic guidance alone., Results: Mean operator dose was approximately 0.8 microSv during vertebroplasty done with combined CT and fluoroscopic guidance and 5.8 microSv in procedures with fluoroscopic guidance alone. Mean patient dose was approximately 6 mSv for combined guidance and 8 mSv for fluoroscopic guidance, a difference that was not found to be statistically significant., Conclusions: Although combined CT and fluoroscopic guidance is normally preferred for difficult areas such as the cervical and upper thoracic vertebrae, to ensure operator radiation protection, the technique should also be considered for areas normally treated under fluoroscopic guidance alone. However, a larger patient series is needed to correctly evaluate the real contribution of low-dose CT to patient exposure.

Purpose: The purpose of this work was to evaluate the statistical distribution of patient dose for different examinations by using the data stored in a DICOM image archive of a direct digital radiography system., Materials and Methods: An automatic procedure to extract dose data and exposure parameters from the image archives was implemented. During a 4.5-month period, 8,292 images were collected. Exposure parameters and the air kerma area product (P (KA)) stored in the image DICOM header were examined for each image. The entrance surface air kerma (K (a,e)), a quantity comparable to the current diagnostic reference levels (DRL), was estimated considering the P (KA) and the geometric parameters of each examination., Results: P (KA) and K (a,e ) distributions showed highly variable values. The obtained K (a,e ) values were substantially lower than the DRL. DRL were more than six times the mean value of K (a,e ) distribution for the abdomen anteroposterior (AP) and lumbar spine lateral (LAT) projections, whereas the ratio was equal to 2.7 for posteroanterior (PA) chest examinations., Conclusions: The method adopted proved to be effective for characterising the dose of each examination by means of the statistical analysis of the dose quantities over extensive samples. The dose values obtained and the comparison with the DRL showed that this radiographic device allows substantial dose savings compared with estimations made for nondigital or for phosphor-based systems.

Purpose: The purpose of this study was to evaluate the radiation dose to patients during radiological contrast studies performed after vertical banded gastroplasty (VBG) or Roux-en-Y gastric bypass (RYGBP) surgery in patients with morbid obesity., Materials and Methods: Dose evaluations were performed on a sample of 39 patients (32 women and 7 men) with a mean weight of 117 kg (range 68-175 kg) and a mean body mass index (BMI) of 43.7 (range 22.2-54.9). Between the second and seventh postoperative day, patients underwent radiological follow-up after oral administration of approximately 70 ml of water-soluble iodinated contrast material (Gastrografin) and images acquired in anteroposterior, right and left oblique projections with the patient upright and then supine. Exposure conditions, dose-area product (DAP) and entrance skin dose (ESD) were recorded for each procedure. On the basis of these data, the effective dose (ED) was calculated using simulation software based on the Monte Carlo method for determining the absorbed dose to organs. To assess the optimal exposure conditions and the dose contributions of fluoroscopy and radiography, the effective dose rates were also evaluated using Plexiglas phantoms of different thickness to simulate different patient sizes., Results: The phantom measurements showed a fourfold dose increase when passing from normal-sized patients to obese patients. Mean DAP value obtained from in-vivo measurements was 70 Gy cm(2) (range 17-147 Gy cm(2)), and mean effective dose was 21 mSv (range 5-45 mSv)., Conclusions: When performing radiological contrast studies in patients with morbid obesity, every possible precaution should be taken to minimise patient dose. Special care should be taken to evaluate justification of the radiological procedure.

Purpose: This study was undertaken to evaluate patient dose in paediatric liver transplant recipients treated by percutaneous biliary drainage and bilioplasty procedures., Materials and Methods: Effective dose rates and entrance skin-dose (ESD) rates per minute of fluoroscopy were measured by using a plexiglas phantom (thickness 10 cm) simulating the patient and by varying the exposure parameters (type of pulsed fluoroscopy, image intensifier diameter, presence of diaphragms) to identify the technique delivering the lowest patient dose. In vivo measurements were performed during three interventional procedures., Results: The effective dose rate proved to be lowest for a particular type of pulsed fluoroscopy, with maximum magnification and with field-limiting diaphragms. The in vivo measurements showed a maximum ESD value of around 50 MGY (the threshold for transient erythema is 2,000 MGY, ICRP 60). The effective dose values were in the range of 0.9-1.5 MSV., Conclusions: We established exposure parameters providing the desired image quality with the lowest dose for the equipment used and for a specific type of interventional procedure. The measured ESD values allow us to exclude the risk of deterministic effects on the skin. The effective dose values and considerations regarding the likelihood of radiation-induced cancer led to the conclusion that the radiological risk for the patient is largely justified by the benefits of these kinds of procedure.

Purpose: The purpose of this paper is to describe the automation of quality control procedures on photo-stimulable imaging plates by means of an image-processing tool providing automatic reading of the images and automatic calculation of the quality parameters monitored., Materials and Methods: Quality-control procedures were performed according to the main available guidelines. The quality assurance programme was applied to several Kodak and Philips devices in four radiological departments. The automatic image-processing tool was developed using public domain software (Java-based ImageJ software) and contains both reading and computation procedures., Results: The quality checks and algorithms described were successfully applied, proving useful for identification of defective plates and for implementation of the quality assurance programme. The use of automation allowed significant savings in the time required for quality checks., Conclusions: Completely automated image reading allows substantial economic and human resources savings, as it eliminates much of the transfer, reproduction, processing and filing procedures.

Purpose: To compare the quality and radiation dose of a conventional film-screen system and a digital system with amorphous selenium detectors in the study of the chest, by verifying overall performance and exposure levels for the main chest structures in patients of different sizes., Materials and Methods: An analogic system (Chest-Changer, Dupont, Day-light model 1000) and a digital system (Directray Rad 1000C, Hologic) were tested on a total of 1000 patients randomly assigned to one of two groups of 500 subjects. The patients were further subdivided according to BMI (Body Mass Index). Image quality was determined by two chest radiologists who evaluated eight anatomical structures. The entrance surface dose (skin-dose), calculated based on the exposure parameters, was taken as the patient dose., Results: Mean dose delivered was very similar for both techniques in the PA view (0.28 mGy), but it was greater in the LL projections obtained with the digital system (1.20 mGy versus 0.83 mGy). The highest overall scores were assigned to 43% and 23.2% analogic radiograms and 64% and 70.2% digital radiograms, for the PA and LL projections respectively. The scores assigned to the various anatomical structures confirmed the better performance of the digital system in almost all of the regions considered., Conclusions: The mean quality of radiograms is definitely higher with the digital system, in particular in the LL projections, where the higher patient doses are counterbalanced by fewer repeated scans. The greater level of exposure in the digital system appears nonetheless tolerable on account of the greater informativeness and therefore diagnostic gain and also considering the possibilities for improving the system.

Purpose: The aim of this study was to optimize acquisition data during multislice multiphasic CT examination of the renal excretory system in order to reduce patient effective dose without deterioration of the imaging quality., Materials and Methods: With the aid of two dedicated software programmes we evaluated the patient effective dose during both multislice multiphasic CT examination of the renal excretory system and excretory urography. With the CT acquisition protocol, images of a test object (Helical CT phantom, CIRS) were examined by two expert radiologists to assess the number of visible inserted test images. Other scans of the test object were then obtained utilizing decreased tube current intensity; among these that with minor information loss was identified. Patient effective dose was measured utilizing correspondent acquisition data., Results: Patient effective dose during multiphasic multislice CT examination before optimization (280 mA tube current intensity) was 22.9 mSv for males and 31.1 mSv for females; after optimization it was 19.6 mSv and 26.7 mSv, respectively, with a 14% decrease. Patient effective dose during CT direct phase before optimization was 8.9 mSv for males and 12.8 mSv for females, after optimization 7.6 mSv and 11 mSv with a 15% decrease. The absorbed dose for males is lower because the females gonads are completely included in the primary CT beam, whereas the testicles are hit by diffuse radiation only., Discussion and Conclusions: During CT direct phase the patient absorbed dose is 1.45 for males and 1.9 for females (1.2 and 1.6 respectively after optimization) higher than that absorbed during intravenous pyelography; the absorbed dose of a complete multiphasic CT examination is 3.7 for males and 4.6 for females (3.2 and 3.9 respectively after optimization) higher than that absorbed during intravenous pyelography. Such dosimetric data may be justified by diagnostic advantages in stone assessment, especially in males, and by the fact that multislice CT may unify different diagnostic tools such as intravenous pyelography, axial CT and angiography, thereby simplifying the entire diagnostic protocol. As far as exposure is concerned radiologists should follow the optimizing principle referred to each clinical query, bearing in mind that diagnostic accuracy is more important than the simple iconographic aspect.

Purpose: To verify the suitability of indicative quantities to evaluate the risk related to patient exposure, in abdominal and vascular interventional radiology, by the study of correlations between dosimetric quantities and other indicators., Material and Methods: We performed in vivo measurements of entrance skin dose (ESD) and dose area product (DAP) during 48 procedures to evaluate the correlation among dosimetric quantities, and an estimation of spatial distribution of exposure and effective dose (E). To measure DAP we used a transmission ionization chamber and to evaluate ESD and its spatial distribution we used radiographic film packed in a single envelope and placed near the patient's skin. E was estimated by a calculation software using data from film digitalisation., Results: From the data derived for measurements in 27 interventional procedures on 48 patients we obtained a DAP to E conversion factor of 0.15 mSv / Gy cm2, with an excellent correlation (r=.99). We also found a good correlation between DAP and exposure parameters such as fluoroscopy time and number of images. The greatest effective dose was evaluated for a multiple procedure in the hepatic region, with a DAP value of 425 Gy cm2. The greatest ESD was about 550 mGy. For groups of patients undergoing similar interventional procedures the correlation between ESD and DAP had conversion factors from 6 to 12 mGy Gy-1 cm-2., Conclusion: The evaluation of ESD and E by slow films represents a valid method for patient dosimetry in interventional radiology. The good correlation between DAP and fluoroscopy time and number of images confirm the suitability of these indicators as basic dosimetric information. All the ESD values found are lower than threshold doses for deterministic effects.

Purpose: To devise and implement a programme of measurements to assess the entrance surface dose for a standard-sized patient and to check the compliance with diagnostic reference levels., Material and Methods: Dose evaluation was performed on 40 radiographic instruments. The exposure parameters were collected for the main radiographic procedures (chest, skull, spine, pelvis, abdomen) each performed with instrument on a standard-sized patient. The output of each X-ray tube at 70, 80, 90, 100, 110 and 120 kV was measured with a solid state detector during quality controls. Beam quality and geometric characteristics of the equipment were also determined. The entrance surface dose for a standard patient was assessed for each procedure carried out with the 40 instruments, thus obtaining a total of 155 radiographic techniques. Finally, the method was validated by comparing the values obtained with the solid state and an ionization chamber for X-ray beam detector., Results: The comparison between the solid state detector and the ionisation chamber demonstrated a good agreement. Results show that reference diagnostic levels are respected in most examinations (147/155) even if exposure values do not always comply with those indicated by European guidelines. The measurement programme seems to be applicable in hospital practice where the large number of radiographics instruments and procedures requires the acquisition and processing of a large number of data., Conclusions: The evaluation of patient dose during quality control is feasible and allows a first check of compliance with reference levels in order to identify which procedures can be optimised by means of more specific measurements and assessments.