The introduction of new flat-panel detector technology often forces us to accept too high dose levels as proposed by the manufacturers. We need a tool to compare the image quality of a new system with the accepted standard. The aim of this study was to obtain a comparable image quality for two systems - storage phosphor plates and a flat-panel system using intravenous urography (IVU) as a clinical model. The image quality figure was calculated using a contrast-detail phantom (CDRAD) for the two evaluated systems. This allowed us to set a dose for the flat-panel system that gave equivalent image quality to the storage phosphor plates. This reduced detector dose was used in an evaluation of clinical images to find out if the dose reduction from the phantom study indeed resulted in images of equal clinical image quality. The image quality was assessed using image criteria of the European guidelines for IVU with visual grading analysis. Equivalent image quality in image pairs was achieved at 30% of the dose. The CDRAD contrast-detail phantom makes it possible to find dose levels that give equal image quality using different imaging systems. © Springer-Verlag 2005.

To find if factorial experiments can be used in the optimisation of diagnostic imaging, a factorial experiment was performed to investigate some of the factors that influence image quality, kerma area product (KAP) and effective dose (E). In a factorial experiment the factors are varied together instead of one at a time, making it possible to discover interactions between the factors as well as major effects. The factors studied were tube potential, tube loading, focus size and filtration. Each factor was set to two levels (low and high). The influence of the factors on the response variables (image quality, KAP and E) was studied using a direct digital detector. The major effects of each factor on the response variables were estimated as well as the interaction effects between factors. The image quality, KAP and E were mainly influenced by tube loading, tube potential and filtration. There were some active interactions, for example, between tube potential and filtration and between tube loading and filtration. The study shows that factorial experiments can be used to predict the influence of various parameters on image quality and radiation dose. © The Author 2005. Published by Oxford University Press. All rights reserved.

Purpose: To compare radiation doses given to patients undergoing IVU (intravenous urography) before and after digitalization of our X-ray department. Material and Methods: IVU examinations were monitored with dose area product meters before and after the X-ray department changed to digital techniques. The first step was a change from film-screen to storage phosphor plates, while the second step involved changing to a flat panel detector. Forty-two patients were included for the film-screen situation, 69 when using the storage phosphor plates, and 70 using the flat panel detector. Results: A dose reduction from 41.8 Gycm(2) to 31.5 Gycm(2) was achieved with the first step when the film-screen system was replaced with storage phosphor plates. A further reduction to 12.1 Gycm(2) was achieved using the flat panel detector. Conclusion: The introduction of the flat panel detectors made a considerable dose reduction possible.

Interventional procedures in radiology are of concern because of irradiation doses to the patients and also to the staff. A questionnaire sent to all radiology departments in Sweden showed that 11,350 procedures were performed annually 1996-1997. In a follow-up study, data from patient procedures were recorded. Type of procedure, dose-area product (DAP) values, fluoroscopy times, number of radiography series and patient data were recorded. For some procedures, staff doses were measured. Skin doses to the patients were also calculated where possible. Results: A total of 380 interventional procedures were described. The procedures were grouped into cranial, neck and thorax, intestine and abdominal, uro/genital and pelvis and extremities. DAP and fluoroscopy times (mean values) were 200 Gy cm2 for 57 min, 57 Gy cm2 for 16 min, 270 Gy cm2 for 35 min, 212 Gy cm2 for 37 min, 67 Gy cm2 for 21 min, respectively, for the named procedures. Maximum patient skin doses exceeded threshold values for erythema (2 Gy) in cranial, neck/thorax and intestine/abdominal procedures. Effective doses to the patients could be high, 200 mSv. Conclusion: It was found that patient doses could exceed threshold values for skin erythema (2 Gy) and temporary epilation (3 Gy). Hence, the procedures require immediate improvement. © The Author 2005. Published by Oxford University Press. All rights reserved.

A national study was performed to investigate radiation doses and associated risks to patients during X-ray fluoroscopy-guided small intestinal biopsies in the investigation of coeliac disease. Thermoluminescent dosemeters (TLD) and questionnaires were sent to 42 of the 43 paediatric departments in Sweden performing these biopsies. During the study period (2 × 3 weeks) 257 biopsies were recorded, representing about 10% of annually performed paediatric investigations. The results show that the absorbed dose during biopsy ranged from 0.04 mGy to 23.8 mGy (mean 1.87 mGy). The fluoroscopy time ranged from 2 s to 663 s (mean 60 s). The collective dose from the procedure amounts to 4.7 manSv year-1. Thus, the annual excess cancer mortality, including severe hereditary effects, can be estimated at 0.6-0.7 cases per year. However, significant dose saving can be obtained by proper choice of sedation and biopsy equipment. © 2005 The British Institute of Radiology.

The purpose of the study was to evaluate the image quality at different tube potential (kV) settings using anteroposterior lumbar spine radiography as a model. An Alderson phantom was used with a flat-panel detector. The tube potential varied between 48 and 125 kV while the tube charge (mAs) was adjusted to keep an effective dose of 0.11 mSv. Image quality was assessed with a visual grading analysis and with a CDRAD contrast-detail phantom together with a computer program. The VGA showed inferior image quality for the higher kV settings, ≥ 96 kV with similar results for the contrast-detail phantom. When keeping the effective dose fixed, it seems beneficial to reduce kV to get the best image quality despite the fact that the mAs is not as high as with automatic exposure. However, this cannot be done with automatic exposure, which is set for a constant detector dose.

The wide dynamic range of the digital detectors and the capabilities of post-processing allow obtaining more information from the radiographic images and avoiding retakes. Using phosphor plates in the image formation process, it has been possible to lower the dose to the patient. In digital radiography, several authors report the possibility to substantially lower the radiation dose to the patient while maintaining or even increasing the image quality. In conventional radiography, increased patient dose results in a dark image. In digital radiography the brightness of the image does not depend on patient dose. High patient doses can result in low-noise, high-contrast digital images, therefore, optimization of examinations is of vital importance in digital radiography. Special emphasis should be directed to paediatrics. The digital technique is very useful in reducing the dose both in fluoroscopy and radiography, however, special procedures for children are needed. © Springer-Verlag 2004.

In paediatric radiology it has been recognised that children have a higher risk of developing cancer from the irradiation than adults (two to three times); therefore, increased attention has been directed towards the dose to the patient. In this study the effect on patient dose and image quality in replacing the exposure in micturating cystourethrography (MCUG) examinations with the stored fluoroscopy image has been investigated. In the intravenous urography (IVU) examination we compared analogue and digital image quality, but the dose measurements were performed on a phantom. Standard clinical X-ray equipment was used. Sixty-eight patients in each of two centres were studied for the MCUG. Doses were measured with a dose-area product (DAP) meter and the image quality was scored. A non-parametric statistical analysis was performed. For the IVU, a phantom was used in the dose measurements but clinical images were scored in the comparison between analogue and digital images. For the MCUG, replacing the exposure with stored fluoroscopy images lowered the DAP value from 0.77 to 0.50 Gy cm². The image quality did not show any difference between the techniques; however, if reflux was to be graded, exposure was needed. For the IVU, the doses could be lowered by a factor of 3 using digital techniques. The image quality showed no statistical difference between the two techniques. There is a potential for a substantial dose reduction in both MUCG and IVU examinations using digital techniques.

Purpose: To find a method of adjusting the mAs-value in relation to the size of the patient undergoing computed tomography (CT) examination as a means of minimizing the radiation dose to the patient. Material and Methods: A correction factor to be applied on the tube charge for each patient was calculated using two mathematical methods. This approach was tested on 4 Perspex phantoms of different sizes and geometries. Noise was measured in the images with and without use of the correction factors. Retrospectively, correction factors were calculated for 12 CT examinations of the abdomen and the dose reduction was estimated for these patient studies. Results: The variations in noise measured in the images of the different phantoms were dramatically reduced by both methods. The retrospectively performed patient study showed that the largest correction factor was 7 times greater than the smallest, which means that a dose reduction factor of 7 is possible in the extreme case. Conclusion: Our proposed methods of adjusting the applied tube charge (mAs-value) in relation to the size of the patient can be used on the vast majority of CT systems. The potential for dose reduction is great, especially for small patients.