Experimental study of X-ray mammography in a fluid bath: reduced radiation dose and improved detail resolution.

OBJECTIVE: To determine the effects on x-ray mammography of embedding the breast in a fluid bath. METHODS: A plexiglass phantom in the shape of a compressed breast was x-rayed in air and water with a mammography unit, and the radiation dose was measured by 20 thermoluminescence dosimeters placed in 20 representative positions on the surface of the phantom. Udders from slaughtered sheep as an animal model and phantoms were examined by mammography in identical positions surrounded by air and different fluids. The images were evaluated for detail resolution subjectively (animal model) and objectively (phantom containing quantifiable structures) by 6 and 15 blinded readers, respectively. The readers' results were analyzed and compared for visualization of the objects in air versus fluid. RESULTS: Mammographic examination in the fluid bath reduced the radiation dose and improved detail resolution in the rounded margin of the breast. Also, viewing conditions in the central region were improved as a result of the uniform optical density across the entire film area. CONCLUSIONS: Performing x-ray mammography in a fluid bath has advantages that make the technical realization of this method desirable.

[Technical success rate, peri-interventional complications and radiation exposure of the transarterial embolization for leiomyomas of the uterus]. / Technische Erfolgsrate, peri-interventionelle Komplikationen und Strahlenexposition der transarteriellen Embolisation bei Uterus myomatosus.

PURPOSE: To analyze the technical success rate, incidence and type of peri-interventional complications, and radiation exposure of uterine artery embolization (UAE) in symptomatic leiomyomas of the uterus. MATERIALS AND METHODS: This prospective study includes 75 patients consecutively treated with UAE from October 2000 through August 2002, with all interventions performed by the same radiologist. Technical success rate, interventional material, and incidence and type of peri-interventional complications (length of hospitalization) were recorded and categorized according to the definitions of the Society of Interventional Radiology (SIR). Fluoroscopy time (FT), dose-area product (DAP), and effective dose (ED) were determined for each intervention and the influence of the radiologist's experience on the radiation exposure analyzed. RESULTS: UAE was technically successful in 97.3 % of the cases. Peri-interventional complications occurred in 14.7 %. Four complications (5.3 %) were classified as major class C according to the SIR (post-embolization syndrome requiring prolonged drug treatment and hospitalization [n = 3] perforation of the uterine artery [n = 1]). None of the complications led to discontinuation of the intervention, subsequent surgical intervention, or permanent sequelae. FT decreased significantly (p < 0.05) until the 35th intervention. The median FT decreased from 18.8 min (13.4 - 28 min [25th to 75th percentile]) to 11.8 min (9.7 - 13.3 min [25th to 75th percentile]). The DAP decreased by 25.3 % to a median of 8.547 (6.527 - 11.590 cGy*cm (2) [25th to 75th percentile]). The median ED was 31.5 mSv from the 36th intervention onward. CONCLUSION: UAE has a high technical success rate with a low rate of peri-interventional complications. The study showed a statistically significant learning effect with a decrease in radiation exposure for the first 35 interventions. The effective dose of UAE is comparable to that of 1 to 2 small bowel enema.

Dose exposure of patients undergoing comprehensive stroke imaging by multidetector-row CT: comparison of 320-detector row and 64-detector row CT scanners.

BACKGROUND AND PURPOSE: Recently introduced 320-detector row CT enables whole brain perfusion imaging compared to a limited scanning area in 64-detector row CT. Our aim was to evaluate patient radiation exposure in comprehensive stroke imaging by using multidetector row CT consisting of standard CT of the head, CTA of cerebral and cervical vessels, and CTP. MATERIAL AND METHODS: Organ doses were measured by using LiF-TLDs located at several organ sites in an Alderson-Rando phantom. Effective doses were derived from these measurements. Stroke protocols including noncontrast head CT, CTA of cerebral and cervical vessels, and CTP were performed on 320- and 64-detector row scanners. RESULTS: Measured effective doses for the different scanning protocols ranged between 1.61 and 4.56 mSv, resulting in an effective dose for complete stroke imaging of 7.52/7.54 mSv (m/f) for 64-detector row CT and 10.56/10.6 mSv (m/f) for 320-detector row CT. The highest organ doses within the area of the primary beam were measured in the skin (92 mGy) and cerebral hemispheres (69.91 mGy). Use of an eye-protection device resulted in a 54% decrease of the lens dose measured for the combo protocol for whole-brain perfusion with the 320-detector row CT scanner. CONCLUSIONS: Phantom measurements indicate that comprehensive stroke imaging with multidetector row CT may result in effective radiation doses from 7.52 mSv (64-detector row CT) to 10.6 mSv (320-detector row CT). The technique of 320-detector row CT offers additional information on the time course of vascular enhancement and whole-brain perfusion. Physicians should weigh the potential of the new technique against the higher radiation dose that is needed. Critical doses that would cause organ damage were not reached.

[Multislice computed tomographic myelography]. / CT-Myelographie in Mehrschichttechnik.

While magnetic resonance imaging (MRI) is the first line modality in depicting intramedullary spinal lesions, computed tomographic (CT) myelography has gained renewed attention due to the introduction of multislice scanning (MS-CT). Compared with conventional CT, MS-CT permits rapid, high-resolution imaging of various spinal pathologies with extended scan length. Although soft tissue contrast is inferior to that with MRI, MS-CT myelography performs best in detailed assessment of osseous pathologies, 3D imaging of orthopedic and anesthesiologic implants, and showing dural leakage and causes of CSF circulation impairment. Whenever MRI is not available or contraindicated, MS-CT myelography is the method of choice for evaluating spinal lesions.

[Extrafocal radiation of medical x-ray tubes with a rotating anode]. / Zur extrafokalen Strahlung von medizinischen Röntgenröhren mit Drehanode.

A method for measuring the fraction of extrafocal radiation in the x-ray output of x-ray tubes was developed and tested under clinical conditions. A fraction of 10% was found, that increases with tube voltage and field size, while tube current and focal spot size have no influence. As a measure for the influence of off-focus radiation on image quality the contrast transfer function was used. Off-focus radiation causes detectable geometric unsharpness. If screen-film-systems are used, the unsharpness is negligible compared with the screen unsharpness. Ways for reducing off-focus radiation from medical x-ray tubes are discussed.

[CT fluoroscopy]. / CT-Durchleuchtung.

Percutaneous biopsy of pulmonary nodules requires precise needle placement, with the goal of attaining a secure position of the needle for therapeutic or diagnostic purposes as quickly as possible and with minimal tissue damage along the access route. The requirements from the image guidance system during the intervention are, in addition to universal applicability, a quick reaction time and a user-friendly interface. CT fluoroscopy fulfils these requirements, although radiation protection for the patient and radiologist becomes an important issue.

[Technical quality assurance in conventional x-ray diagnosis using medico-technical radiologists]. / Technische Qualitätssicherung in der konventionellen Röntgendiagnostik durch die MTR.

Without the x-ray assistant, regularly involved in everyday practice, technical quality assurance can hardly be accomplished. Therefore a model for the organization of quality assurance was developed and tested in practice. It implies accountable technical checks by the technician, that are controlled by a quality supervisor, and are subsequently evaluated by the radiation physics department. This positively influences quality consciousness of the radiographers and therefore the quality itself.

Low-dose spiral CT: applicability to paediatric chest imaging.

BACKGROUND: Spiral CT of the chest is an imaging technique with unequivocal indications and proven higher sensitivity and specificity than conventional chest X-rays. However, particularly in children, attempts should be made to reduce radiation exposure to a minimum. OBJECTIVE. To evaluate whether a low-dose technique in spiral CT scanning results in adequate diagnostic information. MATERIALS AND METHODS: In a prospective study, 27 children (range 3 weeks to 14 years, mean 7 years) underwent a low-dose CT examination of the chest for various indications. The tube energy was 12.5 mAs (n = 5), 25 mAs (n = 17), 50 mAs (n = 3), or 75 mAs (n = 2) per slice. Two radiologists evaluated, in consensus, the CT scans with respect to their diagnostic value and comparison was made with 20 standard-dose chest CT examinations of adults (175 mAs per slice, mean age 56 years) with respect to technical image quality (noise and artefacts). In a second part of the study, dose measurements were carried out by means of exposing thermoluminescent dosimeters attached to a water/air phantom simulating a child's chest. RESULTS: All low-dose CT scans were of diagnostic image quality and no additional studies were necessary. The average image noise was significantly higher than in standard-dose CT examinations (SD 39.5 compared with 12.5 for unenhanced soft tissue, P < 0.01), but did not hinder accurate diagnosis. Artefacts were exclusively due to patient motion. Radiation exposure per slice was approx. 4 mGy at 25 mAs and 34 mGy at 250 mAs, regardless of slice thickness. CONCLUSIONS: For all indications in paediatric CT scanning of the chest, low-dose technique provides adequate image quality without loss of diagnostic information. The radiation exposure is approximately 5-20 % of a standard-dose CT.