[Reduction of radiation exposure by using storage phosphor radiography on pelvis and lumbar spine]. / Reduktion der Strahlenexposition mittels Speicherfolienradiographie an Becken und Lendenwirbelsäule.

PURPOSE: To examine the reduction of radiation dose for radiography of the pelvis and lumbar spine (LS) by using storage phosphor radiography (SPR)? MATERIAL AND METHODS: Each pelvis and LS of 2 phantoms (3 M) and 2 corpses were X-raxed digitally in an anterior-posterior orientation using SPR (ADC compact, Agfa). The tube current time product (mAs) was diminished gradually while keeping the voltage constant. The surface entrance dose was measured by a Dosimax (Wellhöfer) sensor. Five investigators evaluated the images for characteristics and critical features and pathological findings. RESULTS: The images of the 4 various pelvises/LS could be evaluated sufficiently down to an average dose of 34 to 40 %/18 to 35 %. For the assessment of hip joint, region typical corticalis and calcifications (pelvis/LS) 9 to 18 %/8 to 23 % of the initial dose (initial dose is equivalent to a conventional screen film system with a speed class of 400) are enough, spongiosa typical for the region and the sacrum 30 to 56 %/19 to 36 % on average among the readers. CONCLUSION: For the sufficient exclusion of a fracture the dose can be reduced on pelvis/LS to at least 39 %/28 % ( 23 %/17 %), for the assessment of sacroiliitis/osteolyses/demineralisation to at least 78 %/44 % ( 34 to 36 %/22 to 26 %), to position check after fracture to at least 15 %/25 % ( 9 %/10 %). Question-related tube current time products of the pelvis and LS can be deduced for various objects.

[Reduction of radiation dosage by using digital luminescence radiography on a hand phantom]. / Reduktion der Strahlendosis mittels Speicherfolienradiographie am Handphantom.

PURPOSE: How much can the radiation dose be reduced for hand radiography by using digital luminescence radiography (DLR)? METHODS AND MATERIALS: A hand phantom (3M) with a cyst, two fractures and an "amputation" was digitally exposed in an anterior-posterior orientation using DLR (ADC-70, Agfa). The tube current time product (mAs) was reduced gradually while keeping the voltage constant. The surface entrance dose was measured by a Dosimax sensor (Wellhöfer). Five investigators evaluated the images for characteristics and critical features, pathological findings, visual resolution and contrast. RESULTS: The surface entrance dose at 50 kV/5 mAs was 31 microGy. The images could be evaluated very well down to an average dose of 36% (11 microGy); sufficient images were obtained down to an average dose of 26% (8 microGy). The resolution of the line pairs was the same or reduced by 1 level depending on the investigator. Contrast was assessed as being very good to sufficient. CONCLUSION: For the sufficient exclusion of a fracture the dose can be reduced to at least 39%, for the sufficient assessment of bony union and possible inflammatory changes to at least 42%, to position check and foreign body search to at least 23%. By DLR the following question-referred mAs-product at 50 kV are stated: fracture exclusion 2 mAs, bony union, arthritis and osteomyelitis 2.2 mAs, position check and foreign body search 1.25 mAs.

[The reduction of the radiation dosage by means of storage phosphor-film radiography compared to a conventional film-screen system with a grid cassette on a skull phantom]. / Reduktion der Strahlendosis mittels Speicherfolienradiographie im Vergleich zum konventionellen Film-Folien-System mit Rasterkassette am Schädelphantom.

PURPOSE: How much can the radiation dose be reduced for skull radiography by using digital luminescence radiography (DLR) compared to a conventional screen film system with a grid cassette? METHODS AND MATERIALS: A skull phantom (3M) was x-rayed in anterior-posterior orientation using both a conventional screen film system with grid cassette and DLR (ADC-70, Agfa). The tube current time product (mAs) was diminished gradually while keeping the voltage constant. The surface entrance dose was measured by a sensor of Dosimax (Wellhöfer). Five investigators evaluated the images by characteristic and critical features, spatial resolution and contrast. RESULTS: The surface entrance dose at 73 kV/22 mAs was 0.432 mGy in conventional screen film system and 0.435 mGy in DLR. The images could be evaluated very well down to an average dose of 71% (0.308 mGy; SD 0.050); sufficient images were obtained down to an average dose of 31% (0.136 mGy; SD 0.065). The resolution of the line pairs were reduced down to 2 levels depending on the investigator. Contrast was assessed as being very good to sufficient. The acceptance of the postprocessed images (MUSICA-software) was individually different and resulted in an improvement of the assessment of bone structures and contrast in higher dose ranges only. CONCLUSION: For the sufficient assessment of a possible fracture/of paranasal sinuses/of measurement of the skull the dose can be reduced to at least 56% (phi 31%; SD 14.9%)/40% (phi 27%; SD 9.3%)/18% (phi 14%; SD 4.4%). Digital radiography allows question-referred exposure parameters with clearly reduced dose, so e.g. for fracture exclusion 73 kV/12.5 mAs and to skull measurement 73 kV/4 mAs.

[Sound spectrographic studies in the diagnosis of dysfunctions of mechanical heart valve prostheses (Björk-Shiley prostheses)]. / Schallspektrographische Untersuchungen zur Diagnose von Dysfunktionen mechanischer Herzklappenprothesen (Björk-Shiley-Prothesen).

A newly developed real-time sound spectroanalyzer was found to be capable of diagnosing malfunction of prosthetic heart valves (Björk-Shiley prostheses). Sound spectroanalysis was carried out 430 times on 257 patients with a prosthetic heart valve. The valvular click of prosthetic heart valves shows a typical sound spectroanalysis pattern in real time, with a high-frequency peak which diminishes beyond 25 kHz. Thrombosis of the prosthetic heart valve causes loss of the valvular click and reduction in the intensity of the high-frequency components, as shown in 4 patients. Thus the sound spectroanalysis appears to be a noninvasive technique which may allow early diagnosis of a thrombosed prosthetic heart valve. We believe this method to be superior to phonocardiography and echocardiography.