Image intensifying split radiography

This is a report on the testing of a novel system of radiography of the thorax consisting of a combination of moving-slit radiography with a slot-type image intensifier (proximity focussed linear image intensifier), being thus a variant of rotational scanography (or a swinging slot x-ray machine), the image scale being 1:1. The system was compared with conventional x-ray film/foil technique using a group of 115 patients. Special features of the new system are a very low irradiation exposure dose and a 100 x 100 mm size image. It is shown that the imaging method is highly efficient in respect of the examined nine classes of findings and that the image quality of large-size thorax x-ray films is very nearly attained. The low exposure dose, low running cost and advantages in storing and indexing can serve as counter-arguments against the well-known reserved attitude in respect of a medium-size format. The system opens good future possibilities especially with regard to follow-up and monitoring of selected patient groups (e.g. blood donors, medical personnel).     

Segmented-field radiography in scoliosis

A method of scoliosis imaging using segmented fields is presented. The method is advantageous for patients requiring serial radiographic monitoring, as it results in markedly reduced radiation doses to critical organs, particularly the breast. Absorbed dose to the breast was measured to be 8.8 mrad (88 microGy) for a full-field examination and 0.051 mrad (5.1 microGy) for the segmented-field study. The segmented-field technique also results in improved image quality. Experience with 53 studies in 23 patients is reported.     

Plain radiography with a rare-earth screen: comparison with calcium tungstate screen

Plain radiographic examinations were performed on 388 patients (adult and pediatric) using either a calcium tungstate or rare-earth screen. Radiographs were compared for overall image quality, mottle, contrast, density, and detail. The rare-earth screen produced radiographs with significantly more mottle than did the standard screen. However, this was almost never of diagnostic importance. A small but significant decrease in overall image quality also was found with the rare-earth screen. This was the result of minor differences between the grading of optimal and good. A major advantage of rare-earth screens is a 50% or more reduction in radiation exposure. The results here show that rare-earth screens may be used in plain radiographic examinations without a clinically important decrease in image quality.     

Binary screen detector system for single-pulse dual-energy radiography.

Dual-energy radiographic acquisition performed with a single pulse of x rays has been limited to use of stacked detectors such as photo-stimulable phosphor plates. In this study, a binary screen system is introduced that enables single-pulse dual-energy acquisition with nonstacked detectors such as charge-coupled devices (CCDs). Two x-ray phosphors with different K edges, designed to emit light of different wavelengths, were bound together in a single screen. Two CCD cameras, each sensitive to the respective wavelengths emitted by each phosphor, are proposed to be coupled to the binary screen. Optical isolation and detection of the optical emissions from the screen would enable simultaneous acquisition of both low- and high-energy images, which can then be used in dual-energy subtraction. Computer simulation results and experimentally acquired images suggest that the binary screen approach may be a viable alternative to stacked detector technology for dual-energy radiographic imaging.     

Digital radiography of scoliosis with a scanning method: initial evaluation

PURPOSE: To evaluate the radiation dose, image quality, and Cobb angle measurements obtained with a digital scanning method of scoliosis radiography. MATERIALS AND METHODS: Multiple images were reconstructed into one image at a workstation. A low-dose alternative was to use digital pulsed fluoroscopy. Dose measurements were performed with thermoluminescent dosimeters in an Alderson phantom. At the same time, kerma area-product values were recorded. A Monte Carlo dose calculation also was performed. Image quality was evaluated with a contrast-detail phantom and visual grading system. Angle measurements were evaluated with an angle phantom and measurements obtained on patient images. RESULTS: The effective radiation dose was 0.087 mSv for screen-film imaging, 0.16 mSv for digital exposure imaging, and 0.017 mSv for digital fluoroscopy; the corresponding kerma area-product values were 0.43, 0.87, and 0.097 Gy. cm(2), respectively. The image quality of the digital exposure and screen-film images was about equal at visual grading, whereas fluoroscopy had lower image quality. The angle phantom had lower angle values with digital fluoroscopy, although the difference in measured angles was less than 0.5 degrees. The patient images showed no difference in angles. CONCLUSION: The described digital scanning method has acceptable image quality and adequate accuracy in angle measurements. The radiation dose required for digital exposure imaging is higher than that required for screen-film imaging, but that required for digital fluoroscopy is much lower.     

Radiation doses to patients undergoing scoliosis radiography

In this study we computed the radiation doses associated with scoliosis radiography and investigated how these radiation doses are influenced by the weight of the patient. We recorded the radiographic technique factors of 61 consecutive patients (46 females and 15 males) undergoing scoliosis radiography. A wedge-shaped aluminium filter attenuated the X-ray beam in the "chest region" relative to the "abdomen region". X-ray tube air kerma output factors (microGy mAs-1) and half value layers (HVLs) were determined experimentally for the "chest region" and "abdomen region". The energy imparted to each patient was computed from the air kerma area product, X-ray beam HVL and measured patient thickness. Values of patient effective dose were obtained using effective dose-to-energy conversion factors for specified radiographic projections, taking into account each patient's weight. The median patient age was 17 years, and the median patient weight was 53 kg. Entrance skin air kerma values in the "chest region" were approximately a factor of four lower than those in the "abdomen region". The air kerma values increased by a factor of two when the patient weight increased from 30 kg to 70 kg. Approximately 80% of the total energy imparted to a patient undergoing a scoliosis examination was in the "abdomen region", with the remaining 20% imparted to the "chest region". Energy imparted increased with patient weight, and was approximately 3 mJ for a 30 kg patient and approximately 8 mJ for a 70 kg adult patient. Effective doses showed little correlation with patient weight, with an average-sized patient (50 kg) receiving an effective dose of approximately 140 microSv. Patients undergoing scoliosis radiography receive effective doses that are low in comparison with other types of radiographic examination.     

Digital radiography of scoliosis with a scanning method: radiation dose optimization

The aim of this study was optimization of the radiation dose–image quality relationship for a digital scanning method of scoliosis radiography. The examination is performed as a digital multi-image translation scan that is reconstructed to a single image in a workstation. Entrance dose was recorded with thermoluminescent dosimeters placed dorsally on an Alderson phantom. At the same time, kerma area product (KAP) values were recorded. A Monte Carlo calculation of effective dose was also made. Image quality was evaluated with a contrast-detail phantom and Visual Grading. The radiation dose was reduced by lowering the image intensifier entrance dose request, adjusting pulse frequency and scan speed, and by raising tube voltage. The calculated effective dose was reduced from 0.15 to 0.05 mSv with reduction of KAP from 1.07 to 0.25 Gy cm² and entrance dose from 0.90 to 0.21 mGy. The image quality was reduced with the Image Quality Figure going from 52 to 62 and a corresponding reduction in image quality as assessed with Visual Grading. The optimization resulted in a dose reduction to 31% of the original effective dose with an acceptable reduction in image quality considering the intended use of the images for angle measurements. Electronic Publication     

Use of biostereometric analysis as a screen for breast cancer

Biostereometric analysis, a photographic surface imaging technology that is noninvasive, was tested for its effectiveness in selecting breast pathology in a sample of 1000 female subjects, including 80 with cancers, 635 normals, and 285 with benign breast conditions. These individuals were recruited from the population of women undergoing routine mammographic examination. The project was designed specifically to determine whether biostereometric analysis could identify the individuals in the sample with malignant breast disease in the hope of providing information to aid in future development of a breast cancer screening protocol. The overall sensitivity of the method for cancers of all sizes was 76%. Biostereometric analysis was 85% sensitive for selection of cancers in the subjects over 50 years of age, and identified 80% (4 of 5) of the subjects with clinically confirmed breast cancers less than 1 cm in size. The method was 69% specific, but identified benign breast disease in only 51% of cases.     

Experimental study of intensifying screens used in diagnostic radiography (author's transl)

A physical experimental study of intensifying screens for diagnostic radiography was set up. Experimental conditions were identical with those of medical practice. Spectra speeds of several films and spectral emission of intensifying screens were built up. Speeds of screen-film combinations, as well as definitions, were measured. Results are available to range the different screens-film systems after their speed factor, at 40, 70 and 120 kV, with mention of definition of these systems. It so objectively appears that rare-earth intensifying screens make possible a decrease of X-ray exposure for patient under a factor 2 to 2,5 and a less early wearing of apparatus, namely of X-ray tubes.