Cardiovascular CT dose issues.
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Coronary Disease↗
Biomedical subjects
R L Morin
Publications and source records attributed to R L Morin.
Computed radiography printing problems: a quantitative, observer-independent solution.
Even though facilities using computed radiography (CR) operate in an electronic environment, the production of hard-copy films is still necessary during the transition period, as well as for particular needs following complete implementation. We have implemented a quantitative technique to match the response of printed CR film with that of previous screen/film combinations. A stepwedge is radiographed using the conventional system. The same stepwedge is then radiographed (same geometry and technique) using the CR system. Following processing and printing, the plot of optical density versus step for the CR system is compared with that of the screen/film system. Adjustments are made to the printing parameters until the response curves are identical. All other translation tables in the system are set to be linear. This has proven to be a valuable technique for us and provides CR printed image quality that is equivalent to that of our previous screen/film combinations.
Computer Peripherals↗
The implementation of speech recognition in an electronic radiology practice.
For both efficiency and economic reasons, our practice (200,000 examinations) has converted all remote dictation to speech recognition transcription (PowerScribe, L & H, Burlington, MA). The design criteria included complete automation to the existing radiology information system (RIS), with full RIS capabilities immediately available following dictation. All dictations for computed tomography, magnetic resonance imaging, ultrasound, and nuclear medicine were converted from remote transcription to speech recognition over a 2-week period (following a 4-week installation phase and 8 days of training). The average turnaround time for these reports decreased from approximately 2 hours to less than 1 minute. Reports are then sent to the institutional Electronic Medical Record and are available throughout all facilities in a nominal 2 minutes. Speech recognition rates were surprisingly high, although certain phrases caused consistent difficulties and certain staff required retraining. This presents our analysis of both successful and problematic areas during our design and implementation, as well as statistical performance analyses.
Efficiency↗
Fracture interpretation using electronic presentation: a comparison.
The purposes of this study were to determine whether (1) fractures are interpreted differently after digitization and electronic presentation; (2) there are differences in accuracy between screen radiographs and electronic presentation; (3) differences in interpretation are a function of monitor resolution; and (4) differences in interpretation between radiographs and electronic images relate to radiological subspecialty. Forty cases with fractures of varying degrees of subtlety and 35 cases without fractures were interpreted. Radiographs were digitized with 2 different systems and displayed on 3 monitors of different spatial resolution. Four radiologists, with varying experience, were asked to decide whether fractures were present, absent, or they were uncertain. Accuracy of interpretation increased with improved electronic image presentation and monitor resolution. The sensitivity, specificity, and accuracy of fracture detection on System A were 63%, 98%, and 78%, respectively. The results were 72%, 98%, and 84% with System B. System C results were 81%, 97%, and 88% with Lumiscan 75, and 82%, 96%, and 88% with Lumiscan 150. Sensitivity, specificity, and accuracy results of the original radiograph interpretation were 89%, 95%, and 92%. Results were significantly different for System A. No significant differences were found for the other systems compared with film radiographs. System A did not have adequate monitors for interpretation of subtle fractures. Systems B and C were capable of displaying even subtle fractures. Our initial results indicate that interpretation with high-quality 1K x 1K monitors is substantially similar to radiograph interpretation.
Adult↗
Proposition: federally mandated imaging standards (e.g., MQSA) serve the best interests of patients.
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Breast Neoplasms↗
Technical exhibits.
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Exhibitions as Topic↗
Patient doses in bone mineral densitometry.
Procedures were developed to compute effective dose equivalent (H(E)) values for patients undergoing bone mineral densitometry (BMD) measurements such as dual energy X-ray absorptiometry (DEXA) and quantitative computed tomography (QCT). Representative values of H(E) were determined for patients undergoing each type of BMD procedure. Typical DEXA measurements are associated with an H(E) of about 2.5 microSv. For QCT, the values of H(E) are 300 microSv for single energy techniques and 1 mSv for dual energy techniques, respectively. By comparison, a single well collimated abdominal X-ray examination often taken in conjunction with DEXA studies results in an H(E) of about 100 microSv. BMD patient doses are at the lower end of the exposure range encountered in diagnostic radiology. As a result, radiation dose is not a primary factor in choosing the method for BMD determination.
Absorptiometry, Photon↗
Radiation dosimetry for electron beam CT.
PURPOSE: To measure the radiation dose profile, multiple-scan average dose (MSAD), and computed tomography dose index (CTDI) for electron beam CT and to determine the accuracy of ionization-chamber and manufacturer estimates of patient dose. MATERIALS AND METHODS: High-resolution dose profiles along the longitudinal axis were acquired at several positions within the scan plane with use of radiographic film. The full-width-at-half-maximum values, peak radiation dose, CTDI, and MSAD were calculated from the digitized film profiles. CTDI was also measured with an ionization chamber. RESULTS: The full-width-half-maximum value of the radiation profiles were significantly wider than the nominal scan width for the 6-mm single-section and 8-mm multisection modes. In the single-section mode, the CTDI underestimated the MSAD by 15%-30%. The multisection radiation profile was nonuniform and asymmetric. CONCLUSION: Patient doses in electron beam CT are approximately 125% of the ionization-chamber CTDI measurements in the single-section mode. For the multisection mode, the average patient dose over the scan volume is approximately 70%-85% of the ionization-chamber CTDI measurements.
Humans↗
The technical design and performance of ultrafast computed tomography.
The ultrafast radiograph CT scanner utilizes a scanning electron beam and semicircular tungsten targets to produce a moving radiograph source about the patient, thus eliminating mechanical motion within the gantry. This design allows scan times as short as 50 or 100 ms, as well as two levels of image resolution. The short scan time reduces the effects of motion blurring and artifacts and provides the ability to obtain high-quality images of dynamic processes and rapidly moving organs. When utilized in the SS (high-resolution) mode, the UFCT scanner provides contiguous image acquisition through a patient volume at rapid speeds, yet maintains image quality comparable with conventional CT scanners. This technology provides extremely short exposure times, rapid acquisition of multiple slices, continuous scanning without concern for anode heat storage and dissipation, and the ability to image moving organs or flowing contrast media. Many clinical applications exist that exploit these unique features.
Heart Diseases↗
A survey of radiation oncologists regarding their radiation physics instruction.
The American Association of Physicists in Medicine, Committee on Training of Radiologists conducted a survey of radiation oncologists requesting information regarding their radiation oncology physics training. General questions were asked of the oncologist regarding their radiation oncology practice such as number of oncologists, number of new patients treated, and the size and type of facility in which the practice is located. The oncologist also responded to questions regarding their educational background. The survey requested the radiation oncologists to answer questions regarding the adequacy and importance of their training in specific areas of radiation physics. The responders indicated that the importance of most physics topics in their clinical practice corresponded to the level of their understanding. The survey indicated that for most radiation oncologists their physics instruction was an important and interesting part of their residency program.
Health Physics↗
infoRAD: computers for clinical practice and education in radiology. Teleradiology: fundamental considerations and clinical applications.
Teleradiology, the practice of radiology from a distance, involves transmission of images between two locations. Radiologists off site can be consulted easily and quickly whenever critical questions arise. Similarly, long-distance, real-time radiologic monitoring of patients is possible. Second opinions can be obtained from specialists in difficult cases. The result is improved and more efficient delivery of patient care. The large number of teleradiology products and features often confuses radiologists who are considering the incorporation of teleradiology into their practices. It is important that practice patterns and needs be evaluated prior to specification and acquisition of a teleradiology system.
Computer Systems↗
Solitary pulmonary nodule: CT evaluation of enhancement with iodinated contrast material--a preliminary report.
The authors hypothesized that the degree of contrast material enhancement of a pulmonary nodule, measured with computed tomography (CT), may indicate the likelihood of malignancy. Fifty-two patients with uncalcified solitary pulmonary nodules (diameter, 6-30 mm) were studied. Five single serial thin-section CT scans were obtained at 1-minute intervals after injection of 100 mL of nonionic contrast material. Twenty-two patients were excluded because the diagnosis was not clearly established: The observation period was less than 2 years, or the examination was technically inadequate. Malignant nodules were identified in 23 of the 30 remaining patients, and benign nodules were identified in seven. Within the first 2 minutes after the injection, all the malignant nodules had enhanced by 20 HU or greater (only one benign nodule had that degree of enhancement). The authors conclude that the degree of contrast material enhancement of pulmonary nodules as measured with CT may indicate the likelihood of malignancy.
Adult↗
Effect of titanium endoprostheses on bone mineral density measurements, using quantitative computed tomography.
Quantitative computed tomography has been used extensively to measure bone mineral density; particularly in the vertebral column and in the proximal portion of the femur in human beings with osteoporosis. Other potential applications of this technique include evaluation of bone adjacent to metallic endoprostheses and evaluation of fractures as they heal. Unfortunately, metal causes severe image degradation, principally seen as starburst streaking. One method used to decrease these artifacts is by imaging less-attenuating materials, such as titanium alloy. Titanium decreases image degradation sufficiently to allow accurate determination of the geometric properties of cadaveric bone. In our study, the effect of a titanium segmental endoprosthesis on bone mineral density measurement was determined by use of bone specimens from dogs and calibration standards. Titanium decreased the bone mineral density of calibration solutions from 6.8 (500 mg/cm3) to 17.7% (250 mg/cm3), and increased bone mineral density of cortical bone by 5.3%. Titanium did not affect the repeatability of these scans, indicating that the error caused by titanium was systematic and can be corrected. Our data were suggestive that quantitative computed tomography can be used to measure bone mineral density of cortical bone adjacent to titanium endoprostheses, with a predictable increase in density measurement.
Animals↗
Quantitative CT for the evaluation of bone healing.
Quantitative computed tomography (QCT) was used to quantitate the structural strength and local material properties of healing tibial osteotomies in 32 dogs. Dogs were divided into four equal groups, euthanatized at either 2, 4, 8, or 12 weeks and imaged with QCT. Invasive techniques were used to determine (1) the torsional properties of the bone; (2) the local stiffness properties and calcium content within the bone; and (3) histologically determined new bone formation and porosity. QCT was strongly associated with the maximum torque (R2 = 0.44) and torsional stiffness (R2 = 0.69) of the healing bone. QCT had strong correlations with the local stiffness (R2 = 0.64), calcium content (R2 = 0.61), new bone (R2 = 0.84), and porosity (R2 = 0.84) of healing tissues.
Animals↗
The determination of bone fracture properties by dual-energy X-ray absorptiometry and single-photon absorptiometry: a comparative study.
Dual-energy X-ray absorptiometry (DEXA) and single-photon absorptiometry (SPA) were used to quantitate the structural strength and local material properties of healing tibial osteotomies in 32 dogs. Dogs were divided into four equal groups, euthanatized at either 2, 4, 8, or 12 weeks, and imaged with DEXA and SPA. Invasive techniques were used to determine (1) the torsional properties of the bone, (2) the local stiffness properties and calcium content within the bone, and (3) new bone formation and porosity by histology. There were no differences between SPA and DEXA in their associations with the torsional properties of bone. SPA and DEXA had strong correlations with the ultimate torque (R2 = 0.76, 0.51) and the torsional stiffness (R2 = 0.68, 0.53) of bone. SPA and DEXA of periosteal callus, endosteal callus, and cortical bone had similar associations with indentation stiffness, calcium content, new bone formation, and porosity. SPA of gap tissue had significantly stronger associations with these four parameters than DEXA (P less than 0.05). Correlation coefficients (R2) with these local material properties ranged as high as 0.82 for SPA with new bone formation in the gap tissue and 0.73 for DEXA with indentation stiffness of periosteal callus.
Absorptiometry, Photon↗
Hand dose measurements in interventional radiology.
Measurements of radiation dose to the hand were conducted using TLD ring badges for individual interventional radiology cases. Results from over 30 examinations (including transhepatic cholangiograms and biliary and nephrostomy procedures) conducted by four radiologists using identical equipment show an average hand dose of 1.5 mGy (150 mrad) per procedure. Hand dose varied inversely with distance from the patient. Due to variable hand positions during clinical examinations, fluoroscopic time was not found to be a good indicator of hand dose.
Fluoroscopy↗
Technical exhibits.
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Exhibitions as Topic↗
CT evaluation of solitary pulmonary nodules: value of 185-H reference phantom.
The pulmonary nodule CT reference phantom is widely used in the evaluation of nodules 2 cm or less in diameter. It is used to detect benign patterns of calcification that are not visible on thin-section CT scans. Since 1986, the reference nodules have been manufactured with a nominal composition of 185 H. The multicenter study published in 1986 used nodules with a nominal composition of 264 H, 100 H more than the threshold value reported by Siegelman et al. in 1980. In the multicenter study, one of 37 nodules diagnosed as benign with the phantom proved to be malignant. The purpose of this study was to determine the misdiagnosis rate with the 185-H phantom and to ascertain whether the malignant tumors predicted to be benign actually contained calcification. We retrospectively reviewed 296 cases in which examinations had been performed with the 185-H nodules since 1986. Eighty-five nodules were diagnosed as benign by comparison to the reference phantom. These 85 contained no visible calcification on thin-section CT scans. Ten of the 85 cases were shown to be malignant tumors. Eight were diagnosed as having a high probability of benignity. Two were diagnosed as having a moderate probability of benignity. Calcium was present in the tissue of all six nodules available for review. Fifty-nine of the 85 nodules were still clinically indeterminate at the time of this review. Even if all of the clinically indeterminate nodules are benign, the misdiagnosis rate would be significantly higher than in most previous studies. Although analysis by using the reference phantom with 185-H nodules may indicate a high probability of benignity, close radiologic follow-up is necessary.
Adult↗