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Biomedical subjects

E S Amis

Publications and source records attributed to E S Amis.

At least 19 recordsLinked to original sources
PubMed1992

Evaluation of teleradiology for interpretation of intravenous urograms.

The diagnostic yield of a commercial teleradiology/picture archiving and communication system (ATT-Philips Comm View T/PACS) was evaluated for 100 urograms. A single image from each examination was digitized (2048 x 1684 x 12-bit pixels) and transmitted from a satellite hospital over a T-1 line using the T/PACS system. The video display of each digitized image was reviewed independently by four radiologists. The same four radiologists reviewed the original film images at a different time without knowledge of their T/PACS interpretation. There was no statistically significant difference in the sensitivity for clinical findings between T/PACS (86%) and film (89%). The false positive rate, however, was significantly higher with T/PACS than with film (44 versus 32 false positive findings per 100 films). We conclude that T/PACS of the type studied here demonstrates sufficient sensitivity for the detection of clinically important urographic findings in the emergency setting. A final reading of the original films is still necessary, however, to assure appropriate specificity.

Contrast Media↗
PubMed1991

Quality assurance of picture archiving communication systems with laser film digitizers.

A comprehensive quality assurance (QA) program should be implemented for all teleradiology and picture archival and communications (PACS) systems. In this report, we summarize our QA experience with a teleradiology system that includes a laser digitizer for x-ray film. A key component required for the evaluation of laser film scanners is an appropriate test pattern; digitizers should be evaluated with enhanced test patterns specifically designed for this purpose. The phantom pattern should measure high-contrast resolution, low-contrast discrimination, gray scale linearity, geometric distortion, and noise. In addition, a uniformly exposed sheet of film (approximately 0.3 optical density) serves as a good phantom for testing screen nonuniformities of viewing station monitors. It is also suggested that clinical images should be included in a QA program. Finally, it is recommended that any discrepancies in the interpretation of teleradiology images should be monitored and investigated.

Lasers↗
PubMed1991

In-house testing in emergency radiology. A method for teaching and credentialling radiology residents.

Residents frequently learn emergency radiology simply by on-the-job experience. As an educational tool and as a credentialling vehicle, the authors developed an examination consisting of imaging unknowns as well as written questions. The authors have administered the test each of the last three years. After initial apprehension, the residents became comfortable with the annual examination. They now regard the follow-up conferences as the best-organized instruction in emergency radiology in the training program. The authors' experiences suggest that in-house examinations can serve as an important means for teaching and credentialling in emergency radiology.

Credentialing↗
PubMed1991

Retroperitoneal fibrosis.

Retroperitoneal fibrosis is idiopathic in two thirds of cases and is found most commonly as an isolated fibrotic plaque centered over the lower lumbar spine and entrapping one or both ureters. It has been postulated that the fibrosis in the idiopathic cases results from a hypersensitivity reaction to antigens leaking into the retroperitoneum from atheromatous plaques in the aorta or common iliac arteries. In the remaining one third of cases, causes include ergot-derivative drugs, retroperitoneal hemorrhage or urine extravasation, and a desmoplastic response to a variety of tumors. In up to 15% of cases, associated fibrotic processes are found elsewhere in the body. Although the disease is imaged best with CT or MR, neither of these techniques can be used to differentiate benign from malignant plaques. Histologically, the disease is characterized in its early stages by inflammatory cells and edema in a loose collagen network. The mature plaque is composed of dense fibrous tissue with minimal cellular infiltration. This progression is important as it influences MR signal characteristics.

Humans↗
PubMed1991

Radiology of continent urinary diversion.

The continent urinary diversions described in this article represent only a small number of the techniques that have been reported in the urologic literature. An attempt has been made to discuss diversions that are currently in common use or have been recently described and hold potential for becoming more widely accepted. The radiologist with a basic understanding of continent urinary diversions plays an important role in evaluating patients who have had these procedures. Complications can be detected and evaluated and occasionally treated with interventional techniques. As continent urinary diversions become more frequently performed, it is important that radiologists become aware of their construction techniques, radiographic appearance, function, and potential complications.

Cecum↗
PubMed1991

Neurogenic bladder simplified.

Neurogenic bladder dysfunction, if not properly diagnosed and treated, can lead to rapid deterioration of renal function by compromise of the upper urinary tracts. Two major categories of neurogenic bladder (detrusor hyperreflexia areflexia) have been discussed including the pathophysiology of the voiding dysfunction and the typical radiographic findings. Radiologists studying patients with suprasacral cord lesions should be aware of the causes, symptoms, and treatment of autonomic dysreflexia. Although video urodynamics is the state-of-the-art modality for evaluating complex or refractory neurogenic bladder, the practicing radiologist with an understanding of this condition can detect many radiographic changes in the lower urinary tract that suggest neurogenic dysfunction of various types.

Female↗
PubMed1990

MR evaluation of renal space-occupying lesions: diagnostic criteria.

In order to assess the ability of magnetic resonance (MR) imaging to distinguish simple renal cysts from renal tumors, images from 53 patients with 74 lesions were reviewed. MR image characteristics, including signal strength and homogeneity for each lesion, were evaluated and compared with the final diagnoses. There were 53 cysts and 21 tumors. For 56 lesions (76%), MR allowed accurate diagnosis; on T1-weighted images, homogeneous low-intensity lesions were always cysts and inhomogeneous medium- or high-intensity lesions were always tumors. The remaining 18 lesions (24%) could not be distinguished, and T2-weighted images failed to improve differential diagnostic ability. In our experience, MR imaging allows differentiation of renal cysts and tumors less frequently than does computed tomography (CT) or ultrasound (US). MR criteria for simple renal cysts and tumors are offered, with the understanding that modification may be necessary as experience with these lesions increases.

Diagnosis, Differential↗
PubMed1990

Retroperitoneal fibrosis.

Retroperitoneal fibrosis is the formation of a fibrotic plaque in the prelumbar or presacral area which becomes clinically significant when it produces ureteral obstruction. It can occur as a result of taking certain drugs, retroperitoneal fluid collections, inflammatory disease of various intraabdominal organs, previous surgery or radiation therapy, and various metastatic neoplasms. The majority of the causes of retroperitoneal fibrosis are considered idiopathic.

Humans↗
PubMed1990

Quadtree-based data compression of abdominal CT images.

An ROC study was performed to evaluate the effect of quadtree-based data compression on the diagnostic yield of CT images. Seventy images were selected from a series of consecutive abdominal/pelvic CT scans. Following the application of quadtree-based compression, all images were reviewed independently by three radiologists. The images were analyzed at six decreasing irreversible compression ratios (30.6:1 to 7.4:1), as well as after reversible compression (2.9:1). ROC curves reveal a gradual decrease in clinical accuracy with increasing compression ratios. At a compression ratio of 7.4:1, sensitivity for all major abnormalities was 99% with a specificity of 93%. As the compression ratio was increased to 30.6:1, sensitivity and specificity dropped to 75% and 83% respectively. Execution times for compression and decompression of the CT images with a PC-AT based digital radiography system varied from 24.7 to 18.5 seconds and from 16.2 to 5.1 seconds respectively, decreasing with higher levels of compression. We conclude that quadtree-based compression of abdominal CT images may have practical applications for a PC based digital radiography system.

Algorithms↗
PubMed1990

Application of region of interest definition to quadtree-based compression of CT images.

A quadtree-based data compression algorithm can provide different levels of compression within and outside of regions of interest (ROIs). The current study shows whether ROI compression can provide greater compression or diagnostic accuracy than uniform quadtree compression. In 75 single CT images from 75 consecutive abdominal examinations, 43 abnormalities were identified and surrounded by ROIs. Three radiologists interpreted the images following (1) 50:1 compression of the entire image; (2) ROI compression at five decreasing compression ratios (with 50:1 compression outside the ROI); and (3) reversible (lossless) compression of the entire image. Reversible compression (compression ratio 3:1) yielded a sensitivity of 96%. ROI compression of 15:1 was achieved with no loss of sensitivity; ROI compression of 28:1 yielded a sensitivity of 91% (not significantly different). At any given compression ratio, diagnostic sensitivity was greater with ROI compression than with uniform quadtree compression. For purposes of image archiving, quadtree-based ROI compression is superior to uniform compression of CT images.

Algorithms↗
PubMed1989

Nephrogenic adenoma of the bladder: urographic spectrum.

Nephrogenic adenoma is a rare, proliferative response of urothelium to urinary infection or injury of the bladder mucosa. Histologically, the lesion resembles proximal tubules of the nephron. While it can occur throughout the urinary tract, it usually appears in the bladder, with diverse radiographic manifestations. Of 6 patients with nephrogenic adenoma of the bladder, 3 presented with masses in the bladder and 2 with irregularities of the bladder mucosa on urography, while 1 showed no focal urographic abnormalities. There were no distinctive radiographic features of nephrogenic adenoma that would allow it to be differentiated from tumor or other inflammatory lesions. Although it is considered benign, bladder involvement may be extensive and eradication of the tumor may be difficult.

Adenoma↗
PubMed1989

Penile prosthetic implants: a radiographic atlas.

This article provides an atlas of penile prosthetic implants currently in use. It is believed that an understanding of the structure and mechanism of these prostheses is essential to an accurate radiologic assessment of their integrity and to the recognition of the cause in cases of malfunction.

Erectile Dysfunction↗
PubMed1989

Evaluation of a quadtree-based compression algorithm with digitized urograms.

The effect of a quadtree-based data-compression algorithm on the diagnostic yield in digitized radiographs was studied for 100 urograms. Each image was digitized and reviewed at nine decreasing compression ratios ranging from 90:1 to 4.2:1, followed by a review of the uncompressed digital images. Four radiologists independently reviewed the digitized images and the original radiographs and agreed on a reference standard of 201 findings. Sensitivity, measured by the number of findings noted on the compressed digital images, decreased with increasing compression ratios at and above the 11:1 level. No loss of sensitivity was noted with a compression ratio of 4.2:1. Sensitivity decreased more precipitously for calcifications than for soft-tissue masses. Only a minimal loss of sensitivity for bilateral renal function was noted, even with high compression ratios. False-positive rates were unaffected by compression. The authors conclude that quadtree compression ratios of 11:1 and higher may result in loss of sensitivity in clinically relevant findings.

Algorithms↗
PubMed1988

Testing as a teaching tool.

More than four years ago, the authors initiated testing as a means of obtaining data for evaluating residents. The testing process has evolved now and is used for its teaching value and as a means of objective resident self-evaluation. Testing is designed to provide 10 cases an hour, with characteristics allowing a single diagnosis as a unique answer. No history is provided because a common topic and anatomic area provide a context for each examination. Answers are given during the examination after each question, and discussion follows. All answers are written, and answer sheets are collected. Attendance is high. Test scores are routinely lower than in other forms of evaluation. Testing integrates all aspects of radiology training from cognitive through deductive, simulates written consultations, and provides a means of self-evaluation through rapid feedback. Testing is a viable form of teaching that blends self-evaluation with faculty and peer feedback.

Educational Measurement↗