Biomedical subjects
Publications and source records attributed to M L Schiebler.
The computed tomography (CT) and magnetic resonance imaging (MRI) findings of a case of a large rapidly progressive invasive carcinoma of the cervix in an HIV-positive women are presented. It produced retroperitoneal and lymph node metastases that were large, necrotic and rapidly growing. These findings are now recognized as being diagnostic of AIDS.
PURPOSE: To determine magnetic resonance (MR) imaging features that characterize hepatic abscesses. MATERIALS AND METHODS: Clinical records and MR studies of 18 patients with proved hepatic abscesses were evaluated. The abscesses were pyogenic in 15 patients, fungal in two patients, and amebic in one patient. RESULTS: A total of 122 lesions were identified. Most were round (n = 114) with sharp borders (n = 99), hypointense on T1-weighted images (n = 73), and very hyperintense on T2-weighted images (n = 88). After injection of gadopentetate dimeglumine in 43 lesions, all 43 enhanced with sharp margins and 37 showed rim enhancement. All abscesses followed up diminished in size (50 of 50), and perilesional edema resolved before the central cavity did. CONCLUSION: MR imaging findings seen in hepatic abscesses include high signal intensity on T2-weighted images (72%) and perilesional edema (43 of 122 [35%]). Rim enhancement (86%) and increased conspicuity (35 of 43 [81%]) were found after injection of gadopentetate dimeglumine.
The authors present the newer MR imaging techniques and how to use them to diagnose the common benign and malignant causes of adnexal masses. Specific features on MR imaging for adnexal lesions that are stressed include morphologic features, specific chemical shift, magnetic susceptibility, and enhancement pattern.
1H-spectra at 360 MHz from perchloric extracts of 35 human prostate specimens were obtained. First, we sought to define what peaks can be assigned in vitro, and thus, potentially seen in vivo. Second, we sought to try to discriminate between adenocarcinoma, normal peripheral zone and benign prostatic hyperplasia using spectral fingerprints. Thirteen samples of adenocarcinoma, 11 samples of benign prostatic hyperplasia, and 11 samples of normal contralateral peripheral zone were analyzed by obtaining a ratio from the maximum area of each major peak and the area of an added standard (3-trimethyl-silyl-propionic acid). There was a significantly larger benign prostate hyperplasia citrate standardized peak area when compared to the adenocarcinoma citrate standardized peak area for each patient (P < 0.05). However, the citrate standardized peak areas from the normal peripheral zones were not significantly different from those found in the adenocarcinomas. Four out of 13 cases of stromal hyperplasia had similarly low levels of citrate as their respective gland's adenocarcinoma. We also found a sharp peak at 2.05 ppm that was seen in 4 out of 13 adenocarcinoma samples and in only 1 out of 13 of the benign prostate hypertrophy samples which has tentatively been assigned to N-acetyl neuraminic acid. Further studies are required to assess whether low citrate levels alone can serve to exclusively diagnose adenocarcinoma of the prostate.
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To assess the performance of published criteria for differentiation of endometriomas from other hemorrhagic adnexal lesions with magnetic resonance (MR) imaging, 74 lesions with pathologic proof in 46 patients were evaluated by means of a 1.5-T system with use of conventional T1-weighted and either T2-weighted spin-echo (SE) or fast SE sequences. The MR images were independently presented to each of three blinded readers, and receiver operating characteristic (ROC) curve analysis was performed. The criterion of a cyst with high signal intensity on short repetition time (TR)/echo time (TE) images and shading on long TR/TE images had a mean sensitivity of 68%, mean specificity of 83%, and mean accuracy of 76% for diagnosis of endometrioma. Ancillary findings previously reported to be suggestive of endometrioma (eg, low-signal-intensity rims, adhesions, bowel tethering, and implants) were proved inaccurate and showed low interobserver agreement. ROC analysis showed similar area measurements among the three radiologists for diagnosis of endometrioma. MR imaging had only moderate accuracy in distinction of endometriomas from other hemorrhagic adnexal lesions.
PURPOSE: To prospectively evaluate three magnetic resonance (MR) imaging techniques for detection of pulmonary embolism. MATERIALS AND METHODS: Eighteen patients in whom the presence of acute or chronic pulmonary emboli was suspected underwent examination with the following pulse sequences: cardiac-gated spin echo, cine spatial modulation of magnetization, and two-dimensional time-of-flight pulmonary breath-hold (PBH) MR angiography. Three radiologists independently and blindly reviewed each case and graded a total of 518 arterial segments for each pulse sequence with a continuous scale of 0%-100% for likelihood of pulmonary embolism. RESULTS: The overall sensitivity of PBH MR angiography for detection of acute pulmonary emboli was 0.85; for chronic emboli, which were smaller in anteroposterior (AP) diameter, the overall sensitivity was 0.42. Emboli larger than 1 cm in AP diameter were typically identified with > 75% confidence with all pulse sequences. CONCLUSION: Acute pulmonary emboli greater than 1 cm in AP diameter were as accurately identified on PBH MR angiograms obtained in 15 seconds as they were on MR images obtained with longer pulse sequences not dependent on breath holding.
Surgical cure of adenocarcinoma of the prostate (ACP) is possible in over 80% of cases when the disease is confined to the gland capsule. The endorectal probe for magnetic resonance (MR) imaging has increased resolution of the prostate gland and capsule, which has improved the sensitivity and specificity for staging ACP (.65 sensitivity, .69 specificity for body coil; .87 sensitivity, .85 specificity for the endorectal coil). Normal glandular regions in the peripheral zone and central zone have significantly higher citrate levels than ACP and fibromuscular and fibrous benign prostatic hyperplasia at proton spectroscopy. ACP has a higher phosphomonoester-phosphocreatine ratio than normal glandular tissue at phosphorus spectroscopy. The combination of endorectal coil MR imaging for local spread, and body coil MR imaging for advanced disease, makes MR imaging the premier imaging modality for the preoperative staging of ACP.
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Reconstructive vascular surgery is the last resort for limb salvage in patients with vascular insufficiency. Planning the sites of arterial bypass grafts depends on an exact knowledge of the angiographic anatomy. Currently, conventional contrast angiography is the primary preoperative study for surgical planning. Recently, magnetic resonance (MR) arteriography has been shown to be an accurate technique for the evaluation of slow arterial flow in the lower extremities. The purpose of this review will be to show how MR arteriography can be used as both an adjunct to and in some cases instead of conventional angiography for the preoperative assessment of lower-extremity vascular reconstruction. The derivation of common artifacts, the many pitfalls of interpretation, and the evaluation of peripheral arterial occlusion and percentage stenosis will be discussed. MR arteriography of the lower extremities is an important advance for the noninvasive evaluation of disease of the peripheral vasculature.
The spleen and its vasculature are susceptible to damage from pancreatic inflammatory exudates. Fourteen patients were identified who demonstrated splenic or splenic vascular involvement from pancreatitis on computed tomography. Findings included intra- and perisplenic inflammatory fluid collections (n = 6), acute splenic hematomas (n = 3), splenic infarction (n = 1), splenic artery pseudoaneurysm (n = 1), and splenic vein thrombosis (n = 6). Eight of the 14 patients went on to urgent interventions including percutaneous catheter drainage (n = 2) and transcatheter embolotherapy (n = 6) based on the CT findings.
OBJECTIVES: The authors compared the two most common presurgical tests now used for the preoperative staging of adenocarcinoma of the prostate, prostate-specific antigen (PSA) and magnetic resonance imaging (MRI). METHODS: One hundred consecutive radical retropubic prostatectomy patients were imaged at 1.5 Tesla before surgery with routine T1-weighted and T2-weighted transaxial images. The images were analyzed by two experienced radiologists for evidence of extracapsular disease. Radiologists rated each gland on a scale of 0 to 100 for the percentage likelihood of extracapsular disease based on its MRI appearance. Receiver operator characteristic (ROC) curves were plotted, and areas were calculated for the two radiologists and the preoperative PSA values. RESULTS: Comparison of the areas of the ROC curves generated from the two radiologists and those from the preoperative PSA values showed no statistical difference. CONCLUSIONS: In this series, radiologic interpretation of body coil MRI studies in those patients chosen for a radical retropubic prostatectomy was no better in staging adenocarcinoma of the prostate than simply using the preoperative PSA values.
Two-dimensional time-of-flight (TOF) magnetic resonance angiography (MRA) of the lower extremities has recently been rediscovered as a technique that can be used to find small vessels in the foot and leg for surgical revascularization in patients with severe peripheral vascular disease. The purpose of this article is to acquaint the reader with some of the common problems that may be encountered in this imaging technique and to show their derivations and solutions were applicable. In addition, the authors show receiver operator curve analysis of one radiologist's ability to determine the location and patency of arteries using this technique to be outstanding (AZ, 0.9737). This represents a promising new technique for imaging the arterial system in patients with severe peripheral vascular disease.
Patients with adenocarcinoma of the prostate confined to the gland (stage B) are candidates for a potentially curative surgical procedure (radical retropubic prostatectomy). However, patients with adenocarcinoma that penetrates the capsule or invades the seminal vesicles (stage C) are no longer considered good candidates for surgical cure of their disease. The purpose of this study was to compare the ability of four radiologists to detect stage C disease on MR images and to evaluate interobserver variability. One hundred consecutive MR studies of the prostate were reviewed independently by four radiologists to determine whether the cancer was stage C (capsule penetration or seminal vesicle invasion by tumor). A radical prostatectomy was performed in each case, and careful histologic assessment was made of the prostatic capsule and seminal vesicles for any evidence of stage C disease. The sensitivity, specificity, and accuracy (true-positive + true-negative/100 patients) in detecting stage C disease were calculated for each of the four readers. Four receiver-operating-characteristic curves were generated and compared by means of the univariate z score. Percentage agreement was calculated for five specific areas of the prostate on MR images, and observations made by the best reader were compared with the other three to help determine interreader variability. The results showed that the sensitivity and specificity of MR imaging in detecting stage C disease ranged from .24 to .61 (mean, .48) and .49 to .79 (mean, .66), respectively. The accuracy of MR imaging ranged from .47 to .61 (mean, .55). The univariate z score test showed that one of the readers significantly differed from the other three. The average percentage agreement between that reader and the other three was 70% for the five separate anatomic regions. This study shows that considerable interobserver variation exists in the interpretation of MR images for staging cancer of the prostate. The average accuracy among four radiologists in determining the presence of stage C adenocarcinoma of the prostate from MR images was only slightly above a chance guess at .55.
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The article discusses the many types of thoracic magnetic resonance imaging artifacts, their derivations, and their current solutions. Magnetic resonance imaging artifacts of the thorax can be divided into two major categories. First, there are machine-related artifacts related to the machine's hardware: the intrinsic magnetic field, chemical shift, magnetic susceptibility, radio frequency leaks, metal artifacts, B1-homogeneity, gradient coils, truncation, aliasing, zipper artifacts, artifacts related to the surface coil profiles, pulse profiles, and crosstalk. Second, there are artifacts related to motion: voluntary patient motion, involuntary motion, and physiologic motions. Each one of these artifacts, and their solutions, will be discussed.
A series of 25 patients with biopsy proven adenocarcinoma of the prostate underwent preoperative staging evaluation with a digital rectal examination, endorectal ultrasound, and body coil magnetic resonance imaging (MRI) before their radical retropubic prostatectomy. The sensitivity and specificity of the digital rectal examination for the detection of extracapsular disease were 17 and 100%, respectively. The sensitivity and specificity of endorectal ultrasound for the detection of extracapsular disease were 35 and 89%, respectively. The sensitivity and specificity of body coil MRI for the detection of extracapsular disease by adenocarcinoma of the prostate were 47 and 63%, respectively. Microscopic disease of the capsule and seminal vesicles was the principle reason for understaging by both imaging modalities. This small series suggests that both imaging modalities are marginally more sensitive, albeit less specific, for extracapsular disease of the prostate than the digital rectal examination, with ultrasound having a slight edge in specificity and MRI having a slight edge in sensitivity.
Accurate preoperative staging is important for proper selection of patients for radical retropubic prostatectomy. Preoperative staging by digital rectal examination, transrectal ultrasound, magnetic resonance imaging (MRI), Gleason grade and prostate specific antigen was compared to pathological stage for 25 patients who underwent radical retropubic prostatectomy. The predictive value for tumor confinement was 36% by rectal examination, 37% by ultrasound and 30% by MRI. The predictive value for extracapsular disease was 100% by rectal examination, 83% by ultrasound and 66% by MRI. Preoperative determinations of tumor volume by any modality did not correlate with pathological tumor volume. Digital rectal examination, ultrasound and MRI clinically understage the disease in most patients but they may be reliable to predict extracapsular disease.