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Biomedical subjects

M D Rifkin

Publications and source records attributed to M D Rifkin.

At least 37 records · Page 2Linked to original sources
PubMed1994

Fat-suppressed spoiled GRASS imaging of knee hyaline cartilage: technique optimization and comparison with conventional MR imaging.

OBJECTIVE: We studied healthy volunteers with fat-suppressed three-dimensional (3D) spoiled gradient-recalled acquisition in the steady state (SPGR) to determine parameters that maximize positive contrast between knee articular cartilage and fluid, marrow fat, and muscle; and we compared the technique with conventional MR imaging sequences. The purpose was to determine if fat-suppressed 3D SPGR imaging is useful for detecting abnormalities of the articular cartilages. SUBJECTS AND METHODS: The knees of 10 healthy volunteers were imaged in the axial plane. Fat-suppressed 3D SPGR imaging was performed with a TR of 60 msec, a TE ranging from 5 to 15 msec, and a flip angle ranging from 20 degrees to 80 degrees. This was followed by a similar set of fat-suppressed two-dimensional (2D) SPGR images, and conventional T1- and T2-weighted spin-echo and multiplanar gradient studies. Contrast-to-noise (C/N) ratios were determined for cartilage versus a saline fluid phantom, marrow fat, and muscle. Optimal parameters were determined both quantitatively and by a blinded subjective analysis. RESULTS: A TE of 5 msec and a flip angle of 40 degrees demonstrated the greatest C/N ratio between the signals for cartilage and for fluid, marrow, and muscle. C/N ratios in the 3D sequences were higher than in the 2D, spin-echo, and gradient series, although the absolute C/N ratio values for the T2-weighted spin-echo sequence were higher than those for the 3D fat-suppressed SPGR sequence. Subjective analysis showed articular cartilage to have a consistent trilaminar appearance, and independent interpreters favored a 3D fat-suppressed SPGR sequence with a TE of 5 msec and a flip angle of 40 degrees. Three subjects with incidental joint fluid had C/N ratios within a 95% confidence range for cartilage versus the fluid phantom. CONCLUSION: When a fat-suppressed 3D SPGR sequence of 60/5/40 degrees (TR/TE/flip angle) is used, MR images can show high positive contrast between articular hyaline cartilage and adjacent structures. This convenient technique is different from standard MR imaging sequences because it demonstrates greater signal intensity in cartilage than in fluid, marrow fat, and muscle, and because it consistently shows an organized internal architecture of hyaline cartilage. Fat-suppressed 3D SPGR imaging therefore has promise for detecting abnormalities of the articular cartilage.

Adult↗
PubMed1993

Contribution of HER-2/neu oncogene expression to tumor grade and DNA content analysis in the prediction of prostatic carcinoma metastasis.

BACKGROUND: Recent advances in the early detection of prostatic adenocarcinoma have stimulated interest in the development of techniques for determining metastatic potential. METHODS: One hundred cases of adenocarcinoma, including 66 biopsy and radical prostatectomy specimens; 20 biopsies alone; and 14 transurethral resection specimens, were evaluated for Gleason tumor grade, DNA content and HER-2/neu expression. DNA content was determined on Feulgen-stained touch preparations and tissue sections (18 cases) or tissue sections alone. HER-2/neu expression level was determined by image-analysis-assisted quantitative immunocytochemistry. RESULTS: Tumor grade and ploidy status were independent significant predictors of metastasis. HER-2/neu overexpression was found in 16 (16%) of the 100 cases and significantly correlated with high-tumor grade and aneuploid status, but was not of independent value in the prediction of metastasis. CONCLUSIONS: HER-2/neu overexpression is not uncommon in prostatic adenocarcinoma and is associated with high-tumor grade, abnormal DNA content, and distant metastasis. Tumor grade and DNA ploidy values are of the greatest value in determining the presence of metastasis.

Adenocarcinoma↗
PubMed1993

Prostate: techniques, results, and potential applications of color Doppler US scanning.

Color Doppler ultrasound (US) scanning and conventional endorectal gray-scale US of the prostate were performed in 619 patients. Pathologic correlation was available in all cases after US-guided transrectal biopsy. There were 132 cancers in 121 men, 13 foci of atypia in 10 men, 33 foci of inflammation in 31 men, and 469 benign lesions in 457 men. Two hundred seventy patients with abnormal areas of flow identified at color Doppler scanning also underwent spectral waveform analysis of the area of potential concern. No statistical difference in the mean resistive indexes was identified in any patient (P = .25; Scheffe F test, analysis of variance). All malignant lesions had abnormalities demonstrated at gray-scale US and/or focal or diffuse abnormal flow demonstrated at color Doppler scanning. Of the 132 cancers, 123 (93%) had corresponding gray-scale abnormalities and 114 (86%) demonstrated abnormal flow at color Doppler imaging. Nine of the 132 cancers (7%) had no obviously identifiable abnormality at gray-scale scanning but had distinctly abnormal flow at color Doppler scanning. Abnormal findings at color scanning without abnormal findings at gray-scale scanning occurred in eight of the 33 cases of inflammatory foci (24%) and in 24 of the 469 (5%) benign lesions.

Adult↗
PubMed1993

The foramen magnum: the underutilized acoustic window to the posterior fossa.

Visualization of the posterior fossa during neonatal cranial sonography through the anterior fontanelle can at times be limited. To improve visualization of the posterior fossa, the foramen magnum was used as an acoustic window. Scans through the foramen magnum were obtained in addition to routine scans via the anterior fontanelle in 21 preterm infants. A subjective and retrospective evaluation was performed comparing clarity and definition of posterior fossa structures using the anterior fontanelle and foramen magnum. Images of the fourth ventricle, pons, vermis, cerebellar hemispheres, and cisterna magna were considered superior in clarity and definition when obtained via the foramen magnum. The tentorium was visualized equally well with both windows. Foramen magnum scanning demonstrated improved clarity of two Dandy-Walker variants in comparison to anterior fontanelle scanning. The use of the foramen magnum in addition to other acoustic windows can improve perceived clarity and definition of posterior fossa structures and aid in the detection of abnormalities and anomalies occurring in this location.

Cerebellum↗
PubMed1992

Partial angle inversion recovery (PAIR) MR imaging: spin-echo and snapshot implementation.

The effects of varying the inversion or excitation RF pulse flip angles on image contrast and imaging time have been investigated in IR imaging theoretically, with phantoms and with normal volunteers. Signal intensity in an IR pulse sequence as a function of excitation, inversion and refocusing pulse flip angles was calculated from the solution to the Bloch equations and was utilized to determine the contrast behavior of a lesion/liver model. Theoretical and experimental results were consistent with each other. With the TI chosen to suppress the fat signal, optimization of the excitation pulse flip angle results in an increase in lesion/liver contrast or allows reduction in imaging time which, in turn, can be traded for an increased number of averages. This, in normal volunteers, improved spleen/liver contrast-to-noise ratio (9.0 vs. 5.7, n = 8, p less than 0.01) and suppressed respiratory ghosts by 33% (p less than 0.01). Reducing or increasing the inversion pulse from 180 degrees results in shorter TI needed to null the signal from the tissue of interest. Although this decreases the contrast-to-noise ratio, it can substantially increase the number of sections which can be imaged per given TR in conventional IR imaging or during breathold in the snapshot IR (turboFLASH) technique. Thus, the optimization of RF pulses is useful in obtaining faster IR images, increasing the contrast and/or increasing the number of imaging planes.

Abdomen↗
PubMed1992

Polycythemia vera and myelofibrosis: correlation of MR imaging, clinical, and laboratory findings.

Magnetic resonance (MR) imaging was performed in 14 patients with biopsy-proved polycythemia vera (n = 4) or myelofibrosis (n = 10) to determine whether MR imaging findings can be correlated with the clinicopathologic diagnosis and established clinical parameters of severity (serum lactate dehydrogenase [LDH] and cholesterol levels) and chronicity (spleen size). Evaluation of marrow in the proximal femurs showed that patients could be categorized into three distinct groups based on anatomic patterns of normal fatty and abnormal low-signal-intensity (non-fatty) marrow in the femoral capital epiphysis (FCE) and greater trochanter (GT). Patients with nonfatty marrow in both the FCE and GT (n = 8) had significantly higher serum LDH (P less than .02) and lower serum cholesterol (P less than .02) levels than patients with fatty marrow in at least the GT (n = 6). Splenic volume, as measured from MR images, was significantly greater in the myelofibrosis group than in the polycythemia vera group (P less than .001). MR imaging provided a better understanding of these hematologic disorders and novel parameters for classification that are different from conventional histologic and laboratory data.

Adult↗
PubMed1992

MR imaging in adenocarcinoma of the prostate: interobserver variation and efficacy for determining stage C 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.

Adenocarcinoma↗
PubMed1992

Testicular microlithiasis: sonographic and clinical features.

Eleven cases of bilateral diffuse microlithiasis of the testes were evaluated sonographically. The presence of testicular microlithiasis was coincidental to the presence of testicular neoplasms (n = 2), nontesticular malignant lesion in the abdomen or chest (n = 2), subfertility (n = 2), varicocele (n = 1), epididymitis (n = 1), testicular maldescent (n = 1), scrotal trauma (n = 1), and transient scrotal pain (n = 1). Clinical follow-up suggested that testicular microlithiasis is an asymptomatic nonprogressive condition. Sonographic examination of testicular microlithiasis shows diffuse hyperechoic nonshadowing foci measuring 1-2 mm in diameter throughout both testes. The diagnosis of testicular microlithiasis was pathologically proved in five cases. In six cases, the diagnosis was made on the basis of the sonographic appearance (n = 6), clinical information and follow-up (n = 6), and radiologic demonstration of testicular microcalcifications (n = 3). The sonographic appearance of testicular microlithiasis is specific, and we believe that biopsy or orchiectomy in these cases is unnecessary.

Adult↗
PubMed1991

Ultrasound of the prostate--applications and indications.

Endorectal prostate ultrasound has become a clinically useful application. This paper describes the necessary understanding of the newer concepts of anatomy, origins of disease and indications for prostate ultrasound. These indications include: (1) an abnormal digital rectal examination, (2) biopsy guidance, (3) evaluation of the patient with known prostate cancer, (4) follow-up of patients with prostate cancer, (5) certain cases of infertility, (6) prostatic inflammation, (7) voiding studies, and (8) evaluation of prostate in selected patients without previously suspected pathology.

Algorithms↗
PubMed1991

Magnetic resonance chemical shift imaging and spectroscopy of atherosclerotic plaque.

An in vivo magnetic resonance imaging (MRI) technique for identification and characterization of atherosclerotic plaque was assessed in animal and human models. Atherosclerosis was induced in the abdominal aorta of four rabbits by a combination of balloon denudation and a high cholesterol diet. In vivo conventional spin-echo and fat/water suppressed images of the rabbit aortae were obtained at 1.5 T. Chemical shift imaging (CSI) was achieved using a hybridization of selective excitation and modified Dixon techniques. These techniques were then used to obtain images of atherosclerotic lesions in the carotid arteries of four patients prior to endarterectomy. The MRI results were corroborated by histologic and high-resolution proton MR spectroscopic (8.5 T) analysis of rabbit aorta, human carotid endarterectomy, and six additional human superficial femoral and iliac atherectomy specimens. All animal and human lesions were classified as either fatty streaks or fibrotic plaque. When compared to conventional spin-echo images, fat suppression by CSI substantially improved the measured contrast-to-noise ratio between plaque and vessel lumen, and enhanced its discrimination from periadventitial fat. In contrast, water suppression eliminated visualization of plaque due to the negligible amount of isotropic (liquid-like) signal from the immobilized lesion lipids. Magnetic resonance spectroscopy corroborated the CSI results by demonstrating broad, ill-defined fat resonances characteristic of nonmobile lipids in both human and rabbit atherosclerotic lesions. These findings indicate that in vivo MRI of plaque is technically feasible and can be markedly improved using chemical shift imaging.

Animals↗
PubMed1991

Hepatocellular carcinoma within siderotic regenerative nodules: appearance as a nodule within a nodule on MR images.

Large regenerative nodules in cirrhotic livers may accumulate iron and develop internal iron-poor foci of hyperplasia or malignancy. Magnetic resonance examinations were performed on 23 patients with biopsy-proved cirrhosis. A "nodule-within-nodule" appearance was noted in two patients. This appearance consisted of markedly low intensity of a large nodule on gradient-echo images, with one or two internal foci that were isointense to the liver. Each of the large nodules was 2 cm in diameter, and each of the internal foci was less than 1 cm. Serum alpha-fetoprotein levels were normal in both patients. Aspiration biopsy performed in one patient failed to show malignancy, but histologic confirmation of hepatocellular carcinoma was obtained eventually in both cases. The nodule-within-nodule sign, which reflects the unique histopathology of hepatocellular carcinoma in large siderotic regenerative nodules, is strongly suggestive of early hepatocellular carcinoma, even if serologic markers and biopsy results do not support this diagnosis.

Biopsy↗
PubMed1991

Liver and pancreas: improved spin-echo T1 contrast by shorter echo time and fat suppression at 1.5 T.

T1-weighted spin-echo magnetic resonance (MR) images have had limited soft-tissue contrast at 1.5 T. The authors investigated the effects of echo-time (TE) minimization and fat suppression on MR images of the liver and pancreas. Two sets of MR images were obtained with identical repetition times and other parameters. In 10 subjects with seven liver lesions, images with TEs of 20 and 12 msec were compared. In 18 additional subjects with seven liver lesions and five pancreatic carcinomas, images with identical TEs but with and without fat suppression were compared. Contrast-to-noise ratios (CNRs) were greater with a TE of 12 msec than with a TE of 20 msec for liver versus spleen (7.6 vs 4.9, P = .014) and liver versus lesion (6.9 vs 3.9, P = .031). In patients without fatty liver, CNR for six lesions versus liver was greater (9.5 vs 6.0, P = .014) with fat suppression. CNR between glandular pancreas and cancer was most conspicuous with fat suppression, but fat planes were less distinct. Minimization of TE improves T1-weighted images significantly. Fat suppression also improves CNR, but the disadvantages of fat suppression do not allow elimination of conventional T1-weighted images.

Fatty Liver↗
PubMed1991

Palpable masses in the prostate: superior accuracy of US-guided biopsy compared with accuracy of digitally guided biopsy.

The accuracies of digitally guided biopsy versus ultrasound (US)-guided biopsy of the prostate were compared in 112 consecutive men with palpable prostatic lesions who had previously undergone conventional digitally guided biopsy and in which the results were negative for carcinoma. US-guided biopsies were performed with either the transperineal (n = 51) or transrectal (n = 61) approach, by means of previously described methods. All US-guided biopsies were performed within 3 months after the most recent conventional biopsy. In 44 patients (39.3%) with negative results of conventional biopsies, the results of US-guided biopsy revealed cancer. The transrectal and transperineal digitally guided biopsies were equally inaccurate, and the transrectal and transperineal US-guided biopsies showed no statistically significant differences in accuracy. The patients accepted and tolerated both US techniques equally well; neither technique was associated with significant complications. It is concluded that all patients with a palpable nodule should undergo US-guided biopsy if the result of conventional digitally guided biopsy is negative for cancer and the diagnostic US scan suggests an abnormality.

Biopsy, Needle↗
PubMed1991

Parenchymal versus reticuloendothelial iron overload in the liver: distinction with MR imaging.

Parenchymal iron deposition occurs in hemochromatosis, while iron is deposited in reticuloendothelial (RE) cells after blood transfusions or rhabdomyolysis. Magnetic resonance images of patients with decreased liver signal intensity on T2-weighted images at 1.5 T were blindly compared in an effort to distinguish these conditions. In each of five patients with hemochromatosis, the pancreas had low signal intensity, but splenic signal intensity was decreased in only one. In contrast, only three of the 16 patients with RE iron overload had low pancreatic signal intensity, while all of these patients either had low splenic signal intensity (n = 14) or previously underwent splenectomy (n = 2). Distinction among these causes of iron deposition is clinically important because parenchymal iron overload from hemochromatosis may produce significant tissue damage, while the RE iron of transfusions and rhabdomyolysis is of little clinical consequence.

Adolescent↗
PubMed1991

Comparison of Kaopectate with barium for negative and positive enteric contrast at MR imaging.

In an evaluation of safe, inexpensive, orally administered contrast agents for use at magnetic resonance imaging, different concentrations of the clay agents kaolin-pectate and attapulgite were compared in an in vitro phantom by performing spin-echo imaging with variable echo times to estimate T2 relaxation time. Additional phantoms containing from 0% to 100% attapulgite or barium preparations were compared by using spin-echo and spoiled-gradient-echo techniques to estimate T1, T2, and T2* relaxation times. In vivo spin-echo and gradient-echo images were obtained of 10 healthy volunteers and of five patients with pancreatic disease after oral administration of 12-16 oz of attapulgite preparation. T1 and T2 relaxation times obtained with use of attapulgite were slightly lower than those obtained with kaolin-pectate at both 50% and 25% concentrations. Compared with barium, attapulgite had shorter T1, T2, and T2* relaxation times, and concentration-dependent relaxivity was greater by nearly an order of magnitude. All subjects were able to drink the attapulgite, and the only complaints were of bad taste and mildly loose stools.

Barium Sulfate↗
PubMed1991

Color Doppler as an adjunct to prostate ultrasound.

Endorectal ultrasound of the prostate with color Doppler is a new technique to identify internal vasculature and flow. In a period of one year more than 500 men have been examined with this technique. The normal prostate will demonstrate flow within the surrounding vasculature; there is no distinguishing flow among the various zones. In prostate cancer there is an increased flow within or surrounding the lesion. Diffuse prostatitis exhibits a diffusely abnormal flow; in focal prostatitis the flow is not significantly different from cancer. In benign prostatic hyperplasia a significant abnormal flow was seen, usually in the inner gland, and flow was frequently identified in the area of the surgical capsule. Color Doppler can provide additional physiologic information for prostate ultrasound and may increase the specificity and sensitivity of the examination in the evaluation of potential prostatic malignancy.

Humans↗