Biomedical subjects

R Mallek

Publications and source records attributed to R Mallek.

At least 37 records · Page 2Linked to original sources

PubMed1996

Bronchial wall thickness: appropriate window settings for thin-section CT and radiologic-anatomic correlation.

PURPOSE: To analyze the influence of computed tomographic (CT) window settings on bronchial wall thickness and to define appropriate window settings for its evaluation. MATERIALS AND METHODS: Three inflation-fixed lungs were scanned with a section thickness of 1.5 mm by using a high-spatial-frequency algorithm. Wall thickness in 10 bronchial specimens was measured with planimetry. Window centers were altered in a range of -200 to -900 HU and window widths in a range of 400-1,500 HU. Relative and absolute differences between CT and planimetric values were calculated. CT and planimetric measures were correlated. Inter- and intraobserver variabilities were determined. RESULTS: Window widths less than 1,000 HU resulted in a substantial overestimation of bronchial wall thickness, whereas widths greater than 1,400 HU resulted in an underestimation of bronchial wall thickness. There was no interaction between "width" and "center" regarding their influence on bronchial walls (F = 0.23; P = .99). Correlation between CT and planimetry was statistically significant (r = .85; P = .0001). Differences between the two observers were not statistically significant; results of the measurements of the two observers correlated well (r = .97; P = .001). CONCLUSION: Bronchial wall thickness on thin-section CT scans should be evaluated with window centers between -250 and -700 HU and with window widths greater than 1,000 HU. Other than window settings, notably window widths less than 1,000 HU, can lead to substantial artificial thickening of bronchial walls.

Adult↗

PubMed1996

Distinction between obstructive and nonobstructive hydronephrosis: value of diuresis duplex Doppler sonography.

OBJECTIVE: The purpose of this study was to determine the diagnostic accuracy of diuresis duplex Doppler sonography in distinguishing between obstructive and nonobstructive hydronephrosis by calculating the resistive indexes before and after administration of furosemide. SUBJECTS AND METHODS: We prospectively studied 48 kidneys in 26 patients with suspected chronic renal obstruction. All patients underwent diuretic renography and duplex Doppler sonography before and after administration of furosemide. According to the findings at diuretic renography, kidneys were classified as nonobstructed (n = 12), indeterminate (n =9), obstructed (n = 8), or normal (n = 19). The mean resistive index of each kidney and the difference between the mean resistive indexes of both kidneys were calculated before and after administration of 0.5 mg furosemide per kilogram of body weight. A receiver operating characteristic curve was generated to determine the discriminatory resistive index value for diagnosing obstruction. RESULTS: Resistive indexes were not significantly different between kidneys with nonobstructive dilatation and normal kidneys before and after diuresis. Significant differences in resistive indexes before and after diuresis were seen between kidneys with obstructive dilatation and kidneys with nonobstructive dilatation, and between normal kidneys. Kidneys with obstructive dilatation showed a significant increase in resistive index after administration of furosemide. In the indeterminate kidneys, furosemide had a heterogeneous effect on the resistive indexes, indicating obstructive resistive indexes in five kidneys and nonobstructive resistive indexes in four kidneys. Receiver operating characteristic analysis revealed a diuresis resistive index of 0.75, which resulted in an accuracy rate of 95% in diagnosing renal obstruction. CONCLUSION: Diuresis duplex Doppler sonography is accurate in the differentiation of obstructed from nonobstructed kidneys and may facilitate the distinction between obstructive and nonobstructive hydronephrosis, notably in kidneys classified as indeterminate according to diuretic renography.

Diuresis↗

PubMed1996

Spinal cord lesions in patients with multiple sclerosis: comparison of MR pulse sequences.

PURPOSE: To compare T2-weighted conventional spin-echo (CSE), fast spin-echo (FSE), shorttau inversion recovery (STIR) FSE, and fluid-attenuated inversion recovery (FLAIR) FSE sequences in the assessment of cervical multiple sclerosis plaques. METHODS: Twenty patients with clinically confirmed multiple sclerosis and signs of cervical cord involvement were examined on a 1.5-T MR system. Sagittal images of T2-weighted and proton density-weighted CSE sequences, T2-weighted FSE sequences with two different sets of sequence parameters, STIR-FSE sequences, and FLAIR-FSE sequences were compared by two independent observers. In addition, contrast-to-noise measurements were obtained. RESULTS: Spinal multiple sclerosis plaques were seen best on STIR-FSE images, which yielded the highest lesion contrast. Among the T2-weighted sequences, the FSE technique provided better image quality than did the CSE technique, but lesion visibility was improved only with a repetition time/echo time of 2500/90; parameters of 3000/150 provided poor lesion contrast but the best myelographic effect and overall image quality. CSE images were degraded by prominent image noise; FLAIR-FSE images showed poor lesion contrast and strong cerebrospinal fluid pulsation artifacts. CONCLUSIONS: The STIR-FSE sequence is the best choice for assessment of spinal multiple sclerosis plaques. For T2-weighted FSE sequences, shorter echo times are advantageous for spinal cord imaging, long echo times are superior for extramedullary and extradural disease. FLAIR-FSE sequences do not contribute much to spinal imaging for multiple sclerosis detection.

Adult↗

PubMed1994

[Breast ductal carcinoma in situ. The clinical image in the mammogram].

Thirty-one consecutive cases of ductal carcinoma in situ (DCIS) were retrospectively analysed to determine the spectrum of mammographic appearances. 68 per cent of the lesions appeared as microcalcifications, 52% as structural or irregular, poorly defined soft-tissue abnormalities, respectively. A mass lesion was noted in 23% of cases. 4 patients presenting with DCIS had negative mammograms and were diagnosed by means of additional examination techniques such as galactography, sonography, and cytologic evaluation in case of bloody nipple discharge. The authors conclude that there is a wide spectrum of mammographic imaging of DCIS.

Adult↗

PubMed1994

[Extensive intraductal components of invasive ductal breast carcinoma--value of mammography].

The presence of an extensive intraductal component (EIC) in patients with infiltrating ductal carcinoma is a major factor for predicting local recurrence after breast-conserving surgery and radiotherapy. A retrospective study including 67 consecutive cases of stage I and II infiltrating ductal carcinomas of the breast was conducted to determine the predictive values of mammographic features associated with the presence or absence of EIC. 43% of the lesions contained a pathologically verified EIC. 63% (25/40) of lesions showing mammographic evidence of calcifications with or without a mass were associated with an EIC. In contrast, only 17% (4/24) of carcinomas without calcifications demonstrated an EIC. This difference was statistically significant (p < 0.001). Lesions with calcifications greater than 3 cm in extent were significantly (p < 0.01) more likely to have an EIC (8/9; 89%) than those with calcifications less than 3 cm in extent (17/31; 55%). Furthermore, no patient with a palpable mass who had normal findings on mammograms was diagnosed to have an EIC.

Adult↗

PubMed1994

[The long-term changes after the implantation of silicone breast prostheses].

In a prospective study 60 patients with unilateral or bilateral mammary implants underwent mammography and sonography. Location, form and structure of the implants were evaluated. Additionally capsular fibrosis and its influence on the imaging quality of parenchyma was scored. We found increasing implant deformities and increasing density of the implants with increasing postoperative interval. There was poor statistically significant correlation between the thickness of the periprosthetic capsular and the postoperative interval in prepectoral implants (r = 0.555, p < 0.01); in case of subpectoral implants there was no such correlation. In 88% of the cases imaging quality was scored as adequate by two independent observers, with additional views in all cases. We conclude that sufficient imaging quality for the assessment of parenchyma and of potential implants complications may be obtained by the combination of mammography and sonography.

Adult↗

PubMed1993

Renal biopsy: in vitro and in vivo comparison of a new automatic biopsy device and conventional biopsy systems. Work in progress.

A nondisposable full-cut biopsy gun with a disposable needle (system 1, prototype of system 2) and a disposable gun-needle combination (system 2) were compared with conventional needles and Tru-Cut-type biopsy systems in renal parenchymal biopsy procedures. In cadaveric kidneys, more glomeruli were harvested with system 1 than with four other biopsy systems. In native kidneys, more glomeruli were harvested and core quality was better with system 2 than with a Tru-Cut-type biopsy gun.

Adult↗

PubMed1993

Duplex Doppler sonography of celiac trunk and superior mesenteric artery: comparison with intra-arterial angiography.

DDS was compared to intra-arterial angiography for the diagnosis of significant (> 50%) stenoses of the celiac trunk and the SMA in 38 consecutive patients referred for angiographic evaluation of peripheral arterial occlusive disease. Celiac trunk occlusion was correctly identified by DDS in three of three patients. In patients with significant celiac trunk stenoses, mean peak systolic velocity was 246 (+/- 154) cm/sec and differed significantly (P < 0.05) from the peak systolic velocity (101 +/- 22 cm/sec) of 22 patients with no angiographic evidence of significant stenosis. Five false-negative DDS examinations in patients with > 50% celiac trunk stenoses were noted. Using a peak systolic velocity of > 160 cm/sec (mean value in normal vessels plus 3 standard deviations) to diagnose > 50% celiac trunk stenosis, sensitivity of DDS was 57% and specificity was 100%. However, considering celiac trunk stenoses and occlusions as a single group, the sensitivity rate of DDS in diagnosing significant stenosis and occlusion of celiac trunk was 70%.

Adult↗

PubMed1993

[Pseudolesions in liver sonography].

Several common hepatic ultrasound pseudolesions are presented that may closely resemble pathological conditions. The majority of these pitfalls is caused by normal anatomic structures, anatomical variants of the liver or the perihepatic regions, and benign alterations of the echotexture of the liver. Exact knowledge and a precise scanning technique by an experienced sonographer are essential to avoid mistaking such findings for true liver disease. In some instances (especially when dealing with anatomical variants) computed tomography is also helpful.

Diagnosis, Differential↗

PubMed1993

[Possibilities of error and pitfalls in sonography of the gallbladder and bile ducts].

Ultrasound has a primary role in the imaging of biliary disease. Often the diagnosis is straightforward, but in this article the emphasis is placed on unusual and uncommon diseases, variant anatomy and artifacts that may present diagnostic challenges. The pitfalls and differential diagnosis in sonographic imaging of cholecystolithiasis, intraluminal gallbladder echoes, gallbladder wall thickening, artifacts of the gallbladder wall, pericholecystic fluid collections, bile duct dilatation and intraluminal bile duct echoes are discussed.

Artifacts↗

PubMed1993

[Possibilities of error in sonography of the pancreas and spleen].

Sonography plays an essential role in imaging suspected disease in the pancreas and spleen. A variety of different factors, such as artifacts, the close anatomical relationship of the pancreas to other intestinal organs, variant anatomy, and the well-known effect of the skill and experience of the sonographer may cause diagnostic difficulties. In this article, we discuss potential pitfalls and differential diagnoses in ultrasonographic imaging of the pancreas and spleen.

Artifacts↗

PubMed1992

Diagnosis of gallbladder perforation in acute acalculous cholecystitis in critically ill patients.

In the presence of ascites ultrasound is not appropriate to distinguish between gallbladder perforation and acute acalculous cholecystitis. However, the correct and early diagnosis of gallbladder perforation is important for the treatment and prognosis. We report 4 critically ill patients with ascites. All patients had evidence of gallbladder perforation by ultrasound and underwent cholecystectomy: 2 patients had gallbladder perforation, but 2 had acalculous cholecystitis without perforation. Markedly elevated serum alkaline phosphatase was the only discriminating finding indicating gallbladder perforation.

Adult↗

PubMed1992

Polyetiology of renal allograft dysfunction. Does calculation of the resistive index still make sense?

In 101 consecutive patients with renal allograft dysfunction a correlation of Duplex Doppler sonography (DDS) with histopathologic reports of simultaneously performed biopsies was made. Renal vascular impedance was estimated by calculating the resistive index (RI). A total of 290 different specific histologic diagnoses (mean 2.1 +/- 0.84 diagnoses/biopsy) was noted. With increasing time interval to transplantation, single diagnoses as cause of allograft dysfunction decreased. DDS could not reliably differentiate, exclude, or grade any of the common causes of renal allograft dysfunction like vascular and/or cellular rejection, chronic rejection, acute tubular necrosis, cyclosporin nephrotoxicity, relapse of glomerulonephritis and infection. Follow-up studies after established histologic diagnosis in 19 patients with persisting allograft dysfunction demonstrated a lack of sensitivity of DDS to significant superimposed causes of transplant malfunction. We conclude that biopsy is still necessary to direct proper therapy of renal allograft dysfunction.

Adolescent↗

PubMed1992

CT in pancreatic involvement of non-Hodgkin lymphoma.

In an attempt to evaluate characteristic CT features of primary pancreatic involvement in non-Hodgkin lymphoma (NHL), scans of 10 patients were reviewed retrospectively and compared to 50 patients with histologically proved different neoplasms of the pancreas. Setting the correct diagnosis of NHL would be essential for planning of treatment and prognosis. CT findings of NHL were characteristic but not specific. Nevertheless, the presence of a homogeneous pancreatic mass with a diameter of 7 cm or more, infiltrating surrounding tissue accompanied by retroperitoneal and/or mesenteric lymphadenopathy strongly suggests NHL. CT-guided needle biopsy can help to establish the diagnosis of pancreatic NHL.

Adult↗

PubMed1992

[Duplex ultrasound and color-coded Doppler ultrasound of visceral blood vessels in abdominal diseases].

Duplex Doppler sonography (DS) and color-flow Doppler sonography (FDS) are noninvasive diagnostic methods for the evaluation of a patient with suspected vascular disease of the abdomen. They represent a useful adjunct to realtime sonography in the identification of normal and variant visceral vascular anatomy. Aneurysms and pseudo-aneurysms of visceral arteries are readily differentiated from other cystic lesions. DS and FDS have a high sensitivity in the detection of portal vein thrombosis and stenosis. Both methods allow the observation and measurement of splanchnic hemodynamics in patients with chronic liver disease and portal hypertension. Hence, DS and FDS already play an important role in the pre- and postoperative assessment of patients undergoing liver or pancreas transplantation. The possibility that DS and FDS may enable discrimination between hypovascular and hypervascular tumors is under clinical investigation. FDS facilitates an excellent anatomic display of the abdominal vasculature and allows easy placement of the Doppler sample volume. Consequently, quantitative data acquired with DS are accomplished within short scanning times. However, the diagnostic impact of both modalities depends to a great extent on the experience of the investigator.

Abdominal Pain↗

PubMed1991

[Sonographic detection of gas in the vascular system of the liver: an image essay].

Gas within the vascular system of the liver was demonstrated sonographically in 5 patients. In contrast, plain films of the abdomen in these patients failed to demonstrate this serious finding. 3 patients presented with gas within the hepatic portal venous system, 1 patient with gas in the liver veins. In these patients, gas formation was probably caused by sepsis with gas-producing bacteria. In the last patient, air within the hepatic arterial system was caused by insufflation of air thru a port-a-cath catheter located in the main hepatic artery. The characteristic sonographic appearance of intravascular gas are highly echogenic particles flowing within the vessels. Different pathophysiologic mechanisms of gas formation in the hepatic portal venous system include sepsis with gas forming organisms, gastrointestinal necrosis of various origin in combination with elevation of intramural pressure and alteration of gas solubility of blood. The significance of sonography as a very sensitive and specific modality is outlined.

Adult↗

PubMed1991

Duplex Doppler sonography in renal parenchymal disease. Histopathologic correlation.

To evaluate the histopathologic changes influencing Doppler measurements of the resistive index (RI) in renal arteries in renal parenchymal diseases, 68 kidneys in 34 consecutive patients with various forms of renal parenchymal diseases were studied by duplex Doppler ultrasound (duplex US) immediately before percutaneous renal biopsy. The RI, renal length, and renal cortical echogenicity were correlated with the amount of glomerular, interstitial, and vascular changes graded on a scale from 0 to 100. The renal vascular resistance and therefore the RI are significantly correlated with the prevalence of arteriolosclerosis, glomerular sclerosis, arteriosclerosis, edema, and focal interstitial fibrosis. There was no significant difference of the RI in five groups of different renal parenchymal diseases. Of 34 patients, 24 presented with an RI less than 0.7, which was thought to be within the normal range so far. Additionally, the RI increases as the patient's age increases, due to higher incidence of arteriosclerosis. Of our patients, 44% presented with normal cortical echogenicity. Quantitative duplex US using the RI does not reliably distinguish different types of renal medical disorders.

Adult↗

PubMed1990

D-dimer and TAT measurement in patients with deep venous thrombosis: utility in diagnosis and judgement of anticoagulant treatment effectiveness.

The plasma levels of thrombin-antithrombin III-complexes (TAT) and the fibrin split product D-Dimer were measured in 39 patients with phlebographically proven acute DVT: 34 patients had proximal DVT, 5 had calf DVT. The sensitivity of D-Dimer and TAT measurements in the diagnosis of proximal DVT was found to be dependent on the duration of symptoms: 0 to 7 days (n = 27): elevated D-Dimer levels (greater than 120 ng/ml) = 1, D-Dimer Latex test positive (greater than 500 ng/ml) = 1, elevated TAT levels (greater than 6 ng/ml) = 0.88. Eight to 14 days (n = 7): elevated D-Dimer levels = 1, D-Dimer Latex test positive = 0.33, elevated TAT levels = 0.66; specificity: elevated D-Dimer: 0.48, D-Dimer Latex test: 1, elevated TAT: 0.76. Calf DVT patients (n = 5) had elevated D-Dimer levels, negative Latex tests and 3 of them had normal TAT values. Hemostatic and fibrinolytic parameters were also determined in 13 patients during heparin treatment of proximal DVT. Elevated D-Dimer and TAT levels rapidly decreased after initiation of anticoagulant therapy. In 2 of 13 patients a marked increase in D-Dimer and TAT levels was observed in periods of ineffective heparinization, documented by normal or only slightly prolonged thrombin clotting times. We conclude from our results that 1) D-Dimer EIA measurement, in contrast to TAT measurement, shows a very high sensitivity in the diagnosis of DVT, 2) due to low specificity this test can only be used to exclude thrombosis in patients with suspected DVT, and 3) the determination of the plasma levels of D-Dimer and TAT may be useful for judging the effect of anticoagulant treatment on thrombotic processes.

Adult↗