Biomedical subjects

M A Roubidoux

Publications and source records attributed to M A Roubidoux.

9 recordsLinked to original sources

PubMed1995

Dynamic three-dimensional imaging with partial k-space sampling: initial application for gadolinium-enhanced rate characterization of breast lesions.

PURPOSE: To evaluate a method to monitor gadolinium enhancement patterns at magnetic resonance (MR) imaging with high temporal resolution and full coverage through both breasts. MATERIALS AND METHODS: In 12 patients with 13 masses, including nine carcinoma, nonenhanced three-dimensional MR imaging was performed with full-matrix resolution. At dynamic imaging, 32 serial passes were made during bolus administration of contrast material, and temporal resolution was reduced to 12 seconds by collecting the central (low spatial frequency) 32 x 16 or 16 x 16 phase-encode views. Full-matrix dynamic images were reconstructed by complementing central phase-encode data with precontrast data from peripheral high-spatial-frequency views. RESULTS: Results at time-course analysis with a mono-exponential saturation model indicated malignant lesions tend to show rapid (< 60 seconds) contrast change relative to benign masses and normal tissues. One cancer displayed an exceptionally slow contrast change (260 seconds). CONCLUSION: The technical objectives of full tissue coverage, rapid temporal sampling, and quantification of enhancement curves are met with this method for certain lesions (> 5 mm in largest diameter).

Adult↗

PubMed1995

Bilateral breast cancer: early detection with mammography.

PURPOSE: To assess the contribution of mammography in the detection of cancer in the contralateral breast in women with bilateral breast cancer. MATERIALS AND METHODS: Mammograms and clinical records of 77 patients with bilateral breast cancer were reviewed in a retrospective study. RESULTS: The contralateral cancer was detected at mammography in 68 of 77 patients (88%) and identified at mammography alone in 50 patients (65%). No statistically significant differences in either mammographic detection rates or stage of the contralateral cancer were noted in patients younger than 50 years (n = 25) compared with those 50 years of age or older (n = 52). Cancers detected at annual screening mammography were of lower stage than cancers in unscreened patients. In the screened group, 41% of tumors were ductal carcinoma in situ alone and 23% were stage II or III, compared with 22% and 50%, respectively, in the unscreened group. CONCLUSION: Mammographic examination and follow-up in patients with unilateral breast cancer allow detection of the majority of contralateral breast cancers and earlier stage cancers.

Age Factors↗

PubMed1994

MR imaging of hemorrhage and iron deposition in the kidney.

Hemoglobin and its degradation products result in signal intensity changes at T1- and T2-weighted magnetic resonance imaging that can either facilitate or obstruct diagnosis of renal lesions. These substances are deposited in the kidney by means of hemorrhage or systemic intravascular hemolysis. Hemorrhage commonly occurs into a renal cyst, resulting in an appearance that cannot be reliably distinguished from that of renal cell carcinoma without use of contrast material. Hemorrhage may also occur diffusely in the renal medulla, and the resulting low signal intensity on T1- and T2-weighted images is characteristic of the rare disease hemorrhagic fever with renal syndrome. Systemic intravascular hemolysis results in low signal intensity in the renal cortex on T2-weighted images, owing to hemosiderin deposition; this occurs in severe hemolytic anemias. Familiarity with the spectrum of findings in the kidney resulting from hemorrhage or iron deposition is necessary for accurate diagnosis of renal disease.

Hemorrhage↗

PubMed1992

Renal revascularization: indications and results.

Although the prevalence of renovascular hypertension is low, clinical criteria can select a population in which renovascular hypertension is significantly more common (prevalence of 15%). In these selected patients, it is appropriate to proceed to a screening modality to look for a significant renal artery stenosis. Choices of the noninvasive methods include captopril-enhanced renal scintigraphy, magnetic resonance (MR) angiography, and intravenous digital subtraction renal angiography (DSRA). Intraarterial DSRA or conventional arteriography may also be used to reliably detect renal artery stenosis, with the advantage that both the diagnostic and the interventional procedure can be performed at the same setting. A high percentage of a group of patients who are selected by means of clinical and arteriographic studies will benefit from revascularization. Thus, the renal artery angioplasty may be performed during the arteriogram in which the stenosis is confirmed.

Adult↗

PubMed1992

Renal carcinoma: detection of venous extension with gradient-echo MR imaging.

Magnetic resonance (MR) imaging has been proposed as a noninvasive alternative to vena cavography and computed tomography for the detection of venous extension of renal adenocarcinoma. However, spin-echo MR images may be compromised by the presence of flow-related artifacts, extrinsic compression, and respiratory or cardiac motion artifacts. Use of gradient-recalled echo (GRE) sequences is advantageous for imaging of vascular structures. To investigate the detection of vascular extension of tumor with the GRE technique, findings in the preoperative GRE MR images of 26 patients with renal adenocarcinoma were compared with findings at surgery and pathologic examination. Vena cava thrombus was correctly identified in 13 of 13 patients (100%). Renal vein thrombus was correctly identified in 23 of 26 patients (88%), and right atrial thrombus was correctly identified in four of five patients (80%). Use of GRE sequences allows accurate assessment of vascular structures that is sufficient for surgical planning.

Adult↗

PubMed1991

Renal vein renins: inability to predict response to revascularization in patients with hypertension.

To determine whether the captopril-stimulated renal vein renin ratio (CSRVRR) could enable identification of patients with hemodynamically significant renovascular lesions who would respond to revascularization, the authors measured CSRVRRs in 143 consecutive patients with hypertension who had been selected because of clinical features suggestive of renovascular hypertension. All patients underwent conventional renal arteriography. Renovascular hypertension was the final diagnosis if revascularization resulted in cure or improvement in blood pressure. Complete data were available for 133 patients. Twenty patients had renovascular hypertension; CSRVRR was greater than 1.5 in 13 of these 20 patients (sensitivity, 65%). However, it was also greater than 1.5 in 54 of the 113 patients without renovascular hypertension (false-positive rate, 47.8%). The positive predictive value of CSRVRR was 18.6%; the negative predictive value, 89.3%. It is concluded that CSRVRR is not sufficiently sensitive to enable prediction of which patients will respond to revascularization and is not specific enough to exclude patients who do not have renovascular hypertension.

Adult↗

PubMed1990

Percutaneous biopsy of the kidney and adrenal glands.

Percutaneous biopsy techniques play an important role in the diagnosis and management of patients with known or suspected malignancies. With refinements in biopsy techniques and the use of sophisticated guiding modalities, tissue can be reliably obtained for either cytologic or histologic evaluation. These procedures are safer and more cost effective than the surgical option of open biopsy.

Adrenal Glands↗

PubMedDate not supplied

Color flow and image-directed Doppler ultrasound evaluation of iatrogenic arteriovenous fistulas in the groin.

Color flow image-directed Doppler ultrasound was used to image 9 iatrogenic arteriovenous (AV) fistulas in the groin following femoral artery catheterization. Characteristic findings in the color images and spectral waveforms seen in most patients included (1) visible connection between the artery and vein (8 cases); (2) a multicolored speckled mass at the fistula site (7 cases); (3) spreading of color pixels into the extraluminal soft tissues (7 cases); (4) high diastolic flow in the arterial waveform proximal to the fistula site (7 cases); (5) decreased flow in the artery caudal to the fistula (5 cases); and (6) high velocity turbulent flow, sometimes with a pulsatile component, in the vein near the fistula (9 cases). The authors conclude that color flow imaging is useful in differentiating an AV fistula from other complications of femoral artery catheterization, such as pseudoaneurysm or hematoma.

Adult↗

PubMedDate not supplied

MR of the kidneys, liver, and spleen in paroxysmal nocturnal hemoglobinuria.

The magnetic resonance (MR) findings in the liver, kidneys, and spleen in eight patients with paroxysmal nocturnal hemoglobinuria (PNH) were retrospectively reviewed to determine whether characteristic features could be demonstrated. Eight patients underwent abdominal MR examinations by gradient echo sequences (seven patients), spin-echo sequences (seven patients), and inversion recovery (one patient). Signal intensities of the kidneys, liver, and spleen were visually evaluated. Autopsy and liver biopsy correlation were available in one case each. Renal signal intensity was decreased in all eight patients by either gradient-echo or T2-weighted sequences and in the single inversion recovery sequence. Hepatic signal intensity was decreased in three of eight patients on spin- and gradient-echo images. Splenic signal intensity was decreased in three of eight patients on spin- and gradient-echo images, and in two of these was manifest as focal low signal spots (Gamna-Gandy bodies). While the signal intensity in the renal cortex is typically decreased in patients with PNH, signal intensities in the liver and spleen are variable. Low signal intensity in the kidneys is due to hemosiderin deposition resulting from intravascular hemolysis, whereas low signal intensity in the liver or spleen may be due to either transfusion siderosis, or as a consequence of hepatic or portal venous thrombosis.

Adolescent↗