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M A Roubidoux

Publications and source records attributed to M A Roubidoux.

33 records · Page 2Linked to original sources
PubMed1995

Registration of three-dimensional compound ultrasound scans of the breast for refraction and motion correction.

Use of multiple look directions, that is, compound imaging, has been shown previously to increase detection of specular reflectors and averaging of speckle noise in gray-scale images, often at the expense of spatial resolution and other misregistration errors. In color flow imaging, additional view angles can fill in vessels missed due to Doppler angle dropout and increase quantitative and visual Doppler accuracy by triangulation or a simple peak-frequency-shift combination algorithm. Image registration and unwarping throughout multiple three-dimensional (3D) volume sets should correct for many refraction artifacts, motion between and during compounded image sets and even, possibly, positioning errors between image sets, acquired months apart, to display growth of abnormalities. The registration described here does not provide sufficient accuracy for formation of enhanced coherent apertures, but shows promise in some cases to provide superior compound images and possibly comparisons of current and prior studies. In this study, the breast is stabilized by mild compression between a flat plate and a scanning membrane. Registration and unwarping is performed retrospectively on two separate volumetric data sets by defining pairs of corresponding points and, in some cases, line and plane segments. Three-dimensional linear affine transforms are performed using identified points, lines and planes. 3D nonlinear warped transforms are also possible given adequate numbers of identifiable points. More than two data sets are registered by selecting one as the standard, and registering the remainder to match. The most appropriate algorithm, such as averaging or maximum amplitude, may be used to combine the data sets for display. Significant success has been achieved in compound display of a test object and of the breast in vivo, even when there was relative motion or warping between image sets. In pulse-echo imaging, homologous feature registration for compounding appears to have advantages over mechanically registered compounding methods previously employed in the breast and significant increases in lesion and structural conspicuity are noted due to a reduction in speckle noise. The improvements from compounding in 3D, surface-rendered Doppler imaging of vasculature are striking.

Adenocarcinoma↗
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↗
PubMed1993

The emphysemas: radiologic-pathologic correlations.

There are several forms of emphysema that should be considered as distinct disease entities. No university accepted classification system of these forms exists, but correlations of autopsy findings in 1,823 cases over a 12-year period confirm that the radiographic and pathologic features of the emphysemas are readily understood when centrilobular, panlobular, paracicatricial, and localized types of the disease are recognized. Centrilobular emphysema associated with cigarette smoking is the most common form. Panlobular emphysema is associated with alpha 1-protease inhibitor deficiency and pathologically produces uniform enlargement of all air spaces, with a mild basilar predominance. Paracicatricial emphysema is seen adjacent to areas of parenchymal scarring. Localized emphysema represents focal enlargement or destruction of air spaces with otherwise normal lung. A clear understanding of the computed tomographic appearance of all forms of emphysema is essential for the correct diagnosis of parenchymal lung abnormalities.

Adult↗
PubMed1993

CT in the diagnosis of primary aldosteronism: sensitivity in 29 patients.

OBJECTIVE: The most common cause of primary aldosteronism is a small aldosterone-secreting adrenal adenoma. With improvements in CT technology, smaller adrenal lesions can now be detected. We reviewed our experience with 29 patients with primary aldosteronism to assess the sensitivity of CT in detecting aldosterone-secreting adenomas. MATERIALS AND METHODS: The records of all patients with biochemically proved Conn's syndrome who were referred for adrenal CT between 1982 and 1991 were reviewed. The CT examinations of each of these 29 patients were reviewed for evidence of hyperplasia or an adenoma. The interpretations were correlated with subsequent adrenal venous sampling (20 patients) or surgery (17 patients). RESULTS: Fourteen of 17 aldosteronomas were detected on CT scans (sensitivity, 82%). Adrenal tumors were not seen on CT scans in any of the 12 patients with hyperplasia, although the glands appeared diffusely enlarged in only seven of these patients. In no case was an adrenal tumor seen on CT scans that was not found at surgery (positive predictive value, 100%). CONCLUSION: If CT scans of patients with Conn's syndrome show a focal mass, ipsilateral adrenalectomy can be performed with the expectation of cure. If no mass is found, adrenal venous sampling can be used to detect an adenoma not shown on CT.

Adenoma↗
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↗
PubMedDate not supplied

Imaging of nontraumatic hemorrhage of the adrenal gland.

Nontraumatic hemorrhage of the adrenal gland is uncommon. The causes of such hemorrhage can be classified into five categories: (a) stress, (b) hemorrhagic diathesis or coagulopathy, (c) neonatal stress, (d) underlying adrenal tumors, and (e) idiopathic disease. Computed tomography (CT), ultrasonography (US), and magnetic resonance (MR) imaging play an important role in diagnosis and management. CT is the modality of choice for evaluation of adrenal hemorrhage in a patient with a history of stress or a hemorrhagic diathesis or coagulopathy (anticoagulant therapy). CT may yield the first clue to the diagnosis of adrenal insufficiency secondary to bilateral massive adrenal hemorrhage; such insufficiency is rare but life threatening. US is the modality of choice for evaluation of neonatal hematoma, and MR imaging is helpful for further characterization. MR imaging is also useful in the diagnosis of coexistent renal vein thrombosis. When an adrenal abscess is suspected, percutaneous aspiration and drainage under imaging guidance should be performed. Hemorrhage into an adrenal cyst or tumor can cause acute onset of symptoms and signs in a patient without discernible risk factors for adrenal hemorrhage. A hemorrhagic adrenal tumor should be suspected when CT or MR imaging reveals a hemorrhagic adrenal mass of heterogeneous attenuation or signal intensity that demonstrates enhancement.

Adrenal Gland Diseases↗