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Biomedical subjects

R C Brasch

Publications and source records attributed to R C Brasch.

At least 55 records · Page 3Linked to original sources
PubMed1996

MRI mapping of microvascular permeability and tissue blood volume.

A quick and automated method for quantitative spatial mapping of tissue characteristics derived from contrast enhanced MR imaging by a macromolecular contrast medium (MMCM) was used in normal rats. Specifically, an established two compartment unidirectional flow kinetic model was automatically implemented on a pixel by pixel basis to calculate permeability surface area product (PS) and tissue fractional blood volume (BV) from MRI dynamic intensity data. The utility of PS and BV maps were evaluated in the normal rat abdomen where a range of fractional BV was found: from 100% in the vena cava to 1% in skeletal muscles, with intermediate values for liver and kidney. Tissue permeability depicted on the PS maps was generally low for normal tissues.

Animals↗
PubMed1996

Mapping abnormal synovial vascular permeability in temporomandibular joint arthritis in the rabbit using MRI.

An automated method for two-dimensional spatial depiction (mapping) of quantitative physiological tissue characteristics derived from contrast-enhanced MRI was applied to a model of inflammatory disease represented by antigen-induced arthritis of the temporomandibular joint in the rabbit. Specifically, an established two-compartment kinetic model of unidirectional mass transport was implemented on a pixel-by-pixel basis to generate maps of tissue permeability surface area product (PS) and fractional blood volume (BV) based on dynamic MRI intensity data after administration of albumin-(Gd-DTPA)30, a prototype macromolecular contrast medium designed for blood pool enhancement. Maps of PS and BV in a disease model of induced arthritis clearly depicted zones of increased permeability (up to approximately 200 microliters/cc/h-compared to 25 microliters/cc/h in normal tissues).

Animals↗
PubMed1996

Mammary carcinoma model: correlation of macromolecular contrast-enhanced MR imaging characterizations of tumor microvasculature and histologic capillary density.

PURPOSE: To determine the relationship between capillary density, a recognized surrogate of tumor angiogenesis, and magnetic resonance (MR) imaging-derived estimates of plasma volume (PV) and microvascular permeability in two mammary carcinoma models. MATERIALS AND METHODS: Dynamic spin-echo imaging was performed by using albumin-(gadolinium-diethylenetriaminepentaacetic acid)34, a prototype blood-pool contrast medium, in 14 rats with a subcutaneously implanted slow- or fast-growing subtype of R3230 mammary carcinoma. Data were fitted to an established two-compartment kinetic model to estimate PV and permeability. RESULTS: MR imaging-derived tumor PVs and permeabilities increased exponentially with increasing capillary density. MR imaging-derived microvascular characteristics correlated strongly with histologic capillary density, with an r2 of .85. CONCLUSION: Contrast medium-enhanced MR imaging may prove useful in estimating angiogenic activity in carcinomas. MR imaging may be superior to histologic assay because it is noninvasive, can be used to "sample" the entire tumor, and reflects both anatomic and physiologic characteristics.

Albumins↗
PubMed1996

Contrast-enhanced MR imaging assessment of tumor capillary permeability: effect of irradiation on delivery of chemotherapy.

PURPOSE: To assess the effect of x rays on tumor capillary permeability with macromolecular contrast medium (MMCM)-enhanced magnetic resonance (MR) imaging. MATERIALS AND METHODS: One of paired R3230 mammary adenocarcinomas implanted in the flanks of 48 Fischer rats was treated with a single 5- or 15-Gy dose of x rays. After 1 or 3 days, MR imaging in 30 rats was performed unenhanced and enhanced with albumin-(gadolinium diethylenetriaminepentaacetic acid)30 (0.02 mmol gadolinium per kilogram body weight). Signal intensity enhancement was analyzed to estimate fractional blood volume and permeability-surface area product (PS). In 18 irradiated rats, 2.5 mg/kg cisplatin was injected intravenously, and fractional tumor platinum concentrations were measured spectrometrically. RESULTS: MR imaging showed highest capillary permeability 1 day after 15 Gy (PS 110% above control [P<.001]); PS was elevated 57% 1 day after 5 Gy and 63% 3 days after 15 Gy (P<.05). The largest mean tumor platinum fraction occurred 1 day after 15 Gy: 48% versus 20% (control)(P<.05). CONCLUSION: Transient irradiation-induced increase in tumor capillary permeability to cisplatin can be quantified with MMCM-enhanced MR imaging.

Albumins↗
PubMed1995

Quantification of liver blood volume: comparison of ultra short TI inversion recovery echo planar imaging (ULSTIR-EPI), with dynamic 3D-gradient recalled echo imaging.

An ultra-short TI inversion recovery echo-planar imaging (ULSTIR-EPI) sequence was designed to reduce the influence of water exchange on fractional tissue blood volume (BV) estimation by measurement of T1-changes induced by a gadolinium-based macromolecular contrast medium (MMCM). Fractional liver BV in rats, estimated by ULSTIR-EPI was compared for accuracy to a fast T1-weighted three-dimensional gradient-echo (3D-SPGR, 3D-spoiled gradient recalled acquisition in a steady state) sequence using an in vitro inductively coupled plasma atomic emission spectroscopy (ICP-AES) assay for BV as a standard. Liver images for fractional BV estimation were acquired in eight rats using both ULSTIR-EPI and 3D-SPGR before and after (within 3 to 12 min) intravenous bolus administration of albumin-Gd-DTPA30 (0.05 mmol Gd/kg). Whereas both MR techniques may be useful for fractional tissue BV estimation, ULSTIR-EPI offers certain advantages including greater accuracy, direct T1 maps, and minimization of transendothelial proton exchange effects. 3D-SPGR imaging offers better spatial resolution, current availability on standard clinical MR systems, and acceptable accuracy.

Albumins↗
PubMed1995

Femoral neuropathy secondary to the use of a self-retaining retractor. Report of three cases and review of the literature.

PURPOSE: Three recent cases of femoral neuropathy at our institution following colorectal surgery have been ascribed to the use of the self-retaining Bookwalter retractor. The pathophysiology of neural injury includes compression, stretch, transection, ligation, iliopsoas hematoma, ischemia, and cement encapsulation. The aim of this study is to provide a comprehensive review of femoral nerve anatomy and mechanism of retractor injury. METHODS: The relationship of the femoral nerve to the lateral blade of the Bookwalter retractor was evaluated during colorectal surgery and in cadaveric dissections. RESULTS: The lateral blade of the self-retaining retractor was observed to either compress or impinge the intrapelvic portion of the femoral nerve. CONCLUSION: The incidence of postoperative femoral neuropathy is likely underestimated because a majority of cases are self-limited. This debilitating iatrogenic injury can be prevented with a thorough understanding of femoral nerve anatomy and careful placement of self-retaining retractor blades.

Adult↗
PubMed1995

Angiographic properties of Gd-DTPA-24-cascade-polymer--a new macromolecular MR contrast agent.

PURPOSE: A new macromolecular MR contrast agent, Gd-DTPA-24-cascade-polymer, was assessed for MR angiography of peritumoral vessels in rats. MATERIAL AND METHODS: High resolution 3D-SPGR (TR/TE 100/5ms, alpha = 90 degrees) angiograms were acquired in 10 Fischer rats bearing subcutaneous R3230 mammary adenocarcinomas. MRI was performed before, immediately and 40 min after administration of Gd-DTPA (0.1 mmol Gd/kg), and after either Gd-DTPA-cascade-polymer or albumin-(Gd-DTPA)30 (each 0.05 mmol Gd/kg). A semi-quantitative analysis of small peritumoral vessels and tumor rim enhancement was performed on maximum intensity projection (MIP) angiograms using a 4-point scoring system. A quantitative analysis compared vascular signal-to-background-(S/B), signal-to-noise-, and contrast-to-noise-ratio. RESULTS: Gd-DTPA produced a transient and low-scoring vessel definition (0.2 +/- 0.1), but strong rim enhancement (score 1.7 +/- 0.1). The cascade polymer resulted in better but submaximal vessel delineation (score 1.6 +/- 0.3, S/B 5.0 +/- 0.2) and strong rim enhancement (score 1.8 +/- 0.1). Albumin-(Gd-DTPA)30 produced the best and most time-persistent angiograms (score 2.6 +/- 0.2, S/B 7.4 +/- 0.2), but minimal rim enhancement (score 0.3 +/- 0.2). CONCLUSIONS: The Gd-DTPA-24-cascade-polymer demonstrated the useful combination of strong tumor rim enhancement and detailed angiographic definition of peritumoral vessels. These are advantages associated with extracellular and blood pool contrast media, respectively.

Adenocarcinoma↗
PubMed1995

Tumor angiography using high-resolution, three-dimensional magnetic resonance imaging: comparison of gadopentetate dimeglumine and a macromolecular blood-pool contrast agent.

RATIONALE AND OBJECTIVES: We compared the peritumoral vascular definition in rats using either a paramagnetic extracellular or a macromolecular contrast medium in combination with high-resolution magnetic resonance (MR) imaging. METHODS: High-resolution, three-dimensional spoiled gradient-refocused acquisition in a steady state (SPGR) images were acquired from tumor-bearing Fischer-344 rats before, immediately after, and again 40 min after administration of gadopentetate dimeglumine (0.1 mmol Gd/kg; n = 10) and albumin-(Gd-DTPA)30 (0.05 mmol Gd/kg; n = 5). Small peritumoral vessels were analyzed semiquantitatively on maximum intensity projection angiograms using a 4-point scoring system; quantitative analyses included signal-to-background ratios (SBRs) and signal-to-noise ratios. RESULTS: Gadopentetate dimeglumine caused a transient and low-scoring (0.2 +/- 0.1, SBR = 1.9 +/- 0.2) vessel definition but strong rim enhancement (score = 1.4 +/- 0.2). Albumin-(Gd-DTPA)30 produced persistent, high-quality angiograms (score = 2.6 +/- 0.2, SBR = 7.4 +/- 0.2) but minimal rim enhancement (score = 0.3 +/- 0.2). CONCLUSION: Albumin-(Gd-DTPA)30 combined with high-resolution MR imaging produces time-persistent, detailed angiographic definition of peritumoral vessels. Vascular maps obtained with gadopentetate dimeglumine enhancement are not time persistent or of equal quality.

Adenocarcinoma↗
PubMed1994

Contrast-enhanced magnetic resonance imaging estimation of altered capillary permeability in experimental mammary carcinomas after X-irradiation.

RATIONALE AND OBJECTIVES: Dynamic magnetic resonance imaging (MRI) enhanced with a macromolecular contrast medium, albumin-(Gd-DTPA)35, was used to detect changes in microvascular characteristics in R3230 mammary adenocarcinomas induced by x-irradiation. METHODS: Tumors were implanted in either flank in nine rats. One of the tumors was exposed to single-dose x-irradiation (30 Gy) 3 days before MRI. The contralateral control tumor was shielded from irradiation. RESULTS: Capillary permeability to macromolecular contrast medium in irradiated tumors was elevated significantly (P < .05) compared to the control nonirradiated tumors. The mean estimated permeability surface area product for the irradiated tumors increased more than three-fold; 0.511 +/- .046 mL hr-1 cm-3 compared with 0.121 +/- .011 mL hr-1 cm-3 for the nonirradiated tumors. This radiation-induced increase in permeability was corroborated using a macromolecular Evans blue-protein complex measured in the same tumors using an invasive spectrophotometric technique. CONCLUSIONS: Dynamic MRI-enhanced with macromolecular contrast medium permits noninvasive quantitative estimates of capillary permeability in tumors, with and without x-irradiation. Because the transendothelial permeability for macromolecular solutes likely influences tumoral accumulation of macromolecular chemotherapeutic agents, this noninvasive technique may prove to be clinically useful in tailoring tumor treatment programs which combine radiation and chemotherapy.

Adenocarcinoma↗
PubMed1993

Measurement of capillary permeability to macromolecules by dynamic magnetic resonance imaging: a quantitative noninvasive technique.

A simple, linear kinetic model has been developed for the noninvasive assessment of capillary permeability to macromolecules in the rat by dynamic magnetic resonance imaging using albumin-Gd-DTPA. Data required by the model are signal intensity responses from a target tissue and a venous structure such as inferior vena cava before and after bolus intravenous injection of albumin-Gd-DTPA. Additional requirements include an early temporal resolution of approximately one image/min and a blood sample for hematocrit. The model does not require measurement of albumin-Gd-DTPA concentration in either arterial or venous blood. Pilot experiments suggest that this technique is adequate for estimation of the fractional leak rate of macromolecules from plasma to interstitial water as well as tissue plasma volume, the product of which yields a measure of the permeability surface area product of the tissue if the extraction fraction is modest (< 0.2). The technique may be generally applicable to the study of abnormal capillary permeability in humans as well as animals.

Algorithms↗