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Biomedical subjects

A D MacVicar

Publications and source records attributed to A D MacVicar.

11 recordsLinked to original sources
PubMed2001

Effects of androgen deprivation on prostatic morphology and vascular permeability evaluated with mr imaging.

PURPOSE: To assess magnetic resonance (MR) measures of vascular permeability of prostate cancer treated with androgen deprivation and to correlate these with morphologic appearances and serum prostate-specific antigen (PSA) levels. MATERIALS AND METHODS: MR examinations in 56 consecutive patients with prostate cancer were performed before and after luteinizing hormone-releasing hormone analog treatment. T2-weighted and contrast medium-enhanced T1-weighted MR images were obtained. Pre- and posttreatment comparisons of morphologic features, glandular volume, and enhancement-related parameters (capillary permeability, leakage space, gadolinium accumulation) were made. RESULTS: Fifty-five tumors were seen before treatment; 42, after treatment. Signal intensity in the peripheral zone and seminal vesicles decreased on T2-weighted images in 42 (75%) and 25 (45%) patients, respectively. Median volume in tumor decreased by 65% (95% CI: 55%, 76%); in central gland, by 30% (95% CI: 25%, 35%). Reductions in tumor permeability (P <.001) and changes in washout patterns were observed (P <.001). Tumor permeability reductions coincided with a decrease in serum PSA levels in 91% of patients. A weak correlation between tumor permeability and volume change was seen (r = 0.55, P =.04). Reductions in peripheral zone (P <.001) and central gland (P =.009) permeability were noted. CONCLUSION: Androgen deprivation decreases tumor volume and vascular permeability and impairs detection of prostate cancers. Use of MR estimates of permeability may be an additional way of assessing prostatic tumor response to antiandrogen treatment.

Aged↗
PubMed2000

Symptomatic brachial plexopathy following treatment for breast cancer: utility of MR imaging with surface-coil techniques.

PURPOSE: To investigate the clinical utility and diagnostic accuracy of magnetic resonance (MR) imaging in patients with symptomatic brachial plexopathy following treatment for breast cancer. MATERIALS AND METHODS: Fifty patients with symptoms of brachial plexopathy (principally pain, weakness, and paresthesia) who had received treatment for breast cancer, which included surgery, radiation therapy, and cytotoxic chemotherapy, underwent MR imaging at 1.5 T. MR imaging was performed by using a body coil, which was supplemented with surface-coil imaging of the cervical spine and shoulder-coil imaging of the brachial plexus. At review, two observers attempted to discriminate between tumor recurrence and nonmalignant causes of symptoms. The diagnosis was verified with histologic analysis or a follow-up of at least 12 months. RESULTS: Of 27 patients demonstrated to have tumor recurrence, 26 were correctly identified by using MR imaging; the recurrence was directly related to the brachial plexus in 17. During the follow-up, 21 patients remained free of recurrence, 20 of whom were determined to have a nonmalignant cause of symptoms. Two of the 50 patients were excluded from the analysis. The MR criteria used for detection of tumor yielded a sensitivity of 96%, specificity of 95%, positive predictive value of 96%, and negative predictive value of 95%. CONCLUSION: MR imaging is reliable and accurate in the diagnosis of symptomatic brachial plexopathy following breast cancer therapy.

Adult↗
PubMed2000

Magnetic resonance spectroscopy in the evaluation of neurotoxicity following cranial irradiation for childhood cancer.

In order to evaluate the role of proton MR spectroscopy (1H-MRS) in the diagnosis and assessment of long-term radiation-related neurotoxicity, 14 children who had received cranial irradiation for the treatment of childhood leukaemia (n = 6) or brain tumours (n = 8) underwent 1H-MRS, MRI and neuropsychological assessment. Short-term effects at 2 months following treatment were studied in a further three patients. MRI abnormalities were observed in nine patients. No statistically significant differences between patients and controls (n = 17) were seen in any of the calculated 1H-MRS metabolite ratios, in any of the three patient groups. On multivariate logistic regression analysis there was a correlation between the choline/water ratio and a low IQ. It is concluded that any systematic radiation-induced changes in the 1H MRS metabolites must be below the detection threshold of this study.

Adolescent↗
PubMed1998

T1-weighted magnetic resonance imaging in breast cancer vertebral metastases: changes on treatment and correlation with response to therapy.

PURPOSE: To document the MR appearances of vertebral metastases in breast cancer on treatment and to determine whether a single T1-weighted (T1-W) sequence of the spine could provide a quick and effective method of response assessment. PATIENTS AND METHODS: One-hundred and nine spinal magnetic resonance (MR) examinations in 41 metastatic breast cancer patients on treatment were reviewed. The changes in number, size and signal intensity of vertebral metastases during 68 intervals (mean length 6.9 months) were documented. T1-W signal intensity (SI) before and after treatment was assigned to three patterns: (A) low homogeneous SI; (B) low heterogeneous SI; and (C) high homogeneous SI. For each interval between MR examinations, an objective assessment of the overall response (disease regression, no change, disease progression) to treatment of metastases was made based on standard assessment criteria. RESULTS: The number and size of treated vertebral metastases increased in 47% and 43% of cases and showed no change in 53% and 54% of cases, respectively. A reduction in size of lesions was seen in 3% of cases only and no reduction in the number of lesions was seen. T1-W [corrected] signal intensity changes occurred in approximately one-third of cases documented. The most commonly observed SI change in 25% of all intervals (17 of 68) was from type A to type B. There was no correlation between SI change and response to therapy. T1-W [corrected] MR response assessment, based on changes in size and number of vertebral metastases, accurately predicted progression of disease in 79% of cases and stable disease in 75% of cases. It did not predict regression of disease. CONCLUSION: A T1-W MR spinal assessment is a simple and effective method of evaluation of therapeutic response of lytic and sclerotic vertebral metastases in breast cancer being able to distinguish patients with progressive disease from those with a favourable response (no change or disease regression) to therapy. These findings have important clinical implications.

Breast Neoplasms↗
PubMed1998

Correlation of CT with histopathological findings in patients with gastric and gastro-oesophageal carcinomas following neoadjuvant chemotherapy.

UNLABELLED: Gastric carcinoma is the fourth commonest cause of death from malignant disease in United Kingdom. In the Western hemisphere, it usually presents with advanced disease, which contributes to its very poor prognosis. Pre-operative (neoadjuvant) chemotherapy offers the possibility of down-staging such tumours and the potential to render tumours operable. Computed tomography (CT) plays a central role in the assessment of patients presenting with the disease, and in those who undergo chemotherapy, in evaluating their response. OBJECTIVE: This study was undertaken to evaluate the role of CT in predicting loco-regional spread of tumour following neoadjuvant chemotherapy in non-metastatic gastric and gastro-oesophageal cancers. METHODS AND MATERIALS: We correlated CT evidence of loco-regional spread with pathological findings following surgery in 21 patients who received pre-operative chemotherapy. RESULTS: Residual masses were seen on CT in 19 patients, and 15 contained active tumour, although in four patients no viable tumour was demonstrated at histopathology. The overall accuracy of CT in assessing loco-regional disease was disappointing with sensitivities, specificities, positive and negative predictive values of 57%, 43%, 75% and 33%, respectively. CONCLUSIONS: We conclude that CT is not accurate in identifying residual loco-regional spread and therefore should not preclude surgery in those patients who have received neoadjuvant chemotherapy.

Adult↗
PubMed1998

Magnetic resonance imaging of prostate cancer: comparison of image quality using endorectal and pelvic phased array coils.

OBJECTIVE: To compare endorectal coil (ERC) and pelvic phased array (PPA) coil magnetic resonance imaging for delineation of the prostate gland and seminal vesicles. To compare ERC images at different inflation volumes of the ERC air balloon. MATERIALS AND METHODS: Twenty-one patients underwent T2-weighted examinations using PPA and ERC. The ERC evaluations were performed at three balloon inflation volumes (60, 100 and 140 ml). All patients had proven prostate cancer. Images were analysed for visibility of anatomic structures, gland distortion, tumour visualization, artefacts (coil flare, coil-related artefact and rectal movement) and overall image quality. A grading system was used for each parameter. RESULTS: ERC assessments at increasing balloon inflations showed equivalent anatomical detail and overall image quality. However, increasing gland distortion and decreasing coil related flare was found with higher air inflations (P = 0.13 and P = 0.006, respectively). When compared with ERC images, visibility of the anterior gland and neurovascular bundles was better with the PPA coil (P = 0.0001 and 0.002, respectively). The overall image quality was superior with the PPA coil (P = 0.0001). However, no significant difference in visualization of tumour or delineation of tumour extent was observed between the two techniques. CONCLUSIONS: PPA imaging of the prostate gland provides images of superior quality compared with the ERC. This is mainly due to fewer artefacts with the PPA coil and improved anterior gland visibility. When ERC is used, air inflation to at least 100 ml reduces coil flare artefact.

Aged↗
PubMed1997

Treated thymic lymphoma: comparison of MR imaging with CT.

PURPOSE: To determine the appearance of treated thymic lymphoma at magnetic resonance (MR) imaging and to compare the results with findings from posttherapy computed tomography (CT) and clinical outcome. MATERIALS AND METHODS: MR images and CT scans in 25 patients with thymic lymphoma were reviewed. Dimensions of residual masses on MR and CT images were compared. Signal intensity on MR images was assigned to four patterns: (a) low heterogeneous, (b) low homogeneous, (c) high heterogeneous, and (d) high homogeneous. The presence of cysts, calcification, and fatty infiltration was noted. Abnormality of intrathoracic nodes was also documented. RESULTS: Dimensions of residual thymic masses were greater on MR images than on CT scans. The signal intensity pattern was low homogeneous or heterogeneous in 19 patients. Two of these patients had relapse within 1 year. High heterogeneous signal intensity was observed in five patients, four of whom had relapse. Cysts were seen at MR imaging in six patients, of whom one had relapse, but were seen in only one patient at CT. CONCLUSION: Treated thymic lymphoma usually has low signal intensity on MR images regardless of residual mass size, and cysts of high signal intensity may be seen. Relapse occurred mainly in large-volume masses or masses of high heterogeneous signal intensity, indicating that close follow-up or biopsy should be considered in such cases.

Adolescent↗
PubMed1996

Primary breast cancer: mammographic changes after neoadjuvant chemotherapy, with pathologic correlation.

PURPOSE: To correlate changes depicted at mammography during neo-adjuvant chemotherapy for operable breast carcinoma with subsequent pathologic status. MATERIALS AND METHODS: Patients (n = 107) underwent mammography before and after neoadjuvant chemotherapy, prior to surgery. Four retrospectively determined grades of response at mammography included complete, mammographic (decreased size and/or density), stable disease, or progressive disease. RESULTS: In 95 fully assessable patients, grade of response to chemotherapy was complete in eight (9%), mammographic in 78 (82%), stable disease in seven (7%), and progressive disease in two (2%). Before and after treatment, respectively, 64 (67%) and 20 (21%) masses were greater than 2 cm in bidimensional diameter. Response was not complete in any of the 44 (46%) cases of microcalcifications. At histologic examination after surgery in 95 fully assessable patients, five of eight patients with complete response were found to have residual tumor (three with an invasive component); eight were found to have no residual tumor (response in three was complete; in four, mammographic; and in one, stable disease). CONCLUSION: Whereas mammograms in most patients showed some response to chemotherapy, prediction of pathologic outcome was not possible.

Antineoplastic Agents↗
PubMed1992

Multiple myeloma: appearance at MR imaging.

Magnetic resonance (MR) imaging examinations of the lumbar spine and clinical and laboratory findings in 32 patients with multiple myeloma were reviewed. On T1-weighted images, signal intensity (SI) of the vertebrae approximated that of muscle in 14 cases and was intermediate (between the SIs of muscle and fat) in 18. Definite foci of decreased SI were seen in eight cases (25%), and foci of increased SI, representing fatty infiltration, were seen in 12 (38%). On T2-weighted images, SI approximated that of muscle in 17 cases and was intermediate in 15. Definite foci of increased SI were seen in 17 (53%). Of 38 vertebral compression fractures (including 18 in nine additional patients), foci of abnormal SI consistent with tumor on either T1- or T2-weighted images were seen in 19 cases (50%). There was no correlation between MR imaging findings and laboratory or bone marrow findings. Foci of presumed tumor were better or exclusively shown on T2-weighted images in 11 of 17 patients (65%) with identifiable focal disease. Other suggestions of multiple myeloma on T1-weighted images may be the absence of fatty replacement or a generalized decrease in SI.

Female↗
PubMed1992

Ewing sarcoma: MR imaging of chemotherapy-induced changes with histologic correlation.

In a study group of 18 consecutive patients with Ewing sarcoma proved by means of biopsy, the signal intensity characteristics of tumor on magnetic resonance (MR) images were assessed before and after chemotherapy. Sixteen patients underwent MR imaging at 1.5 T before chemotherapy; all 18 patients underwent MR imaging at 1.5 T within 10 days after chemotherapy. Standard spin-echo sequences were used with T1 and T2 weighting in all patients. The primary tumor was visualized in all 16 patients who underwent MR imaging before chemotherapy. Histologic correlation, obtained in 14 patients, showed that areas of high T2-weighted signal intensity on MR images obtained after chemotherapy may represent tumor necrosis, cystic hemorrhagic areas, and fibroblastic repair tissue. In 10 patients (71%), microscopic clusters of viable tumor cells were depicted in areas of both low and high signal intensity after treatment. It is concluded that MR imaging is unreliable for exclusion of active disease, although a pattern of change in signal intensity is qualitative evidence of chemotherapeutic effect.

Adolescent↗