Biomedical subjects

A J Knowles

Publications and source records attributed to A J Knowles.

7 recordsLinked to original sources

PubMed1999

In vivo magnetic resonance spectroscopy and dynamic contrast enhanced imaging of the prostate gland.

The quantitation of in vivo 1H MR spectroscopy and dynamic contrast enhanced MR imaging is described for patients with histologically confirmed prostate adenocarcinoma and benign prostatic hypertrophy (BPH). Results are presented which suggest that combined use of these techniques may be helpful in improving the characterization of prostate pathologies and ultimately increase the staging accuracy of magnetic resonance.

Aged↗

PubMed1999

Differentiation of prostatic carcinoma and benign prostatic hyperplasia: correlation between dynamic Gd-DTPA-enhanced MR imaging and histopathology.

One of the major factors limiting the staging accuracy of conventional magnetic resonance imaging (MRI) for prostatic carcinoma, is the similarity in signal intensity between tumor and coexisting benign prostatic hyperplasia (BPH). As neovascularity is an independent indicator of pathological state, dynamic contrast-enhanced MRI may yield additional information. This study correlates the histopathological findings from 12 radical prostatectomy patients on a region-by-region basis, with pharmacokinetic modeling of dynamic contrast-enhanced (0.2 mmol dimeglumine gadopentetate/kg), fast multiplanar spoilt gradient-recalled echo images, using a two-compartment simplex minimization technique. Quantitative analysis demonstrated differences in the amplitude of the initial contrast upslope and contrast exchange rate between tumor and fibromuscular BPH (P<0.03 and P<0.03, respectively) and for the contrast exchange rate between tumor and fibroglandular BPH (P<0.04), providing improved delineation of intraprostatic tumor extent compared with conventional imaging techniques.

Aged↗

PubMed1997

In vivo quantification of citrate concentration and water T2 relaxation time of the pathologic prostate gland using 1H MRS and MRI.

We have previously reported a striking correlation between water T2 relaxation time and citrate concentration in the normal prostate (Liney G.P.; Lowry M.; Turnbull L.W.; Manton D.J.; Knowles A.J.; Blackband S.J.; Horsman A. Proton MR T2 maps correlate with the citrate concentration in the prostate. NMR Biomed. 9:59-64; 1996). In this study we present data from similar studies of the pathologic gland. The findings support the hypothesis that measurement of both citrate concentration and water T2 relaxation time in vivo may aid the differentiation of prostatic carcinoma from benign disease and normal tissue.

Adenocarcinoma↗

PubMed1996

Proton MR T2 maps correlate with the citrate concentration in the prostate.

A significant correlation between water T2 relaxation time and citrate concentration in the normal prostate is demonstrated using spatially localized spectroscopy and water T2 maps. These data imply that MR images may be used to infer the concentration of citrate at high spatial resolution. Preliminary results in patients demonstrate that this relationship is maintained in benign prostatic hyperplasia (BPH) and prostatic carcinoma. The determination of citrate concentration and water T2 may aid the differentiation of prostate carcinoma from BPH and normal tissue.

Adult↗

PubMed1996

Improved peripheral MR angiography with temperature regulation in healthy patients.

Peripheral magnetic resonance (MR) angiography was performed in eight volunteers, with a temperature-controlled water blanket. After warming of the right foot, unobserved vessels became conspicuous in all patients: Average increase in signal intensity was nearly twofold in the major artery and vein depicted. A similar improvement was observed in an examination in one patient with diabetes. Peripheral MR angiography performed after warming provided additional diagnostic information.

Adult↗

PubMedDate not supplied

Comparison of conventional single echo and multi-echo sequences with a fast spin-echo sequence for quantitative T2 mapping: application to the prostate.

The accuracy of water T2 maps generated from a fast spin-echo (FSE) sequence was compared with data obtained by conventional single and multi-echo spin-echo pulse sequences using a commercial gel phantom. Spatially localized stimulated echo acquisition mode (STEAM) proton spectroscopy was also used to confirm the reported water T2 values of the gels contained in the phantom. The FSE sequence was shown to be superior in accuracy to both the single and multi-echo spin echo sequences and comparable to STEAM, producing results that were within 10% of known values. The effectiveness of the FSE sequence was further demonstrated by generating T2 maps of the normal and diseased prostate in clinically acceptable imaging times, resulting in comparable T2 values to those obtained using STEAM. Accurate quantitative T2 maps can be produced with the FSE sequence.

Carcinoma↗

PubMedDate not supplied

A simple method for the correction of endorectal surface coil inhomogeneity in prostate imaging.

A simple method is described that corrects for the intensity inhomogeneity experienced when using endorectal surface coils in prostate imaging. The method uses a series of proton-density-weighted images, which are acquired to demonstrate the sensitivity profile of the coil and used to correct T2-weighted images acquired in the same plane. The results demonstrate improved image uniformity and visualization of prostatic anatomy.

Aged↗