Gary P Liney

Correlation of ADC and T2 Measurements With Cell Density in Prostate Cancer at 3.0 Tesla

Objectives:To assess the relationship between MRI derived parameters (apparent diffusion coefficient (ADC) and T2 relaxation time) and tumor cellularity as determined from whole mounted radical prostatectomy specimens, for both prostatic carcinoma and normal peripheral zone tissue. Materials and Methods:Over a 16-month period, 20 patients (mean age: 61 years, range: 42–70 years) were prospectively recruited. Diffusion and T2 imaging were performed on a 3.0 Tesla scanner to enable subsequent ADC and T2 calculation. After radical retropubic prostatectomy specimens were whole-mounted and regions of interest (ROIs) drawn in areas of prostatic carcinoma and normal peripheral zone. Cell density was then determined using an adaptive histogram thresholding technique. Differences in tissue type were explored using the unpaired t test while the relationship between parameters was assessed using scatter-plots and the Pearson correlation coefficient. Results:Significant differences (P < 0.0001 in all cases) were noted between peripheral zone tissue and prostatic carcinoma in terms of ADC (1.88 ± 0.22 vs. 1.43 ± 0.19 × 10−3 mm2/s), T2 (142 ± 24 vs. 109 ± 20 milliseconds), and cell density (9.4% ± 3.0% vs. 19.8% ± 5.3%). A significant negative correlation with cell density was noted for both ADC (R = −0.695, P < 0.0001) and T2 (R = −0.505, P = 0.001). Trends for increased cell density, decreased ADC, and decreased T2 with increasing Gleason score were also noted. Conclusions:ADC and to a lesser extent T2 are good indicators of cell density. Because of the potential link with Gleason score, MRI derived parameters may have a prognostic role with regard to potential metastatic activity and tumor aggressiveness.

Correlation of diffusion-weighted magnetic resonance data with cellularity in prostate cancer

To assess the relationship between the apparent diffusion coefficient (ADC) on magnetic resonance imaging (MRI) and cell density (CD) obtained from radical prostatectomy (RP) specimens.

Comparison of quantitative T2 mapping and diffusion-weighted imaging in the normal and pathologic prostate.

In this study, diffusion‐weighted images of the human prostate were successfully obtained, enabling quantification of apparent diffusion coefficients (ADCs) in normal and pathologic regions. A dual acquisition fast spin‐echo sequence was used for accurate T2 calculation. T2 values were significantly higher in the peripheral zone than the central gland (P = 0.015). No significant correlations were found in either normal or pathologic tissue between ADC values and relaxation rates for all three gradient directions and the orientationally averaged water diffusion coefficient. Evidence suggesting that diffusional anisotropy is present in normal prostatic tissue is also detailed, with significant differences noted between the z‐component and both the x‐ and y‐components of the ADC for peripheral zone (P < 0.040) and central gland (P < 0.001). Magn Reson Med 46:1054–1058, 2001.

Magnetic resonance imaging screening in women at genetic risk of breast cancer: imaging and analysis protocol for the UK multicentre study

The imaging and analysis protocol of the UK multicentre study of magnetic resonance imaging (MRI) as a method of screening for breast cancer in women at genetic risk is described. The study will compare the sensitivity and specificity of contrast-enhanced MRI with two-view x-ray mammography. Approximately 500 women below the age of 50 at high genetic risk of breast cancer will be recruited per year for three years, with annual MRI and x-ray mammography continuing for up to 5 years. A symptomatic cohort will be measured in the first year to ensure consistent reporting between centres. The MRI examination comprises a high-sensitivity three-dimensional contrast-enhanced assessment, followed by a high-specificity contrast-enhanced study in equivocal cases. Multiparametric analysis will encompass morphological assessment, the kinetics of contrast agent uptake and determination of quantitative pharmacokinetic parameters. Retrospective analysis will identify the most specific indicators of malignancy. Sensitivity and specificity, together with diagnostic performance, diagnostic impact and therapeutic impact will be assessed with reference to pathology, follow-up and changes in diagnostic certainty and therapeutic decisions. Mammography, lesion localisation, pathology and cytology will be performed in accordance with the UK NHS Breast Screening Programme quality assurance standards. Similar standards of quality assurance will be applied for MR measurements and evaluation.

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. J. Magn. reson. Imaging 1999; 9:311–316.

Age, gender, and skeletal variation in bone marrow composition: A preliminary study at 3.0Tesla

To evaluate the efficacy of MR Spectroscopy (MRS) at 3.0 Tesla for the assessment of normal bone marrow composition and assess the variation in terms of age, gender, and skeletal site.

Dynamic contrast-enhanced MRI in the differentiation of breast tumors: user-defined versus semi-automated region-of-interest analysis.

Dynamic contrast‐enhanced MR mammography is an increasingly used method of evaluating breast pathology. The purpose of this study was to compare two semi‐automated methods of region of interest (ROI) analysis with a user‐defined method, in the discrimination of breast tumors using dynamic contrast‐enhanced MRI. Results are presented from the retrospective analysis of 81 malignant and 36 benign breast lesions. The study demonstrates the importance of a consistent ROI strategy and also shows that semi‐automated approaches offer a standardized method, which may improve the discrimination of primary breast tumors. J. Magn. Reson. Imaging 1999; 10:945–949.

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.

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. Copyright

The Potential for an Enhanced Role for MRI in Radiation-Therapy Treatment Planning

The exquisite soft-tissue contrast of magnetic resonance imaging (MRI) has meant that the technique is having an increasing role in contouring the gross tumor volume (GTV) and organs at risk (OAR) in radiation therapy treatment planning systems (TPS). MRI-planning scans from diagnostic MRI scanners are currently incorporated into the planning process by being registered to CT data. The soft-tissue data from the MRI provides target outline guidance and the CT provides a solid geometric and electron density map for accurate dose calculation on the TPS computer. There is increasing interest in MRI machine placement in radiotherapy clinics as an adjunct to CT simulators. Most vendors now offer 70 cm bores with flat couch inserts and specialised RF coil designs. We would refer to these devices as MR-simulators. There is also research into the future application of MR-simulators independent of CT and as in-room image-guidance devices. It is within the background of this increased interest in the utility of MRI in radiotherapy treatment planning that this paper is couched. The paper outlines publications that deal with standard MRI sequences used in current clinical practice. It then discusses the potential for using processed functional diffusion maps (fDM) derived from diffusion weighted image sequences in tracking tumor activity and tumor recurrence. Next, this paper reviews publications that describe the use of MRI in patient-management applications that may, in turn, be relevant to radiotherapy treatment planning. The review briefly discusses the concepts behind functional techniques such as dynamic contrast enhanced (DCE), diffusion-weighted (DW) MRI sequences and magnetic resonance spectroscopic imaging (MRSI). Significant applications of MR are discussed in terms of the following treatment sites: brain, head and neck, breast, lung, prostate and cervix. While not yet routine, the use of apparent diffusion coefficient (ADC) map analysis indicates an exciting future application for functional MRI. Although DW-MRI has not yet been routinely used in boost adaptive techniques, it is being assessed in cohort studies for sub-volume boosting in prostate tumors.