FieldStrength Publication for the Philips MRI Community Issue 35 September / October 2008 Multi-parametric 3.0T MRI provides excellent prostate imaging Three different centers show that advances in imaging facilitate diagnosis, localization, staging and treatment of prostate lesions This article is part of Field Strength issue 35, Sept./Oct. 2008
Multi-parametric 3.0T MRI provides excellent prostate imaging Three different centers show that advances in imaging facilitate diagnosis, localization, staging and treatment of prostate lesions The combination of the Achieva 3.0T MRI scanner and the 3.0T Endo coil is facilitating diagnosis, staging, pre-surgical or pre-radiation planning and follow up for patients who have had suspicious findings on PSA tests or biopsies. With more signal and more power, 3.0T MR imaging can help delineate areas of abnormality that can be used for targeted biopsies in men who have had standard sextant biopsies without conclusive findings. And MR spectroscopy at 3.0T provides unique functional data on molecular biomarkers in the prostate that typically indicate the presence of cancer. MR prostate imaging is becoming more widely used, and Philips is ahead of the curve with the development of a 3.0T solution for high quality, robust imaging of the prostate. The 3.0T Endo coil a co-development of Philips and Medrad for use with Achieva 3.0T X-series conforms to the shape and size of the prostate for reliable contact. The coil provides optimum signal-tonoise ratio, especially when combined with a multi-element coil such as the Philips 6-channel SENSE Cardiac coil. lesion recurrence. Spectroscopy is a signal-to-noise limited technique, so at 3.0T, clinicians have access to smaller voxels than at 1.5T, which creates higher resolution spectroscopic images. After acquiring these images, Philips SpectroView provides simple, efficient processing and analysis of 3D spectroscopic datasets for improved workflow. SpectroView automatically delivers quantification of metabolites, with a clear display of the choline-to-citrate ratio. Advanced imaging techniques such as 3D MR spectroscopy add to the specificity of prostate MR imaging. MR spectroscopy provides information about the chemical balance within the prostate by showing levels of certain indicative metabolites such as choline, polyamines and citrate. In healthy prostate tissue, citrate and polyamine levels are high and choline levels are low. In tumors, the ratio is inverted. Spectroscopy thus helps to distinguish between healthy and abnormal prostate tissue by virtue of its ability to determine these metabolite levels, and can support that a low signal intensity on a T2-weighted MR image is actually an abnormal lesion. These metabolite levels can also be tested after treatment, to check for a possible Philips MR clinical scientist Harry Friel worked with several sites during development and integration of the Endo coil on the Achieva 3.0T. The extraordinary signal of the 3.0T Endo coil enables high resolution T2-weighted, diffusion weighted, DCE and spectroscopic imaging. 14 FieldStrength Issue 35 September / October 2008
University of Texas appreciates large field of view The University of Texas Health Science Center (UTHSCSA, San Antonio, Texas, USA) was the first 3.0T prostate imaging center in Texas. The center takes referral patients from all over the U.S. and performs up to five prostate MR exams every week on the Achieva 3.0T. Adam Jung, M.D., P.I., Prostate Imaging Group at UTHSCSA, says, Going from 1.5T to 3.0T, there is a theoretical two-fold increase in the SNR, so we get increased signal from the prostate. That SNR increase can be utilized in several ways. Of course, we get much greater detail and better resolution. We can decrease acquisition time, which is much more comfortable for the patient. We can also improve dynamic temporal resolution and diffusion weighted image quality. The increased SNR also shows apparent improvements in MR spectroscopy with smaller voxel resolution and metabolite dispersion. The center s current protocol starts with taking multiplanar survey images to assess for coil placement, explains Dr. Jung. We then get a large-fov T1- weighted scan that extends from the pubic symphysis all the way to the aortic bifurcation, primarily to image the lymph nodes and bones. We also use the T1-weighted images to evaluate for post-biopsy hemorrhage. We then acquire multiplanar T2-weighted images and diffusion weighted imaging to assess for macroscopic and microscopic structural changes respectively. Lastly, we acquire dynamic contrast-enhanced (DCE) images, which are great for looking at the neovascular and angiogenesis changes of the prostate lesion. Dr. Jung uses both the 3.0T Endo coil and the SENSE Cardiac coil for signal acquisition. We simply plug both coils into the scanner interface and set the machine to acquire the signal in dual-coil mode, he says. Fig. 1 Prostate cancer 58-year-old male with minimal disease on ultrasound guided biopsy two years ago and recent PSA rise. Axial T2-weighted image shows discrete focal region of decreased signal (left circle), which shows early contrast uptake on DCE and diffusion restriction on DWI/ADC imaging. The right circle indicates a relatively uncommonly localized benign prostatic hyperplastic nodule. This exam illustrates that 3.0T MRI with combined Endo coil and SENSE Cardiac coil provides higher resolution than 1.5T, allows use of SENSE and diminished overall scan time, as well as improved DWI image quality and DCE temporal resolution. Contributed by Dr. Jung. T2-weighted ADC DCE When imaging lower risk patients, the so-called watchful waiting or active surveillance patients, Dr. Jung often performs an MRI scan and advises the urologist to re-biopsy specific locations. Using this method in about 22 patients, he has seen sensitivity and specificity greater than 80 percent in his preliminary findings. This has never been documented before in a group of these lower risk patients and the preliminary results are very encouraging. FieldStrength 15
3.0T spectroscopy offers more signal and better spectral dispersion of the peaks. UTHSCSA Prostate MR team: Gilbert Cortez, Steve Ware, R.N., Adam J. Jung, M.D., Rulon Hardman, M.D., Abelardo Gonzalez, Chris Peng, Ph.D. Using a 3.0T system for MR spectroscopy provides the proper peaks, says Dr. Jung. 3.0T spectroscopy offers more signal and better spectral dispersion of the peaks. At 1.5T, the peaks were overlapping, but at 3.0T these are dispersed further, because of the improved spectral resolution. The increased SNR also provides for smaller voxel sizes (i.e., better spatial resolution) and hence, less volume averaging. MR spectroscopy combined with diffusion weighted, dynamic and anatomic T2-weighted imaging provides a multi-parametric MR approach and a much more complete picture of the prostate lesion. Dr. Jung notes, While the learning curve for prostate imaging at 3.0T is still in place, the images that we get are superbly detailed. We are still gaining a lot of experience in interpreting these high resolution images and there are things we see now that we just did not see at 1.5T, especially post-biopsy related morphologic changes. Symbion Research Clinical Imaging Center values more homogeneous image Ron Shnier, M.D. Ron Shnier, M.D, is using 3.0T prostate MR to image several patients a week at Symbion Research Clinical Imaging Center (Prince of Wales Research Imaging Center, Randwick, Sydney, Australia). There is a definite role for prostate MR in patients with a slowly rising PSA, whose Gleason score and clinical evaluation and/or PSA do not match, says Dr. Shnier. After doing endorectal MRI for years at 1.5T, we find that 3.0T provides better imaging and spectroscopy to help us diagnose suspicious prostate lesions, says Dr. Shnier. And the 3.0T endorectal coil has given us superb image quality. Using a combination of the Endo coil and the SENSE Torso coil, Dr. Shnier is getting a much more homogenous signal around the prostate, as well as better visualization of the anterior prostatic tissue. The combination enables us to comment on the degree, if any, of macroscopic spread beyond the prostatic capsule and peri-prostatic lymph nodes, he explains. Dr. Shnier says MR imaging and MR spectroscopy are always used in tandem for prostate patients. With the added benefit of MR spectroscopy, we have had the occasional case where the anatomical MR image was normal but the spectroscopy was abnormal. 16 FieldStrength Issue 35 September / October 2008
After doing endorectal MRI for years at 1.5T, we find that at 3.0T the examination using the Endo coil has given us superb image quality. T2-weighted T2-weighted DWI ADC map Spectroscopy left side Spectroscopy right side Fig. 2 Prostate carcinoma A 65-year-old male with positive prostate biopsy underwent 3.0T MRI with SENSE Torso and Endo coil. This exam helped to localize the area of neoplastic change in the left side of prostate and confined to the gland. On high resolution T2-weighted TSE the lesion shows low signal. On DWI and the corresponding ADC image the lesion is seen as an area of restricted diffusion. 3D CSI showed decreased citrate peak in area of disease. The patient was therefore a candidate for radical prostatectomy. Contributed by Dr. Shnier. FieldStrength 17
National Cancer Institute uses Endo coil with Achieva for higher matrix size, better resolution Peter L. Choyke, M.D. Peter L. Choyke, M.D., Chief of Molecular Imaging at the National Cancer Institute (NCI, Bethesda, Maryland, USA), is a leading U.S. expert in the field of prostate imaging and associated research. He says that in addition to assisting diagnosis and staging, prostate MR is changing the way prostate lesion treatment is planned. Until now, lesions were treated by different modalities depending upon whether they went beyond the prostate or not. For instance, if there were lesions outside the prostate gland, that patient wouldn t be a surgical candidate. But with more accurate techniques such as MR, surgeons can plan to take a wider margin of tissue at the site where extracapsular extension is suspected. Many times the margin at the time of pathological evaluation is negative, indicating that the lesion has escaped from the gland but not from the surgical specimen. Similarly, radiation oncologists are able to deliver radiation to the tumor site but avoid the surrounding healthy tissue and nerves. These precise margins are the key to aggressively treating the lesion while sparing the nerves that determine erectile and urinary function after treatment. Dr. Choyke uses the Endo coil with his Achieva 3.0T for higher matrix size and better resolution. I believe there is a common misconception about how uncomfortable the endorectal coil is, he says. But having done hundreds of these exams, very few men have had significant discomfort during an exam. It s not something that men should be fearful of, or radiologists should be reluctant to do because of patient discomfort. Fig. 3 Prostate adenocarcinoma A 73-year-old male with a PSA value of 45 ng/ml and negative sextant transrectal ultrasound guided prostate biopsy underwent an MR examination on Achieva 3.0T using the Endo coil 3.0T and the SENSE Cardiac coil. The T2-weighted images show a round shaped suspicious lesion of low signal intensity in the right mid peripheral zone (arrows). The apparent diffusion coefficient (ADC) map reconstructed from diffusion weighted images confirms the right mid peripheral zone lesion (lower arrow). Moreover, it demonstrates an additional lesion in the right transitional zone (upper arrow). The green DCE curve corresponding to the ROI on the lesion (left) shows faster wash-in and wash-out than to the normal side (right). The blue curve corresponds to the arterial signal in the left femoral artery. MR Spectroscopy demonstrates elevated choline (Cho) compared to Citrate (Cit) in the lesion (left), while the opposite side of the prostate shows normal spectral signal. Images on top of spectra show (left to right) the low signal lesion on the sagittal T2-weighted image, the spectral grid with voxels of displayed spectra highlighted and the Choline to Citrate ratio map superimposed on the axial T2-weighted image. Contributed by Peter Choyke, Baris Turkbey, M.D., National Cancer Institute. Axial T2-weighted Sagittal T2-weighted Coronal T2-weighted ADC map 18 FieldStrength Issue 35 September / October 2008
Net Forum Extended cases and ExamCards are in preparation for www.philips.com/netforum Better prostate care with MR imaging and MR spectroscopy Because of the increased resolution of 3.0T imaging, MR is expected to become a more routine part of the diagnostic armamentarium for prostate lesions. We continue to see improvement in MR imaging, and there will be even better technologies looking forward, says Dr. Choyke. For instance, if we can identify the location of the lesion more accurately, we can potentially focally treat patients, to reduce the disability that comes from a radical prostatectomy. MR imaging is definitely a part of that possibility. Having done hundreds of Endo coil exams, very few men have had significant discomfort during an exam. DCE lesion DCE normal MR Spectroscopy abnormal MR Spectroscopy normal FieldStrength 19
2008 Koninklijke Philips Electronics N.V. All rights are reserved. Philips Healthcare reserves the right to make changes in specifications and/ or to discontinue any product at any time without notice or obligation and will not be liable for any consequences resulting from the use of this publication. Philips Healthcare is part of Royal Philips Electronics www.philips.com/healthcare healthcare@philips.com fax: +31 40 27 64 887 Printed in The Netherlands Sept 2008 Philips Healthcare Global Information Center P.O. Box 1286 5602 BG Eindhoven The Netherlands