Treatment planning for prostate implants using magnetic-resonance spectroscopy imaging Journal Article


Authors: Zaider, M.; Zelefsky, M. J.; Lee, E. K.; Zakian, K. L.; Amols, H. I.; Dyke, J.; Cohen, G.; Hu, Y. C.; Erdi, A. K.; Chui, C. S.; Koutcher, J. A.
Article Title: Treatment planning for prostate implants using magnetic-resonance spectroscopy imaging
Abstract: Purpose: Recent studies have demonstrated that magnetic-resonance spectroscopic imaging (MRSI) of the prostate may effectively distinguish between regions of cancer and normal prostatic epithelium. This diagnostic imaging tool takes advantage of the increased choline plus creatine versus citrate ratio found in malignant compared to normal prostate tissue. The purpose of this study is to describe a novel brachytherapy treatment-planning optimization module using an integer programming technique that will utilize biologic-based optimization. A method is described that registers MRSI to intraoperative-obtained ultrasound images and incorporates this information into a treatment-planning system to achieve dose escalation to intraprostatic tumor deposits.Methods: MRSI was obtained for a patient with Gleason 7 clinically localized prostate cancer. The ratios of choline plus creatine to citrate for the prostate were analyzed, and regions of high risk for malignant cells were identified. The ratios representing peaks on the MR spectrum were calculated on a spatial grid covering the prostate tissue. A procedure for mapping points of interest from the MRSI to the ultrasound images is described. An integer-programming technique is described as an optimization module to determine optimal seed distribution for permanent interstitial implantation. MRSI data are incorporated into the treatment-planning system to test the feasibility of dose escalation to positive voxels with relative sparing of surrounding normal tissues. The resultant tumor control probability (TCP) is estimated and compared to TCP for standard brachytherapy-planned implantation.Results: The proposed brachytherapy treatment-planning system is able to achieve a minimum dose of 120% of the 144 Gy prescription to the MRS positive voxels using 125I seeds. The preset dose bounds of 100-150% to the prostate and 100-120% to the urethra were maintained. When compared to a standard plan without MRS-guided optimization, the estimated TCP for the MRS-optimized plan is superior. The enhanced TCP was more pronounced for smaller volumes of intraprostatic tumor deposits compared to estimated TCP values for larger lesions.Conclusions: Using this brachytherapy-optimization system, we could demonstrate the feasibility of MRS-optimized dose distributions for 125I permanent prostate implants. Based on probability estimates of anticipated improved TCP, this approach may have an impact on the ability to safely escalate dose and potentially improve outcome for patients with organ-confined but aggressive prostatic cancers. The magnitude of the TCP enhancement, and therefore the risks of ignoring the MR data, appear to be more substantial when the tumor is well localized; however, the gain achievable in TCP may depend quite considerably on the MRS tumor-detection efficiency. Copyright (C) 2000 Elsevier Science Inc.
Keywords: treatment planning; nuclear magnetic resonance imaging; radiotherapy dosage; algorithms; ultrasound; prostate cancer; prostatic neoplasms; prostate; feasibility studies; brachytherapy; magnetic resonance spectroscopy; creatine; radiotherapy planning, computer-assisted; cancer control; radiation dose distribution; physics; ultrasonography, interventional; implantation; optimization; radiobiology; radiation tolerance; tumor control probability; humans; human; male; priority journal; article
Journal Title: International Journal of Radiation Oncology, Biology, Physics
Volume: 47
Issue: 4
ISSN: 0360-3016
Publisher: Elsevier Inc.  
Date Published: 2000-07-01
Start Page: 1085
End Page: 1096
Language: English
DOI: 10.1016/s0360-3016(00)00557-5
PUBMED: 10863082
PROVIDER: scopus
DOI/URL:
Notes: Export Date: 18 November 2015 -- Source: Scopus
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MSK Authors
  1. Michael J Zelefsky
    750 Zelefsky
  2. Gilad N Cohen
    173 Cohen
  3. Howard I Amols
    157 Amols
  4. Marco Zaider
    170 Zaider
  5. Kristen L Zakian
    82 Zakian
  6. Jason A Koutcher
    275 Koutcher
  7. Yu-Chi Hu
    106 Hu
  8. Chen Chui
    144 Chui
  9. Jonathan   Dyke
    10 Dyke
  10. Alev K Erdi
    12 Erdi