Have an account? Please log in.
Text size: Small font Default font Larger font
Radiology Daily
Radiology Daily PracticalReviews.com Radiology Daily

Distinguishing Radiation Necrosis From Tumor Recurrence with ADC Analysis

September 14, 2009
Posted by: , Filed in: Nuclear Medicine
  • Comments

One of the more perplexing problems in when treating gliomas is the differentiation of recurrent cerebral neoplasm from radiation necrosis.

The challenge is that the presence of an enhancing mass following radiation can be either recurrent cerebral neoplasm or radiation necrosis, and the treatment will change based on the diagnosis.

Methods that have been investigated include perfusion imaging, MR spectroscopy, PET, and SPECT.

A retrospective study postulated that diffusion-weighted imaging may be helpful in distinguishing tumor recurrence from radiation injury.

The Study
Patients who had received radiation treatment for proven high-grade gliomas.

MRI scans of patients were reviewed, and 18 patients with abnormal areas of enhancement were identified. Apparent diffusion coefficient (ADC) maps were calculated, as well as mean ADC values of areas of enhancement and ratios of the ADC in these areas compared with contralateral normal white matter. Results were compared with final diagnosis as established histologically or by clear progression of disease.

ADC ratios and mean ADC in the recurrence patients were significantly lower than in the nonrecurrence patients. ADC ratios measured 1.43 +/- 0.11 in recurrence compared with 1.82 +/- 0.07 for nonrecurrence, and mean ADCs measured 1.18 +/- 0.13 x 10-3 mm/s2 compared with 1.40 +/- 0.17. Mean difference of ADC of enhancing areas from areas of normal contralateral tissue was 0.36 +/- 0.11 x 10-3 mm/s2 and 0.63 +/- 0.10 x 10-3 mm/s2 for nonrecurrence. Additional measurements assessed were not helpful in differentiating recurrence from nonrecurrence.

CME Courses Available:


PET/CT and SPECT/CT To Plan and Monitor the Treatment of Cancer The precise tailoring of treatment for patients with cancer is an unmet challenge. The goal is to only administer treatments that have a high probability of being effective. Imaging with PET/CT and SPECT/CT provides methods that will help achieve this goal. The program covers the current clinical challenges, the new emerging answers from imaging, and how these methods can be applied to patient care. Read more: Nuclear Medicine: PET/CT and SPECT/CT


-- Diagnostic Imaging Review: For Residents, Fellows and Radiologists UCSF’s Department of Radiology and Biomedical Imaging recently conducted its annual radiology review course. It will soon be available in two video formats to meet your needs— DVD and MP4. Order now to get your special pre-publication discount. Read more or order: Diagnostic Imaging Review

Differentiation of tumor recurrence/progression and radiation effects can be determined on the basis of mean ADC ratios. A ratio >1.62 is indicative of treatment-related necrosis, and lower ratios are indicative of recurrence.

Mean difference of ADC values was also useful. Although statistical differences were seen in other measures such as mean ADC values, the results overlapped sufficiently to make them less useful clinically.

Reviewer’s Comments
If future studies confirm this finding, this will be a useful and easy way to differentiate a difficult problem in neuroradiology.

Diffusion imaging is a very fast and easily performed sequence that is becoming a part of routine imaging in more and more centers.

The take-home message is this: Radiation necrosis has higher ADC ratios than tumor recurrence.

Author: Yaron Lebovitz, MD

Hein PA, Eskey CJ, et al. Diffusion-Weighted Imaging in the Follow-Up of Treated High-Grade Gliomas: Tumor Recurrence Versus Radiation Injury. AJNR; 2004; 25 (February): 201-209

  • Comments

Would you like to keep current with radiological news and information?

Post Your Comments and Responses

Comments are closed.