|
Anne,
here is something you may want to discuss with docs:
Performed together, MRI and MRS (magnetic resonance spectroscopy) produce an image of the brain that shows both morphology and tissue metabolism. Certain metabolites are present in greater or lesser quantities in tumors, compared to normal brain tissue. Choline is a cell-member marker that is found in increased quantities in malignant tumors.
MRS Applications in Oncology
By Pia C. Sundgren MD, PhD, Suresh K. Mukherji MD
Lately, MRS has been shown to be a helpful tool in evaluation of a new contrast-enhancing lesion at the site of a previously identified and treated primary intracranial neoplasm, differentiating recurrent tumor from radiation injury.
Radiation injury versus recurrent brain tumor . Contrast-enhancing lesions that arise on routine brain MR imaging at the site of a previously identified and treated primary intracranial neoplasm present a significant diagnostic dilemma. These lesions are in regions that have been subjected to radiation, with or without chemotherapy, and in some instances surgical resection. Many do not have specific imaging characteristics that will enable the neuroradiologist to discriminate tumor recurrence from the inflammatory or necrotic changes that can result from treatment with radiation. 28 Both recurrent tumors and radiation injury typically demonstrate enhancement with gadolinium. Specific spectroscopic changes that occur with radiation-induced necrosis have been reported and include slight depression of NAA and variable changes in choline. 29-32 A recent study reported a 93% success rate in differentiating recurrent tumor from radiation injury with significantly increased Cho/NAA and Cho/Cr ratios (P < 0.001) in areas of recurrent tumor compared to areas of radiation injury and compared to normal adjacent brain tissue. 33 These results also are supported by previous work utilizing SVS, where the authors claim that a Cho/Cr ratio over 1.79 or lipid-lactate/Cho ratio less than 0.75 has a sevenfold increased odds of indicating tumor compared to pure necrosis.
|