| Comparison of MRI Finding of Metastatic Brain Tumor between Diagnosis and Gamma Knife Radiosurgery Planning |
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Ki-Hun Kwon, Yong-Seok Im, Jung-Il Lee, Do-Hyun Nam, Kwan Park, Jong Hyun Kim |
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Department of Neurosurgery, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea |
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| Abstract |
Objective
Magnetic resonance imaging (MRI) is an important tool for not only diagnosis of metastatic brain tumor but also treatment, particularly image-dependent modality such as gamma knife radiosurgery (GKRS). Because of different imaging techniques routinely used for diagnosis or radiosurgical planning and rapid progression of metastatic lesions, it is common that there is significant discrepancy of MRI finding at diagnosis and actual treatment with radiosurgery. This study was undertaken to investigate the difference of MRI finding between images at initial diagnosis and images subsequently obtained for radiosurgery.
Methods
In this retrospective study, MRI finding of 60 patients (30 patients with single lesion and 30 with 2-5 lesions detected at diagnosis) were investigated at the time of diagnosis and GKRS planning. The same apparatus was used in each patient for MRI, however, imaging techniques such as MRI sequence, slice interval, thickness, and amount of contrast agent were different between diagnostic imaging and imaging for radiosurgery. For the comparison of images at different time point, the number of the detected lesions was counted and tumor size was measured by the longest diameter or the product of the two perpendicular diameters at the largest cross sectional image of the tumor.
Result: The additional lesions not detected at initial diagnosis were identified at the images obtained for GKRS in 3 patients
(5%). For 30 patients with single metastatic tumor, the mean value of the absolute change in tumor size was 1.12mm (SD= 1.10) in the longest diameter and 38.39mm2 (SD=39.70) in the product of two perpendicular diameters. Concerning tumor progression, there were progressive disease in one case of by RECIST criteria and three cases by WHO criteria.
Conclusion
There was significant difference between at the time of diagnosis and GKRS in the number of lesions and their size.
It is thought that the discrepancy reflects different sensitivity according to imaging techniques and natural course of tumor progression. Metastatic brain tumors should be treated within acceptable range of time interval between diagnosis and GKRS, preferentially as soon as possible. Diagnostic imaging for the patients with probable metastatic lesion needs to be further refined to reduce the discrepancy which may influence the decision of optimal treatment. |
| Key Words:
Metastatic brain tumor, Gamma knife radiosurgery, Tumor size. |
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