Abstract

Background: MRS is an advanced examination of MRI producing a spectra that describe metabolite information of tissues. ROI setting becomes very important in generating the spectral diagnostic value called Full-Width at Half Maximum (FWHM). All collected FWHM data will assist physicians to determine the stage of brain tumors. In clinical applications, Radiographers select several ROIs in obtaining FWHM values without any particular benchmark which directly affects the accuracy of the brain tumor stage. 

Objective: The purpose of this study is to examine the FWHM profiles based on the ROI selections and to determine the effect of selected ROIs on to FWHM values.

Methods: This research is a quantitative study with an experimental approach. Data were collected by an expert Radiographer during 30 days in June 2016 at Department of Radiology, Siloam Hospital Kebon Jeruk Jakarta using a particular bottle phantom MRI 2000 ml. The phantom was scanned with 1.5 Tesla MRI scanner, from which various selection of the ROIs sized 20 mm, 25 mm, 30 mm, 35 mm and 40 mm; at the several positions.  The positions employed were the centre, 12 o'clock, 3 o'clock, 6 o'clock and 9 o'clock. The analysis was performed to define the adequate size of ROI generating an optimum FWHM values. Linear regression applied to conclude whether or not there is an influence of the ROI size in generating FWHM values.

Results: The results showed the optimum FWHM values of 12-20 were generated from the ROI size 20-30 mm at the center position. Regression analysis deemed significant (p-value <0.05) leading to a conclusion that the ROI size setting affects the FWHM values. The smaller the ROI size, FWHM value will decrease with higher homogeneity and vice versa.

Conclusion:  ROI size setting affects FWHM value, and optimum FWHM value is generated by ROI size of 20 – 30 mm at the center position.

Keywords: Magnetic Resonance Spectroscopy, Region of Interest, Full Width at Half Maximum,