Pituitary Macroadenoma – Evaluation of Mean Metabolic Ratios and Mean and Normalized Apparent Diffusion Coefficient Values Using Magnetic Resonance Spectroscopy and Diffusion-weighted Imaging in a Central Indian Rural Hospital Setup
Authors: Mishra Gaurav Vedprakash , Gowda K. B. Harshith , Bhansali Pratik J. , Nagendra Vadlamudi , Raj Nishant 
Published: February 2023

Background:
MRS and disregard MRI spectroscopy offers the capability of using magnetic resonance imaning (MRI) to noninvasively study tissue biochemistry. MRS is noninvasive technique that is used to study metabolic variance in brain tumors. Furthermore, diffusion-weighted imaging depicts the degree of water molecules diffusing across the unit volume of the region of interest as a result of sophisticated and dedicated software packages. Differences in apparent diffusion coefficient (ADC) values are related to changes in cellularity, cell membrane permeability, intracellular and extracellular diffusion, and tissue structure. Diffusion-weighted MRI is a powerful tool in the characterization of brain neoplasms. The present study attempts to derive the mean metabolite ratios as well as mean values of ADC with normalization in the setting of pituitary macroadenoma.

Aim:
(1) To evaluate mean metabolic ratios in pituitary macroadenomas using magnetic resonance spectroscopy (MRS) in rural hospital setup in Central India, (2) To evaluate mean apparent diffusion coefficient value with normalization in pituitary macroadenoma using magnetic resonance spectroscopy in a rural hospital setup in Central India.

Materials and Methods:
A cross-sectional hospital-based observational study conducted over 2 years. All cases registered with Acharya Vinoba Bhave Rural Hospital Sawangi, Wardha, diagnosed as pituitary macroadenomas were included in the present study. All patients were examined on GE Brivo MRI machine with 1.5 Tesla magnetic field strength in the Department of Radiodiagnosis. Diagnostic acumen was augmented with radiological features of brain tumors with metabolic ratios derived from metabolic values and ADC values.

Results:
Out of 142 patients included, pituitary macroadenoma cases were 18 in number. Observed metabolite ratios were derived from metabolic values obtained on MRS for choline (Cho), creatinine (Cr), lipid lactate, myoinositol, and n-acetyl aspartate (NAA). Ratios were calculated for Cho: Cr, Cho: NAA, Cho: myoinositol and Cho: lipid lactate. The range for Cho: Cr, Cho: NAA, Cho: myoinositol, and Cho: lipid lactate was 1.04–4.73, 0.96–4.12, 1.21–3.12, and 0.72–1.812, respectively. The mean values for Cho: Cr, Cho: NAA, Cho: myoinositol, and Cho: lipid lactate were 1.8655, 1.6094, 1.5561, and 1.4567, respectively. The range of ADC values observed was from 0.821 × 10−3 mm2/s to 1.523 × 10−3 mm2/s. Normalized ADC values were calculated on basis of observed ADC values in the numerator and the average ADC value of gray matter in the denominator which is taken as 0.8 and was in the range of 1.02625 × 10−3 mm2/s to 1.90375 × 10−3 mm2/s. The mean ADC value was calculated as 1.22 × 10−3 mm2/s. The mean normalized ADC value was calculated as 1.52 × 10−3 mm2/s.

Conclusion:
The research gap analysis toward which research question was framed stands filled up by generated new knowledge in terms of “mean metabolic ratios” and “ADC” values with reference to pituitary macroadenomas in the present study.