Vijay Indal Naik^1*, Vinod Narayanrao Chaudhari²

^1,2Associate Professor, Department of Radio Diagnosis, Dr. Ulhas Patil Medical College, Jalgaon, Maharashtra, INDIA.

Email: drvinodchoudhari@yahoo.co.in

RESULTS

100 patients underwent DW MRI during study period, most common age group was 51-60 years (36%), followed by 41-50 years (29%). Male patients (67%) were more than female (33%).

Table 1: General characteristic

Majority of patients had infarcts (48%) of which 25 were acute, 10 were chronic 3 were subacute. Other were tumors (32%), intra-axial tumours were 15, which includes GBM (5), Low grade glioma (2), Medulloblastomas (3), Lymphomas (3), anaplastic astrocytoma (1) hemangioblastoma (1). Extra-axial tumours were 17, which includes Meningiomas (10), arachnoid cysts (4) pituitary macroadenoma (3).24% had infective etiology tubercular granulomas (14%), NCC granulomas (3%), Abscesses (4%) Encephalitis (3%) were infective etiologies. 3% had demyelination all had multiple sclerosis.

Table 2: Etiology DW-MRI picture

On DW MRI, most common finding was True diffusion restriction - hyperintensity on T2W images hypointensity on ADC images noted in 55 patients.

Table 3: Primary finding on DW MRI

DISCUSSION

DWI explores the molecular characteristic of diffusivity of particles within a region. It is based on the application of two gradients at a set interval of time, in such a way that only a molecule that experiences both gradients at the same position produces signal. Therefore regions of the brain that show “restricted diffusion” are hyperintense on DWI. This restricted diffusion appears as hyperintense area on DWI and needs to be corroborated with computer generated apparent diffusion coefficient (ADC) maps which show corresponding hypointense area. This corroboration rules out T2-shine through effect.⁴ Diffusion‑weighted imaging (DWI) has a well‑defined role in differentiating between important intracranial lesions, namely, brain abscess, arachnoid cyst, cystic/necrotic tumor, and epidermoid tumor. Quantitative analysis allows one to clearly delineate vascular, inflammatory, metabolic, infectious, and nonvascular disorders.^5,6 In a similar study, Pradeep Kumar⁷ had infarcts comprised the majority of lesions at 56 cases (50.9% of the total cases studied). Of these acute infarcts constituted 34 cases (60.7%); 19 (33.9%) were chronic infarcts and 3 (5.3%) were subacute infarcts. All cases of acute infarcts and 66.7% of subacute infarcts showed diffusion restriction. Among intra axial tumors true restriction was noted in 7 cases. 75% of glioblastoma multiforme showed true diffusion restriction. 100% of medulloblastomas and 100% of lymphomas showed diffusion restriction. Similar findings were noted in present study. Kamini Gupta⁸ studied 67 patients who underwent Conventional MR sequences along with DW and MRS were done after taking localisers in all the three planes. Most common cerebral neoplasms were metastases followed by Glioblastoma Multiforme (GBM). Male: female ratio was 1.5:1. Headache was the most common presenting complaint. Apparent Diffusion Coefficient (ADC) values were similar in GBM and metastases but were higher in low grade gliomas. On MRS, choline levels in the areas of diffusion restriction were higher and NAA levels were lower in cases of GBM, metastases and lymphoma as compared to low grade gliomas. DW imaging with ADC values and MRS in combination with conventional MRI are very useful in detection of brain tumours and distinguishing low grade from high grade tumours. DWI plays an important role in the differentiation of these abscesses from necrotic neoplasms, which usually demonstrate high ADC values within the core. Luthra G et al.. observed diffusion restriction with low ADC value in both tubercular and pyogenic abscesses.⁹ Bacterial as well as tubercular abscesses show central diffusion restriction due to highly viscous necrotic tissue within.⁹ Reddy JS¹⁰ noted a high sensitivity and specificity of DWI for the diagnosis of brain abscess vs nonabscess cystic mass lesions. High specificity and sensitivity of DWI in the present and previously reported studies indicate reproducibility of the DWI over a number of studies High specificity and sensitivity of DWI for differentiation of abscess from nonabscess lesions is due to the difference in the contents of the cavities of both the etiology revealed by differences in macromolecular concentration, cell density, and viscosity of the fluid.^11,12

CONCLUSION

Diffusion weighted MRI has been proven to be of excellent use in the characterization of infarcts and in the detection of acute infarcts. Diffuse-weighted imaging should be used routinely as a valuable noninvasive tool besides conventional MRI, whenever available, to reach a definitive final diagnosis.

REFERENCES

1. Bukte Y, Paksoy Y, Genc E, et al. Role of diffusion-weighted MR in differential diagnosis of intracranial cystic lesions. Clin Radiol 2005; 60:375 - 83.;
2. Zainab Yazdi Sotoodeh*, Vida Sargazi, Ali, Jafari Kalil Abadi, Diffusion-weighted MR Imaging and ADC map of Brain Tumors, Ambient Science, 2018: Vol. 05(Sp1)
3. Mishra AM, Gupta RK, Jaggi RS, et al. Role of diffusion-weighted imaging and in vivo proton magnetic resonance spectroscopy in the differential diagnosis of ring-enhancing intracranial cystic mass lesions. J Comput Assist Tomogr 2004;28:540 - 7.
4. Desprechins B, Stadnik T, Koerts G, Shabana W, Breucq C, Osteaux M. Use of diffusion-weighted MR imaging in differential diagnosis between intracerebral necrotic tumors and cerebral abscesses. AJNR Am J Neuroradiol 1999; 20: 1252-1257
5. Mascalchi M, Filippi M, Floris R, Fonda C, Gasparotti R, Villari N. Diffusion‑weighted MR of the brain: Methodology and clinical application. Radiol Med 2005;109:155‑97.
6.  Naggara O, Letourneau-Guillon L, Mellerio C, Belair M, Pruvo JP, Leclerc X, et al. [Diffusion-weighted MR imaging of the brain]. J Radiol 2010;91:329-51.
7. P. Pradeep Kumar Reddy, P. Madhu. Diffusion weighted magnetic resonance imaging features of intracranial lesions. International Journal of Contemporary Medicine Surgery and Radiology. 2018;3(2):B24-B30.
8. Kamini Gupta, Nikhil Jain, Kavita Saggar, Role of Diffusion Weighted Imaging and MR Spectroscopy in Characterisation of Intracranial Neoplasms, International Journal of Anatomy, Radiology and Surgery. 2018, Jul, Vol-7(3): RO55-RO61
9. Luthra G, Parihar A, Nath K, Jaiswal S, Prasad KN, Husain N, Husain M et al. Comparative evaluation of fungal, tubercular, and pyogenic brain abscesses with conventional and diffusion MR imaging and proton MR spectroscopy. AJNR Am J Neuroradiol. 2007 Aug; 28(7):1332-
10. Reddy JS, Mishra AM, Behari S, Husain M, Gupta V, Rastogi M, Gupta RK. The role of diffusion-weighted imaging in the differential diagnosis of intracranial cystic mass lesions: a report of 147 lesions. Surg Neurol. 2006 Sep;66(3):246-50;
11. Mishra AM, Gupta RK, Saksena S, et al. Biological correlates of diffusivity in brain abscess. Magn Reson Med 2005;54:878- 85.
12. Kumar S, Mishra AM, Reddy JS, et al. Comparative evaluation of magnetization transfer and fluid-attenuating inversion recovery imaging in cystic intracranial mass lesions and their correlation with biological parameters. Proceedings 13th Annual Scientific Meeting of the International Society for Magnetic Resonance in Medicine. 2005. Miami, Fla; 2005. p. 227.