European Journal of Cardiovascular Medicine

In neuroimaging, Magnetic Resonance Imaging (MRI) is a cornerstone technique that allows clinicians to see fine aspects of brain architecture and pathology with unparalleled clarity. Ring-enhancing lesions (RELs) in the brain pose a particularly difficult diagnostic scenario among the many abnormalities found. ^[1] Ring-enhancing lesions in brain imaging are widespread in the Indian subcontinent. The two most common causes of inflammatory granulomas seen in pediatric clinical practice are neurocysticercosis (NCC) and tuberculomas.^[2] The size, form, and wall thickness of ring-enhancing lesions, the amount of surrounding oedema, and, most significantly, the patient's clinical history and age should all be considered when distinguishing the illness.^[3]

MRS scans can help diagnose a wide range of diseases, including malignancies, cerebral ischemia, and trauma, when performed in conjunction with an MRI.^[4] It examines the resonant frequencies of several metabolites in the brain, such as choline (Cho), creatinine (Cr), and NAA, and displays the results in the form of a line graph with amplitudes. These readings alone are not diagnostic; nevertheless, they must be analyzed in conjunction with an MRI.^[5]

MRS can be utilized for diagnostic and prognostic purposes, particularly in paediatric age ranges. Thus, MRS is considered the future of neuroimaging. ^[6]

Magnetic resonance spectroscopy (MRS) analyzes the presence and/or ratio of tissue metabolites such as NAA, creatine, choline, and lactate, among others, to determine the potential degree and character of alterations on a typical MRI scan.[5] The widespread use of faster MRS applications with a higher signal-to-noise ratio (SNR) and spatial resolution enables us to detect functional metabolic changes, providing more data for understanding the exact nature of the tumor as well as the morphological and physiological changes occurring in the surrounding brain parenchyma.^[7]

Based on the metabolite level, MRS could distinguish tuberculoma from other lesions with clarity. Based on CT and MRI scans, lesions from neurocysticercosis and tuberculoma were similar in many ways, but they could be distinguished by their location, number, enhancement pattern, and constitutional symptoms. Metabolite levels allowed MRS to distinguish between these lesions. The current study set out to evaluate the utility of magnetic resonance spectroscopy in the assessment of brain lesions that enhance rings.

Objectives:

1. To differentiate neoplastic from non-neoplastic brain lesions using conventional and advanced MR imaging techniques.
2. To study the characteristic imaging findings of various ring enhancing lesions on MRI.
3. To establish differential diagnosis of various ring enhancing lesions on conventional MRI.
4. To study the role of MR spectroscopy in the evaluation of various ring enhancing lesions in the brain with a single voxel proton MR spectroscopy.

Study Design: A prospective hospital-based observational study.

Study area: Department of Radio Diagnosis, Subbaiah Institute of medical sciences, Shivamogga, Karnataka.

Study Period: 1 year.

Study population: All patients referred to the Department of Radio diagnosis with clinically suspected cerebral ring-enhancing lesions.

Sample size: The study consisted of 60 subjects.

Sampling method: Simple random technique.

Inclusion criteria:

• All cerebral ring enhancing lesions detected on contrast MR studies are taken up retrospectively.
• All patients with incidentally diagnosed ring enhancing lesion by CT. Cases of all age groups irrespective of sex.

Exclusion Criteria:

• Patient having history of claustrophobia.
• Patient having history of metallic implants insertion, cardiac pacemakers and metallic foreign body in situ.

Ethical consideration: Institutional Ethical committee permission was taken prior to the commencement of the study.

Study tools and Data collection procedure:

EQUIPMENT USED: The evaluation of cases in the department of radio diagnosis will be done using Siemens Avanto 1.5 Tesla MRI

SEQUENCES:  Conventional spin echo sequences, axial T1, T2 and FLAIR: Coronal T2; Sagittal T1; Post-contrast axial, coronal and sagittal; DWI; T2 GRE Single voxel spectroscopy; multi-voxel spectroscopy will be performed at TE of 135ms and 35ms, TR at 2000 ms. In single voxel studies, the voxel is placed on the lesion so that it covers the maximum area of the solid tumoral area. Spectroscopy was avoided in small lesions close to the bone. Special sequences such as CISS 3D, and VENBOLD were used as and when required.

Statistical analysis:Data wasanalysed using SPSS 21.0 software. Descriptive parameters were represented as mean with SD or median. Continuous variables were compared using unpaired t-test/Mann Whitney u test. Chi-square or t-test will be used to determine significant outcome differences. Categorical data was represented as frequency with percentage. For all tests, a p-value of <0.05 was considered statistically significant.

A total 60 patients presented with various ring-enhancing lesions.

Table 1: Incidence of Various Ring Enhancing Lesions

Table 2: Age-Wise Distribution of Various Ring-Enhancing Lesions

Table 3: Male Female Incidence of Ring Enhancing Lesions

Table 4: Clinical Symptoms Presented by a Patient with Various Ring-Enhancing Lesions

Table 5: DWI in Ring Enhancing Lesions

Table 6: List of Dominant Metabolite Peaks Noted in Various ring enhancing lesions

Table 7: Number of Ring Enhancing Lesions in a Patient

Table 8: Size of Lesion of Various Ring Enhancing Lesions

Case1: TUBERCULOMA

.

Fig.1: On Axial images: Hyperintense lesion with hypointense rim and perilesional edema is noted on left high parital region on T2, postcontrast image showing ring enhancement, showingnorestrictionondiffusion, lipidpeakonMRSSuggestiveofTUBERCULOMA.

Case2: METASTASIS

Fig.4: OnAxialImages: MultipleHyperintenseLesionsNotedinbilateralthalamiOn T2, On Post Contrast, lesions showing ring enhancement, On MRS CholinepeakisnotedsuggestiveofMetastasis.

Case3:NCC

Fig.5: IntraventricularcysticlesionnotedinAXIALFLAIRimage, secondpostcontrastimage showing ring enhancing and nodular enhancing lesions in left temporal regionwithMRSshowing lactate antipodeans suggestiveofNCC.

Case4: Abscess

Fig.6: On axial images: The lesion in right Temporal lobe on postcontrast image showing ring enhancement, diffusion restriction present, MRS showing lactatepeaksuggestive of ABCCESS.

Case6: GBM

Fig.7: onaxialimages: The lesion was multilobulated presentin leftparieto-occipitalregion, Onpostcontrast, lesionsshowingirregularringenhancement, fewareasofdiffusionrestrictionnoted, on MRS showing cholinepeakandreducedNAAsuggestiveofGBM.

Magnetic resonance imaging is a noninvasive, multiplanar, and highly accurate approach with improved intrinsic contrast that accurately depicts the lesion. MRI enables a reliable assessment of brain alterations in various ring-enhancing lesions, allowing for precise diagnosis and rapid therapy.

60 patients were evaluated, whose age group ranged from 4 to 67 years. The highest incidence of RELswas found in the 21-30 years age group accounting for 31.6% of cases and the least was seen in the age group of 41-50 years constituting 5%.This does not correspond to studies done by Ps Mahato⁸ and Jernail Singh Bava⁹.Sixty patients were evaluated of which 37 (62%) were males and 23 (38%) were females.About 62% of patients were males and 38% were females which was nearly consistent with the study conducted by Jernail Singh Bava⁹ in his study also males were dominant comprising 54% and 46% were females.

Out of 60 patients evaluated, Seizures were the most common presenting complaint in 70% of cases. Headache (18%), fever (6.6%), vomiting (15%), ataxia (5%) and motor weakness (6%) were the other presenting complaints.Our findings were compared with the study conducted by ps mahato⁸ in which headache(57.5%)   was the most common symptom followed by seizures (52.5%).

Out of the 60 patients who were evaluated, tuberculomas (47%) were the most common pathology followed by NCC (30%), Abscesses (8%), metastasis (12%), primary brain tumour (2%) and tumefactive demyelination (2%). And it correlated with the study conducted by Jernail Singh Bava⁹ demonstrating that tuberculoma 36% was the most common pathology followed by Ncc 34%.In a study conducted by Ps Mahato⁸tuberculoma (58%) was common pathology followed by metastasis (17.5%).In a study conducted by Schwartz et al¹⁰ 40% of cases were gliomas.The higher incidence of tuberculomas in the present study is probably due to the higher prevalence of tuberculosis in India.

Among the 60 patients with RELs noted 23 (38%) were noted on the right side, 15 (25%) were noted on the left side, 20(34%) were seen bilaterally and 2 (3%) in the midline. 60 patients were evaluated - 21(35%) of them presented with a single lesion. 2-5 lesions were noted in 24 (40%) of cases and > 5 RELs were seen in 15(25%) of cases. 60 patients were evaluated - the majority 38 (63%) of them showed RELs < 2cm, 16 (27%) of them showed lesions of sizes between 2-4 cm and only 6 (10%) lesions size greater than 4 cm. In the case of multiple lesions size of the maximum number of lesions thatfell in one category was considered.60 patients were evaluated - 32 (53%) of patients show diffusion restricting lesions (partial/complete) and 28 (47%) of cases shows no diffusion restriction.

Out of the 60 patients evaluated spectroscopy was possible in only 56 cases and was not performed in 4 cases because of presence of the lesion close to the bone. Choline peak was observed in 09 cases, Lipid in 15 cases, Lactate in 16 cases, reduced NAA peak in 17 cases and amino acids in 3 cases.

MR spectroscopy shows minor metabolite peaks at short mAs (35) and dominant metabolite peaks at 135 mAs. multiple overlapping peaks are noticed in patients having necrotic SOL because the central cystic and non-enhancing part of the tumour always show significant lactate and lipid peaks along with few creatinine peaks with significant choline peaks along the periphery of the lesion. In the present study, the dominant metabolite peak was considered for making the final radiological diagnosis and subtle peaks like raised nonspecific metabolites were not considered while making the statistical data for MRS.

Riley and coworkers¹¹ concluded that Ring enhancing lesions of the brain remain a diagnostic challenging dilemma including a wide differential diagnosis of neoplastic and non-neoplastic lesions. MRI stands as the main diagnostic imaging modality, using conventional as well as advanced sequences can help in accurate verification and differentiation between these lesions for better diagnostic accuracy.

The presence of ring-enhancing lesions on brain MRI studies constitutes a frequent and quite challenging diagnostic dilemma. The differential diagnosis of lesions presenting as ring-enhancing is quite extensive and varies significantly with the patient’s age and geographical region. Unfortunately, clinical history and symptomatology along with conventional MRI cannot accurately differentiate and establish a diagnosis of these lesions. Proton MRS may contribute to narrowing down their differential diagnosis and may enhance, alone or in combination with other advanced MR Imaging modalities, the specificity and the diagnostic accuracy of conventional MRI. Proton MRS is a non-invasiveMR-based diagnostic modality, which provides a direct spectroscopic signature of the examined brain parenchymal area and its underlying pathology, and an indirect evaluation of the lesion’s metabolism.

Out of 60 patients evaluated, tuberculomas were seen in 28 (46.6%) of cases. Among the 28 cases (males = 18: females = 10). Single lesions were noted in 9 cases (32.1%) and multiple in 19   cases (67.9%). They were seen as conglomerate lesions which were hypointense on both T1 and T2. On T1 weighted images15 cases showed an iso to hyperintense ring. 21 cases (75%)showed partial/complete restriction.Subhasis Mukherjee, Runa Das, and Shabana Begum (2015)¹² conclude that Conventional neuroimaging like CT scan of the brain with contrast and MRI brain ± contrast alone is insufficient diagnostic tools for a confident etiological diagnosis of intracranial ring-enhancing lesions like tuberculoma. In patients with focal seizures with solitary or multiple ring-enhancing lesions in CT or MRI brain, MRS of the brain should be done in all cases to look for the characteristic lipid peak to confirm a diagnosis of tuberculoma.

Out of 60 patients evaluated neurocysticercosis was seen in 18 (males=11; females=7) cases. 7 patients presented with single lesions whereas 11 patients presented with multiple lesions. All the cases showedthe intraparenchymal form of NCC with spinal cysticercosis seen in one case and subarachnoid cysticercosis in 2 cases. Scolex was identified in 8 cases. MRS showed non-specificpeaksie; lipid, lactate, and amino acid peaks and reduced NAA peak. Gradient echo imaging played a significant role in identifying calcified lesions which were seen in 6 cases (33.5 %). All the lesions were hypo to isointense on T1 weighted images and 12 cases were hyperintense on T2. Out of these 12 lesions, 9 lesions showed inversion on FLAIR suggesting that the contents are similar to that of CSF. Intense ring enhancement with surrounding perilesional oedema was seen in all cases suggestive of active lesions. In the present study, only a single case of intraventricular cysticercosis was found, probably because of the small sample of the study. Martinez et al reported intraventricular neurocysticercosis in 22 % of cases.¹³

Out of the 60 patients, abscesses were found in 5 cases ie,8.3% (males =3; females =2). Single abscess was found in 2 cases whereas the other 3 cases had multiple abscesses. One patient presented with a history of congenital heart disease - tetralogy of Fallot. All the cases showed sizes >2 cm and one case was >4 cm. All were hypointense on T1 weighted images with a hyperintense rim noted in 3 patients and were hyperintense on T2 weighted images with a surrounding hypointense rim (5 cases). They showed complete diffusion restriction and MRS showed Lactate peak in all 5 cases suggesting anaerobic glycolysis with amino acids like glutamine seen in 3 cases.Halmes et al.¹⁴ described the appearance of abscesses on MR. We correlated the findings of the present study with those described and distinguished peripheral oedema, central necrosis and the characteristic pattern of peripheral enhancement of the abscess capsule.

Out of the 60 patients, 7 cases were metastasis (males = 4; females = 3). Multiple lesions were identified in all 7 cases. All the cases showed high Cho / Cr and Cho / NAA ratios. All 7 cases were hyperintense on T2 with 2 cases showing inversion on FLAIR suggestive of cystic metastasis. Primary was identified in three cases which were breast, lung and prostate. A thick, irregular type of ring enhancement was noted after contrast administration. The findings of the present study were similar to the study conducted by Vieth RG and co-workers.¹⁵

Out of the 60 patients, 1 case was tumefactive demyelination was noted in females, the case showed multiple demyelinating lesions,of which one was tumefactive demyelination.ie; it appeared as hypointense on T1W, hyperintense on T2W,FLAIRwith perilesional edema,open ring enhancement on T1+C(open side of ring being towards grey matter).on DWI the lesion showed mild low ADC(suggestive of restricted diffusion).the tumefactivedemyelinating lesion on MRS showed a significant choline peak with decreased NAA. Of the 60 patients,1 case of GBM was seen in a male. The lesion was multilobulatedand located in the left parietooccipital region being hypointense on T1W, and irregularly hyper-intense on T2W. The lesion showed irregular ring-like enhancement on T1+C images,few areas of restriction on DWI and a significant increase in choline and decreased NAA on MRS. The findings of the present study were similar to a study conducted by LIA Metwally, SE El-din, O Abdelazizand coworkers,¹⁶ where they concluded that Mi/Cr ratio and Mi is an important predictor for grading of gliomas, wherein the low-grade glioma have a high Mi peak as compared to anaplastic glioma and GBM.

From our study, it can be concluded thatMRI is the most sensitive modality in the characterization of intracranial ring-enhancing lesions.MRI being non-invasive and non-radiating is an ideal imaging modality.The multiplanar capability of MRI helped identify precise anatomical locations and the exact extent of lesions.MRI plays a critical role in patient management by suggesting the correct diagnosis based on characteristic imaging findings.MRS helps in the characterization of various ring-enhancing lesions. However, no lesion can be diagnosed based on the findings of MRS as the sole criterion.MRS by analyzing the presence and/or ratio of tissue metabolites such as NAA, creatine, choline, and lactate helps in narrowing done the differential diagnosis of ring-enhancing lesions.

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