MR spectroscopy in diagnosing intracranial lesions: comparison of diagnostic accuracy at different TE Poster No.: C-1359 Congress: ECR 2013 Type: Authors: Keywords: DOI: Scientific Exhibit A. S. DUNGDUNG; Bokaro/IN Neuroradiology brain, MR-Spectroscopy, Imaging sequences, Diagnostic procedure, Neoplasia 10.1594/ecr2013/C-1359 Any information contained in this pdf file is automatically generated from digital material submitted to EPOS by third parties in the form of scientific presentations. References to any names, marks, products, or services of third parties or hypertext links to thirdparty sites or information are provided solely as a convenience to you and do not in any way constitute or imply ECR's endorsement, sponsorship or recommendation of the third party, information, product or service. ECR is not responsible for the content of these pages and does not make any representations regarding the content or accuracy of material in this file. As per copyright regulations, any unauthorised use of the material or parts thereof as well as commercial reproduction or multiple distribution by any traditional or electronically based reproduction/publication method ist strictly prohibited. You agree to defend, indemnify, and hold ECR harmless from and against any and all claims, damages, costs, and expenses, including attorneys' fees, arising from or related to your use of these pages. Please note: Links to movies, ppt slideshows and any other multimedia files are not available in the pdf version of presentations. www.myesr.org Page 1 of 17
Purpose Magnetic Resonance spectroscopy (MRS) is a non invasive physiologic imaging which uses measurement of relative levels of various tissue metabolites in evaluation of metabolic derangements that are specific to certain diseases. It is based on chemical shift imaging. Echo time (TE) has a large influence on the appearance of spectra in proton MR spectroscopy. At long TE (135-288 msec), important metabolites like - N-acetylaspartate (NAA), Choline (Cho), Creatine/phosphocreatine (Cr) & Lactate (Lac) are evaluated. More no of metabolites can be evaluated at short TE which includes Glutamate, Glutamine, GABA, MI, Alanine, Glucose, lipids and proteins, Scyllo-inositol, taurine. The choice of TE to be used should be decided by the clinical question being asked.t1 relaxation time of choline is longer than that of either creatine or N-acetyl aspartate; thus, the ratios of Cho/Cr and Cho/NAA will be proportionally larger at echo times greater than 135 msec compared to echo times less than 30 msec. In MRS, changing the TE changes the type of information that can be obtained as well as the appearance of the frequency domain spectrum. The echo time should be set according to indication for the examination. For tumor grading, a TE of 135 or 270 msec should be used to examine differences in the N-acetyl aspartate/creatine (NAA/Cr) and choline/creatine (Cho/Cr) ratios. At these echo times, differences between NAA, Cho, and Cr signal intensities are maximized because of the differences in the concentration of these metabolites and T1 relaxation times in tumors versus normal tissue. With this background knowledge the proposed purpose of the study is - To compare the Diagnostic Accuracy of MR spectroscopy at short, intermediate and long TE in diagnosing and grading intracranial lesions. Images for this section: Page 2 of 17
Fig. 1: Magnetic ResonanceSpectroscopy Of brain at long and short TE Page 3 of 17
Fig. 2: Magnetic Resonance Spectroscopy of normal brain taken at short, intermediate and long TE Page 4 of 17
Fig. 3: Magnetic Resonance Spectroscopy Of Intracranial SOL taken at short, intermediate and long TE Page 5 of 17
Methods and Materials It is a hospital based prospective cohort study in patients presenting with symptoms suggestive of intracranial SOL or with positive CT study conducted at Department of Radio Diagnosis and Imaging, Bokaro General Hospital, Bokaro Steel City, Jharkhand, a 910 bedded public sector tertiary care hospital from june 2011 to present. The patients with diagnosis of brain SOL on MRI were studied with MR spectroscopy to characterize the lesions whether they are neoplastic - low grade, high grade or no neoplastic. The findings were correlated clinically. The MRS findings were corroborated with follow-up and/or histopathology. MR spectroscopy was performed at 1.5T in 65 patients with intracranial SOLs. The spectra was obtained at short (30 ms), intermediate (135 ms) and long (270ms) TE. Metabolite levels of N-acetylaspartate (NAA), choline (Cho) and creatine (Cr) and metabolite ratios of choline (Cho)/creatine (Cr), N-acetylaspartate (NAA)/ choline (Cho) and N-acetylaspartate (NAA)/ creatine (Cr) were calculated and compared between short, intermediate and long TEs in each case. Comparison of metabolite levels and metabolite ratios at different TEs was done using box-and-whisker plot. Diagnostic accuracy of grading intracranial SOLs at different TE was evaluated using Receiver Operating Characteristic Curve. Results Total 65 patients were initially included in the study. Follow up of only 53 patients were available. Rest of the cases were dropped out either due to death (in 2 cases), unavailability of HPE report (many of the patients could not undergo surgery due to poor financial condition, neither did they undergo any biopsy) or follow up investigations (10). So the result is calculated with 53 patients. Of total 53 patients, 25 (47%) were male and 28 (53%) were female. In our study, 2% patients were #10 years, 26% between 11-30 years, 28% between 31-50 years & 43 % above 50 years. Page 6 of 17
Most of the patients presented with headache and vomiting (36%) & seizure (25%) - mainly because of raised intracranial pressure due to mass effect & involvement of tracks. 9 were follow up cases of known brain tumour and 4 were studied to rule out metastases from primary elsewhere in body. 28% of the singular lesions were found to be located in parietal region. Posterior fossa was the next most common location accounting for 19% of the lesions. 6 were found in sella. CP angle & temporal region were next common site. Frontal lobe & frontoparietal region were the least common site. Final diagnosis was confirmed by histopathology & clinical and lab tests where biopsy was not possible. 26% of cases were non neoplastic. In neoplastic lesions, 25 were low grade tumour, 10 high grade tumour and 4 were found to be secondaries from known / unknown primary tumours. NAA - NAA is a neuronal marker which is decreased in brain tumours and less so in non neoplastic lesions. Differntiation between non neoplastic and neoplastic lesions was seen better at higher TE. However the differntiation between low grade and high grade tumours based on NAA level was appreciated better when low echo time is used while conducting the examination. Box whisker plot for NAA at different TE levels (figure 5) shows this differentiaton. Choline - Increased Choline reflects increased membrane synthesis and/or an increased number of cells such as in neoplastic lesions. This increase in choline level with increase in aggressiveness of tumour was well correlated at high TE as seen in the Box whisker plot for Cho at different TE levels (Figure 6). The differerentiation between non neoplastic, low and high grade tumours was best seen at intermediate TE. Creatinine - Creatinine plays a role in maintaining energy dependent systems in brain cells by serving as a reserve of high energy phosphates. It is increased in hypometabolic states and decreased in hypermetabolic states such as brain tumours particulary in malignant ones. As demonstrated by our Box whisker plot grap for Cr at different TE levels, this feature is best demonstrated at higher TE (figure 7). Cho/Cr Ratio - At intermediate TE, the choline peak is higher than creatine, whereas at low TE, choline is lower than creatine due to the fact that creatine has a shorter T2 and decays faster than choline. This variation in appearance of choline peak at different TE results in different Cho / Cr ratio depending on TE. Cho /Cr ratio is high in malignant lesions and is best correlated at higher TEs. Box whisker plot for Cho/Cr at different TE levels (figure 8). Page 7 of 17
NAA/Cho ratio - Box whisker plot for NAA/Cho at different TE levels reveals a decreased ratio in high grade tumors which is best seen at high TE (figure 9). Receiver Operating Characteristic Curve - Comparison of diagnostic accuracy of Cho/ Cr ratio and NAA/Cho ratio in differentiating low grade and high grade tumours at low, intermediate and high TE was done by assessing area under curve of all the three TEs for both Cho/Cr and NAA/Cho ratio. In both cases, ROC curve revealed better diagnostic accuracy when intermediate TE was used (figure 10 & 11). Images for this section: Fig. 4: Demographic Data Page 8 of 17
Fig. 5: NAA - Box Whisker Plot for non neoplastic, low grade, high grade and metastastes at low, intermediate and high TE Page 9 of 17
Fig. 6: Choline - Box Whisker Plot for non neoplastic, low grade, high grade and metastastes at low, intermediate and high TE Page 10 of 17
Fig. 7: Creatinine - Box Whisker Plot for non neoplastic, low grade, high grade and metastastes at low, intermediate and high TE Page 11 of 17
Fig. 8: Cho / Cr ratio - Box Whisker Plot for non neoplastic, low grade, high grade and metastastes at low, intermediate and high TE Page 12 of 17
Fig. 9: NAA/Cho ratio - Box Whisker Plot for non neoplastic, low grade, high grade and metastastes at low, intermediate and high TE Page 13 of 17
Fig. 10: Cho /Cr ratio ROC Curve - Comparison of diagnostic accuracy of low, intermediate and high TE in differentiating low grade and high grade tumours using Cho / Cr ratio Page 14 of 17
Fig. 11: NAA/Cho ratio ROC Curve - Comparison of diagnostic accuracy of low, intermediate and high TE in differentiating low grade and high grade tumours using NAA/ Cho ratio Page 15 of 17
Conclusion The findings of our study are as follows :- NAA - NAA is decreased in brain tumours and less so in non neoplastic lesions. Differentiation between non neoplastic and neoplastic on the basis of comparative NAA level is seen better at higher TE. Low grade high grade differntiation better seen at low TE. Cho - Neoplastic brain lesions show increased choline best noted at higher TEs. The differentiation between non neoplastic, low, high and metastases is best seen in TE 135 Cr - Cr values tend to be abnormally reduced in brain tumors, particularly malignant ones.this feature is best depicted at higher TEs Cho / Cr - At intermediate TE, the choline peak is higher than creatine, whereas at low TE, choline is lower than creatine due to the fact that creatine has a shorter T2 and decays faster than choline.cho / Cr ratio best seen at TE 270 NAA/Cho ratio - decreases in high grade tumors. Best seen at high TE. Best differentiation of low grade and high grade is at TE 135 ROC curve analysis of TE 30, 135 & 270 for differentiation of low grade and high grade tumour on the basis of Cho/Cr ratio and NAA/Cho ratio was found to be most accurate at TE 135. So in conclusion, metabolite ratios were different between short, intermediate and long TEs. The differentiation between non neoplastic, low grade and high grade neoplasm was most accurate at TE 135. If only a single spectroscopic sequence is to be acquired, intermediate TE seems preferable, because of higher diagnostic accuracy and sensitivity at 1.5 T 1 H-MR spectroscopy as compared to short and long TE. References 1. John R Haaga. CT and MRI of the Whole Body 5 th edition 2. J.H. Kim, K.H. Chang, D.G. Na, I.C. Song, B.J. Kwon, M.H. Han and K. Kim. 3T 1 H-MR Spectroscopy in Grading of Cerebral Gliomas: Comparison of Short and Intermediate Echo Time Sequences. AJNR August 2006 27: 1412-1418 3. Carles Majós, Margarid, Julià-Sapé, Juli Alonso, Carles Aguilera, Juan J. Acebes, Carles Arús and Jaume Gili. Brain Tumor Classification by Proton MR Spectroscopy: Comparison of Diagnostic Accuracy at Short and Long TE. AJNR 2004 25: 1696-1704 Page 16 of 17
4. Juan M. García-Gómez, Salvador Tortajada, César Vidal, Margarida Julià- Sapé, Jan Luts, Sabine Van Huffel,Carles Arús, Montserrat Robles. On the Use of Long TE and Short TE SV MR Spectroscopy to improve the Automatic Brain Tumor Diagnosis - ftp://ftp.esat.kuleuven.ac.be/pub/sista/ ida/reports/07-55.pdf 5. L. Lukas, A. Devos, J.A.K. Suykens, L. Vanhamme, F.A. Howe,C. Majo s, A. Moreno-Torres, M. Van Der Graaf, A.R. Tate,C. Aru s, S. Van Huffel. Brain tumor classi#cation based on long echo proton MRS signals. Arti#cial Intelligence in Medicine (2004) 31, 73-89 6. Janet Cochrane Miller.Magnetic Resonance Spectroscopy in the Brain. Massachusetts General Hospital Radiology Rounds July 2012 volume 10 issue 7 7. H Watanabe, H Fukatsu, M Katsuno, M Sugiura, K Hamada, Y Okada, M Hirayama, T Ishigaki, G Sobue. Multiple regional 1 H-MR spectroscopy in multiple system atrophy: NAA/Cr reduction in pontine base as a valuable diagnostic marker. J Neurol Neurosurg Psychiatry 2004;75:103-109 Personal Information Page 17 of 17