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DW-MRI and MRS to Differentiate Radiation Necrosis and Recurrent Disease in Gliomas P13 Exam 4019, Validity Revisited Thomas Chong
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P13 Exam 4019 Valid Voxel Maps S43 S53 S63 - many borderline valid cases where NAA peak corrupted by broad, large underlying peak, possibly lactate. - These were counted as not valid
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Low Percentage of “Valid” MRS Spectra No metabolite amount info obtainable from most data best, cleanest P1, P2, P5 Motivated investigation into possible spatial correlations No clear correlations obvious. Need more data Slide 6 of 25 from 12/17/07 status
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Low Percentage of “Valid” MRS Spectra Artifacts present in MRS protocol data are consistent with those seen by other researchers large baseline distortions exceptionally broadened metabolite peaks large phase errors Other observed data corrupting factor SNR of cho, cre, or naa peaks reduced by large unknown resonance peak broad non-metabolite peak, or non-constant floor MRS signal interpretation for tumors recognized as a complicated task – see INTERPRET project (International Network for Pattern Recognition of Tumours Using Magnetic Resonance), a consortium of 10 EU countries [1] Slide 7 of 25 from 12/17/07 status
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INTERPRET MRS project – so? what of it? Still, how to distinguish artifacts from presence of unwanted/unknown substances? Common recognition that MRS data interpretation is not easy: see above name of the big EU project rigorous process for deciding validity of MRS voxel data in their database entailed up to 3 expert spectrologists. Slide 11 of 25 from 12/17/07 status
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INTERPRET MRS project – so? what of it? Useful SNR and WBW measures defined phantom reference gives info on data variability (it's noisy, based on successive bimonthly meas.) automated program to check spectrum for WBW 10 Tumor recognition tool does not utilize track of time trend changes in data Slide 12 of 25 from 12/17/07 status
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Cho/ NAA, P13 Exam 4019 S43 S53 S63
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Vox 174: Low S/N in S53 from Lactate Peak May Affect Accuracy of Ratio Value S43 INVERTED PEAK AREA CALCULATIONS Voxel Number174 Choline (65-77img)/ (3.31-3.12ppm)= 63836577 Creatine (77-87img)/ (3.12-2.97ppm)= 56947787 NAA (144-153img)/ (2.10-1.96ppm)= 4849144153 Cho/NAA:1.32 Choline shift from ref 3.22 =0.01 Creatine shift from ref 3.03 =0.02 NAA shift from ref 2.02 =0.02 S53 Voxel Number174 Choline (68-74img)/ (3.26-3.17ppm)= 17556874 Creatine (75-83img)/ (3.15-3.03ppm)= 29707583 NAA (140-150img)/ (2.16-2.01ppm)= 6150140150 Cho/NAA:0.29 Choline shift from ref 3.22 =0.02 Creatine shift from ref 3.03 =0.06 NAA shift from ref 2.02 =0.08
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Large Cho/NAA Difference Between Adjacent S53 Voxels 174 & 188 Shows Variability from User- Boundary Selection Error Voxel Number174 Choline (68-74img)/ (3.26-3.17ppm)= 17556874 Creatine (75-83img)/ (3.15-3.03ppm)= 29707583 NAA (140-150img)/ (2.16-2.01ppm)= 6150140150 Cho/NAA:0.29 Choline shift from ref 3.22 =0.02 Creatine shift from ref 3.03 =0.06 NAA shift from ref 2.02 =0.08 Voxel Number188 Choline (59-71img)/ (3.40-3.21ppm)= 38405971 Creatine (76-85img)/ (3.14-3.00ppm)= 30007685 NAA (141-151img)/ (2.14-1.99ppm)= 3855141151 Cho/NAA:1.00 Choline shift from ref 3.22 =0.06 Creatine shift from ref 3.03 =0.05 NAA shift from ref 2.02 =0.05
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Voxel Number174 Choline (68-74img)/ (3.26-3.17ppm)= 17556874 Creatine (75-83img)/ (3.15-3.03ppm)= 29707583 NAA (140-150img)/ (2.16-2.01ppm)= 6150140150 Cho/NAA:0.29 Choline shift from ref 3.22 =0.02 Creatine shift from ref 3.03 =0.06 NAA shift from ref 2.02 =0.08 Voxel Number174 Choline (64-74img)/ (3.32-3.17ppm)= 32706474 Creatine (75-83img)/ (3.15-3.03ppm)= 29707583 NAA (141-153img)/ (2.14-1.96ppm)= 6210141153 Cho/NAA:0.53 Choline shift from ref 3.22 =0.07 Creatine shift from ref 3.03 =0.06 NAA shift from ref 2.02 =0.08 Effect of User Boundary Selection Error on Cho/NAA Increased Sensitivity of Cho/NAA to “Noise” when Cho S/N is Low
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2/29/08 Status Proceed with pursuit of qualitative measure of quality? Requires: collection of background intensity (for S/N calculation) > 4ppm, computation of water bandwidth Requires: Access to pfiles (waiting on Scott)
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