DW-MRI and MRS to Differentiate Radiation Necrosis and Recurrent

Disease in Gliomas

P13 Exam 4019, Validity Revisited

Thomas Chong

P13 Exam 4019Valid 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

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

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

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

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 <

8Hz, SNR > 10 Tumor recognition tool does not utilize track of

time trend changes in data

Slide 12 of 25 from 12/17/07 status

Cho/ NAA, P13 Exam 4019

S43

S53

S63

Vox 174: Low S/N in S53 from Lactate Peak May Affect Accuracy of Ratio Value

S43

INVERTED PEAK AREA CALCULATIONSVoxel Number 174Choline (65-77img)/ (3.31-3.12ppm)= 6383 65 77Creatine (77-87img)/ (3.12-2.97ppm)= 5694 77 87NAA (144-153img)/ (2.10-1.96ppm)= 4849 144 153Cho/NAA: 1.32Choline shift from ref 3.22 = 0.01Creatine shift from ref 3.03 =0.02NAA shift from ref 2.02 = 0.02

S53

Voxel Number 174Choline (68-74img)/ (3.26-3.17ppm)= 1755 68 74Creatine (75-83img)/ (3.15-3.03ppm)= 2970 75 83NAA (140-150img)/ (2.16-2.01ppm)= 6150 140 150Cho/NAA: 0.29Choline shift from ref 3.22 = 0.02Creatine shift from ref 3.03 =0.06NAA shift from ref 2.02 = 0.08

Large Cho/NAA Difference Between Adjacent S53 Voxels 174 & 188 Shows Variability from User-

Boundary Selection Error

Voxel Number 174Choline (68-74img)/ (3.26-3.17ppm)= 1755 68 74Creatine (75-83img)/ (3.15-3.03ppm)= 2970 75 83NAA (140-150img)/ (2.16-2.01ppm)= 6150 140 150Cho/NAA: 0.29Choline shift from ref 3.22 = 0.02Creatine shift from ref 3.03 =0.06NAA shift from ref 2.02 = 0.08

Voxel Number 188Choline (59-71img)/ (3.40-3.21ppm)= 3840 59 71Creatine (76-85img)/ (3.14-3.00ppm)= 3000 76 85NAA (141-151img)/ (2.14-1.99ppm)= 3855 141 151Cho/NAA: 1.00Choline shift from ref 3.22 = 0.06Creatine shift from ref 3.03 =0.05NAA shift from ref 2.02 = 0.05

Voxel Number 174Choline (68-74img)/ (3.26-3.17ppm)= 1755 68 74Creatine (75-83img)/ (3.15-3.03ppm)= 2970 75 83NAA (140-150img)/ (2.16-2.01ppm)= 6150 140 150Cho/NAA: 0.29Choline shift from ref 3.22 = 0.02Creatine shift from ref 3.03 =0.06NAA shift from ref 2.02 = 0.08

Voxel Number 174Choline (64-74img)/ (3.32-3.17ppm)= 3270 64 74Creatine (75-83img)/ (3.15-3.03ppm)= 2970 75 83NAA (141-153img)/ (2.14-1.96ppm)= 6210 141 153Cho/NAA: 0.53Choline shift from ref 3.22 = 0.07Creatine shift from ref 3.03 =0.06NAA 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

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)