1. Beyond FLAIR: Expanding the Role of Inversion Recovery in MR Imaging of the Brain Ali Batouli 1 Michael Spearman 1 Michael Goldberg 1 Emmanuel Kanal 2 1 Allegheny Health Network 2 University of Pittsburgh Poster # EP-58

2. DISCLOSURES The authors have no disclosures

3. What is inversion recovery? Inversion Recovery (IR) pulses have the power to null the signal from a desired background tissue to accentuate underlying pathology This allows for greater contrast and improved diagnostic accuracy

4. How does IR work? IR is a conventional spin echo sequence preceded by a 180° inverting pulse The time between the 180° inverting pulse and the 90°-pulse is called the inversion time (TI) Traditional Spin Echo: {90°−180°−echo} Inversion Recovery: 180° — {90°−180°−echo} Image modified from http://mri-q.com/what-is-ir.html © 2014 AD Elster, ELSTER LLChttp://mri-q.com/what-is-ir.html

5. How does IR work? The inverting pulse flips initial longitudinal magnetization of tissues to point opposite of Bo During TI interval, tissues undergo T1 relaxation and reestablish magnetization in the z-direction at different rates Image modified from http://mri-q.com/what-is-ir.html © 2014 AD Elster, ELSTER LLChttp://mri-q.com/what-is-ir.html +Mo -Mo

6. How does IR work? Longitudinal magnetizations of different tissues are separated based on intrinsic T1 relaxation times at the start of signal acquisition The TI controls degree of separation of varying tissues and hence image contrast Signal from any particular tissue can be nulled by carefully choosing TI in relation to TR FLAIR – nulled CSF signal TR: 8,000-11,000 ms TI: 2,000-2,600 ms

7. What are the traditional uses of IR in imaging of the brain? T2 weighted Fluid- attenuated inversion recovery (FLAIR) – Fluid is nulled to highlight periventricular and perisulcal pathology – FLAIR improves MS lesion detection in the supratentorial brain by 7% compared to T2 (Woo et al. 2006) FLAIRT2 Image from Woo et al. 2006

8. What are newer uses of IR in imaging of the brain? T2 weighted double inversion recovery (DIR) – 2 inversion times used to null CSF and white matter – DIR improved MS lesion detection in the infratentorial brain by 56% compared to FLAIR (p=0.02) (Wattjesa et al. 2007) Figure from: Wattjes et al. 2007

9. PURPOSE Develop new partially T1 weighted MRI sequences that utilize the power of inversion recovery to null signal from gray matter (GM) and white matter (WM) Improve diagnosis of T1 hyperintense and enhancing pathology at the gray white junction

10. Materials and Methods Siemens Avanto 1.5T MRI system Standard circular polarized head coil used on healthy adult volunteer. Following variables were held constant: – Echo time (TE) of 11 ms – Receiver bandwith of 16 kHz – Single excitation – Slice thickness of 5 mm – 29 sections – 256 x 256 matrix size. – Field of view: 220 mm – Phase oversampling: 20%

11. Materials and Methods Multiple TR and TI times were chosen in order to optimize white matter and gray matter signal nulling. White matter inversion recovery (WMIR) and Gray matter inversion recovery (GMIR) sequences were chosen at mild and moderate T1 weighting High fat signal was maintained on all sequences to ensure high conspicuity of T1 hyperintense pathology

12. Results Four overall sequences were chosen Mild and moderate T1 weighted WMIR TR ranged from 1000-1700 ms TI ranged from 300-350 ms Mild and moderate T1 weighted GMIR TR ranged from 1000-2500 ms TI ranged from 350-630 ms TI: 300-630 TR: 1000-2500 TE: 11 Times not to scale. TI, TE and TR in milliseconds. Image modified from http://mri-q.com/what-is-ir.html © 2014 AD Elster, ELSTER LLChttp://mri-q.com/what-is-ir.html

13. Results Four overall sequences were chosen Mild and moderate T1 weighted WMIR TR ranged from 1000-1700 ms TI ranged from 300-350 ms Mild and moderate T1 weighted GMIR TR ranged from 1000-2500 ms TI ranged from 350-630 ms TI: 300-630 TR: 1000-2500 TE: 11 Times not to scale. TI, TE and TR in milliseconds. Image modified from http://mri-q.com/what-is-ir.html © 2014 AD Elster, ELSTER LLChttp://mri-q.com/what-is-ir.html

14. Results: Mildly T1 weighted WMIR TR 1700 TI 350 Signal intensities: WM – 25GM – 180CSF – 250Fat – 520 Ratio of WM to GM: 14%Ratio of WM to Fat: 5%

15. Results: Moderately T1 weighted WMIR TR 1000 TI 300 Signal intensities: WM – 25GM – 55CSF – 65Fat – 380 Ratio of WM to GM: 45%Ratio of WM to Fat: 7%

16. Results: Mildy T1 weighted GMIR TR 2500 TI 630 Signal intensities: WM – 220GM – 20CSF – 205Fat – 650 Ratio of GM to WM: 9%Ratio of GM to Fat: 4%

17. Results: Moderately T1 weighted GMIR TR 1000 TI 350 Signal intensities: WM – 90GM – 10CSF – 60Fat – 525 Ratio of GM to WM: 14%Ratio of GM to Fat: 2%

18. Results Substantial nulling of WM and GM signal was achieved. Sequences had both mild and intermediate T1 and T2 weighting, with the nulled tissue having near zero signal Fat signal intensity was maintained

19. Conclusion Inversion recovery is a powerful tool that increases image contrast by nulling background tissue T1 weighted GMIR and WMIR are new sequences which may improve diagnosis of T1 hyperintense pathology such as: – Metastastic disease – Small vascular malformations Further research is necessary to test these new sequences

20. 1. Hori M, Okubo T, Uozumi K, et al. T1-weighted fluid-attenuated inversion recovery at low field strength: a viable alternative for T1-weighted intracranial imaging. AJNR 2003;24:648–51. 2. Lee JK, Choi HY, Lee SW, et al. Usefulness of T1-weighted image with fast inversion recovery technique in intracranial lesions: comparison with T1-weighted spin echo image. Clin Imaging 2000;24:263–69. 3. Wattjesa MP, Lutterbeya GG, Giesekea J,et al. Double Inversion Recovery Brain Imaging at 3T: Diagnostic Value in the Detection of Multiple Sclerosis Lesions. AJNR 2007;28:54-59. 4. Qiana YF, Yua CL, Zhanga C, et al. MR T1-Weighted Inversion Recovery Imaging in Detecting Brain Metastases: Could It Replace T1-Weighted Spin-Echo Imaging? AJNR 2008;29:701-704. 5. Melhem ER, Bert RJ, Walker RE. Usefulness of optimized gadolinium-enhanced fast fluid-attenuated inversion recovery MR imaging in revealing lesions of the brain. AJR Am J Roentgenol 1998;171:803–07. 6. Woo JH, Henry LP, Krejza J, Melhem ER. Detection of Simulated Multiple Sclerosis Lesions on T2-weighted and FLAIR Images of the Brain: Observer Performance. Radiology 2006 241:1, 206-212. References

21. Thank You!