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Validation of daily 0.35 T diffusion-weighted MRI for MRI-guided glioblastoma radiotherapy
Natalia Lutsik1, Siamak P Nejad-Davarani1, Alessandro Valderrama1
1Department of Radiation Oncology, Sylvester Comprehensive Cancer Center, University of Miami Miller School of Medicine, Miami, Florida, USA.
Background:
MRI-Linac systems enable daily diffusion-weighed imaging (DWI) MRI scans for assessing glioblastoma tumor changes with radiotherapy treatment.
Purpose:
Our study assessed the image quality of echoplanar imaging (EPI)-DWI scans compared with turbo spin echo (TSE)-DWI scans at 0.35 Tesla (T) and compared the apparent diffusion coefficient (ADC) values and distortion of EPI-DWI on 0.35 T MRI-Linac compared to high-field diagnostic MRI scanners.
Methods:
The calibrated National Institute of Standards and Technology (NIST)/Quantitative Imaging Biomarkers Alliance (QIBA) Diffusion Phantom was scanned on a 0.35 T MRI-Linac, and 1.5 T and 3 T MRI with EPI-DWI. Five patients were scanned on a 0.35 T MRI-Linac with a TSE-DWI sequence, and five other patients were scanned with EPI-DWI on a 0.35 T MRI-Linac and a 3 T MRI. The quality of images was compared between the TSE-DWI and EPI-DWI on the 0.35 T MRI-Linac assessing signal-to-noise ratios and presence of artifacts. EPI-DWI ADC values and distortion magnitude were measured and compared between 0.35 T MRI-Linac and high-field MRI for both phantom and patient studies.
Results:
The average ADC differences between EPI-DWI acquired on the 0.35 T MRI-Linac, 1.5 T and 3 T MRI scanners and published references in the phantom study were 1.7%, 0.4% and 1.0%, respectively. Comparing the ADC values based on EPI-DWI in glioblastoma tumors, there was a 3.36% difference between 0.35 and 3 T measurements. Susceptibility-induced distortions in the EPI-DWI phantoms were 0.46 ± 1.51 mm for 0.35 MRI-Linac, 0.98 ± 0.51 mm for 1.5 T MRI and 1.14 ± 1.88 mm for 3 T MRI; for patients -0.47 ± 0.78 mm for 0.35 T and 1.73 ± 2.11 mm for 3 T MRIs. The mean deformable registration distortion for a phantom was 1.1 ± 0.22 mm, 3.5 ± 0.39 mm and 4.7 ± 0.37 mm for the 0.35 T MRI-Linac, 1.5 T MRI, and 3 T MRI scanners, respectively; for patients this distortion was -0.46 ± 0.57 mm for 0.35 T and 4.2 ± 0.41 mm for 3 T. EPI-DWI 0.35 T MRI-Linac images showed higher SNR and lack of artifacts compared with TSE-DWI, especially at higher b-values up to 1000 s/mm2.
Conclusion:
EPI-DWI on a 0.35 T MRI-Linac showed superior image quality compared with TSE-DWI, minor and less distortions than high-field diagnostic scanners, and comparable ADC values in phantoms and glioblastoma tumors. EPI-DWI should be investigated on the 0.35 T MRI-Linac for prediction of early response in patients with glioblastoma.
Insights
Diffusion-weighed imaging (DWI) on a 0.35 T MRI-Linac offers superior image quality and less distortion than high-field scanners. This technique shows comparable apparent diffusion coefficient (ADC) values, making it promising for glioblastoma response prediction.
Area of Science:
- Radiology
- Oncology
- Medical Imaging
Background:
- MRI-Linac systems facilitate daily diffusion-weighed imaging (DWI) for monitoring glioblastoma during radiotherapy.
- Assessing treatment response in glioblastoma requires high-quality MRI scans.
Purpose of the Study:
- Compare image quality of echoplanar imaging (EPI)-DWI versus turbo spin echo (TSE)-DWI at 0.35 T.
- Evaluate apparent diffusion coefficient (ADC) values and image distortion of EPI-DWI on a 0.35 T MRI-Linac against high-field MRI scanners.
Main Methods:
- Scanned a NIST/QIBA Diffusion Phantom using EPI-DWI on 0.35 T, 1.5 T, and 3 T MRI scanners.
- Acquired TSE-DWI and EPI-DWI sequences on a 0.35 T MRI-Linac in patients.
- Compared image quality (SNR, artifacts) between TSE-DWI and EPI-DWI on the 0.35 T MRI-Linac.
- Measured EPI-DWI ADC values and distortion in phantoms and patients across different MRI strengths.
Main Results:
- EPI-DWI on the 0.35 T MRI-Linac demonstrated higher signal-to-noise ratios and fewer artifacts than TSE-DWI, particularly at higher b-values.
- Average ADC differences in phantoms were minimal: 1.7% (0.35 T), 0.4% (1.5 T), and 1.0% (3 T).
- Glioblastoma tumor ADC values showed a 3.36% difference between 0.35 T and 3 T EPI-DWI.
- Susceptibility-induced distortions were generally lower on the 0.35 T MRI-Linac compared to 1.5 T and 3 T scanners in both phantom and patient studies.
Conclusions:
- EPI-DWI on a 0.35 T MRI-Linac provides superior image quality and reduced distortion compared to TSE-DWI and high-field scanners.
- ADC values obtained with EPI-DWI on the 0.35 T MRI-Linac are comparable to those from high-field systems.
- EPI-DWI on the 0.35 T MRI-Linac warrants further investigation for predicting early glioblastoma treatment response.
