Daily Intravoxel Incoherent Motion (IVIM) In Prostate Cancer Patients During MR-Guided Radiotherapy—A Multicenter Study

Abstract

PurposeDaily quantitative MR imaging during radiotherapy of cancer patients has become feasible with MRI systems integrated with linear accelerators (MR-linacs). Quantitative images could be used for treatment response monitoring. With intravoxel incoherent motion (IVIM) MRI, it is possible to acquire perfusion information without the use of contrast agents. In this multicenter study, daily IVIM measurements were performed in prostate cancer patients to identify changes that potentially reflect response to treatment.Materials and MethodsForty-three patients were included, treated with 20 fractions of 3 Gy on a 1.5 T MR-linac. IVIM measurements were performed on each treatment day. The diffusion coefficient (D), perfusion fraction (f), and pseudo-diffusion coefficient (D*) were calculated based on the median signal intensities in the non-cancerous prostate and the tumor. Repeatability coefficients (RCs) were determined based on the first two treatment fractions. Separate linear mixed-effects models were constructed for the three IVIM parameters.ResultsIn total, 726 fractions were analyzed. Pre-treatment average values, measured on the first fraction before irradiation, were 1.46 × 10−3 mm2/s, 0.086, and 28.7 × 10−3 mm2/s in the non-cancerous prostate and 1.19 × 10−3 mm2/s, 0.088, and 28.9 × 10−3 mm2/s in the tumor, for D, f, and D*, respectively. The repeatability coefficients for D, f, and D* in the non-cancerous prostate were 0.09 × 10−3 mm2/s, 0.05, and 15.3 × 10−3 mm2/s. In the tumor, these values were 0.44 × 10−3 mm2/s, 0.16, and 76.4 × 10−3 mm2/s. The mixed effects analysis showed an increase in D of the tumors over the course of treatment, while remaining stable in the non-cancerous prostate. The f and D* increased in both the non-cancerous prostate and tumor.ConclusionsIt is feasible to perform daily IVIM measurements on an MR-linac system. Although the repeatability coefficients were high, changes in IVIM perfusion parameters were measured on a group level, indicating that IVIM has potential for measuring treatment response.

Quantification of Tumor Hypoxia through Unsupervised Modelling of Consumption and Supply Hypoxia MR Imaging in Breast Cancer

“…Diffusion has high SNR and has been shown to be very stable [ 29 ]. CSH imaging is an appealing candidate for dose painting [ 30 ] to achieve dose escalation within hypoxic areas because it is non-invasive, the imaging time is a few minutes, and neither contrast media nor ionizing radiation are needed. Furthermore, integration of MRI and linear accelerators is anticipated to revolutionize cancer treatment, allowing real time adaptation of radiotherapy to MR-derived biomarkers of physiological changes, such as hypoxia [ 31 ].…”

In Vivo and Phantom Repeatability of Diffusion-Weighted MRI Sequences on 1.5T MRI-Linear Accelerator (MR-Linac) and MR Simulator Devices for Head and Neck Cancers: Results from a Prospective R-IDEAL Stage 2a Evaluation of Tumor and Normal Tissue Apparent Diffusion Coefficients as Quantitative Imaging Biomarkers

“…wCV values on the MR-linac were within 5% and were comparable to the diagnostic system. Kooreman et al [15] assessed the reproducibility of intravoxel incoherent motion parameters in prostate cancer patients on the MR-linac and found the RDC of the diffusion coefficient to be 0.09x10 biomarkers and standardization of scan protocols across sites is necessary for large-cohort, multi-center studies [13,19].…”

“…wCV values on the MR-linac were within 5% and were comparable to the diagnostic system. Kooreman et al [15] assessed the reproducibility of intravoxel incoherent motion parameters in prostate cancer patients on the MR-linac and found the RDC of the diffusion coefficient to be 0.09×10 −3 mm 2 /s for non-cancerous prostate and 0.44×10 −3 mm 2 /s for tumors. For a HNC cohort on a 0.35T MR-linac, Yang et al [17] did not explicitly calculate reproducibility metrics but found the ADC of the brainstem to be within 0.47-0.57×10 −3 mm 2 /s across repeat imaging sessions.…”

“…The clinical implementation of hybrid MRI/linear accelerator (MR-linac) devices has made it possible to acquire quantitative MRI sequences during every RT treatment fraction [13][14][15][16][17]. Current MR-linac systems enable on-line treatment plan adaptation based on changes in tumor size and shape and anatomical deformations.…”

Longitudinal Correlations Between Intravoxel Incoherent Motion (IVIM) and Dynamic Contrast-Enhanced (DCE) MRI During Radiotherapy in Prostate Cancer Patients

“…Scan parameters can be found in Table 2 . The IVIM sequence was optimized for the MR-linac system, which has lower gradient performance compared to diagnostic systems and lower SNR due to the simpler receive coil system ( 15 , 23 ). To compensate this, the highest b-value was limited to 500 s/mm 2 , and a relatively large isotropic acquisition voxel size of 4 mm 3 was used.…”