Conformance of a 3T radiotherapy MRI scanner to the QIBA Diffusion Profile

Abstract

Purpose To assess the technical performance of the apparent diffusion coefficient (ADC) on a dedicated 3T radiotherapy scanner, using a standardized phantom and sequences. Investigations into factors that could impact the technical performance of ADC in the clinic were also completed, including changing the slice‐encoded imaging direction and the reference sample ADC value. Methods ADC acquisitions were performed monthly on an isotropic diffusion phantom over 1 year. Measurements of ADC %bias, coefficients of variation for short‐/long‐term repeatability and precision (CVST/CVLT and CVP), and b‐value dependency (Depb) were calculated. The measurements were then assessed according to the Quantitative Imaging Biomarker Alliance (QIBA) Diffusion Profile specifications. Results The average of all measurements over the year was within Profile recommended ranges. This included when testing was performed in different imaging directions, and on samples that had different ADC reference values (0.4–1.1 μm2/ms). Results in the axial plane for the central water vial included a bias of +0.05%, CVST /CVLT/CVP = 0.1%/ 0.9%/0.4% and Depb = 0.4%. Conclusions The technical performance of ADC on a radiotherapy dedicated MRI scanner over the course of 12 months was considered conformant to the QIBA Profile. Quantifying these metrics and factors that may affect the performance is essential in progressing the use of ADC clinically: ensuring that the observed change of ADC in a tissue is due to a physiological response and not measurement variability.

Phantoms for Quantitative Body MRI: a review and discussion of the phantom value

“…Numerous studies have corroborated the effectiveness of MRI phantoms in reproducibility studies. Phantoms with materials designed for a particular application, such as T1 and T2 measurement, are widely used to evaluate reproducibility [5,[45][46][47][48][49]. MRI phantoms are essential in multi-center studies, as they provide a standardized approach for assessing reproducibility across different platforms, which is vital for improving diagnostic accuracy [14,22,[50][51][52][53].…”

“…Quantitative MRI methods can be paired with radiotherapy treatment to assess response to treatment and progression of disease [90]. As a result, phantoms have been used to measure the reproducibility of ADC on MR-Linac [91,92] and MRI systems used by radiotherapy teams [48]. Given the necessity of phantoms for ensuring proper radiation dose, the MR-Linac community has readily adopted the use of phantoms for MRI measurements.…”

Delivering a Quantitative Imaging Agenda

“…Vendors and researchers implement and test these solutions to assess their feasibility and efficacy. To be clinically feasible, the consensus Profile should ideally be tested for conformance in at least three clinical imaging centres [8]. Each Profile includes a checklist that summarises all the necessary steps an imaging site needs to fulfil to achieve the described performance of the quantitative imaging biomarker.…”