Considering tumour volume for motion corrected DWI of colorectal liver metastases increases sensitivity of ADC to detect treatment-induced changes

Abstract

ADC is a potential post treatment imaging biomarker in colorectal liver metastasis however measurements are affected by respiratory motion. This is compounded by increased statistical uncertainty in ADC measurement with decreasing tumour volume. In this prospective study we applied a retrospective motion correction method to improve the image quality of 15 tumour data sets from 11 patients. We compared repeatability of ADC measurements corrected for motion artefact against non-motion corrected acquisition of the same data set. We then applied an error model that estimated the uncertainty in ADC repeatability measurements therefore taking into consideration tumour volume. Test-retest differences in ADC for each tumour, was scaled to their estimated measurement uncertainty, and 95% confidence limits were calculated, with a null hypothesis that there is no difference between the model distribution and the data. An early post treatment scan (within 7 days of starting treatment) was acquired for 12 tumours from 8 patients. When accounting for both motion artefact and statistical uncertainty due to tumour volumes, the threshold for detecting significant post treatment changes for an individual tumour in this data set, reduced from 30.3% to 1.7% (95% limits of agreement). Applying these constraints, a significant change in ADC (5 th and 20 th percentiles of the ADC histogram) was observed in 5 patients post treatment. For smaller studies, motion correcting data for small tumour volumes increased statistical efficiency to detect post treatment changes in ADC. Lower percentiles may be more sensitive than mean ADC for colorectal metastases.

MRI Apparent Diffusion Coefficient (ADC) as a Biomarker of Tumour Response: Imaging-Pathology Correlation in Patients with Hepatic Metastases from Colorectal Cancer (EORTC 1423)

“…The stability and repeatability of ADC measurements in this multicentre setting, which critically affects the performance of a biomarker [2], should have been adequate to test our hypothesis. The baseline reproducibility of ADC metrics on three of the scanners from different vendors in this study investigated in a preliminary study of 20 patients with colorectal liver metastases and imaged using the same protocols as in the current study showed a coefficient of variation (CoV) of 6.2% and 95% limits of agreement of 21% [7]. This is highly comparable with the results from other single centre studies; the CoV of ADC measurements in abdominal organs in single centre studies has been shown to vary between 1.7 and 7% [7,23] with 95% limits of agreement ranging from approximately 10-30%.…”

“…The baseline reproducibility of ADC metrics on three of the scanners from different vendors in this study investigated in a preliminary study of 20 patients with colorectal liver metastases and imaged using the same protocols as in the current study showed a coefficient of variation (CoV) of 6.2% and 95% limits of agreement of 21% [7]. This is highly comparable with the results from other single centre studies; the CoV of ADC measurements in abdominal organs in single centre studies has been shown to vary between 1.7 and 7% [7,23] with 95% limits of agreement ranging from approximately 10-30%. In comparison, in multicentre studies, ADC measurement variability is greater as a result of differences between imaging platform, manufacturer, scanner model, and field strength [6,24].…”

“…Multicentre assessment of ADC has previously been challenging. Variations in imaging sequence implementation across scanning platforms, modified acquisition techniques designed to compensate for physiological motion, and variation in analysis techniques [6,7] affect the stability and reproducibility of ADC measurements. Therefore, to mitigate these risks, we designed a prospective study that employed validated data acquisition protocols and standardized analyses within a strong quality assurance and quality control framework [8].…”

Recommendations for improved reproducibility of ADC derivation on behalf of the Elekta MRI-linac consortium image analysis working group

“…Other specific points of attention when calculating ADC include pre-processing of the image data. For example, to minimize the effect of motion, registration between b-values is recommended [ 51 ], and is available on most MRI scanner software, including the Unity MRI-linac. As a minimum, b-value images should visually be inspected for motion and artefacts.…”

Comparison of different ROI analysis methods for liver lesion characterization with simplified intravoxel incoherent motion (IVIM)

“…First, it was a retrospective study with inherent methodological limitations. For example, due to the lack of raw data, no motion correction of the individual images 43 could be performed before averaging. Second, although the total number of lesions included was relatively large, only common lesion types were analyzed, which may affect the generalizability of the results.…”