Implementation of a high-resolution, high-contrast magnetic resonance imaging protocol with extended delayed phases for peritoneal mesothelioma

Our plain-English summary of Implementation of a high-resolution, high-contrast magnetic resonance imaging protocol with extended delayed phases for peritoneal mesothelioma, by M. Medved, H.D.D. Witmer, A. Dhiman, et al (Quantitative Imaging in Medicine and Surgery, 2024).

The study

• Authors: M. Medved, H.D.D. Witmer, A. Dhiman, Y. Berger, S.K. Sherman, E.S. Hindi, S.G. Armato, I.S. Reiser, A. Oto, R.M. Engelmann, H.L. Kindler, N.C. Oren, C.B. Harmath, K.K. Turaga
• Journal: Quantitative Imaging in Medicine and Surgery
• Published: 2024;14(3):2580-2589
• Read it: PubMed · Publisher · Free full text

Abstract

Background: Imaging of peritoneal malignancies using conventional cross-sectional imaging is challenging, but accurate assessment of peritoneal disease burden could guide better selection for definitive surgery. Here we demonstrate feasibility of high-resolution, high-contrast magnetic resonance imaging (MRI) of peritoneal mesothelioma and explore optimal timing for delayed post-contrast imaging.

Methods: Prospective data from inpatients with malignant peritoneal mesothelioma (MPM), imaged with a novel MRI protocol, were analyzed. The new sequences augmenting the clinical protocol were (I) pre-contrast coronal high-resolution T2-weighted single-shot fast spin echo (COR hr T2w SSH FSE) of abdomen and pelvis; and (II) post-contrast coronal high-resolution three-dimensional (3D) T1-weighted modified Dixon (COR hr T1w mDIXON) of abdomen, acquired at five delay times, up to 20 min after administration of a double dose of contrast agent. Quantitative analysis of contrast enhancement was performed using linear regression applied to normalized signal in lesion regions of interest (ROIs). Qualitative analysis was performed by three blinded radiologists.

Results: MRI exams from 14 participants (age: mean ± standard deviation, 60±12 years; 71% male) were analyzed. The rate of lesion contrast enhancement was strongly correlated with tumor grade (cumulative nuclear score) (r=-0.65, P<0.02), with 'early' delayed phase (12 min post-contrast) and 'late' delayed phase (19 min post-contrast) performing better for higher grade and lower grade tumors, respectively, in agreement with qualitative scoring of image contrast.

Conclusions: High-resolution, high-contrast MRI with extended post-contrast imaging is a viable modality for imaging peritoneal mesothelioma. Multiple, extended (up to 20 min post-contrast) delayed phases are necessary for optimal imaging of peritoneal mesothelioma, depending on the grade of disease.

2024 Quantitative Imaging in Medicine and Surgery. All rights reserved.

In plain English

This phase II clinical trial at the University of Chicago tested a new, more detailed MRI scanning method for malignant peritoneal mesothelioma, a mesothelioma of the abdominal lining. Fourteen patients with surgery planned, enrolled from those screened between February 2019 and August 2020, were scanned with added high-resolution sequences and a double dose of contrast agent. Images were taken at several times up to 20 minutes after the injection. The article did not study asbestos exposure. The authors tracked how 52 lesions took up contrast over time. Some lesions kept brightening up to 20 minutes, while others were already fading by 4 minutes. The rate of uptake was correlated with tumor grade, measured as cumulative nuclear score (Spearman coefficient minus 0.65, P=0.017). Three radiologists rated the later images (about 19 minutes) better than the earlier images (about 12 minutes) in 55% of scans, equal in 14% and worse in 31%. The authors concluded that several extended delayed image phases are needed, depending on tumor grade. They noted the small number of participants and that the study was not designed to test diagnostic accuracy.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Prospective phase II clinical trial (NCT03867578) testing the feasibility of a new MRI imaging protocol
• Who was studied: 14 patients with biopsy-proven malignant peritoneal mesothelioma and cytoreductive surgery planned within 60 days. They were enrolled from patients at a multi-disciplinary mesothelioma clinic at the University of Chicago who were screened between February 2019 and August 2020; the number screened is not reported. Median age was 60 (range 26 to 74). There were 10 men and 4 women. 13 had epithelioid and 1 had biphasic mesothelioma. Sixteen scans were done, and one pre-chemotherapy scan per subject was analyzed.
• Exposure: No asbestos exposure was studied or reported. What was studied was an MRI protocol. It added high-resolution T2-weighted and post-contrast T1-weighted sequences and used a double dose (0.2 mmol/kg) of the gadolinium contrast agent gadoterate meglumine (Dotarem). Images were taken at delays of about 4, 7, 13, 16 and 20 minutes.
• Main results:
  • In the per-subject analysis, the average rate of lesion contrast enhancement was correlated with age at -0.33 (P=0.24), with nuclear grade at -0.62 (P=0.025), and with cumulative nuclear score at -0.65 (P=0.017). The significance threshold for the grade measures was set at 0.025.
  • A mean of 3.7 lesions per subject was outlined (range 2 to 6), for a total of 52 lesions (38 mass type, 14 linear type). The mean lesion slope was below zero (P<0.001). There was no significant difference between mass and linear lesions in mean slope (P=0.24) or in the proportion of lesions with positive slopes (P=0.28).
  • A large percentage of lesions kept enhancing up to 20 minutes after contrast, while some were already washing out at 4 minutes.
  • In the radiologists' review, late delayed images (about 19 minutes) were rated superior to early delayed images (about 12 minutes) in 55% of scans, equal in 14%, and inferior in 31%.
  • For reader 1, cumulative nuclear score was significantly correlated with reader preference (r=0.65, P=0.02). There was no significant correlation when all readers' results for both regions were combined (r=0.27, P=0.40).
  • No statistically significant differences in enhancement rate were found between subjects with and without cardiac disease (P=0.08), prior chemotherapy (P=0.62), or prior cancer reduction surgery (P=0.44).
• The authors' conclusion: The authors concluded that the high-resolution, high-contrast MRI protocol is feasible for peritoneal mesothelioma. They also concluded that multiple, extended delayed-phase images are necessary because lesions of different nuclear grade take up contrast differently.
• Limitations the authors state:
  • The low number of participants limited statistical power.
  • The optimal number and timing of delayed images is still unclear, because early post-contrast timepoints were not analyzed.
  • The high-resolution T1-weighted sequence did not cover the entire abdomen.
  • The study was not designed to evaluate the diagnostic performance of the new MRI protocol. A comparison with operative findings is underway.

Topics

Medical terms in this study, explained in our Lexicon: Peritoneal Mesothelioma.

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