Gastric Carcinoma: Ex Vivo MR Imaging at 7.0 T-Correlation with Histopathologic Findings

Advances in the Imaging of Esophageal and Gastroesophageal Junction Malignancies

Accurate imaging is key for the diagnosis and treatment of esophageal and gastroesophageal junction cancers . Current imaging modalities, such as computed tomography (CT) and 18F-FDG (2-deoxy-2-[18F]fluoro-D-glucose) positron emission tomography (PET)/CT, have limitations in accurately staging these cancers. MRI shows promise for T staging and residual disease assessment. Novel PET tracers, like FAPI, FLT, and hypoxia markers, offer potential improvements in diagnostic accuracy. 18F-FDG PET/MRI combines metabolic and anatomic information, enhancing disease evaluation. Radiomics and artificial intelligence hold promise for early detection, treatment planning, and response assessment. Theranostic nanoparticles and personalized medicine approaches offer new avenues for cancer therapy.

Differentiating T1a-T1b from T2 in gastric cancer lesions with three different measurement approaches based on contrast-enhanced T1W imaging at 3.0 T

Background

To explore the diagnostic value of three different measurement approaches in differentiating T1a–T1b from T2 gastric cancer (GC) lesions.

Methods

A total of 95 consecutive patients with T1a–T2 stage of GC who performed preoperative MRI were retrospectively enrolled between January 2017 and November 2020. The parameters MRI T stage (subjective evaluation), thickness, maximum area and volume of the lesions were evaluated by two radiologists. Specific indicators including AUC, optimal cutoff, sensitivity, specificity, accuracy, positive likelihood ratio (PLR), negative likelihood ratio (NLR), positive predictive value (PPV) and negative predictive value (NPV) of MRI T stage, thickness, maximum area and volume for differentiating T1a–T1b from T2 stage lesions were calculated. The ROC curves were compared by the Delong test. Decision curve analysis (DCA) was used to evaluate the clinical benefit.

Results

The ROC curves for thickness (AUC = 0.926), maximum area (AUC = 0.902) and volume (AUC = 0.897) were all significantly better than those of the MRI T stage (AUC = 0.807) in differentiating T1a–T1b from T2 lesions, with p values of 0.004, 0.034 and 0.041, respectively. The values corresponding to the thickness (including AUC, sensitivity, specificity, accuracy, PPV, NPV, PLR and NLR) were all higher than those corresponding to the MRI T stage, maximum area and volume. The DCA curves indicated that the parameter thickness could provide the highest clinical benefit if the threshold probability was above 35%.

Conclusions

Thickness may provide an efficient approach to rapidly distinguish T1a–T1b from T2 stage GC lesions.

Esophagus and Stomach: Is There a Role for MR Imaging?

MR imaging has been increasingly used in the diagnostic work-up of benign and malignant conditions of the gastroesophageal tract. The use of an adequate MR imaging protocol is crucial, although standardization of imaging studies is still far from being implemented. Research on MR imaging-based biomarkers show promising results in assessing tumor aggressiveness and prognosis, and in the evaluation of response to treatment, both in esophageal and gastric cancers.

Improving MR sequence of 18F-FDG PET/MR for diagnosing and staging gastric Cancer: a comparison study to 18F-FDG PET/CT

Purpose

Evaluate the feasibility of fluorine-18 (¹⁸F) fluorodeoxyglucose (FDG) positron emission tomography (PET) and magnetic resonance (MR) imaging in patients with gastric cancer by optimizing the scan protocol and to compare the image quality to ¹⁸F FDG PET and computed tomography (CT).

Methods

The PET/CT and PET/MR imaging were sequentially performed in 30 patients with gastric cancer diagnosed by gastroscope using a single-injection-with-dual-imaging protocol. After intravenous injection of ¹⁸F-FDG (mean, 249 MBq), PET/CT imaging including low-dose CT was performed (mean uptake time, 47 ± 6 min), and PET/MR imaging including a T1-weighted Dixon sequence for attenuation correction and two different T2-weighted sequences was subsequently acquired (88 ± 15 min after ¹⁸F-FDG injection). Four series of images (CT from PET/CT, T1W, T2W Half-Fourier acquisition single-shot turbo spin-echo [T2W-HASTE] and T2W-BLADE from PET/MR) were visually evaluated using a 3–4 points scale for: (1) image artifacts, (2) lesion conspicuity and (3) image fusion quality. The characteristics of the primary lesions were assessed and compared between the PET/CT and PET/MR acquisitions.

Results

The image quality and lesion conspicuity of the T2W-HASTE images were significantly improved compared to that of the T2W-BLADE images. A significantly higher number of artifacts were seen in the T2W-HASTE images compared with the T1W and CT images (p < 0. 05). No differences in the accuracy of image fusion between PET/MR and PET/CT (p > 0. 05); however, significant difference was seen in the lesion conspicuity measurements (p < 0.05) with T2W-HASTE being superior. For information about the primary lesion characteristics, the T2W-HASTE images provided the most successful identifications compared with those of the T1W and PET/CT (13vs7vs5) images.

Conclusions

PET/MR with the T2W-HASTE was better at revealing the details of local stomach lesions compared with PET/CT imaging. Combining the PET/MR with the T2W-HASTE technique is a promising imaging method for diagnosing and staging gastric cancer.

Correlation of ultra-high field MRI with histopathology for evaluation of rectal cancer heterogeneity

Current clinical MRI techniques in rectal cancer have limited ability to examine cancer stroma. The differentiation of tumour from desmoplasia or fibrous tissue remains a challenge. Standard MRI cannot differentiate stage T1 from T2 (invasion of muscularis propria) tumours. Diffusion tensor imaging (DTI) can probe tissue structure and organisation (anisotropy). The purpose of this study was to examine DTI-MRI derived imaging markers of rectal cancer stromal heterogeneity and tumour extent ex vivo. DTI-MRI at ultra-high magnetic field (11.7 tesla) was used to examine the stromal microstructure of malignant and normal rectal tissue ex vivo, and the findings were correlated with histopathology. Images obtained from DTI-MRI (A0, apparent diffusion coefficient and fractional anisotropy (FA)) were used to probe rectal cancer stromal heterogeneity. FA provided the best discrimination between cancer and desmoplasia, fibrous tissue and muscularis propria. Cancer had relatively isotropic diffusion (mean FA 0.14), whereas desmoplasia (FA 0.31) and fibrous tissue (FA 0.34) had anisotropic diffusion with significantly higher FA than cancer (p < 0.001). Tumour was distinguished from muscularis propria (FA 0.61) which was highly anisotropic with higher FA than cancer (p < 0.001). This study showed that DTI-MRI can assist in more accurately defining tumour extent in rectal cancer.

Imaging strategies in the management of gastric cancer: current role and future potential of MRI

Accurate preoperative staging of gastric cancer and the assessment of tumor response to neoadjuvant treatment is of importance for treatment and prognosis. Current imaging techniques, mainly endoscopic ultrasonography (EUS), computed tomography (CT) and ¹⁸F-fluorodeoxyglucose positron emission tomography (¹⁸F-FDG PET), have their limitations. Historically, the role of magnetic resonance imaging (MRI) in gastric cancer has been limited, but with the continuous technical improvements, MRI has become a more potent imaging technique for gastrointestinal malignancies. The accuracy of MRI for T- and N-staging of gastric cancer is similar to EUS and CT, making MRI a suitable alternative to other imaging strategies. There is limited evidence on the performance of MRI for M-staging of gastric cancer specifically, but MRI is widely used for diagnosing liver metastases and shows potential for diagnosing peritoneal seeding. Recent pilot studies showed that treatment response assessment as well as detection of lymph node metastases and systemic disease might benefit from functional MRI (e.g. diffusion weighted imaging and dynamic contrast enhancement). Regarding treatment guidance, additional value of MRI might be expected from its role in better defining clinical target volumes and setup verification with MR-guided radiation treatment.

MRI evaluation of vulvar squamous-cell carcinoma in fresh radical local excision specimens for cancer localization and prediction of surgical tumor-free margins

In the surgical treatment of vulvar squamous-cell carcinoma (VSCC), tumor-free margins of 8 mm or more are considered adequate. However, limited perioperative information on the tumor-free margins other than the surgeon's own estimation is available. The purpose of this study was therefore to investigate the feasibility of ex vivo MRI in localizing VSCC and to assess the surgical tumor-free margins in fresh radical local excision (RLE) specimens to guide the surgeon during resections. Nine patients with biopsy-proven VSCC scheduled for RLE were prospectively included. Intact fresh specimens were scanned using a 7 T preclinical MR-scanner. Whole mount H&E-stained slides were obtained every 3 mm and correlated with ex vivo MRI. A pathologist annotated VSCC and minimal tumor-free margins (3 o'clock, 9 o'clock, basal) on the digitalized histological slides. An observer with knowledge of histology (the non-blinded annotation) and a radiologist blinded to histology (the blinded annotation) separately performed annotation of the same features on ex vivo MRI. Linear correlation and agreement of the ex vivo MRI measurements with histology were assessed. Diagnostic performance for VSCC localization and identification of margins less than 8 mm was expressed as positive and negative predictive values (PPV, NPV). In 153 matched ex vivo MRI slices, the observer correctly identified 79/91 margins as less than 8 mm (PPV 87%) and 110/124 margins as 8 mm or greater (NPV 89%). The radiologist correctly annotated absence of VSCC in 73/81 (NPV 90%) and presence in 65/72 (PPV 90%) slices. Sixty-four of 90 margins were correctly identified as less than 8 mm (PPV 71%) and 83/102 margins as 8 mm or greater (NPV 81%). Both non-blinded and blinded annotations were linearly correlated and demonstrated good agreement with histology. Accurate localization of VSCC and measurements of the surgical tumor-free margins in fresh RLE specimens using ex vivo MRI seems feasible. High diagnostic performance in VSCC localization and identification of margins less than 8 mm suggest ex vivo MRI to be clinically applicable.

Feasibility of free-breathing dynamic contrast-enhanced MRI of gastric cancer using a golden-angle radial stack-of-stars VIBE sequence: comparison with the conventional contrast-enhanced breath-hold 3D VIBE sequence

OBJECTIVES

To investigate the feasibility and diagnostic value of free-breathing, radial, stack-of-stars three-dimensional (3D) gradient echo (GRE) sequence ("golden angle") on dynamic contrast-enhanced (DCE) MRI of gastric cancer.

METHODS

Forty-three gastric cancer patients were divided into cooperative and uncooperative groups. Respiratory fluctuation was observed using an abdominal respiratory gating sensor. Those who breath-held for more than 15 s were placed in the cooperative group and the remainder in the uncooperative group. The 3-T MRI scanning protocol included 3D GRE and conventional breath-hold VIBE (volume-interpolated breath-hold examination) sequences, comparing images quantitatively and qualitatively. DCE-MRI parameters from VIBE images of normal gastric wall and malignant lesions were compared.

RESULTS

For uncooperative patients, 3D GRE scored higher qualitatively, and had higher SNRs (signal-to-noise ratios) and CNRs (contrast-to-noise ratios) than conventional VIBE quantitatively. Though 3D GRE images scored lower in qualitative parameters compared with conventional VIBE for cooperative patients, it provided images with fewer artefacts. DCE parameters differed significantly between normal gastric wall and lesions, with higher Ve (extracellular volume) and lower Kep (reflux constant) in gastric cancer.

CONCLUSIONS

The free-breathing, golden-angle, radial stack-of-stars 3D GRE technique is feasible for DCE-MRI of gastric cancer. Dynamic enhanced images can be used for quantitative analysis of this malignancy.

KEY POINTS

• Golden-angle radial stack-of-stars VIBE aids gastric cancer MRI diagnosis. • The 3D GRE technique is suitable for patients unable to suspend respiration. • Method scored higher in the qualitative evaluation for uncooperative patients. • The technique produced images with fewer artefacts than conventional VIBE sequence. • Dynamic enhanced images can be used for quantitative analysis of gastric cancer.

Evaluation of tongue squamous cell carcinoma resection margins using ex-vivo MR

Purpose

Purpose of this feasibility study was (1) to evaluate whether application of ex-vivo 7T MR of the resected tongue specimen containing squamous cell carcinoma may provide information on the resection margin status and (2) to evaluate the research and developmental issues that have to be solved for this technique to have the beneficial impact on clinical outcome that we expect: better oncologic and functional outcomes, better quality of life, and lower costs.

Methods

We performed a non-blinded validation of ex-vivo 7T MR to detect the tongue squamous cell carcinoma and resection margin in 10 fresh tongue specimens using histopathology as gold standard.

Results

In six of seven specimens with a histopathologically determined invasion depth of the tumor of \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${\ge }3$$\end{document}≥3 mm, the tumor could be recognized on MR, with a resection margin within a 2 mm range as compared to histopathology. In three specimens with an invasion depth of \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${<}1$$\end{document}<1 mm, the tumor was not visible on MR. Technical limitations mainly included scan time, image resolution, and the fact that we used a less available small-bore 7T MR machine.

Conclusion

Ex-vivo 7T probably will have a low negative predictive value but a high positive predictive value, meaning that in tumors thicker than a few millimeters we expect to be able to predict whether the resection margin is too small. A randomized controlled trial needs to be performed to show our hypothesis: better oncologic and functional outcomes, better quality of life, and lower costs.