Negative signals for adenomyomatosis of the gallbladder upon diffusion-weighted whole body imaging with background body signal suppression/T2-weighted image fusion analysis

Magnetic Resonance Diffusion-Weighted Imaging for Detecting Fundal Intracholecystic Papillary Neoplasm inside Rokitansky-Aschoff Sinuses: A Comparison of Two Cases and a Literature Review

Rokitansky-Aschoff sinuses (RAS) are a common imaging finding in gallbladder adenomyomatosis (ADM), often presenting as fundal cystic spaces. Intracholecystic papillary neoplasm (ICPN) is a relatively uncommon pre-invasive tumor of the gallbladder epithelium that rarely involves RAS mucosa. We compare two cases that showed similar fundal cystic spaces resembling RAS, in which Magnetic Resonance Diffusion-Weighted Imaging (MR-DWI) was valuable for detecting (or ruling out) an underlying malignant ICPN. Evidence from the literature overall supports the role of MR-DWI for detecting intracholecystic malignant tissue.

The Influence of Bowel Preparation on ADC Measurements: Comparison between Conventional DWI and DWIBS Sequences

Background and objectives: The aim of the study was to assess whether there were differences between apparent diffusion coefficient (ADC) values of diffusion-weighted imaging (DWI) and diffusion-weighted imaging with background body signal suppression (DWIBS) sequences in non-prepared and prepared bowels before and after preparation with an enteric hyperosmolar agent, to assess whether ADC measurements have the potential to avoid bowel preparation and whether ADC-DWIBS has advantages over ADC-DWI. Materials and Methods: 106 adult patients without evidence of inflammatory bowel disease (IBD) underwent magnetic resonance (MR) enterography before and after bowel preparation. ADC-DWI and ADC-DWIBS values were measured in the intestinal and colonic walls demonstrating high signal intensity (SI) at DWI tracking images of b = 800 s/mm² before and after preparation. Results: There were significant difference (p < 0.0001) in both ADC-DWI and ADC-DWIBS results between non-prepared and prepared jejunum for DWI being 1.09 × 10⁻³ mm²/s and 1.76 × 10⁻³ mm²/s, respectively, and for DWIBS being 0.91 × 10⁻³ mm²/s and 1.75 × 10⁻³ mm²/s, respectively. Both ADC-DWI and DWIBS also showed significant difference between non-prepared and prepared colon (p < 0.0001), with DWI values 1.41 × 10⁻³ mm²/s and 2.13 × 10⁻³ mm²/s, and DWIBS—1.01 × 10⁻³ mm²/s and 2.04 × 10⁻³ mm²/s, respectively. No significant difference between ADC-DWI and ADC-DWIBS was found in prepared jejunum (p = 0.84) and prepared colon (p = 0.58), whereas a significant difference was found in non-prepared jejunum and non-prepared colon (p = 0.0001 in both samples). Conclusions: ADC between DWI and DWIBS does not differ in prepared bowel walls but demonstrates a difference in non-prepared bowel. ADC in non-prepared bowel is lower than in prepared bowel and possible overlap with the ADC range of IBD is possible in non-prepared bowel. ADC-DWIBS has no advantage over ADC-DWI in regard to IBD assessment.

Diagnostic performance of diffusion-weighted imaging for differentiating benign and malignant gallbladder lesions: A systematic review and meta-analysis

BACKGROUND

Although diffusion-weighted imaging (DWI) has been characterized as an alternative imaging modality for gallbladder (GB) lesions, it has not been routinely used in clinical practice because of relatively low signal-to-noise ratio.

PURPOSE

To assess the sensitivity and specificity of the diagnostic performance of DWI for differentiating benign and malignant GB lesions.

STUDY TYPE

Meta-analysis.

POPULATION

Patients with GB lesions.

FIELD STRENGTH/SEQUENCE

DWI at 3.0T or 1.5T.

ASSESSMENT

PubMed and EMBASE were searched following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses of Diagnostic Test Accuracy guidelines.

STATISTICAL TESTS

Bivariate modeling and hierarchical summary receiver operating characteristic (HSROC) modeling were performed to compare the overall diagnostic performance of DWI. Subgroup analyses were performed for qualitative and quantitative assessment of the DWI. Meta-regression analyses were performed according to the characteristics of the patients, study, and MRI.

RESULTS

Eight studies (including 557 patients) were included. The DWI exhibited a pooled sensitivity of 91%, a pooled specificity of 87%, and HSROC of 0.95. In subgroup analyses, qualitative assessment (sensitivity, 90%; specificity, 87%; HSROC, 0.94) was more accurate than quantitative assessment (sensitivity, 82%; specificity, 86 %; HSROC, 0.88). On meta-regression analysis, studies that used 3.0T field strength and thinner slices (≤5 mm) reported a significantly higher sensitivity (P ≤ 0.02) than those using only 1.5T field strength and thicker slices (>5 mm).

DATA CONCLUSION

DWI can discriminate malignant from benign GB lesions with excellent diagnostic performance in both qualitative and quantitative assessments. To enhance the diagnostic ability of DWI, images obtained with thinner slices (≤5 mm) with 3T field strength and qualitative assessment are recommended.

LEVEL OF EVIDENCE

3 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2018;47:1375-1388.