Diagnostic accuracy of RBC scintigraphy and CTA for detection of patients with suspected lower gastrointestinal bleeding: a systematic review and meta-analysis.

OBJECTIVE: Detection of lower gastrointestinal bleeding (LGIB) through noninvasive modalities is very important in the successful management of LGIB. RBC scintigraphy and CT have a role in the detection of LGIB and guiding the management of patient by localization of the bleeding site. However, only a small number of studies have evaluated the role of RBC scintigraphy and CT in the diagnosis of LGIB. This systematic review was conducted to evaluate the diagnostic performance of RBC scintigraphy and CT in the detection of LGIB in patients with clinical or biochemical findings suspicious of LGIB. METHODS: This systematic review followed PRISMA guidelines. Searches in PubMed, Scopus, and Embase were conducted using relevant keywords, and articles published through 30 April 2022, were included. Using endoscopy or surgical outcomes as the reference standard, the numbers of true and false positives and true and false negatives were extracted. Pooled estimates of diagnostic test accuracy - including sensitivity, specificity, positive likelihood ratio, negative likelihood ratio, and summary ROC (SROC) curve - were generated using bivariate random-effects meta-analysis. RESULTS: Three studies comprising 171 patients were included in the systematic review and meta-analysis. The pooled sensitivity, specificity, positive likelihood ratio, and negative likelihood ratio for the detection of LGIB using RBC scintigraphy were 0.787 (95% CI, 0.643-0.893), 0.289 (95% CI, 0.164-0.443), 1.214 (95% CI, 0.923-1.597) and 0.576 (95% CI, 0.296-1.121) respectively. The area under the SROC curve was 0.73. The pooled sensitivity, specificity, positive likelihood ratio, and negative likelihood ratio for the detection of LGIB using CT were 0.931 (95% CI, 0.772-0.992), 0.870 (95% CI, 0.737-0.951), 6.085 (95% CI, 0.840-44.097), 0.126 (95% CI, 0.006-2.509) respectively. The area under the SROC curve was 0.095. CONCLUSION: RBC scintigraphy has overall good sensitivity and CTA has excellent sensitivity specificity, positive and negative likelihood ratio in the detection of LGIB in patients with clinical or biochemical findings suspicious for LGIB.CTA along with RBC scintigraphy can be used algorithmically to rule out patients who do not have a localization for the site of LGIB thereby helping these patients to avoid invasive procedures like endoscopy or surgical explorations.

PET/CT imaging in invasive endometriosis: a way to minimize missed diagnosis and reduce invasive interventions.

INTRODUCTION: Heterogeneous and nonspecific symptoms make invasive endometriosis a difficult entity to diagnose. Small lesions with absent associated changes can be easily missed in cross-sectional imaging. Even when the lesions satisfy the thresholds for various investigations, their appearance changes with cyclical fluctuations in the hormonal levels. Therefore, newer approaches are needed to achieve correct diagnosis. METHODS: Six females in reproductive age group (mean age = 32.5 ±â€…4.3 years) were retrospectively selected, wherein the diagnosis of invasive endometriosis was confirmed after 18F-FDG-PET/CT. Indications for PET/CT were staging in 4 patients, suspected progression in 1 and suspected inflammatory bowel disease in one patient. The study was repeated in proliferative phase in two patients and in the menstrual phase in another patient. FNAC was available in two patients and a drop in CA125 was documented in the last patient. RESULTS: In five patients metabolically active lesions were seen in PET/CT and in the last, activity was absent despite symptoms. Repeat menstrual phase imaging in the last patient confirmed the diagnosis. In two patients with metabolically active lesions at baseline, resolution was seen in proliferative phase PET/CT. In the other two patients, repeat study was not indicated as FNAC revealed normal endometrial tissue and in the last patient, significant drop in CA125 was documented after just 2 weeks. In all of these patients, the final diagnosis was of invasive endometriosis. CONCLUSION: In reproductive-age women, PET/CT acquisition should be optimized in the context of menstrual cycle. This approach can be used to non-invasively rule in/rule out endometriosis, especially with repeat imaging in proper menstrual phase.

Denoising Tc-99m DMSA images using Denoising Convolutional Neural Network with comparison to a Block Matching Filter.

INTRODUCTION: A DnCNN for image denoising trained with natural images is available in MATLAB. For Tc-99m DMSA images, any loss of clinical details during the denoising process will have serious consequences since denoised image is to be used for diagnosis. The objective of the study was to find whether this pre-trained DnCNN can be used for denoising Tc-99m DMSA images and compare its performance with block matching 3D (BM3D) filter. MATERIALS AND METHODS: Two hundred forty-two Tc-99m DMSA images were denoised using BM3D filter (at sigma = 5, 10, 15, 20, and 25) and DnCNN. The original and denoised images were reviewed by two nuclear medicine physicians and also assessed objectively using the image quality metrics: SSIM, FSIM, MultiSSIM, PIQE, Blur, GCF, and Brightness. Wilcoxon signed-rank test was applied to find the statistically significant difference between the value of image quality metrics of the denoised images and the corresponding original images. RESULTS: Nuclear medicine physicians observed no loss of clinical information in DnCNN denoised image and superior image quality compared to its original and BM3D denoised images. Edges/boundaries of the scar were found to be well preserved, and doubtful scar became obvious in the denoised image. Objective assessment also showed that the quality of DnCNN denoised images was significantly better than that of original images at P -value <0.0001. CONCLUSION: The pre-trained DnCNN available with MATLAB Deep Learning Toolbox can be used for denoising Tc-99m DMSA images, and the performance of DnCNN was found to be superior in comparison with BM3D filter.

Molecular Imaging Assessment of Hormonally Sensitive Breast Cancer: An Appraisal of 2-[18F]-Fluoro-2-Deoxy-Glucose and Newer Non-2-[18F]-Fluoro-2-Deoxy-Glucose PET Tracers.

Hormone-sensitive breast cancer, which demonstrates hormone receptor positivity, accounts for approximately 75% of newly diagnosed breast cancer. 2-[18F]-Fluoro-2-deoxy-glucose is the nonspecific radiotracer of glucose metabolism as opposed to specific receptor based tracers like 16α-[18F]-fluoro-17ß-estradiol and [18F]-fluoro-furanyl-norprogesterone, which provide essential information about receptor status in the management of hormonally active malignancies. The complementary information provided by (a) 2-[18F]-fluoro-2-deoxy-glucose imaging for staging and prognostication along with (b) analyzing the hormonal receptor status with receptor-based PET imaging in breast cancer can optimize tumor characterization and influence patient management.

PET/computed tomography enterography.

Interpretation of gastrointestinal PET/computed tomography (PET/CT) is often complicated by anatomy including bowel folds, flexures, variant redundancy, decompressed bowel segments and physiological uptake. This makes it very difficult to identify both true positives and true negatives, compromising both sensitivity and specificity. CT enterography is increasingly being integrated into the field of nuclear medicine to address these issues. This technique uses the combination of negative/neutral contrast to distend the lumen of the gut and iodinated contrast to enhance the gastrointestinal wall and pathological findings. Apart from augmentation in the diagnostic performance, the technique also improves the quality of the imaging, confidence of the reporting physician and inter-rater agreement. Therefore, this technique has found favor among nuclear medicine physicians, in the imaging of chronic inflammatory disorders and malignancies in and of the gut. It is a feasible and easily executable procedure with minimal and manageable side-effects and should be routinely recommended in cases where interference from physiologic findings is expected.