Computed Tomography Abdomen-pelvis Research Articles

The effect of contact radiation shielding on breast dose during CT abdomen-pelvis: a phantom study.

This study aims to investigate if contact shielding reduces breast radiation dose during computed tomography (CT) abdomen-pelvis examinations using automatic tube current modulation to protect one of the four most radiosensitive organs during CT examinations. Dose measurements were taken with and without contact shielding across the anterior and lateral aspects of the breasts and with and without organ dose modulation (ODM) to quantify achievable dose reductions. Although there are no statistically significant findings, when comparing with and without shielding, the mean breast surface dose was reduced by 0.01μSv without ODM (1.92-1.91μSv, p=0.49) and increased by 0.03μSv with ODM (1.53-1.56μSv, p=0.44). Comparing with and without ODM, the mean breast surface dose was reduced by 0.35μSv with shielding (1.91-1.56μSv, p=0.24) and by 0.39μSv without shielding (1.92-1.53μSv, p=0.17). The addition of contact shielding does not provide significant breast surface radiation dose reduction during CT abdomen-pelvis.

Establishment of CT diagnostic reference levels (DRLs) for a Singapore healthcare cluster

IntroductionThe use of computed tomography (CT) in healthcare institutions has increased rapidly in recent years. The Singapore Health Services (SingHealth) cluster of healthcare institutions has taken the first step in establishing a local cluster-wide CT Diagnostic Reference Levels (DRL) in Singapore. CT dose data from each institution were collected through two primary dosimetry metrics: volume CT dose index (CTDIvol measured in mGy) and dose-length product (DLP measured in mGy.cm). MethodsData from 19 CT scanners in seven institutions under one of Singapore healthcare cluster were retrospectively collected and analysed. The five common adult CT examinations analysed were CT Brain (non-contrast enhanced), CT Chest (IV contrast enhanced), CT Kidney-Ureter-Bladder (CT KUB, non-contrast enhanced), CT Pulmonary Angiogram (CT PA, IV contrast enhanced) and CT Abdomen-Pelvis (CT AP, IV contrast enhanced, single phase). Median CTDIvol and DLP values for the five CT examinations from each institution were derived, with the cluster DRLs determined as the 75th percentile of the distribution of the institution median dose values. ResultsA total of 2413 dose data points were collected over a six-month period from June to November 2020. The cluster CT DRLs for the five CT examinations were determined to be 47 mGy and 820 mGy.cm for CT Brain, 5.4 mGy and 225 mGy.cm for CT Chest, 6.7 mGy and 248 mGy.cm for CT PA, 4.6 mGy and 190 mGy.cm for CT KUB and 6.9 mGy and 349 mGy.cm for CT AP. ConclusionThe establishment of the cluster CT DRLs provided individual institutions with a better understanding if their CT doses are unusually high or low, while emphasising that these DRLs are not meant as hard dose limits or constraints to follow strictly.

S2168 The Use of Rituximab for IgG4–Related Sclerosing Mesenteritis

Introduction: Sclerosing mesenteritis (SM) is an uncommon fibro-inflammatory disease affecting the abdominal mesentery. Although some patients are asymptomatic or have minimal symptoms, SM can present with complications such as bowel obstruction, chylous ascites, and mesenteric ischemia. First-line therapy includes glucocorticoids in combination with tamoxifen in those who are symptomatic. Case Description/Methods: An 82-year-old man with a history of prostate cancer and melanoma in remission and lymphocytic colitis presented with 4-months of poor appetite and 40-pound unintentional weight loss. Computed tomography (CT) abdomen showed an irregular 8.6 cm mesenteric mass with surrounding misty mesentery (Figure, Panel 1). CT-guided biopsy demonstrated fibro-adipose tissue with increased IgG4-positive plasma cells, supporting a diagnosis of IgG4-related SM. Follow-up CT abdomen 6 months later demonstrated enlargement of the mass with new encasement of the jejunal and ileal branches of the superior mesenteric artery and vein. Given impending mesenteric ischemia, he was treated with rituximab, a monoclonal anti-CD20 antibody, with 2 infusions 2 weeks apart without side-effects. He had contraindications to first-line therapy with glucocorticoids given prior suicidal ideation while on budesonide for microscopic colitis. Three months following treatment, his erythrocyte sedimentation rate improved from 52 to 25 (reference range, 3-28 mm/h) and IgG4 level from 851 to 267 (2.4-121 mg/dL). CT abdomen demonstrated a 50% decrease in the volume of the mesenteric mass without significant vascular involvement (Figure, Panel 2) and he had regained 30 pounds. Discussion: Although rituximab has been studied for IgG4-related disease in general, the use of rituximab specifically for IgG4-related SM is not well-known. We report a case of a patient with IgG4-related SM treated effectively with rituximab, suggesting this may be a suitable medication for those who have contraindications or do not respond to current first-line therapy, especially if IgG4-related. Whether this drug would also work in patients with SM not related to IgG4 disease is unknown. Patients treated with rituximab should be closely monitored for infections, as well as allergic and infusion-related reactions.Figure 1.: CT abdomen pelvis of sclerosing mesenteritis before (1) and after (2) rituximab treatment.

SP9.1.3 Colorectal Cancer Referrals During COVID-19: The Use of CT and qFIT in Triaging Patients in NHS Grampian

Abstract Introduction The COVID-19 outbreak resulted in fundamental changes to clinical practice for patients referred to secondary care with lower gastrointestinal symptoms. The use of colonoscopy services was reduced due to a perceived risk of viral transmission. Resultantly, computed tomography abdomen pelvis (CTAP) scans were utilised to triage patients. This study aimed to assess the accuracy of CTAP and qFIT in triaging patients at risk of colorectal cancer. Methods This study retrospectively gathered data on patients referred via the urgent suspected cancer (USC) pathway from the start of lockdown over a 6-month period in a single Scottish Health Board. Data were collected on presenting symptoms, qFIT levels, vetting decision, investigations, and subsequent diagnosis. Patients were vetted into one of five pathways: CTAP, direct to colonoscopy, downgraded from assessment, flexible sigmoidoscopy, or CT colonography. Results The overall cancer detection rate was 6.4%. Of the patients with cancer on the CTAP pathway, 22.9% had cancer undetected on CTAP which was later identified on colonoscopy. In the cohort of patients with colorectal malignancy, 7.5% had a negative qFIT value (<10 ug/g). Conclusion CTAP alone may not be accurate in detecting colorectal cancers. One should consider the whole clinical picture and decide whether further imaging is warranted following a negative CTAP scan. Additionally, qFIT remains the leading laboratory investigation within screening programmes, however, it should not be used in isolation to rule out colorectal malignancy.

S3178 Eosinophilic Gastroenteritis Presenting as Hypoalbuminemia

Introduction: Eosinophilic gastritis and gastroenteritis (EG/EGE) are inflammatory disorders characterized by eosinophilic infiltration of the stomach and/or duodenum, rarely also impacting the distal small bowel and colon. Case Description/Methods: We present a challenging case of eosinophilic gastroenteritis in a 64-year-old male with history of IgG Kappa monoclonal smoldering multiple myeloma who developed hypoalbunemia and lower and upper extremity edema. He was referred for concern for protein losing enteropathy. Lab work up was significant for an albumin level of 2.6 g/dl, and peripheral eosinophils were elevated to 9.5 %. Workup showed no cardiac etiology or deep venous thrombosis. Urine analysis was negative for protein loss. Computed tomography abdomen pelvis was normal. Infectious workup including stool testing for ova and parasites, HIV screening, and strongyloides IgG were negative. Stool tryptase was negative. Endoscopy was notable for impressively enlarged gastric folds with diffuse, patchy erythema (Fig. 1 right side). Mucosa was otherwise unremarkable on upper and lower endoscopy. Pathology of gastric biopsies showed >30 eosinophils per high-power field in the lamina propria, and biopsies of the ileum and colon were also notable for an increased eosinophilic infiltrate (Fig.1 left side). The patient was started on oral prednisone 40 mg daily, with improvement in peripheral eosinophil counts and albumin, though lab values were suggestive of recurrence with completion of steroid taper. The patient is currently planned for additional workup including bone marrow biopsy, as well as referral to a dietician for food elimination diet trial and allergist for environmental allergy evaluation. Discussion: The natural history and disease course of EG/EGE is not well defined. Dietary therapy and treatment with prednisone have been described as possible interventions, largely extrapolated from studies on eosinophilic esophagitis. Patients are often followed for response to treatments based upon their symptoms and the changes in peripheral eosinophilia. Other therapies like anti-Immunoglobulin E (IgE) monoclonal antibody, Leukotriene antagonist, H1-antihistamine and mast cell stabilizer and anti-Siglec-8 antibody that depletes eosinophils and inhibits mast cells, have bSeen looked into some case series but not routinely used.Figure 1.: Endoscopy with Narrow Band Imaging: (a) gastric body, (b) pre-pyloric stomach. Surgical pathology: (c) Active gastritis. Insert: H pylori (arrows), (d) Single focus of signet-ring adenocarcinoma (arrows).

S2498 Lemmel Syndrome: An Unusual Presentation with Gastric Outlet Obstruction

Introduction: Lemmel syndrome is a rare clinical entity characterized by a periampullary duodenal diverticulum causing compression and dilatation of the pancreatic and common bile ducts, classically accompanied by obstructive jaundice. Gastric outlet obstruction (GOO) is not a known complication of this syndrome, nor are there standardized approaches to its treatment. We present the first documented case of Lemmel syndrome presenting as GOO and its successful treatment with endoscopic diverticular lavage. Case Description/Methods: An 82-year-old woman presented with abdominal pain and non-bloody non-bilious emesis. On arrival, she was hemodynamically stable and anicteric. Computed tomography (CT) with contrast revealed a 2.7x3.7x5.2 cm complex pancreatic head mass containing air and debris, contiguous with the duodenum at the junction of the 2nd and 3rd segments with dilatation of the common bile (1 cm) and main pancreatic duct (0.6 cm), concerning for a pancreatic neoplasm. There was also GOO manifested as a markedly distended stomach with distal gastric and proximal duodenal wall thickening and hyperenhancement. Esophagogastroduodenoscopy (EGD) with endoscopic ultrasonography (EUS) showed no signs of significant abnormalities within the pancreas. However, a large non-bleeding periampullary diverticulum in the second portion of the duodenum containing a large amount of food debris was visualized and was found to be obstructing the common bile and main pancreatic ducts causing ductal dilatation. Endoscopic diverticular lavage with removal of food debris was performed. Her diet was quickly escalated, her symptoms resolved, and she was discharged the following afternoon. Repeat CT 11 days post-procedure showed resolution of GOO and reduced biliary ductal dilation and diverticular size. At 1-month follow-up, she remained asymptomatic and was tolerating high-fiber diet without clinical signs of gastric outlet or biliary obstruction. Discussion: Lemmel syndrome is a rare cause of GOO in the setting of pancreatic and common bile duct compression and dilatation with or without the presence of jaundice. Until now, there have been no reported cases of GOO secondary to Lemmel syndrome, nor its successful treatment with a simple diverticular lavage. It is important that physicians consider this diagnosis and treatment strategy in order to deliver cost-effective and appropriate care to patients presenting with GOO in the setting of a periampullary diverticulum with evidence of dilated biliary and pancreatic ducts.Figure 1.: CT abdomen pelvis demonstrating a 2.7 x 3.7 x 5.2 cm complex pancreatic head mass containing air and debris (A), contiguous with the duodenum at the junction of the second and third segments (B) with moderate 1.0 cm dilatation of the common bile duct (C) and 0.6 cm dilatation of the main pancreatic duct (D, E). CT abdomen pelvis demonstrating gastric outlet obstruction manifested as markedly distended stomach with distal gastric and proximal duodenal wall thickening and hyperenhancement (F).Figure 2.: Endoscopic ultrasonography (EUS) of the head (A), neck (B), and body (C) of the pancreas without signs of significant endosonographic abnormalities.Figure 3.: Large non-bleeding periampullary diverticulum in the second portion of the duodenum containing a large amount of food debris visualized and found to be obstructing the common bile and main pancreatic ducts causing ductal dilatation.Figure 4.: CT abdomen pelvis demonstrating improvement in common bile duct dilation (A) and diverticular size with resolution of radiographic evidence of gastric outlet obstruction (B, C) 10 days after endoscopic diverticular lavage. Bile duct measuring 0.7 cm, previously 1.0 cm. Diverticular dimensions measuring 1.9 x 3.6 x 3.7 cm (AP by transverse by craniocaudal), previously 2.7 x 3.7 x 5.2 cm. Pancreatic duct was poorly visualized, and comparison could not be made.

Mini invasive approaches in the treatment of small renal masses: TC-guided renal cryoablation in elderly

Today, the goal of surgery is to achieve oncological efficacy with the lowest complication rate. Computed Tomography (CT)-guided cryoablation is proposed as a safe and effective technique. We report, our series of small renal masses treated with cryoablation in elderly (> 70 years). From May 2014 to April 2019, 32 patients with median (IQR) age of 75.5 years (range 71-80) with small renal masses (< T1a) diagnosis, clinical anesthesia contraindications to nephron-sparing surgery or patient's will previous informed consent have been selected at our Urology Department. All patients underwent CT-guided cryoablation, preceded by needle biopsy. The cryoablation consisted in a procedure with an argon/helium gas-based system under local anesthesia. The follow-up included CT abdomen at 3, 6 and 12 months. The definition of incomplete treatment was the persistence of the lesion contrast enhancement (CE) at the end of the scan; the definition of relapse was the appearance of the CE to the 6-month control CT. The median follow-up was 30 months (IQR 1-59). The median size of the tumor was 3.85 cm (IQR 1.6-4.5). All patients underwent lesion biopsy resulting in diagnosis of Renal Cell Carcinoma (RCC) in 29 patients (90.7%) and oncocytoma in 3 patients (9.3%). A median of 2 cryoprobes (IQR 1- 3) was used and 2/3 cycles of freeze-thaw of the duration of 10 minutes or 5 minutes were performed. Complications were: 3 asymptomatic transitional perirenal effusion, 2 lumbar pain well-controlled by analgesic drug. Hospital stay was 2 days (range 1-3). No case showed incomplete treatment and local relapse or metastates at the CT abdomen-pelvis with contrast medium at 12 months. This study shows the efficacy and safety of percutaneous cryoablation of small renal masses in elderly population. The procedure is easy to perform, with low complication rates and well tolerated by the elderly patients.

CORRIGENDUM TO: TOWARD NATIONAL CT DIAGNOSTIC REFERENCE LEVELS IN THE UNITED ARAB EMIRATES: A MULTICENTER REVIEW OF CT DOSE INDEX AND DOSE LENGTH PRODUCT

This multicenter study evaluated computed tomography dose index volume (CTDIvol) and dose length product (DLP) to contribute to establishing computed tomography (CT) national diagnostic reference levels (NDRLs) in the United Arab Emirates (UAE). Data from 240 patients, who underwent CT head, chest, abdomen-pelvis and urography examinations, were analyzed, including patient age, sex and weight, CTDIvol (mGy) and DLP (mGy cm). The proposed DRLs for each examination were calculated as the third quartile. DRLs are proposed using CTDIvol (mGy) and DLP (mGy cm) for CT head (67 and 1189, respectively), chest (8 and 302, respectively), abdomen-pelvis (28 and 1122, respectively) and urography (20 and 714, respectively). These values are comparable with the initial NDRLs and published international DRLs. Baseline values for International Radiology Center (IRC) CT DRLs were calculated on frequently performed CT examinations. Implementation of DRL values improves dose optimization based on procedures, scanner type and patient characteristics while maintaining acceptable image quality and diagnostic confidence.

Adaptive iterative dose reduction (AIDR) 3D in low dose CT abdomen-pelvis: Effects on image quality and radiation exposure

The widespread use of computed tomography (CT) has increased the medical radiation exposure and cancer risk. We aimed to evaluate the impact of AIDR 3D in CT abdomen-pelvic examinations based on image quality and radiation dose in low dose (LD) setting compared to standard dose (STD) with filtered back projection (FBP) reconstruction. We retrospectively reviewed the images of 40 patients who underwent CT abdomen-pelvic using a 80 slice CT scanner. Group 1 patients (n=20, mean age 41 ± 17 years) were performed at LD with AIDR 3D reconstruction and Group 2 patients (n=20, mean age 52 ± 21 years) were scanned with STD using FBP reconstruction. Objective image noise was assessed by region of interest (ROI) measurements in the liver and aorta as standard deviation (SD) of the attenuation value (Hounsfield Unit, HU) while subjective image quality was evaluated by two radiologists. Statistical analysis was used to compare the scan length, CT dose index volume (CTDIvol) and image quality of both patient groups. Although both groups have similar mean scan length, the CTDIvol significantly decreased by 38% in LD CT compared to STD CT (p<0.05). Objective and subjective image quality were statistically improved with AIDR 3D (p<0.05). In conclusion, AIDR 3D enables significant dose reduction of 38% with superior image quality in LD CT abdomen-pelvis.