Namita Gandhi

Contrast-to-Noise Ratio and Low-Contrast Object Resolution on Full- and Low-Dose MDCT: SAFIRE Versus Filtered Back Projection in a Low-Contrast Object Phantom and in the Liver

OBJECTIVE The purpose of this article is to evaluate the effect of sinogram-affirmed iterative reconstruction (SAFIRE) on contrast-to-noise ratio (CNR) compared with filtered back projection (FBP) and to determine whether SAFIRE improves low-contrast object detection or conspicuity in a low-contrast object phantom and in the liver on full- and low-dose examinations. SUBJECTS AND METHODS A low-contrast object phantom was scanned at 100%, 70%, 50%, and 30% dose using a single-source made of a dual-source MDCT scanner, with the raw data reconstructed with SAFIRE and FBP. Unenhanced liver CT scans in 22 patients were performed using a dual-source MDCT. The raw data from both tubes (100% dose) were reconstructed using FBP, and data from one tube (50% dose) were reconstructed using both FBP and SAFIRE. CNR was measured in the phantom and in the liver. Noise, contrast, and CNR were compared using paired Student t tests. Six readers assessed sphere detection and conspicuity in the phantom and liver-inferior vena cava conspicuity in the patient data. The phantom and patient data were assessed using multiple-variable logistic regression. RESULTS The phantom at 70% and 50% doses with SAFIRE had decreased noise and increased CNR compared with the 100% dose with FBP. In the liver, the mean CNR improvement at 50% dose with SAFIRE compared with FBP was 31.4% and 88% at 100% and 50% doses, respectively (p < 0.001). Sphere object detection and conspicuity improved with SAFIRE (p < 0.001). However, smaller spheres were obscured on both FBP and SAFIRE images at lower doses. Liver-vessel conspicuity improved with SAFIRE over 50%-dose FBP in 67.4% of cases (p < 0.001), and versus 100%-dose FBP, improved in 38.6% of cases (p = 0.085). As a predictor for detection, CNR alone had a discriminatory ability (c-index, 0.970) similar to that of the model that analyzed dose, lesion size, attenuation difference, and reconstruction technique (c-index, 0.978). CONCLUSION Lower dose scans reconstructed with SAFIRE have a higher CNR. The ability of SAFIRE to improve low-contrast object detection and conspicuity depends on the radiation dose level. At low radiation doses, low-contrast objects are invisible, regardless of reconstruction technique.

Diagnostic Accuracy of CT Enterography for Active Inflammatory Terminal Ileal Crohn Disease: Comparison of Full-Dose and Half-Dose Images Reconstructed with FBP and Half-Dose Images with SAFIRE

Purpose To compare the diagnostic accuracy and image quality of computed tomographic (CT) enterographic images obtained at half dose and reconstructed with filtered back projection (FBP) and sinogram-affirmed iterative reconstruction (SAFIRE) with those of full-dose CT enterographic images reconstructed with FBP for active inflammatory terminal or neoterminal ileal Crohn disease. Materials and Methods This retrospective study was compliant with HIPAA and approved by the institutional review board. The requirement to obtain informed consent was waived. Ninety subjects (45 with active terminal ileal Crohn disease and 45 without Crohn disease) underwent CT enterography with a dual-source CT unit. The reference standard for confirmation of active Crohn disease was active terminal ileal Crohn disease based on ileocolonoscopy or established Crohn disease and imaging features of active terminal ileal Crohn disease. Data from both tubes were reconstructed with FBP (100% exposure); data from the primary tube (50% exposure) were reconstructed with FBP and SAFIRE strengths 3 and 4, yielding four datasets per CT enterographic examination. The mean volume CT dose index (CTDIvol) and size-specific dose estimate (SSDE) at full dose were 13.1 mGy (median, 7.36 mGy) and 15.9 mGy (median, 13.06 mGy), respectively, and those at half dose were 6.55 mGy (median, 3.68 mGy) and 7.95 mGy (median, 6.5 mGy). Images were subjectively evaluated by eight radiologists for quality and diagnostic confidence for Crohn disease. Areas under the receiver operating characteristic curves (AUCs) were estimated, and the multireader, multicase analysis of variance method was used to compare reconstruction methods on the basis of a noninferiority margin of 0.05. Results The mean AUCs with half-dose scans (FBP, 0.908; SAFIRE 3, 0.935; SAFIRE 4, 0.924) were noninferior to the mean AUC with full-dose FBP scans (0.908; P < .003). The proportion of images with inferior quality was significantly higher with all half-dose reconstructions than with full-dose FBP (mean proportion: 0.117 for half-dose FBP, 0.054 for half-dose SAFIRE 3, 0.054 for half-dose SAFIRE 4, and 0.017 for full-dose FBP; P < .001). Conclusion The diagnostic accuracy of half-dose CT enterography with FBP and SAFIRE is statistically noninferior to that of full-dose CT enterography for active inflammatory terminal ileal Crohn disease, despite an inferior subjective image quality. (©) RSNA, 2016 Online supplemental material is available for this article.

Role of tissue expanders in patients with loss of abdominal domain awaiting intestinal transplantation

Abdominal closure is a complex surgical problem in intestinal transplant recipients with loss of abdominal domain, as graft exposure results in profound morbidity. Although intraoperative coverage techniques have been described, this is the first report of preoperative abdominal wall augmentation using tissue expanders in patients awaiting intestinal transplantation. We report on five patients who received a total of twelve tissue expanders as a means to increase abdominal surface area. Each patient had a compromised abdominal wall (multiple prior operations, enterocutaneous fistulae, subcutaneous abscesses, stomas) with loss of domain and was identified as high risk for an open abdomen post‐transplant. Cross‐sectional imaging and dimensional analysis were performed to quantify the effect of the expanders on total abdominal and intraperitoneal cavity volumes. The overall mean increase in total abdominal volume was 958 cm3 with a mean expander volume of 896.5 cc. Two expanders were removed in the first patient due to infection, but after protocol modification, there were no further infections. Three patients eventually underwent small bowel transplantation with complete graft coverage. In our preliminary experience, abdominal tissue expander placement is a safe, feasible, and well‐tolerated method to increase subcutaneous domain and facilitate graft coverage in patients undergoing intestinal transplantation.

Imaging Evaluation of Pancreatic Cancer

Imaging studies are critical for the detection, characterization, initial staging, management, and monitoring of pancreatic cancer cases. Treatment of pancreatic cancer requires a multidisciplinary approach. Ideally, assessing resectablility with imaging and subsequent treatment decisions should be made at a high-volume center of excellence with a multidisciplinary team. This article reviews the major imaging modalities used to evaluate pancreatic neoplasms, with an emphasis on pancreatic imaging protocols. The imaging appearance of solid pancreatic neoplasms and the imaging criteria used to stage and determine resectability for pancreatic ductal adenocarcinoma are described. An approach to standardized radiologic reporting is also reviewed.

Does secretin stimulation add to magnetic resonance cholangiopancreatography in characterising pancreatic cystic lesions as side-branch intraductal papillary mucinous neoplasm?

AbstractObjectivesTo assess the value of secretin during magnetic resonance cholangiopancreatography (MRCP) in demonstrating communication between cystic lesions and the pancreatic duct to help determine the diagnosis of side-branch intraductal papillary mucinous neoplasm (SB-IPMN).MethodsThis is an IRB-approved, HIPAA-compliant retrospective study of 29 SB-IPMN patients and 13 non-IPMN subjects (control) who underwent secretin-enhanced MRCP (s-MRCP). Two readers blinded to the final diagnosis reviewed three randomised image sets: (1) pre-secretin HASTE, (2) dynamic s-MRCP and (3) post-secretin HASTE. Logistic regression, generalised linear models and ROC analyses were used to compare pre- and post-secretin results.ResultsThere was no significant difference in median scores for the pre-secretin [reader 1: 1; reader 2: 2 (range -2 to 2)] and post-secretin HASTE [reader 1: 1; reader 2: 1 (range -2 to 2)] in the SB-IPMN group (P = 0.14), while the scores were lower for s-MRCP [reader 1: 0.5 (range -2 to 2); reader 2: 0 (range -1 to 2); P = 0.016]. There was no significant difference in mean maximum diameter of SB-IPMN on pre- and post-secretin HASTE, and s-MRCP (P > 0.05).ConclusionSecretin stimulation did not add to MRCP in characterising pancreatic cystic lesions as SB-IPMN.Key Points• Magnetic resonance cholangiopancreatography (MRCP) is used to evaluate pancreatic cystic lesions. • Intraductal papillary mucinous neoplasm (IPMN) is a type of pancreatic cystic neoplasm. • Secretin administration does not facilitate the diagnosis of IPMN on MRCP.

Imaging mimics of pancreatic ductal adenocarcinoma

Pancreatic ductal adenocarcinoma is the most common primary malignancy of the pancreas. The classic imaging features are a hypovascular mass with proximal ductal dilatation. Different pancreatic pathologies can mimic the imaging appearance of carcinoma including other tumors involving the pancreas (pancreatic neuroendocrine tumors, lymphoma, metastasis, and rare tumors like pancreatic acinar cell carcinoma and solid pseudopapillary tumors), inflammatory processes (chronic pancreatitis and autoimmune pancreatitis), and anatomic variants (annular pancreas). Differentiation between these entities can sometimes be challenging due to overlap of imaging features. The purpose of this article is to describe the common entities that can mimic pancreatic cancer on imaging with illustrative examples and to suggest features that can help in differentiation of these entities.

Gastroenterology and pancreatic adenocarcinoma: what the radiologist needs to know

In this article, we review the information that radiologists need to know regarding the endoscopic approach to the diagnosis and management of pancreatic cancer. This includes a review of the indications, techniques, and complications of endoscopic ultrasound. We also review information regarding endoscopic retrograde cholangiopancreatography, including the various biliary drainage techniques and the use of endoscopic palliation for patients with pancreatic cancer.

Total Abdominal Wall Transplantation: An Anatomical Study and Classification System

Background: Candidates for multivisceral transplantation present with complex defects often beyond traditional reconstructive options. In this study, the authors describe a dissection technique for a total abdominal wall vascularized composite flap. In addition, the authors suggest a classification system for complex abdominal wall defects. Methods: Forty fresh, cadaveric hemiabdomens were dissected, with care taken to preserve the iliofemoral, deep circumflex iliac, superficial circumflex iliac, deep inferior epigastric, and superficial inferior epigastric arteries and corresponding veins. Perfusion patterns of the flaps were then studied using computed tomographic angiography. Results: The deep circumflex iliac, superficial circumflex iliac, deep inferior epigastric, and superficial inferior epigastric arteries were identified along a 5-cm cuff of the iliofemoral artery centered on the inguinal ligament. Perfusion with an intact deep circumflex iliac artery yielded improvement in lateral perfusion based on computed tomographic angiography. Conclusions: The authors propose an algorithm for abdominal wall reconstruction based on defect size and abdominal wall perfusion, and their technique for harvesting a total vascularized composite abdominal wall flap for allotransplantation. Total abdominal wall transplantation should be considered in the subset of patients already receiving visceral organ transplants who also have concomitant abdominal wall defects.

Mo1587 Pre-Operative Radiographic Findings Predictive of Laparoscopic Conversion to Open Procedures in Crohn's Disease

Purpose: Enhanced recovery after surgery (ERAS) lowers complications and shortens lengths of stay (LOS) compared with standard recovery. A key management strategy of ERAS protocols, especially if goal-directed fluid management is not available, is restrictive fluid management. However, it is unknown whether this is a safe strategy. Thus we aimed to evaluate whether restrictive fluid management was associated with increased acute kidney injury. Methods: We performed a retrospective review of consecutive patients undergoing abdominal surgery by a single ERAS-trained colorectal surgeon at an academic medical center from 1/11/2012 8/15/2013. Demographics, operative data, and short-term (30-day) outcomes are presented. Univariate analysis assessed between group differences to test the hypothesis that ERAS patients managed with restrictive fluids did not have an increased rate of post-operative acute kidney injury. Results are reported as median (interquartile range) or frequency (proportion). Results: One hundred twenty-eight patients were included: 82 (64%) ERAS and 46 (36%) STD recovery. Patient in the two groups were of similar age (52.4 vs. 54.8 years old, p=0.74), and BMI (26.8 vs. 27.4 kg/m2, p=0.98). Similar proportions underwent protectomy (22% vs. 28%, p=0.52), but more ERAS patients underwent minimally invasive surgery (61% vs. 41%, p=0.04), primary anastomosis (61% vs. 43%, p=0.04), and fewer had an ostomy (40% vs. 63%, p=0.02). Perioperative fluids (in cc/kg/hour) and creatinine levels are shown in Table 1. There was a trend towards ERAS patients receiving significantly less intra-operative fluids (p=0.07), and ERAS patients made significantly less urine intra-operatively (p=0.04). Post-operatively ERAS patients received significantly less IV fluids on POD#1 and POD#2 (p<0.0001), but had similar urine output on POD#1 and a trend toward reduced UOP on POD#2 (p=0.06). A total of 11 patients (8.6%) had a peak post-op creatinine ≥1.5; of these 8 (73%) recovered to <1.5 except three patients (2 ERAS1 malignant ureteral obstruction, 1 chronic renal insufficiency; 1 STD contrast induced nephropathy). No patients in the series required dialysis. ERAS patients, compared with STD patients, had earlier bowel function (POD 1.7 vs. 2.3, p=0.02), and shorter LOS 4 (36) vs. 6 (4-7) days, p=0.0002, and a similar readmission rate (8.5% vs. 10.9%, p=0.75), and need for return to the operating room (9.8% vs. 6.5%, p=0.75) Conclusions: Restrictive perioperative management after colorectal surgery is safe and does not result in a clinically or statistically increased rate of post-operative acute kidney injury.

Post liver transplant presentation of needle-track metastasis of hepatocellular carcinoma following percutaneous liver biopsy.

Hepatocellular carcinoma (HCC) is one of the few malignant tumours often treated without prior histological confirmation (in the patient with cirrhosis). Contrast-enhanced cross-sectional imaging is frequently diagnostic of HCC with a high degree of accuracy. However, on occasion, a liver biopsy is required, a complication of which can be needle-track metastasis. We present the case of a 57-year-old man who had previously undergone a liver transplant; he was found to have abdominal wall metastasis at the site of a prior percutaneous biopsy. This is the second case until now date of needle-track metastasis that presented following liver transplantation.