Iodine quantification of renal lesions: Preliminary results using spectral-based material extraction on photon-counting CT.

Objectives: To assess the range of quantitative iodine values in renal cysts (RC) (with a few renal neoplasms [RNs] as a comparison) to develop an expected range of values for RC that can be used in future studies for their differentiation. Material and Methods: Consecutive patients (n = 140) with renal lesions who had undergone abdominal examination on a clinical photon-counting computed tomography (PCCT) were retrospectively included. Automated iodine quantification maps were reconstructed, and region of interest (ROI) measurements of iodine concentration (IC) (mg/cm3) were performed on whole renal lesions. In addition, for heterogeneous lesions, a secondary ROI was placed on the area most suspicious for malignancy. The discriminatory values of minimum, maximum, mean, and standard deviation for IC were compared using simple logistic regression and receiver operating characteristic curves (area under the curve [AUC]). Results: A total of 259 renal lesions (243 RC and 16 RN) were analyzed. There were significant differences between RC and RN for all IC measures with the best-performing metrics being mean and maximum IC of the entire lesion ROI (AUC 0.912 and 0.917, respectively) but also mean and minimum IC of the most suspicious area in heterogeneous lesions (AUC 0.983 and 0.992, respectively). Most RC fell within a range of low measured iodine values although a few had higher values. Conclusion: Automated iodine quantification maps reconstructed from clinical PCCT have a high diagnostic ability to differentiate RCs and neoplasms. The data from this pilot study can be used to help establish quantitative values for clinical differentiation of renal lesions.

Quantitative myocardial T2 mapping adds value to Japanese circulation society diagnostic criteria for active cardiac sarcoidosis.

Noninvasive identification of active myocardial inflammation in patients with cardiac sarcoidosis plays a key role in management but remains elusive. T2 mapping is a proposed solution, but the added value of quantitative myocardial T2 mapping for active cardiac sarcoidosis is unknown. Retrospective cohort analysis of 56 sequential patients with biopsy-confirmed extracardiac sarcoidosis who underwent cardiac MRI for myocardial T2 mapping. The presence or absence of active myocardial inflammation in patients with CS was defined using a modified Japanese circulation society criteria within one month of MRI. Myocardial T2 values were obtained for the 16 standard American Heart Association left ventricular segments. The best model was selected using logistic regression. Receiver operating characteristic curves and dominance analysis were used to evaluate the diagnostic performance and variable importance. Of the 56 sarcoidosis patients included, 14 met criteria for active myocardial inflammation. Mean basal T2 value was the best performing model for the diagnosis of active myocardial inflammation in CS patients (pR2 = 0.493, AUC = 0.918, 95% CI 0.835-1). Mean basal T2 value > 50.8 ms was the most accurate threshold (accuracy = 0.911). Mean basal T2 value + JCS criteria was significantly more accurate than JCS criteria alone (AUC = 0.981 vs. 0.887, p = 0.017). Quantitative regional T2 values are independent predictors of active myocardial inflammation in CS and may add additional discriminatory capability to JCS criteria for active disease.

Use of dual energy CT to identify gastrointestinal anastomotic leak by assessment of percutaneous drain contents.

Anastomotic leakage is a feared complication of many different types of gastrointestinal surgery. It is important to identify patients with leaks early because sepsis may develop quickly. Suspected leaks are typically confirmed by either fluoroscopy or computed tomography with oral contrast. This article presents a novel method to confirm the presence of a gastrointestinal anastomotic leak when standard imaging and clinical presentation are ambiguous.

Use of novel photon - counting detector CT for diagnosis of bowel infarction.

A 75 year old male with a history of thoraco-abdominal surgery presented with acute onset epigastric pain. CT of the abdomen and pelvis with contrast performed on a novel photon-counting detector CT demonstrated dilated loops of small bowel herniating into the thoracic cavity through a defect in the left hemidiaphragm. On conventional CT reconstructions, the bowel wall demonstrated a thin rim of hyper-density which could have been interpreted as normal mucosal enhancement in viable bowel. However, spectral-imaging data including the iodine map revealed a complete lack of enhancement within the herniated loops of bowel compatible with infarction. With the added diagnostic information, the patient was taken rapidly to surgery for small bowel resection, with good outcome.

Multi-Center Follow-up Study to Develop a Classification System Which Differentiates Mucinous Cystic Neoplasm of the Liver and Benign Hepatic Cyst Using Machine Learning.

RATIONALE AND OBJECTIVES: To date, no clinically useful classification system has been developed for reliably differentiating mucinous cystic neoplasm (MCN) from a benign hepatic cyst (BHC) in the liver. The objective was to use machine learning and a multi-center study design to develop and assess the performance of a novel classification system for predicting whether a hepatic cystic lesion represents MCN or BHC. MATERIALS AND METHODS: A multi-center cohort study identified 154 surgically resected hepatic cystic lesions in 154 subjects which were pathologic confirmed as MCN (43) or BHC (111). Readers at each institution recorded seven pre-determined imaging features previously identified as potential differentiating features from prior publications. The contribution of each of these features to differentiating MCN from BHC was assessed by machine learning to develop an optimal classification system. RESULTS: Although several of the assessed imaging features demonstrated statistical significance, only 3 imaging features were found by machine learning to significantly contribute to a potential classification system: (1) solid enhancing nodule (2) all septations arising from an external macro-lobulation (3) whether the lesion was solitary or one of multiple cystic liver lesions. The optimal classification system had only four categories and correctly identified 144/154 lesion (93.5%). CONCLUSION: This multi-center follow-up study was able to use machine learning to develop a highly accurate classification system for differentiation of hepatic MCN from BHC, which could be readily applied to clinical practice.

A case report of inverted Meckel's diverticulum.

Inverted Meckel's diverticulum is an entity often discovered incidentally or through a clinical evaluation for gastrointestinal bleeding. While rare, inverted Meckel's diverticulum should be considered in the evaluation of a patient presenting with gastrointestinal bleeding, intestinal obstruction, or intussusception. In this case, a 67-year-old female with a remote history of surgically treated breast cancer presents to an urgent care facility with weakness and fatigue. She was found to be anemic with hemoglobin of 4. Imaging revealed a blind-ending pouch in the mid to distal ileum consistent with an inverted Meckel's diverticulum. Inverted Meckel's diverticulum is identified on computerized tomography as an intraluminal, blind-ending structure in the mid to distal ileum. The possibility of a lead point should be investigated and surgical resection is indicated to prevent intestinal obstruction.

Assessment of magnetic resonance imaging derived fat fraction as a sensitive and reliable predictor of myosteatosis in liver transplant recipients.

BACKGROUND: Measures of skeletal muscle abnormalities are rapidly emerging as independent predictors of outcomes after liver transplantation (LT). We describe a simple, novel assessment of myosteatosis acquired prior to liver transplantation using Magnetic Resonance Imaging (MRI) derived fat fraction. METHODS: A retrospective longitudinal cohort study included clinical and biochemical data from patients who underwent liver transplantation at our institution between Feb 2008 and Aug 2014. Patients transplanted for a diagnosis of hepatocellular carcinoma were excluded from the study. The fat fraction of erector spinae muscles was estimated using MRI at the level where muscle volume was highest, with myosteatosis defined at a cut-off value of 0.8. RESULTS: 180 patients were included. At baseline, those with myosteatosis were, on average, older, more likely to be female, and more likely to receive a multi-organ transplant (p < 0.05). Patients with pre-transplant myosteatosis, as delineated by MRI derived fat fraction, also had increased length of hospital stay. CONCLUSION: This preliminary study suggests myosteatosis, as measured by fat fraction on MRI prior to LT, may be associated with increased graft loss and mortality after transplant.

Combined Qualitative and Quantitative Assessment of Low-Attenuation Renal Lesions Improves Identification of Renal Malignancy on Noncontrast Computed Tomography.

OBJECTIVE: The objective of this study was to assess renal lesions measuring less than 20 Hounsfield units (HU) on noncontrast computed tomography (NCT). METHODS: Twenty-one (18.1%) of 116 consecutive pathologically proven renal cell carcinomas measured less than 20 HU on NCT and were compared with 40 confirmed benign cysts also measuring less than 20 HU. All lesions were assessed qualitatively (heterogeneous or homogenous) by 3 blinded readers and quantitatively with commercially available textural analysis software. Finally, a combined assessment was performed. RESULTS: Qualitative assessment performed well (sensitivity, 76%-90%; specificity, 70%-88%). Quantitative assessment revealed mean positive pixels as having the highest performance (area under the curve, 0.912; sensitivity, 90%; specificity, 80% at a cutoff value of 21). The combined assessment, using the mean positive pixel cutoff, improved the sensitivity (reader 1, 100%; reader 2, 95%; and reader 3, 95%). CONCLUSION: Qualitative and quantitative assessments have relatively good performance, but the combination can nearly eliminate renal cell carcinomas being missed on NCT.

A noise-optimized virtual monoenergetic reconstruction algorithm improves the diagnostic accuracy of late hepatic arterial phase dual-energy CT for the detection of hypervascular liver lesions.

OBJECTIVES: To assess the image quality and diagnostic accuracy of a noise-optimized virtual monoenergetic imaging (VMI+) algorithm compared with standard virtual monoenergetic imaging (VMI) and linearly-blended (M_0.6) reconstructions for the detection of hypervascular liver lesions in dual-energy CT (DECT). METHODS: Thirty patients who underwent clinical liver MRI were prospectively enrolled. Within 60 days of MRI, arterial phase DECT images were acquired on a third-generation dual-source CT and reconstructed with M_0.6, VMI and VMI+ algorithms from 40 to 100 keV in 5-keV intervals. Liver parenchyma and lesion contrast-to-noise-ratios (CNR) were calculated. Two radiologists assessed image quality. Lesion sensitivity, specificity and area under the receiver operating characteristic curves (AUCs) were calculated for the three algorithms with MRI as the reference standard. RESULTS: VMI+ datasets from 40 to 60 keV provided the highest liver parenchyma and lesion CNR (p ≤0.021); 50 keV VMI+ provided the highest subjective image quality (4.40±0.54), significantly higher compared to VMI and M_0.6 (all p <0.001), and the best diagnostic accuracy in < 1-cm diameter lesions (AUC=0.833 vs. 0.777 and 0.749, respectively; p ≤0.003). CONCLUSIONS: 50-keV VMI+ provides superior image quality and diagnostic accuracy for the detection of hypervascular liver lesions with a diameter < 1cm compared to VMI or M_0.6 reconstructions. KEY POINTS: • Low-keV VMI+ are characterized by higher contrast resulting from maximum iodine attenuation. • VMI+ provides superior image quality compared with VMI or M_0.6. • 50-keV_VMI+ provides higher accuracy for the detection of hypervascular liver lesions < 1cm.

Differentiating biliary cystadenomas from benign hepatic cysts: Preliminary analysis of new predictive imaging features.

OBJECTIVE: To identify performance of imaging features in differentiating hepatic cysts from biliary cystadenomas of the liver. METHODS: 25 pathologically confirmed hepatic cystic lesions (hepatic cysts or biliary cystadenomas) were evaluated retrospectively and predetermined imaging features assessed for performance in differentiation. RESULTS: Any septation which arose from a cyst wall without external indentation had a very high association with biliary cystadenoma, while the presence of a thick septation had only a moderate association. CONCLUSIONS: The relationship between septations and the wall of the cystic lesion performed better than previously reported features including thick septations.

Single- and dual-energy CT of the abdomen: comparison of radiation dose and image quality of 2nd and 3rd generation dual-source CT.

OBJECTIVES: To compare single-energy (SECT) and dual-energy (DECT) abdominal CT examinations in matched patient cohorts regarding differences in radiation dose and image quality performed with second- and third-generation dual-source CT (DSCT). METHODS: We retrospectively analysed 200 patients (100 male, 100 female; mean age 61.2 ± 13.5 years, mean body mass index 27.5 ± 3.8 kg/m2) equally divided into four groups matched by gender and body mass index, who had undergone portal venous phase abdominal CT with second-generation (group A, 120-kV-SECT; group B, 80/140-kV-DECT) and third-generation DSCT (group C, 100-kV-SECT; group D, 90/150-kV-DECT). The radiation dose was normalised for 40-cm scan length. Dose-independent figure-of-merit (FOM) contrast-to-noise ratios (CNRs) were calculated for various organs and vessels. Subjective overall image quality and reader confidence were assessed. RESULTS: The effective normalised radiation dose was significantly lower (P < 0.001) in groups C (6.2 ± 2.0 mSv) and D (5.3 ± 1.9 mSv, P = 0.103) compared to groups A (8.8 ± 2.3 mSv) and B (9.7 ± 2.4 mSv, P = 0.102). Dose-independent FOM-CNR peaked for liver, kidney, and portal vein measurements (all P ≤ 0.0285) in group D. Subjective image quality and reader confidence were consistently rated as excellent in all groups (all ≥1.53 out of 5). CONCLUSIONS: With both DSCT generations, abdominal DECT can be routinely performed without radiation dose penalty compared to SECT, while third-generation DSCT shows improved dose efficiency. KEY POINTS: • Dual-source CT (DSCT) allows for single- and dual-energy image acquisition. • Dual-energy acquisition does not increase the radiation dose in abdominal DSCT. • Third-generation DSCT shows improved dose efficiency compared to second-generation DSCT. • Dose-independent figure-of-merit image contrast was highest with third-generation dual-energy DSCT. • Third-generation DSCT shows improved dose efficiency for SECT and DECT.

Can dual-energy computed tomography improve visualization of hypoenhancing liver lesions in portal venous phase? Assessment of advanced image-based virtual monoenergetic images.

PURPOSE: The purpose was to assess image quality of portal-venous phase dual-energy computed tomography (DECT) for liver lesions. METHODS: We performed 120-kVp-equivalent linear-blended (LB) and monoenergetic reconstructions from 40 to 190 keV by standard (VMI) and advanced virtual monoenergetic (VMI+) methods. Diagnostic performance, and quantitative and qualitative image analyses were assessed and compared. RESULTS: Liver contrast to noise ratio peaked at 40 keV_VMI+, while image quality and reader preference peaked at 50 keV_VMI+. 50 keV_VMI+ scored overall higher diagnostic performance: lesion sensitivity 95.4% vs. 83.3% for both 75 keV_VMI and LB. CONCLUSIONS: DECT improves assessment of hypoenhancing liver lesions on portal venous phase. 50 keV_VMI+ demonstrated the highest image quality and diagnostic performance over VMI and LB.

Limitation of Virtual Noncontrasted Images in Evaluation of a Liver Lesion Status Post Transarterial Chemoembolization.

The authors describe a case of a patient with a solitary hepatocellular carcinoma status post transarterial chemoembolization. Follow-up imaging was performed using dual-energy computed tomography. The study was performed with and without contrast and a virtual noncontrast data set was constructed from the postcontrast images. The evaluation of this patient status post transarterial chemoembolization with virtual noncontrast alone erroneously suggested enhancement and viable tumor. However, examination of true noncontrast images revealed these findings to be due to the subtraction of iodine in Ethiodol within the treated lesion.

Optimization of window settings for virtual monoenergetic imaging in dual-energy CT of the liver: A multi-reader evaluation of standard monoenergetic and advanced imaged-based monoenergetic datasets.

OBJECTIVES: To evaluate optimal window settings for display of virtual monoenergetic reconstructions in third-generation dual-source, dual-energy computed tomography (DECT) of the liver. METHODS: Twenty-nine subjects were prospectively evaluated with DECT in arterial (AP) and portal venous (PVP) phases. Three reconstructed datasets were calculated: standard linearly-blended (LB120), 70-keV standard virtual monoenergetic (M70), and 50-keV advanced image-based virtual monoenergetic (M50+). Two readers assessed optimal window settings (width and level, W/L), establishing a mean for each reconstruction which was used for a blinded assessment of liver lesions. RESULTS: The optimal W/L for M50+ were significantly higher for both AP (W=429.3 ± 44.6 HU, L=129.4 ± 9.7 HU) and PVP (W=376.1 ± 14.2HU, L=146.6 ± 7.0 HU) than for LB120 (AP, W=215.9 ± 16.9 HU, L=82.3 ± 9.4 HU) (PVP, W=173.4 ± 8.9 HU, L=69.3 ± 6.0 HU) and M70 (AP, W=247.1 ± 22.2 HU, L=72.9 ± 6.8 HU) (PVP, W=232.0 ± 27.9 HU, L=91.6 ± 14.4 HU). Use of the optimal window setting for M50+ vs. LB120 resulted in higher sensitivity (AP, 100% vs. 86%; PVP, 96% vs. 63%). CONCLUSIONS: Application of dedicated window settings results in improved liver lesion detection rates in advanced image-based virtual monoenergetic DECT when customized for arterial and portal venous phases.

Imaging Requirements for Utilization of T2*-Weighted Magnetic Resonance Imaging for Identification of Hepatocellular Carcinoma in Cirrhosis: Effect of Hepatic Iron Content.

PURPOSE: To evaluate the impact of the level of inherent hepatic iron deposition on the ability of multiecho T2*-weighted magnetic resonance imaging (T2*WI) to identify hepatocellular carcinoma. This is relevant to the ancillary features described in the Liver Imaging Reporting and Data System reporting system. METHODS: This retrospective review identified liver transplant patients with a preoperative magnetic resonance imaging at 1.5 T including gradient-recalled echo T2*WI (echo time, 9.5, 19.3, 29.0 milliseconds). A blinded, randomized reading was performed by a single reader of each of the images at each echo time. Hepatic iron content (HIC) was calculated for each participant and compared with the results of the blinded read. RESULTS: Ninety-eight HCCs were identified on explant pathology in 73 participants. Of these, 57 HCCs (58%) were identified on T2*WI. However, no HCCs were visible in participants with HIC < 1.0 mg/g. For participants with HIC > 1.0 mg/g, 57 (88%) of 65 HCCs were visible. CONCLUSIONS: Most of HCCs can be identified on T2*WI without gadolinium; however, performance is significantly affected by background HIC.

Dual-energy CT of the pancreas: improved carcinoma-to-pancreas contrast with a noise-optimized monoenergetic reconstruction algorithm.

PURPOSE: To evaluate a novel monoenergetic reconstruction algorithm (nMERA) with improved noise reduction for dual-energy CT (DECT) of pancreatic adenocarcinoma. MATERIALS AND METHODS: Sixty patients with suspected pancreatic carcinoma underwent dual-source dual-energy CT with arterial phase. Images were reconstructed as linearly-blended 120-kV series (M_0.6) and with the standard monoenergetic (sMERA) and the novel monoenergetic algorithm (nMERA) with photon energies of 40, 55, 70 and 80 keV. Objective image quality was compared regarding image noise, pancreas attenuation, signal-to-noise ratio (SNR) and pancreas-to-lesion contrast. Subjective image quality was assessed by two observers. RESULTS: Thirty pancreatic adenocarcinomas were detected. nMERA showed significantly reduced image noise at low keV levels compared with sMERA images (55 keV: 7.19 ± 2.75 vs. 20.68 ± 7.01 HU; 40 keV: 7.33 ± 3.20 vs. 37.22 ± 14.66 HU) and M_0.6 (10.69 ± 3.57 HU). nMERA pancreatic SNR was significantly superior to standard monoenergetic at 40 (47.02 ± 23.41 vs. 9.37 ± 5.83) and 55 keV (28.29 ± 16.86 vs. 9.88 ± 7.01), and M_0.6 series (11.42 ± 6.00). Pancreas-to-lesion contrast peaked in the nMERA 40 keV series (26.39 ± 16.83) and was significantly higher than in all other series (p<0.001). nMERA 55 keV images series were consistently preferred by both observers over all other series (p<0.01). CONCLUSIONS: nMERA DECT can significantly improve image quality and pancreas-to-lesion contrast in the diagnosis of pancreatic adenocarcinoma.

Application of an Advanced Image-Based Virtual Monoenergetic Reconstruction of Dual Source Dual-Energy CT Data at Low keV Increases Image Quality for Routine Pancreas Imaging.

PURPOSE: To compare image quality on contrast-enhanced dual-energy computed tomography (DECT) during the pancreatic parenchymal phase of pancreatic masses between linearly-blended simulated 120 kVp images (routine) and advanced image-based virtual monoenergetic reconstructions at 55 keV. METHODS: This was a retrospective evaluation of 24 nonconsecutive adults found to have a focal pancreatic mass on a multiphasic abdominal dual-source DECT (12 adenocarcinoma, 5 neuroendocrine, 7 cystic tumors). For pancreatic-parenchymal phase images, subjects had routine and 55 keV images reconstructed at the time of clinical evaluation. Quantitative evaluation by contrast-to-noise ratio and qualitative evaluations of image quality by (1) direct comparison of image pairs (preference) and (2) blinded assessment of image quality measures based on Likert scores were performed. RESULTS: Mean patient weight was 205.8 ± 26.6 lbs. Mean pancreatic lesion contrast-to-noise ratio was significantly higher at 55 keV (6.8 ± 4.1) compared to the routine image series (5.8 ± 3.8; P = 0.0002). All 3 readers preferred the 55-keV images over routine blended images in 70.1% to 95.8% of cases. No significant differences were observed for subjective sharpness of the mass, visualization of internal mass structures, or image noise. CONCLUSIONS: Use of a single advanced image-based virtual monoenergetic reconstruction at 55 keV in pancreatic DECT showed improved objective image quality and reader preference compared to routine images. As this image reconstruction can be incorporated into the scan protocol, this technique should be considered for routine clinical use.

Improved differentiation between hepatic hemangioma and metastases on diffusion-weighted MRI by measurement of standard deviation of apparent diffusion coefficient.

BACKGROUND: Diffusion-weighted magnetic resonance imaging (DW-MR) can be useful in the differentiation of hemangiomata from liver metastasis, but improved methods other than by mean apparent diffusion coefficient (mADC) are needed. METHODS: A retrospective review identified 109 metastatic liver lesions and 86 hemangiomata in 128 patients who had undergone DW-MR. For each lesion, mADC and the standard deviation of the mean ADC (sdADC) were recorded and compared by receiver operating characteristic analysis. RESULTS: Mean mADC was higher in benign hemangiomata (1.52±0.12 mm(2)/s) than in liver metastases (1.33±0.18 mm(2)/s), but there was significant overlap in values. The mean sdADC was lower in hemangiomata (101±17 mm(2)/s) than metastases (245±25 mm(2)/s) and demonstrated no overlap in values, which was significantly different (P<.0001). CONCLUSIONS: Hemangiomata may be better able to be differentiated from liver metastases on the basis of sdADC than by mADC, although further studies are needed.

The breadth of imaging findings of groove pancreatitis.

The pathogenesis of groove pancreatitis involves progressive cystic degeneration of hamartomatous pancreas rests which lie within the duodenal wall. Hamartomatous pancreatic rests can occur in other locations, but when located within the pancreaticoduodenal groove can lead to a particular clinical presentation following the development of fibrotic and inflammatory tissue. Although this is not a disease of the pancreas itself, the pancreatic duct and biliary system is frequently secondarily involved in this regional process. Identification of this entity and its varied appearances as a distinct pathology is essential given the unique management issues of groove pancreatitis.