White Paper of the Society of Computed Body Tomography and Magnetic Resonance on Dual-Energy CT, Part 4: Abdominal and Pelvic Applications.

This is the fourth of a series of 4 white papers that represent expert consensus documents developed by the Society of Computed Body Tomography and Magnetic Resonance through its task force on dual-energy computed tomography. This article, part 4, discusses DECT for abdominal and pelvic applications and, at the end of each, will offer our consensus opinions on the current clinical utility of the application and opportunities for further research.

White Paper of the Society of Computed Body Tomography and Magnetic Resonance on Dual-Energy CT, Part 3: Vascular, Cardiac, Pulmonary, and Musculoskeletal Applications.

This is the third of a series of 4 white papers that represent Expert Consensus Documents developed by the Society of Computed Body Tomography and Magnetic Resonance through its Task Force on dual-energy computed tomography. This paper, part 3, describes computed tomography angiography and thoracic, cardiac, vascular, and musculoskeletal clinical applications. At the end of the discussion of each application category (vascular, cardiac, pulmonary, and musculoskeletal), we present our consensus opinions on the current clinical utility of the application and opportunities for further research.

White Paper of the Society of Computed Body Tomography and Magnetic Resonance on Dual-Energy CT, Part 2: Radiation Dose and Iodine Sensitivity.

This is the second of a series of 4 white papers that represent Expert Consensus Documents developed by the Society of Computed Body Tomography and Magnetic Resonance through its task force on dual-energy computed tomography. This paper, part 2, addresses radiation dose and iodine sensitivity in dual-energy computed tomography.

White Paper of the Society of Computed Body Tomography and Magnetic Resonance on Dual-Energy CT, Part 1: Technology and Terminology.

This is the first of a series of 4 white papers that represent Expert Consensus Documents developed by the Society of Computed Body Tomography and Magnetic Resonance through its task force on dual-energy computed tomography (DECT). This article, part 1, describes the fundamentals of the physical basis for DECT and the technology of DECT and proposes uniform nomenclature to account for differences in proprietary terms among manufacturers.

Effect of Anticoagulation Medication on the Thyroid Fine-Needle Aspiration Pathologic Diagnostic Sufficiency Rate.

OBJECTIVES: This study examined whether ultrasound-guided thyroid fine-needle aspiration (FNA) biopsy performed on patients taking anticoagulation medication results in a greater number of nondiagnostic pathologic samples due to a higher propensity to bleed, and thus fill the needle with blood rather than cellular material, compared to patients not taking anticoagulation medication. METHODS: In this retrospective review, data were collected on 1100 patients who underwent ultrasound-guided thyroid FNA over a 4-year period. Of these patients, 438 were included. Each thyroid FNA was performed by a board-certified radiologist using a 6-pass capillary fill technique. Data including patient age, sex, nodule size, nodule consistency, and whether the patient was or was not taking anticoagulation medication (and, if they were, which medication) were recorded from the electronic medical record, and the nodule characteristics were confirmed on imaging by a senior radiology resident (postgraduate year 5). RESULTS: Of the 438 patients included, 12 (2.7%) had an FNA aspirate that was deemed insufficient for diagnostic evaluation. Nondiagnostic pathologic yields were seen in 7 of the 309 patients (2.3%) who were not taking anticoagulation medication and 5 of 129 patients (3.9%) who were taking aspirin, warfarin, or clopidogrel, resulting in no statistically significant difference in the rates of nondiagnostic pathologic yields between the two groups (P = .35). CONCLUSIONS: Based on these data, cessation of anticoagulation medication before thyroid FNA is not necessary to obtain sufficient cellular material for diagnosis, thus eliminating the need for procedural delays, patient inconvenience, and risks associated with anticoagulation medication cessation.

Abdominal rapid-kVp-switching dual-energy MDCT with reduced IV contrast compared to conventional MDCT with standard weight-based IV contrast: an intra-patient comparison.

PURPOSE: Perform intra-patient comparison of attenuation values on lower keV dual-energy abdominal CT images using reduced IV contrast dose compared to conventional single energy polychromatic beam abdominal MDCT images using standard IV contrast dose. METHODS: IRB approved retrospective evaluation of consecutive adults who had both standard IV contrast dosage conventional multiphasic MDCT (SECT) and reduced IV contrast dosage rapid kV-switching dual-energy multiphasic MDCT (rsDECT) of the abdomen. Arterial phase dual-energy 52, 70 and 78 keV simulated monoenergetic HU were compared (t test) to arterial phase SECT HU for: aorta, liver, pancreas, psoas, and hepatic/pancreatic tumors. Contrast to noise ratios (CNR), IV contrast dose reduction and dose-length product (DLP) were recorded. Two blinded independent readers evaluated the CT datasets for subjective image quality based on a five point scale. RESULTS: Twenty-nine scan pairs in 24 subjects (13 M, mean age 64, weight 76.7 kg) were evaluated. Mean reduction in IV contrast dose was 37 %. Mean ± SD HU on 52 keV rsDECT vs. SECT were: aorta 534 ± 138 vs. 271 ± 69; liver 88 ± 24 vs. 67 ± 16; pancreas 140 ± 60 vs. 89 ± 40; psoas 63 ± 15 vs. 50 ± 12 (all p < 0.001). Noise was higher for 52 keV compared to SECT (p < 0.001); CNRs were not significantly different. Mean ± SD DLP for rsDECT was 1421 ± 563 and SECT 1335 ± 562 mGy·cm (p = 0.640). For tumor vs. nontumoral parenchyma, mean absolute contrast difference was 58.4 HU on 52 keV, and 29.0 HU on SECT. Nearly all images were rated as good or excellent and there were no statistically significant differences in image quality between the DECT and SECT images. CONCLUSION: Statistically significant gains in vascular and parenchymal enhancement without adverse effect on CNR or lesion contrast were observed in this intra-patient comparison using reduced IV contrast dose rsDECT compared to standard weight-based IV dose conventional SECT.

Adjuvant stereotactic body radiotherapy following transarterial chemoembolization in patients with non-resectable hepatocellular carcinoma tumours of ≥ 3 cm.

OBJECTIVES: The optimal locoregional treatment for non-resectable hepatocellular carcinoma (HCC) of ≥ 3 cm in diameter is unclear. Transarterial chemoembolization (TACE) is the initial intervention most commonly performed, but it rarely eradicates HCC. The purpose of this study was to measure survival in HCC patients treated with adjuvant stereotactic body radiotherapy (SBRT) following TACE. METHODS: A retrospective study of patients with HCC of ≥ 3 cm was conducted. Outcomes in patients treated with TACE alone (n = 124) were compared with outcomes in those treated with TACE + SBRT (n = 37). RESULTS: There were no significant baseline differences between the two groups. The pre-TACE mean number of tumours (P = 0.57), largest tumour size (P = 0.09) and total tumour diameter (P = 0.21) did not differ significantly between the groups. Necrosis of the HCC tumour, measured after the first TACE, did not differ between the groups (P = 0.69). Local recurrence was significantly decreased in the TACE + SBRT group (10.8%) in comparison with the TACE-only group (25.8%) (P = 0.04). After censoring for liver transplantation, overall survival was found to be significantly increased in the TACE + SBRT group compared with the TACE-only group (33 months and 20 months, respectively; P = 0.02). CONCLUSIONS: This retrospective study suggests that in patients with HCC tumours of ≥ 3 cm, treatment with TACE + SBRT provides a survival advantage over treatment with only TACE. Confirmation of this observation requires that the concept be tested in a prospective, randomized clinical trial.

Predictors of repeat transarterial chemoembolization in the treatment of hepatocellular carcinoma.

OBJECTIVES: Repeat transarterial chemoembolization (TACE) is a common intervention performed for hepatocellular carcinoma (HCC). The aim of this study was to identify predictors of the need for repeat TACE. METHODS: Between 2008 and 2012, data on patient and tumour variables were collected for 262 patients treated with a first TACE procedure for HCC. The decision to perform repeat TACE procedures was made at the completion of the first TACE or after follow-up imaging demonstrated the subtotal treatment of HCC tumours. RESULTS: Repeat TACE was performed in 67 of 262 (25.6%) patients. Necrosis of HCC, measured after the first TACE, was lower in patients who subsequently received repeat TACE (P = 0.042). On multivariable analysis, total tumour diameter of >5 cm [odds ratio (OR) 2.76, 95% confidence interval (CI) 1.45-5.25; P = 0.002] and increasing age (OR 1.04/year, 95% CI 1.00-1.07; P = 0.030) were predictive of the need for repeat TACE. Measures of liver function and TACE approach (selective versus non-selective) were not predictive of repeat TACE. Median survival did not differ significantly between patients who did (median survival: 21.1 months) and did not (median survival: 26.1 months) receive a repeat TACE procedure (P = 0.574). CONCLUSIONS: The requirement for repeat TACE is associated with older age, increased HCC tumour burden and subtotal TACE-induced HCC necrosis. Importantly, repeat TACE was not associated with reduced survival.

Dual-energy computed tomographic scanners: principles, comparisons, and contrasts.

The underlying principles of dual-energy computed tomography are reviewed, with comparison and contrast of the primary dual-energy computed tomographic scanners that are currently in use. Practical clinical implications of the differences in hardware, software, and imaging processing implementations are discussed, noting the rationale for convergence of technology and terminology.

Assessment of adverse reaction rates during gadoteridol-enhanced MR imaging in 28,078 patients.

PURPOSE: To determine adverse reaction rates in a tertiary care clinical setting after adoption of gadoteridol as the institutional routine magnetic resonance (MR) imaging contrast agent. MATERIALS AND METHODS: With institutional review board approval, informed consent waiver, and HIPAA compliance, a prospective observational study of 28 078 patients who underwent intravenous gadoteridol-enhanced MR imaging from July 2007 to December 2009 was performed. Reactions were recorded by technologists who noted types of reactions, method of injection, and treatment. Reactions were classified as mild, moderate, or severe per American College of Radiology definitions. Comparisons of reaction rates with dose and method of injection were analyzed with the Fisher exact and χ(2) tests. RESULTS: Overall reaction rate was 0.666% (187 patients), including 177 mild, six moderate, and four severe reactions. Treatment was given in 27 patients (14.4%). The most frequent reaction was nausea (and/or vomiting) in 149 patients (79.7% of patients with any adverse reaction, 0.530% of overall population). Method of injection did not affect reaction rate or severity. There was no difference in type or severity of reactions in comparison of patients receiving half the dose versus patients receiving the standard dose (P = .33-.75). CONCLUSION: The observed adverse reaction rate to gadoteridol was lower than previously reported. Specifically, the rate of nausea (0.530%) was less than half the rate (1.4%) in clinical trials of 1251 patients, leading to FDA approval in 1992. Rates of adverse reactions for this macrocyclic contrast agent are comparable to those published for linear gadolinium-based contrast agents.

Irreversible Electroporation as a Bridge to Liver Transplantation.

Hepatocellular carcinoma (HCC) in proximity to major hepatic vasculature poses a risk for invasion, which would contraindicate liver transplantation, yet, is difficult to treat with thermal ablation. This study was undertaken to evaluate the feasibility of irreversible electroporation (IRE) as a bridge to transplantation for high-risk tumors. All patients with HCC in proximity to major hepatic vasculature treated with laparoscopic IRE as bridge to transplantation were studied. Patient and tumor characteristics, length of stay, and treatment-related complications were recorded. Tumor response was assessed with CT and explant pathology. Five patients with a median Model for End Stage Liver Disease (MELD) of 13 (7-21) underwent IRE. The median tumor size was 2.7 cm (1.5-3.7 cm). Adjacent structures included the right portal vein, hepatic veins/inferior vena cava (IVC) and left portal vein. Length of stay was one day for all patients. One patient suffered portal vein thrombosis. The transplant occurred at a median of 142 days (47-264) after IRE. Pathologic necrosis ranged from 30 to 100 per cent, without any vascular invasion. Four patients remain alive with no evidence of disease with median follow-up of 403 (227-623) days. The remaining patients died because of transplant-related complications on post IRE day 297. IRE shows promise as a bridge to liver transplant for high risk HCC in a preliminary series, justifying further prospective evaluation.

Effective use of the Hounsfield unit in the age of variable energy CT.

BACKGROUND: The increasing use of dual-energy computed tomography (CT) and of reduced kVp protocols exposes the marked energy dependence of the Hounsfield unit (HU) as a measure of X-ray attenuation. This dependence of HU on energy limits its use as a quantitative diagnostic parameter, potentially leading to inaccurate diagnoses. PURPOSE: To describe a method for annotating the HU using superscripts and subscripts that inform the observer of the origin of the unit. METHODS: First, we review the HU and describe its use and limitations with variable energy CT. Examples of energy dependence and measureable curve effects are then discussed. The significance of HU value variation and its effects on diagnostic criteria will be presented. Improved annotation based on superscript and subscript methods that are derived from international nomenclature guidelines is proposed. CONCLUSION: The increasing use of variable energy CT allows for improved diagnostic techniques, and reduced radiation exposure, but at the expense of increasing the complexity of interpreting the meaning of HU values in various diagnostic contexts. A method for precise HU description is presented, streamlining diagnostic criteria.

Gadoxetate Disodium enhanced spectral dual-energy CT for evaluation of cholangiocarcinoma: Preliminary data.

PURPOSE: Evaluate Gadoxetate Disodium enhanced dual-energy CT for visualization of perihilar cholangiocarcinoma by exploiting the hepatobiliary uptake of Gadoxetate Disodium and viewing images at the k-edge of gadolinium on the spectrum of simulated monoenergetic energies available with Dual Energy CT. MATERIAL AND METHODS: In this prospective, IRB-approved study in patients with suspected cholangiocarcinoma, subjects who underwent a clinically indicated Gadoxetate Disodium liver MRI were immediately scanned without further IV contrast administration using rapid kVp-switching dual energy CT (rsDECT). Initial Gadoxetate Disodium dose was the FDA approved clinical dose, 0.025 mmol/kg; after additional IRB/FDA approval, 10 subjects were scanned with 0.05 mmol/kg. Both 50 keV and 70 keV simulated monoenergetic images as well as gadolinium(-water) material density images were viewed qualitatively and measured quantitatively for gadolinium uptake in the hepatic parenchyma and any focal lesions identified. RESULTS: Of 18 subjects (mean age 55 years, 10M, 8F, weight 84 kg), eight were scanned with 0.025 mmol/kg (Group 1) and 10 with 0.05 mmol/kg Gadoxetate Disodium (Group 2). Five patients had cholangiocarcinoma (all in Group 1). On synthetic monoenergetic images using standard and double Gadoxetate Disodium dose, the liver parenchyma did not appear enhanced qualitatively. Comparison of mean hepatic parenchymal HU at 50 and 70 keV showed a measurable increase in attenuation at the lower viewing energy, which corresponded to the k-edge of gadolinium. No statistically significant difference was observed on quantitative gadolinium measurement of hepatic parenchyma for single versus double Gadoxetate Disodium dose using rsDECT gadolinium material density images. Of the five cholangiocarcinomas, the tumor to nontumoral hepatic tissue HU differences were 51.1 (32.2) (mean and std dev) and 49.0(26.5) at 50 and 70 keV, respectively. CONCLUSION: In this small pilot population, evaluation of potential hilar/perihilar cholangiocarcinoma using dual energy CT at both the single FDA-approved dose and double dose of gadolinium demonstrated observed differences in attenuation between the hepatic parenchyma and lesions. However, small sample size and heterogeneity of lesions warrants further investigation.

Does the Degree of Hepatocellular Carcinoma Tumor Necrosis following Transarterial Chemoembolization Impact Patient Survival?

Purpose. The association between transarterial chemoembolization- (TACE-) induced HCC tumor necrosis measured by the modified Response Evaluation Criteria In Solid Tumors (mRECIST) and patient survival is poorly defined. We hypothesize that survival will be superior in HCC patients with increased TACE-induced tumor necrosis. Materials and Methods. TACE interventions were retrospectively reviewed. Tumor response was quantified via dichotomized (responders and nonresponders) and the four defined mRECIST categories. Results. Median survival following TACE was significantly greater in responders compared to nonresponders (20.8 months versus 14.9 months, p = 0.011). Survival outcomes also significantly varied among the four mRECIST categories (p = 0.0003): complete, 21.4 months; partial, 20.8; stable, 16.8; and progressive, 7.73. Only progressive disease demonstrated significantly worse survival when compared to complete response. Multivariable analysis showed that progressive disease, increasing total tumor diameter, and non-Child-Pugh class A were independent predictors of post-TACE mortality. Conclusions. Both dichotomized (responders and nonresponders) and the four defined mRECIST responses to TACE in patients with HCC were predictive of survival. The main driver of the survival analysis was poor survival in the progressive disease group. Surprisingly, there was small nonsignificant survival benefit between complete, partial, and stable disease groups. These findings may inform HCC treatment decisions following first TACE.