Bhavik N. Patel

Radiation Necrosis in the Brain: Imaging Features and Differentiation from Tumor Recurrence

Radiation necrosis in the brain commonly occurs in three distinct clinical scenarios, namely, radiation therapy for head and neck malignancy or intracranial extraaxial tumor, stereotactic radiation therapy (including radiosurgery) for brain metastasis, and radiation therapy for primary brain tumors. Knowledge of the radiation treatment plan, amount of brain tissue included in the radiation port, type of radiation, location of the primary malignancy, and amount of time elapsed since radiation therapy is extremely important in determining whether the imaging abnormality represents radiation necrosis or recurrent tumor. Conventional magnetic resonance (MR) imaging findings of these two entities overlap considerably, and even at histopathologic analysis, tumor mixed with radiation necrosis is a common finding. Advanced imaging modalities such as diffusion tensor imaging and perfusion MR imaging (with calculation of certain specific parameters such as apparent diffusion coefficient ratios, relative peak height, and percentage of signal recovery), MR spectroscopy, and positron emission tomography can be useful in differentiating between recurrent tumor and radiation necrosis. In everyday practice, the visual assessment of diffusion-weighted and perfusion images may also be helpful by favoring one diagnosis over the other, with restricted diffusion and an elevated relative cerebral blood volume being seen much more frequently in recurrent tumor than in radiation necrosis.

Single-source dual-energy spectral multidetector CT of pancreatic adenocarcinoma: Optimization of energy level viewing significantly increases lesion contrast

AIM To evaluate lesion contrast in pancreatic adenocarcinoma patients using spectral multidetector computed tomography (MDCT) analysis. MATERIALS AND METHODS The present institutional review board-approved, Health Insurance Portability and Accountability Act of 1996 (HIPAA)-compliant retrospective study evaluated 64 consecutive adults with pancreatic adenocarcinoma examined using a standardized, multiphasic protocol on a single-source, dual-energy MDCT system. Pancreatic phase images (35 s) were acquired in dual-energy mode; unenhanced and portal venous phases used standard MDCT. Lesion contrast was evaluated on an independent workstation using dual-energy analysis software, comparing tumour to non-tumoural pancreas attenuation (HU) differences and tumour diameter at three energy levels: 70 keV; individual subject-optimized viewing energy level (based on the maximum contrast-to-noise ratio, CNR); and 45 keV. The image noise was measured for the same three energies. Differences in lesion contrast, diameter, and noise between the different energy levels were analysed using analysis of variance (ANOVA). Quantitative differences in contrast gain between 70 keV and CNR-optimized viewing energies, and between CNR-optimized and 45 keV were compared using the paired t-test. RESULTS Thirty-four women and 30 men (mean age 68 years) had a mean tumour diameter of 3.6 cm. The median optimized energy level was 50 keV (range 40-77). The mean ± SD lesion contrast values (non-tumoural pancreas - tumour attenuation) were: 57 ± 29, 115 ± 70, and 146 ± 74 HU (p = 0.0005); the lengths of the tumours were: 3.6, 3.3, and 3.1 cm, respectively (p = 0.026); and the contrast to noise ratios were: 24 ± 7, 39 ± 12, and 59 ± 17 (p = 0.0005) for 70 keV, the optimized energy level, and 45 keV, respectively. For individuals, the mean ± SD contrast gain from 70 keV to the optimized energy level was 59 ± 45 HU; and the mean ± SD contrast gain from the optimized energy level to 45 keV was 31 ± 25 HU (p = 0.007). CONCLUSION Significantly increased pancreatic lesion contrast was noted at lower viewing energies using spectral MDCT. Individual patient CNR-optimized energy level images have the potential to improve lesion conspicuity.

Severe contrast reaction emergencies high-fidelity simulation training for radiology residents and technologists in a children's hospital.

RATIONALE AND OBJECTIVES Severe reactions to radiographic contrast agents can be life threatening, and although they are rare, effective recognition and management are essential to improving outcomes. A high-fidelity radiology simulation course for radiology residents and technologists focusing on severe contrast reactions and immediate treatments was designed to test the hypothesis that knowledge would improve with this educational intervention. MATERIALS AND METHODS A prospective pretest and posttest study design was used. Residents and technologists worked in teams of three to five members. Learning objectives focused on demonstrating when and how to use basic life support skills and epinephrine auto-injectors. Each resident and technologist was administered a pretest prior to the start of the case scenarios and a posttest following the debriefing session. Scores from the pretest and posttest for the residents and technologists were compared using a paired-samples t test. RESULTS Nineteen radiology residents and 11 radiology technologists participated. The average test scores were higher and improved significantly following the simulation experience for both the radiology residents (57% vs 82%, P < .001) and technologists (47% vs 72%, P = .006). Anonymous evaluations demonstrated that the experience was well received by residents and technologists, with 97% of learners (29 of 30) rating the experience as extremely or very helpful. Important learning themes included the knowledge of epinephrine auto-injector use and basic life support skills. DISCUSSION High-fidelity simulation for radiology residents and technologists focusing on epinephrine auto-injector use and basic life support skills during the first 5 minutes of a severe contrast reaction can significantly improve recognition and knowledge in treating patients having severe contrast reactions.

Radiologic resident educationSevere Contrast Reaction Emergencies: High-fidelity Simulation Training for Radiology Residents and Technologists in a Children's Hospital

RATIONALE AND OBJECTIVES Severe reactions to radiographic contrast agents can be life threatening, and although they are rare, effective recognition and management are essential to improving outcomes. A high-fidelity radiology simulation course for radiology residents and technologists focusing on severe contrast reactions and immediate treatments was designed to test the hypothesis that knowledge would improve with this educational intervention. MATERIALS AND METHODS A prospective pretest and posttest study design was used. Residents and technologists worked in teams of three to five members. Learning objectives focused on demonstrating when and how to use basic life support skills and epinephrine auto-injectors. Each resident and technologist was administered a pretest prior to the start of the case scenarios and a posttest following the debriefing session. Scores from the pretest and posttest for the residents and technologists were compared using a paired-samples t test. RESULTS Nineteen radiology residents and 11 radiology technologists participated. The average test scores were higher and improved significantly following the simulation experience for both the radiology residents (57% vs 82%, P < .001) and technologists (47% vs 72%, P = .006). Anonymous evaluations demonstrated that the experience was well received by residents and technologists, with 97% of learners (29 of 30) rating the experience as extremely or very helpful. Important learning themes included the knowledge of epinephrine auto-injector use and basic life support skills. DISCUSSION High-fidelity simulation for radiology residents and technologists focusing on epinephrine auto-injector use and basic life support skills during the first 5 minutes of a severe contrast reaction can significantly improve recognition and knowledge in treating patients having severe contrast reactions.

Material density hepatic steatosis quantification on intravenous contrast-enhanced rapid kilovolt (peak)-switching single-source dual-energy computed tomography.

Purpose The purpose of this study was to evaluate intravenous (IV) contrast-enhanced single-source rapid kilovolt (peak)–switching dual-energy (RSDE) multidetector computed tomography (CT) material density assessment of hepatic steatosis compared to conventional unenhanced (CU) Multidetector computed tomography (MDCT). Materials and Methods This is an institutional review board–approved intrapatient study of 363 consecutive adults (189 men, 174 women; mean age, 59 years) evaluated with multiphasic IV abdominal RSDE. Material density virtual unenhanced water and fat hepatic parenchymal values were measured and correlated to Hounsfield units (HUs) on CU CT using linear regression. Study population was dichotomized into steatotic or nonsteatotic liver parenchyma on the basis of CU liver-spleen (L-S) difference. The RSDE fat(-iodine) values (in milligram per milliliter) were compared (t test), correlated to the L-S difference in HU, and a milligram-per-milliliter fat threshold for clinically significant steatosis was calculated using receiver operator curve (ROC) analysis. Results Regression analysis revealed r value of 0.86 for mg/mL water (P < 0.001) and 0.87 for milligram-per-milliliter fat (P < 0.001). Twenty-seven participants were excluded from the L-S analysis (splenectomy). A total of 107 (32%) had steatosis (mean L-S, − 6.3; mean fat(-iodine) milligram per milliliter, 1018.4); 229 (68%) had no steatosis (mean L-S, 9.4; milligram per milliliter, 1028.4 [P < 0.001]). The RSDE fat material density measurement correlated to L-S less than 1 with r value of 0.74 (P < 0.001), with an area under receiver operator curve of 0.847. A threshold of 1023-mg/mL fat had 71% sensitivity and 80% specificity, and a threshold of 1027-mg/mL fat had 90% sensitivity and 61% specificity for steatosis. Conclusions The RSDE milligram-per-milliliter fat values correlate well with hepatic steatosis defined by the L-S difference less than 1 on conventional MDCT. A threshold of 1027 mg/mL can identify 90% of steatotic livers when post-IV contrast RSDE is used, without obtaining additional CU scans. However, regression equations were not helpful to convert an individual participant’s milligram-per-milliliter fat or milligram-per-milliliter water-derived from RSDE material density images to CU MDCT HU for the estimation of liver fat content.

Effect of a Noise-Optimized Second-Generation Monoenergetic Algorithm on Image Noise and Conspicuity of Hypervascular Liver Tumors: An In Vitro and In Vivo Study

OBJECTIVE The purpose of this study is to investigate whether the reduction in noise using a second-generation monoenergetic algorithm can improve the conspicuity of hypervascular liver tumors on dual-energy CT (DECT) images of the liver. MATERIALS AND METHODS An anthropomorphic liver phantom in three body sizes and iodine-containing inserts simulating hypervascular lesions was imaged with DECT and single-energy CT at various energy levels (80-140 kV). In addition, a retrospective clinical study was performed in 31 patients with 66 hypervascular liver tumors who underwent DECT during the late hepatic arterial phase. Datasets at energy levels ranging from 40 to 80 keV were reconstructed using first- and second-generation monoenergetic algorithms. Noise, tumor-to-liver contrast-to-noise ratio (CNR), and CNR with a noise constraint (CNRNC) set with a maximum noise increase of 50% were calculated and compared among the different reconstructed datasets. RESULTS The maximum CNR for the second-generation monoenergetic algorithm, which was attained at 40 keV in both phantom and clinical datasets, was statistically significantly higher than the maximum CNR for the first-generation monoenergetic algorithm (p < 0.001) or single-energy CT acquisitions across a wide range of kilovoltage values. With the second-generation monoenergetic algorithm, the optimal CNRNC occurred at 55 keV, corresponding to lower energy levels compared with first-generation algorithm (predominantly at 70 keV). Patient body size did not substantially affect the selection of the optimal energy level to attain maximal CNR and CNRNC using the second-generation monoenergetic algorithm. CONCLUSION A noise-optimized second-generation monoenergetic algorithm significantly improves the conspicuity of hypervascular liver tumors.

Carbon Dioxide as an Intravascular Imaging Agent: Review

Patients with renal impairment and/or contrast allergies pose a challenge with regard to diagnostic evaluations. CO(2) may serve as a suitable alternative intravascular contrast agent in these patients with arteriographic applications, including evaluation of peripheral vascular disease, and venographic applications, such as transjugular intrahepatic portosystemic shunt procedure, to name a few. Unique properties of CO(2), such as low viscosity, lack of an allergic reaction, and renal toxicity, have afforded it its diagnostic capabilities. However, certain properties of CO(2) also pose a technical challenge in terms of its delivery. Although it remains a relatively safe alternative contrast agent, potential adverse effects have been reported and exist.

Characterization of Small Focal Renal Lesions: Diagnostic Accuracy with Single-Phase Contrast-enhanced Dual-Energy CT with Material Attenuation Analysis Compared with Conventional Attenuation Measurements

Purpose To determine whether single-phase contrast material-enhanced dual-energy material attenuation analysis improves the characterization of small (1-4 cm) renal lesions compared with conventional attenuation measurements by using histopathologic analysis and follow-up imaging as the clinical reference standards. Materials and Methods In this retrospective, HIPAA-compliant, institutional review board-approved study, 136 consecutive patients (95 men and 41 women; mean age, 54 years) with 144 renal lesions (111 benign, 33 malignant) measuring 1-4 cm underwent single-energy unenhanced and contrast-enhanced dual-energy computed tomography (CT) of the abdomen. For each renal lesion, attenuation measurements were obtained; attenuation change of greater than or equal to 15 HU was considered evidence of enhancement. Dual-energy attenuation measurements were also obtained by using iodine-water, water-iodine, calcium-water, and water-calcium material basis pairs. Mean lesion attenuation values and material densities were compared between benign and malignant renal lesions by using the two-sample t test. Diagnostic accuracy of attenuation measurements and dual-energy material densities was assessed and validated by using 10-fold cross-validation to limit the effect of optimistic bias. Results By using cross-validated optimal thresholds at 100% sensitivity, iodine-water material attenuation images significantly improved specificity for differentiating between benign and malignant renal lesions compared with conventional enhancement measurements (93% [103 of 111]; 95% confidence interval: 86%, 97%; vs 81% [90 of 111]; 95% confidence interval: 73%, 88%) (P = .02). Sensitivity with iodine-water and calcium-water material attenuation images was also higher than that with conventional enhancement measurements, although the difference was not statistically significant. Conclusion Contrast-enhanced dual-energy CT with material attenuation analysis improves specificity for characterization of small (1-4 cm) renal lesions compared with conventional attenuation measurements.

Sonographic Detection of Extracapsular Extension in Papillary Thyroid Cancer

To identify and evaluate sonographic features suggestive of extracapsular extension in papillary thyroid cancer.

How the radiologist can add value in the evaluation of the pre- and post-surgical pancreas

Abstract Disease involving the pancreas can be a significant diagnostic challenge to the interpreting radiologist. Moreover, the majority of disease processes involving the pancreas carry high significant morbidity and mortality either due to their natural process or related to their treatment options. As such, it is critical for radiologists to not only provide accurate information from imaging to guide patient management, but also deliver that information in a clear manner so as to aid the referring physician. This is no better exemplified than in the case of pre-operative staging for pancreatic adenocarcinoma. Furthermore, with the changing healthcare landscape, it is now more important than ever to ensure that the value of radiology service to other providers is high. In this review, we will discuss how the radiologist can add value to the referring physician by employing novel imaging techniques in the pre-operative evaluation as well as how the information can be conveyed in the most meaningful manner through the use of structured reporting. We will also familiarize the radiologist with the imaging appearance of common complications that occur after pancreatic surgery.