A prototype assembled 3D-printed phantom of the glenohumeral joint for fluoroscopic-guided shoulder arthrography.

PURPOSE: To describe the methodology of constructing a three-dimensional (3D) printed model of the glenohumeral joint, to serve as an interventional phantom for fluoroscopy-guided shoulder arthrography training. MATERIALS AND METHODS: The osseous structures, intra-articular space and skin surface of the shoulder were digitally extracted as separate 3D meshes from a normal CT arthrogram of the shoulder, using commercially available software. The osseous structures were 3D-printed in gypsum, a fluoroscopically radiopaque mineral, using binder jet technology. The joint capsule was 3D printed with rubber-like TangoPlus material, using PolyJet technology. The capsule was secured to the humeral head and glenoid to create a sealed intra-articular space. A polyamide mold of the skin was printed using selective laser sintering. The joint was stabilized inside the mold, and the surrounding soft tissues were cast in silicone of varying densities. Fluoroscopically-guided shoulder arthrography was performed using anterior, posterior, and rotator interval approaches. CT arthrographic imaging of the phantom was also performed. RESULTS: A life-size phantom of the glenohumeral joint was constructed. The radiopaque osseous structures replicated in-vivo osseous corticomedullary differentiation, with dense cortical bone and less dense medullary cancellous bone. The glenoid labrum was successfully integrated into the printed capsule, and visualized on CT arthrography. The phantom was repeatedly used to perform shoulder arthrography using all three conventional approaches, and simulated the in vivo challenges of needle guidance. CONCLUSIONS: 3D printing of a complex capsule, such as the glenohumeral joint, is possible with this technique. Such a model can serve as a valuable training tool.

Comparing Dose-Length Product-Based and Monte Carlo Simulation Organ-Based Calculations of Effective Dose in 16- and 64-MDCT Examinations Using Automatic Tube Current Modulation.

OBJECTIVE: The purpose of this study is to compare dose-length product (DLP)-based calculation of effective dose (EDDLP) with Monte Carlo simulation organ-based calculation of effective dose (EDMCO) in 16- and 64-MDCT examinations, with the use of clinical examinations with automatic tube current modulation. MATERIALS AND METHODS: Dose data were obtained from 50 consecutive unenhanced head CT examinations, unenhanced chest CT examinations, and unenhanced and contrast-enhanced abdominopelvic CT examinations performed using 16- and 64-MDCT scanners, as well as from 50 pulmonary CT angiography (CTA) examinations performed using a 64-MDCT scanner and 31 pulmonary CTA examinations performed using a 16-MDCT scanner. The EDMCO and the mean patient effective diameter were calculated using commercially available software. The EDDLP was also calculated. Both the mean difference and percentage difference between EDDLP and EDMCO were calculated, and they were statistically compared according to patient sex, type of examination performed, and type of scanner used. RESULTS: EDDLP significantly underestimated the EDMCO by 0.3 mSv (19%) for men who underwent unenhanced head CT, 0.5 mSv (29%) for women who underwent unenhanced head CT, 0.9-1.4 mSv (9-13%) for men who underwent chest CT, and 4.7-4.8 mSv (39%) for women who underwent chest CT (p < 0.001). The EDDLP overestimated the EDMCO by 1.9-2.0 mSv (12-14%) for men who underwent abdominopelvic CT (p < 0.001), with no significant difference noted for women who underwent abdominopelvic CT's. No significant difference was noted in the percentage difference in ED between the 16- and 64-MDCT scanners (p ≥ 0.13). CONCLUSION: EDDLP underestimates EDMCO, the reference standard for dose calculation, by 19-39% in unenhanced head CT examinations and, among women, in chest CT examinations. EDDLP deviates from EDMCO by less than 15% for chest CT examinations of men and for abdominopelvic CT. These differences can be attributed to variable patient body habitus, automatic tube current modulation, and sex-neutral k-coefficients, and they should be considered when calculating ED, particularly in women.

Retrospective comparison of the Low Risk Ankle Rules and the Ottawa Ankle Rules in a pediatric population.

BACKGROUND: A recent multicenter prospective Canadian study presented prospective evidence supporting the Low Risk Ankle Rules (LRAR) as a means of reducing the number of ankle radiographs ordered for children presenting with an ankle injury while maintaining nearly 100% sensitivity. This is in contrast to a previous prospective study which showed that this rule yielded only 87% sensitivity. OBJECTIVE: It is important to further investigate the LRAR and compare them with the already validated Ottawa Ankle Rules (OAR) to potentially curb healthcare costs and decrease unnecessary radiation exposure without compromising diagnostic accuracy. METHODS: We conducted a retrospective chart review of 980 qualifying patients ages 12months to 18years presenting with ankle injury to a commonly staffed 310 bed children's hospital and auxiliary site pediatric emergency department. RESULTS: There were 28 high-risk fractures identified. The Ottawa Ankle Rules had a sensitivity of 100% (95% CI 87.7-100), specificity of 33.1% (95% CI 30.1-36.2), and would have reduced the number of ankle radiographs ordered by 32.1%. The Low Risk Ankle Rules had a sensitivity of 85.7% (95% CI 85.7-96), specificity of 64.9% (95% CI 61.8-68), and would have reduced the number of ankle radiographs ordered by 63.1%. The latter rule missed 4 high-risk fractures. CONCLUSION: The Low Risk Ankle Rules may not be sensitive enough for use in Pediatric Emergency Departments, while the Ottawa Ankle Rules again demonstrated 100% sensitivity. Further research on ways to implement the Ottawa Ankle Rules and maximize its ability to decrease wait times, healthcare costs, and improve patient satisfaction are needed.

Retrospective Evaluation of Artificial Intelligence Leveraging Free-Text Imaging Order Entry to Facilitate Federally Required Clinical Decision Support.

OBJECTIVE: The Protecting Access to Medicare Act mandates clinical decision support (CDS) at imaging order entry, necessitating the use of structured indications to map CDS scores. We evaluated the performance of a commercially available artificial intelligence (AI) tool leveraging free-text order entry to facilitate provider selection of the necessary structured indications. METHODS: Our institution implemented an AI tool offering predicted structured indications based upon the ordering provider's entry of a free-text reason for examination. Providers remained able to order via the traditional direct search for structured indications. Alternatively, they could take the new free-text-AI approach allowing them to select from AI-predicted indications, perform additional direct searches, indicate no matching indication, or exit CDS workflow. We hypothesized the free-text-AI approach would be elected more often and the AI tool would be successful in facilitating selection of structured indications. We reviewed advanced imaging orders (n = 40,053) for the first 3 months (February to May 2020) since implementation. RESULTS: Providers were more likely (P < .001) to choose the free-text-AI approach (23,580; 58.9%) to order entry over direct search for structured indications (16,473; 41.1%). The AI tool yielded alerts with predicted indications in 91.7% (n = 21,631) of orders with free text. Ultimately, providers chose AI-predicted indications in 57.7% (n = 12,490) of cases in which they were offered by the tool. DISCUSSION: Providers significantly more often elected the new free-text-AI approach to order entry for CDS, suggesting provider preference over the traditional approach. The AI tool commonly predicted indications acceptable to ordering providers.

Use of a Commercially Available Clinical Decision Support Tool to Expedite Prior Authorization in Partnership With a Private Payer.

PURPOSE: The aim of this study was to determine if a clinical decision support (CDS) tool could be used in partnership with a private payer to successfully expedite the prior authorization process for advanced (ie, MRI, CT, PET, nuclear medicine) imaging requests. METHODS: A single academic institution integrated a commercially available CDS tool utilizing the ACR Appropriateness Criteria into the ordering process for outpatient advanced imaging tests within the electronic health record. Ordering providers could elect to use the CDS tool or ignore the available technology. In partnership with a health care insurance company and a contracted radiology benefits management company, orders deemed as "usually indicated" by the CDS tool underwent expedited prior authorization in a pilot program from June 2018 to October 2019. RESULTS: Providers used the CDS tool for 15% (1,453 of 9,640) of outpatient advanced imaging orders. Of these orders with elective CDS scores, 69% (n = 997) qualified for an expedited prior authorization process. CONCLUSIONS: Under specific circumstances, a commercially available CDS tool was used in partnership with a private payer and a radiology benefits management company to expedite prior authorization of outpatient advanced imaging examination orders deemed likely to be appropriate by multispecialty professional guidelines.

Effect of electrode orientation on lesion sizes produced by irrigated radiofrequency ablation catheters.

BACKGROUND: Irrigated radiofrequency (RF) ablation catheters may produce different lesion sizes dependent upon the electrode orientation to the tissue. This study examined the effect of irrigated electrode orientation on the lesion size and explores a potential mechanism for this effect. METHODS AND RESULTS: Lesions were created in isolated porcine myocardium using an open irrigation, closed irrigation, and nonirrigated RF catheter (all 3.5-4 mm tips). Lesions were created with the electrodes with all permutations of electrode orientation (vertical or horizontal), contact pressure (6 or 20 g), and saline superfusate flow (0.2 or 0.4 m/sec) over tissue interface. The effect of electrode irrigation without RF delivery on tissue temperature was assessed with intramyocardial temperature probes and infrared thermal imaging. For both irrigated catheters, the horizontal orientation produced 25-30% smaller lesion volumes than the vertical orientation despite equal or greater power deliveries. The horizontal orientation produced larger lesion volumes for the nonirrigated catheter. Higher superfusate flow rates were associated with decreased lesion volumes for the irrigated catheters but greater lesion volumes for the nonirrigated catheter. Catheter irrigation alone without RF delivery reduced intramyocardial temperatures up to 4.9 degrees C and the horizontal orientation produced a 2-fold greater area of tissue cooling than the vertical orientation. CONCLUSION: Horizontal electrode orientations reduce lesion volumes for irrigated RF catheters. This effect may be in part due to greater areas of active tissue cooling in the horizontal orientation.

FDG PET/CT Findings of Erdheim-Chester Disease: Radiologic Response to a Novel Treatment Regimen.

Erdheim-Chester disease (ECD) is a rare form of non-Langerhans histiocytosis with deposition of lipid-laden macrophages in numerous organs. A 74-year-old man with a history of coronary artery disease, hypertension, and hyperlipidemia presented with nonspecific symptoms including back pain, nausea, vomiting, vertigo, and left leg pain. A neutrophil-predominant elevated WBC count and a bone biopsy revealing histiocytic proliferation positive for CD68 and CD163 and negative for S100 was noted. FDG PET/CT, MRA, and CTA images were obtained. We review the radiologic hallmarks of ECD and demonstrate the radiologic manifestations of response to combined BRAF and MEK inhibitor treatment.

Microbubbles during radiofrequency catheter ablation: composition and formation.

OBJECTIVES: The purpose of this study was to measure tissue temperatures associated with microbubble formation during radiofrequency (RF) ablation. BACKGROUND: Microbubble formation visualized by echocardiography has been used to indicate excessive tissue heating during RF pulmonary vein isolation. However, little is known about the tissue temperatures associated with microbubble formation. METHODS: Optical fluorometric thermometry probes were used to record tissue temperatures in isolated porcine atrium overlying either lung or esophageal tissue in a saline bath. RF energy was delivered through an irrigated ablation electrode during echocardiographic monitoring for microbubble formation. RESULTS: The maximal recorded tissue temperatures were 81.0 +/- 5.0 degrees C and 88.3 +/- 8.1 degrees C at the time of intermittent (type 1) microbubble formation for lung and esophageal preparations, respectively. During continuous (type 2) microbubble formation, the temperatures were 91.4 +/- 8.2 degrees C and 99.2 +/- 7.8 degrees C, respectively (both P < .001 vs type 1). Tissue temperatures averaged >100 degrees C at the time of "pops." The maximal recorded temperature occurred up to 4 mm deep in the tissues and frequently occurred external to the atrial tissue. The total RF lesion volumes for lung and esophageal preparations were related to the pattern of microbubble formation but not to total power delivered. After generation of type 1 bubbles, up to 60% reductions in RF energy were needed to restore target tissue temperatures of 65 degrees C. Gas chromatographic analysis of the microbubbles was consistent with steam formation. CONCLUSIONS: Microbubble formation during RF ablation represents excessive tissue heating to the point of steam formation. Maximal tissue heating may occur in the adjacent lung and esophagus during cooled ablation.

Efficacy of a cooled bipolar epicardial radiofrequency ablation probe for creating transmural myocardial lesions.

OBJECTIVE: Creation of transmural myocardial lesions with epicardial surgical devices to treat atrial fibrillation is difficult. A new cooled bipolar radiofrequency ablation probe was used to create transmural myocardial lesions under controlled conditions. METHODS: The Coolrail (AtriCure, Inc, West Chester, Ohio) is a handheld probe with 2 parallel 30-mm long radiofrequency conductors. Conductors are cooled by water irrigation. Lesions were delivered to epicardial surface of isolated bovine myocardium sliced 3- to 8-mm thick, with blood flow beneath tissue at 0 or 0.4 m/s. Contact pressure between probe and tissue was either 450 g or 900 g. Tissue temperatures were measured. Tissue was sectioned every 5 mm along lesion long axis to determine lesion dimensions. RESULTS: For 80 experiments with 450-g contact pressure, epicardial lesion length was 31.3 mm (interquartile range, 30.1-32.8 mm); endocardial lesion length was 14.1 mm (interquartile range, 0.0-22.6 mm). Average lesion depth was 4.2 +/- 0.74 mm. Temperature at probe interface was 81 degrees C +/- 21 degrees C; that at blood pool interface was 53 degrees C +/- 12 degrees C. Lesions were always transmural when tissue thickness was 4.0 mm or less. Endocardial blood flow did not influence lesion depth. With 900-g contact pressure, increased depth was always transmural at 4.8-mm tissue thickness or less. CONCLUSIONS: This irrigated bipolar radiofrequency probe consistently produced transmural lesions in tissue 4 mm or thinner under controlled conditions in vitro. Lesion depth was increased by greater pressure on probe and not affected by blood flow. Endocardial lesions were smaller than epicardial dimensions.

Determinants of lesion sizes and tissue temperatures during catheter cryoablation.

BACKGROUND: Factors which influence lesion size from catheter-based cryoablation have not been well described. This study describes factors which influence lesion size during catheter cryoablation. METHODS AND RESULTS: Cryoablation was delivered to porcine left ventricular myocardium in a saline bath using 4- or 8-mm electrode catheters. Ablation was delivered with the electrodes either vertical or horizontal to the tissue and both with and without superfusate flow over the electrode. The effect of electrode contact pressure was tested. Lesion dimensions were measured. All experiments were duplicated to measure tissue temperatures at 1-, 2-, 3-, and 5-mm deep to the ablation electrode. The 8-mm electrode produced lower tissue temperatures and larger lesion volumes when compared with the 4-mm electrode (all P < 0.05). Superfusate flow slowed the rate of tissue cooling, markedly warmed tissue temperatures, and reduced lesion volume when compared with no flow conditions. By linear regression modeling, lesion sizes and tissue temperatures were related to the presence of superfusate flow, electrode orientation, contact pressure and electrode size, or catheter refrigerant flow rate (r2 for models = 0.90-0.96, all P < 0.001). Electrode temperature predicted lesion size or tissue temperatures only when analyzed independent of electrode size or refrigerant flow rate. CONCLUSIONS: Lesion sizes and tissue temperatures during catheter cryoablation are related to convective warming, electrode orientation, electrode contact pressure, and any of the following: electrode size, catheter refrigerant flow rate or electrode temperature. However, electrode temperature may be a poor predictor of lesion size and tissue temperature for a given catheter size.