Custom 3-Dimensional Printed Ultrasound-Compatible Vascular Access Models: Training Medical Students for Vascular Access.

PURPOSE: To generate 3-dimensional (3D) printed ultrasound (US)-compatible vascular models (3DPVAM) and test them for noninferiority in training medical students in femoral artery access. MATERIALS AND METHODS: A 3DPVAM of normal femoral artery (FA) anatomy was developed from an anonymized computerized tomography (CT) examination. Students were randomized to a 3DPVAM or a commercial model (CM) simulation experience (SE) for US-guided FA access. Students completed a pre-SE questionnaire ranking their self-confidence in accessing the artery on a 5-point Likert scale. A standardized SE was administered by interventional radiology faculty or trainees. Students completed a post-SE questionnaire ranking comfort with FA access on a Likert scale. Student questionnaire results from the 3DPVAM group were compared with those from the CM group by using chi-square, Wilcoxon signed-rank, and noninferiority analyses. RESULTS: Twenty-six and twenty-three students were randomized to 3DPVAM and commercial model training, respectively. A total of 76.9% of 3DPVAM trainees and 82.6% of CM trainees did not feel confident performing FA access prior to the SE. In both groups, training increased student confidence by 2 Likert points (3DPVAM: P < 0.001; CM P < 0.001). The confidence increase in 3DPVAM trainees was noninferior to that in CM trainees (P < 0.001). CONCLUSIONS: Generation of a custom-made 3DPVAM is feasible, producing comparable subjective training outcomes to those of CM. Custom-made 3D-printed training models, including incorporation of more complex anatomical configurations, could be used to instruct medical students in procedural skills.

Financial Impact of Imaging Examination Site of Service in the Medicare Population.

PURPOSE: The financial sustainability of the US healthcare system is a growing concern in an environment of declining reimbursement and rising costs. Variable Centers for Medicare and Medicaid (CMS) reimbursement and denial rates for specific imaging examinations exist across sites of service, adding complexity to financial planning for healthcare organizations. Understanding the financial implications of site of service in existing CMS reimbursement for imaging may be of strategic importance for organizations going forward. MATERIALS AND METHODS: Current Procedural Terminology (CPT) codes were obtained for common cross-sectional imaging examinations using the 2022 CMS Medicare Physician Fee Schedule. Using reimbursement rates with historical volumes and denial rates, a simulation was created to estimate the overall reimbursement of paired hospital outpatient departments (HOPD) and free-standing office (FSO) sites. A baseline simulation was performed with random allocation of imaging examinations between sites of service, and an optimized simulation was performed to estimate the maximum financial impact of targeted allocation between sites. These simulations were performed for paired CT and MR scanners separately. RESULTS: For CT, the baseline simulation estimated annual average reimbursement for combined HOPD and FSO was $3.25M. Reimbursement increased to $3.51M after optimized reallocation of studies between sites of service, resulting in an expected gain of $260,162 for a set of paired HOPD and FSO scanners. For MR, the same approach resulted in baseline reimbursement of $2.51M, increasing to $2.60M upon reallocation between sites for an expected gain of $87,532. Assuming a stable cost of service delivery, this approach would result in improved margins of 8% for CT and 3.5% for MR. There were 28 CT and 19 MRI daily patient imaging appointments at each respective HOPD and FSO scanners, unchanged between baseline and optimized cases. Differences in reimbursement rates between sites were the dominant driver of increased margins at low denial rates, although denial rates became dominant at values greater than 50%. CONCLUSION: Given CMS payment and denial rate variability, optimally allocating imaging studies between sites of service may improve reimbursement for the same services delivered. Although financial incentives exist for site allocation, such decisions should require physician input to assess safety and appropriate level of care. This work contributes to an understanding of financial incentives of existing reimbursement policy and may guide future policy design towards high value care.

Investigation of the Local Environment of Hydrophobic End Groups on Polyethylene Glycol (PEG) Brushes Using Fluorometry: Relationship to Click Chemistry Conjugation Reactions on PEG-Protected Nanoparticles.

Targeted nanoparticles often require conjugating targeting ligands to polyethylene glycol (PEG) chains of a nanoparticle's dense protecting corona. "Click" chemistries are commonly employed for their bioorthogonality, with strain-promoted azide-alkyne cycloadditions (SPAAC) increasingly chosen to avoid cytotoxic copper catalysts. However, conjugation becomes compromised if reactive PEG chain ends cannot encounter their reaction counterparts. We use fluorescence to probe the location of Nile Red, methylpyrene, and butylpyrene, dyes with comparable hydrophobicities to SPAAC alkynes (logP = 3.2-5.7), tethered to PEG chains on 100 nm NPs. Using fluorescence peak shifts, we find that Nile Red resides 43% of the time in the 5k PEG corona and 57% at the more hydrophobic nanoparticle core. Increasing the PEG MW to 67k doubles the corona dye fraction to 86% (14% core). More hydrophobic methylpyrene and butylpyrene, monitored with I1/I3 ratios, reside 1% in the corona (99% core). These results explain difficulties with using SPAAC reactions for conjugating large ligands to nanoparticles with PEG coronae.