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Objective: To report data from the first three years of operation of the RSNA-ACR 3D Printing Registry., Methods: Data from June 2020 to June 2023 was extracted, including demographics, indications, workflow and user assessments. Clinical indications were stratified by 12 organ systems. Imaging modalities, printing technologies and number of parts per case were assessed. Effort data was analyzed, dividing staff into provider and non-provider categories. The opinions of clinical users were evaluated through a Likert-scale questionnaire, and estimates of procedure time saved were collected., Results: A total of 20 sites and 2,637 cases were included, consisting of 1,863 anatomic models and 774 anatomic guides. Mean patient age for models and guides was 42.4 ± 24.5 years and 56.3 ± 18.5 years respectively. Cardiac models were the most common type of models (27.2%), and neurologic guides were the most common type of guides (42.4%). Material jetting, vat photopolymerization and material extrusion were the most common printing technologies used overall (85.6% of all cases). On average, providers spent 92.4 minutes and non-providers spent 335.0 minutes per case. Providers spent most time on consultation (33.6 minutes), while non-providers focused most on segmentation (148.0 minutes). Confidence in treatment plans increased after using 3D printing (p<.001). Estimated procedure time savings for 155 cases was 40.5 ± 26.1 minutes., Conclusion: 3D printing is performed in healthcare facilities for many clinical indications. The registry provides insight into the technologies and workflows used to create anatomic models and guides, and the data shows clinical benefits from 3D printing., (Copyright © 2024. Published by Elsevier Inc.)

While radiological imaging is presented as two-dimensional images either on radiography or cross-sectional imaging, it is important for interpreters to understand three-dimensional anatomy and pathology. We hypothesized that virtual reality (VR) may serve as an engaging and effective way for trainees to learn to extrapolate from two-dimensional images to an understanding of these three-dimensional structures. We created a Google Cardboard Virtual Reality application that depicts intracranial vasculature and aneurysms. We then recruited 12 medical students to voluntarily participate in our study. The performance of the students in identifying intracranial aneurysms before and after the virtual reality training was evaluated and compared to a control group. While the experimental group's performance in correctly identifying aneurysms after virtual reality educational intervention was better than the control's (experimental increased by 5.3%, control decreased by 2.1%), the difference was not statistically significant (p-value of 0.06). Significantly, survey data from the medical students was very positive with students noting they preferred the immersive virtual reality training over conventional education and believed that VR would be a helpful educational tool for them in the future. We believe virtual reality can serve as an important tool to help radiology trainees better understand three-dimensional anatomy and pathology., (© 2023. The Author(s) under exclusive licence to Society for Imaging Informatics in Medicine.)

Background and Purpose- Cervical artery dissection is a major cause of ischemic stroke in the young and presents with various imaging findings, including stenosis and intramural hematoma (IMH). Our goal was to determine the relative contribution of lumen findings and IMH to acute ischemic stroke and whether a heavily T1-weighted sequence could more reliably detect IMH. Methods- Institutional review board approval was obtained for this retrospective study of 254 patients undergoing magnetic resonance imaging/magnetic resonance angiography for suspected dissection. Imaging included standard turbo spin-echo (TSE) T1-fat saturation and heavily T1-weighted flow-suppressed magnetization-prepared rapid acquisition gradient-recalled echo sequences. Subjects with stents (1) or atherosclerotic disease (26) were excluded, leaving 227 subjects. Kappa analysis was used to determine IMH interrater reliability on magnetization-prepared rapid acquisition gradient-recalled echo and T1-fat saturation in 4 vessels per subject. Lumen findings, cardiovascular risk factors, medications, and nondissection stroke sources were recorded. Mixed-effects multivariate Poisson regression was used to determine the prevalence ratio of each factor with acute ischemic stroke, accounting for 4 vessels per patient with backward elimination to a threshold P value of 0.10. Results- Patients were 41.9% men, mean age of 47.3±16.6 years, with 114 dissections and 107 strokes. IMH interrater reliability was significantly higher for magnetization-prepared rapid acquisition gradient-recalled echo (κ=0.83; 95% CI, 0.78-0.86) versus T1-fat saturation (0.58; 95% CI, 0.57-0.68). The final acute stroke prediction model included magnetization-prepared rapid acquisition gradient-recalled echo-detected IMH (prevalence ratio, 2.0; 95% CI, 1.1-3.9; P=0.034), stenosis, pseudoaneurysm, male sex, current smoking, and nondissection stroke sources. The final model had high discrimination for acute stroke (area under the curve, 0.902; 95% CI, 0.872-0.932), compared with models without stenosis (0.861; 95% CI, 0.821-0.902), and without stenosis and IMH (0.831; 95% CI, 0.783-0.879). All 3 models were significantly different at P<0.05. Conclusions- Along with stenosis, IMH detection significantly contributed to acute ischemic stroke pathogenesis in patients with suspected cervical artery dissection. In addition, IMH detection can be made more reliable with heavily T1-weighted sequences.

Background and Purpose: The C1-2 intrathecal puncture is routinely performed when lumbar puncture is not feasible. Usage has steadily decreased in part because of the perceived high risk of injury to the cervical cord. Up to this point, vague fluoroscopic guidelines have been used, creating uncertainty about the actual needle location relative to the spinal cord. We present a novel osseous landmark to aid in C1-2 intrathecal puncture, corresponding to the posterior spinal cord margin on lateral fluoroscopic views. This landmark, which we have termed the "flare point," represents the triangular "flaring" of the posterior C1 arch at its junction with the anterior arch., Materials and Methods: Cervical spine CT myelograms were reviewed. High-resolution axial images were reformatted into the sagittal plane, and maximum-intensity-projection images were created to simulate a lateral fluoroscopic view. Tangential lines were drawn along the superior cortices of the anterior and posterior C1 arches, with the point of intersection used to approximate the flare point. Chart review was performed for all C1-2 punctures using the flare point technique in the past 3 years., Results: Forty-two cervical myelograms were reviewed. The average flare point was 0.2 ± 0.5 mm posterior to the dorsal spinal cord margin. In 37/42 subjects, the flare point was localized posterior to the spinal cord. Targeting by means of the flare point was used in 16 C1-2 punctures without complications., Conclusions: The C1 posterior arch flare point accurately approximates the dorsal spinal cord margin on myelography. Targeting between the flare point and the spinolaminar line, at the mid-C1-2 interspace, allows safe and optimal needle positioning., (© 2018 by American Journal of Neuroradiology.)

Purpose: To present the results of a high-volume oculoplastic surgical outreach in a remote region of Simbu Province in the Eastern Highlands of Papua New Guinea. The authors describe the clinical features and evaluation and treatment of a novel ptosis syndrome found in this area., Design: A team of 4 international ophthalmologists and 3 local doctors and 3 local nurses involved in a high-volume field intervention for all patients presenting with a bilateral ptosis to Mingende Rural Hospital., Methods: Patients were systematically evaluated and treated during a 6-day surgical outreach and followed daily for 1 week and as needed via telemedicine. Visiting surgeons provided skills-transfer instruction for 3 local doctors and 3 nurses. Data collected included demographic information, history of present illness, past medical history, family history, social history, and a complete ophthalmologic and targeted neurologic evaluation. Patients were offered surgical intervention if they met criteria for safe eyelid elevation and could present for follow ups. Detailed notes of patient geographic location, history, and risk factors were collected in addition to pre- and postoperative photos., Main Outcome Measures: Efficient triage and treatment of all patients referred to the remote oculoplastic clinic., Results: A total of 97 patients presented to the camp; of these, 87 underwent complete evaluation. There were 72 patients with ptosis, of which 60 were found to be of Simbu-type. These patients were grouped clinically by degree of ptosis: mild, moderate, and severe. Thirty-eight patients had moderate ptosis of which 34 underwent surgical intervention. Eleven patients with mild ptosis were counseled and observed. The 10 patients with severe ptosis and 2 with moderate ptosis were treated medically with ptosis crutches manufactured on site. A new technique for creating ptosis crutch glasses was developed., Conclusions: A new variant of progressive myogenic ptosis was identified. A high-volume oculoplastic surgical camp is an efficient way to systematically evaluate and treat this new entity. Skills-transfer training for local doctors and staff ensured continuity of care for the surgical patients.

Background and Study Aims: Conventional treatment strategies for the management of symptomatic chronic subdural hematoma (cSDH) in the elderly include observation, operative burr holes or craniotomy, and bedside twist drill drainage. The decision on which technique to use should be determined by weighing the comorbidities and symptoms of the patient with the potential risks and benefits. The goal of this study was to identify radiographic characteristics on computed tomography scan that might be used to guide surgical decision making in terms of operative versus bedside removal of cSDH., Methods: We retrospectively reviewed clinical and radiographic features in patients who underwent bedside twist drill evacuation of a cSDH and those for a cohort of patients who underwent operative intervention via burr holes., Results: We did not identify any clinical features or preoperative imaging characteristics to suggest an advantage of one procedure over the other. Additionally, complete radiographic resolution of cSDH on postoperative imaging is not required to relieve patient symptoms., Conclusion: Although bedside twist drill evacuation may avoid operating room costs and anesthetic complications in an elderly patient population and allow earlier resumption of anticoagulation treatment if necessary, there is also a risk of morbidity if uncontrolled bleeding is encountered or the patient is unable to tolerate the bedside procedure. However, bedside twist drill craniostomy is a reasonable and effective option for the treatment of subacute/chronic SDH in patients who may not be optimal surgical candidates., (Georg Thieme Verlag KG Stuttgart · New York.)

Background and Purpose: While enhanced T1WI is considered the "gold standard" for detection of internal auditory canal pathology, unenhanced fluid-sensitive sequences have shown high sensitivity for lesion identification. Our purpose was to evaluate the diagnostic accuracy of an unenhanced MR imaging protocol using axial CISS and coronal T2WI for detection of small (10 mm or less) internal auditory canal lesions., Materials and Methods: Twenty-three patients with small internal auditory canal lesions and 13 patients without lesions who had undergone MR imaging using the screening protocol and confirmatory gadolinium-enhanced thin section T1WI were identified. Two blinded neuroradiologists retrospectively evaluated all examinations using 1) only axial CISS, 2) only coronal T2WI, and 3) axial and coronal sequences together. Accuracy, specificity, sensitivity, and interobserver agreement were assessed., Results: Median maximum lesion dimension was 4 mm (range, 2-10 mm). Accuracy, specificity, and sensitivity for axial CISS alone were 0.94, 0.96, and 0.91 for observer 1 and 0.94, 0.92, and 1.00 for observer 2. The data for the coronal T2WI sequence only were 0.94, 0.96, and 0.91 for observer 1, and 0.99, 1.00, and 0.96 for observer 2. Using axial and coronal sequences, the data were 0.97, 0.96, and 1.00 for observer 1, and 0.99, 0.98, and 1.00 for observer 2. κ coefficients were 0.84 for the axial sequence only, 0.90 for coronal only, and 0.91 for axial and coronal both., Conclusions: Screening noncontrast MR imaging using a combination of axial CISS and coronal T2WI sequences can detect small internal auditory canal lesions with 100% sensitivity and excellent interobserver agreement., (© 2014 by American Journal of Neuroradiology.)

We describe a patient with vision loss from an optic neuropathy caused by Propionibacterium acnes pachymeningitis. The patient's optic neuropathy was stabilized with appropriate antibiotic therapy.

Apoplexy of the pituitary gland is a rare complication of pituitary adenomas, involving hemorrhage with or without necrosis within the tumor. This condition may be either asymptomatic or may present with severe headache, visual impairment, ophthalmoplegia, and pituitary failure. Transsphenoidal surgery is the treatment of choice, and early intervention is usually required to ensure reversal of visual impairment. Reports of pituitary apoplectic lesions exceeding 60.0mm in diameter are very rare. A 39-year-old man with long-standing history of nasal congestion, decreased libido and infertility presented with a sudden onset of severe headache and diplopia. MRI of the head demonstrated a massive skull base lesion of 70.0 × 60.0 × 25.0mm, compatible with a giant pituitary macroadenoma. The lesion failed to enhance after administration of a contrast agent, suggesting complete necrotic apoplexy. Urgent surgical decompression was performed, and the lesion was resected via a transnasal transsphenoidal approach. Pathological analysis revealed evidence of necrotic pituitary apoplexy. At the 2 month follow-up, the patient had near-complete to complete resolution of his visual impairment. To the authors' knowledge, this report is unique as the patient demonstrated complete necrotic apoplexy and it underlines the diagnostic dilemma in such a case., (Copyright © 2012 Elsevier Ltd. All rights reserved.)

Introduction: Our objective is to determine the utility of noncontrast Hounsfield unit values, Hounsfield unit values corrected for the patient's hematocrit, and venoarterial Hounsfield unit difference measurements in the identification of intracranial venous thrombosis on noncontrast head computed tomography., Methods: We retrospectively reviewed noncontrast head computed tomography exams performed in both normal patients and those with cerebral venous thrombosis, acquiring Hounsfield unit values in normal and thrombosed cerebral venous structures. Also, we acquired Hounsfield unit values in the internal carotid artery for comparison to thrombosed and nonthrombosed venous structures and compared the venous Hounsfield unit values to the patient's hematocrit., Results: A significant difference is identified between Hounsfield unit values in thrombosed and nonthrombosed venous structures. Applying Hounsfield unit threshold values of greater than 65, a Hounsfield unit to hematocrit ratio of greater than 1.7, and venoarterial difference values greater than 15 alone and in combination, the majority of cases of venous thrombosis are identifiable on noncontrast head computed tomography., Conclusion: Absolute Hounsfield unit values, Hounsfield unit to hematocrit ratios, and venoarterial Hounsfield unit value differences are a useful adjunct in noncontrast head computed tomographic evaluation of cerebral venous thrombosis.

Background and Purpose: Advances in multidetector CT provide exquisite detail with improved delineation of the normal anatomic structures in the head and neck. The carotid body is 1 structure that is now routinely depicted with this new imaging technique. An understanding of the size range of the normal carotid body will allow the radiologist to distinguish patients with prominent normal carotid bodies from those who have a small carotid body paraganglioma., Materials and Methods: We performed a retrospective analysis of 180 CTAs to assess the imaging appearance of the normal carotid body in its expected anatomic location., Results: The carotid body was detected in >80% of carotid bifurcations. The normal size range measured from 1.1 to 3.9 mm ± 2 SDs, which is consistent with the reported values from anatomic dissections., Conclusions: An ovoid avidly enhancing structure at the inferomedial aspect of the carotid bifurcation within the above range should be considered a normal carotid body. When the carotid body measures >6 mm, a small carotid body paraganglioma should be suspected and further evaluated.

Background and Purpose: Occlusion of the AOP results in a characteristic pattern of ischemia: bilateral paramedian thalamus with or without midbrain involvement. Although the classic imaging findings are often recognized, only a few small case series and isolated cases of AOP infarction have been reported. The purpose of this study was to characterize the complete imaging spectrum of AOP infarction on the basis of a large series of cases obtained from multiple institutions., Materials and Methods: Imaging and clinical data of 37 patients with AOP infarction from 2000 to 2009 were reviewed retrospectively. The primary imaging criterion for inclusion was an abnormal signal intensity on MR imaging and/or hypoattenuation on CT involving distinct arterial zones of the bilateral paramedian thalami with or without rostral midbrain involvement. Patients were excluded if there was a neoplastic, infectious, or inflammatory etiology., Results: We identified 4 ischemic patterns of AOP infarction: 1) bilateral paramedian thalamic with midbrain (43%), 2) bilateral paramedian thalamic without midbrain (38%), 3) bilateral paramedian thalamic with anterior thalamus and midbrain (14%), and 4) bilateral paramedian thalamic with anterior thalamus without midbrain (5%). A previously unreported finding (the "V" sign) on FLAIR and DWI sequences was identified in 67% of cases of AOP infarction with midbrain involvement and supports the diagnosis when present., Conclusions: The 4 distinct patterns of ischemia identified in our large case series, along with the midbrain V sign, should improve recognition of AOP infarction and assist with the neurologic evaluation and management of patients with thalamic strokes.

The direct role of the dioxolane group on the gating and single-channel conductance of different stereoisomers of the dioxolane-linked gramicidin A (gA) channels reconstituted in planar lipid bilayers was investigated. Four different covalently linked gA dimers were synthesized. In two of them, the linker was the conventional dioxolane described previously (SS and RR channels). Two gAs were covalently linked with a novel modified dioxolane group containing a retinal attachment (ret-SS and ret-RR gA dimers). These proteins also formed ion channels in lipid bilayers and were selective for monovalent cations. The presence of the bulky and hydrophobic retinal group immobilizes the dioxolane linker in the bilayer core preventing its rotation into the hydrophilic lumen of the pore. In 1 M HCl the gating kinetics of the SS or RR dimers were indistinguishable from their retinal counterparts; the dwell-time distributions of the open and closed states in the SS and ret-SS were basically the same. In particular, the inactivation of the RR was not prevented by the presence of the retinal group. It is concluded that neither the fast closing events in the SS or RR dimers nor the inactivation of the RR are likely to be a functional consequence of the flipping of the dioxolane inside the pore of the channel. On the other hand, the inactivation of the RR dimer was entirely eliminated when alkaline metals (Cs(+) or K(+)) were the permeating cations in the channel. In fact, the open state of the RR channel became extremely stable, and the gating characteristics of both the SS and RR channels were different from what was seen before with permeating protons. As in HCl, the presence of a retinal in the dioxolane linker did not affect the gating behavior of the SS and RR in Cs(+)- or K(+)-containing solutions. Alternative hypotheses concerning the gating of linked gA dimers are discussed.

The association of two gramicidin A (gA) peptides via H-bonds in lipid bilayers causes the formation of an ion channel that is selective for monovalent cations only. In this study, two gAs were covalently linked with a dioxolane group (SS dimer). Some functional properties of natural gA channels were compared to that synthetic dimer in Na(+)- or Cs(+)-containing solutions. The SS dimer remained in the open configuration most of the time, while natural gA channels had a relatively brief mean open time. Single channel conductances to Na(+) (g(Na)) or Cs(+) (g(Cs)) in the SS dimer were smaller than in natural gA. However, g(Na) was considerably more attenuated than g(Cs). This probably results from a tight solvation of Na(+) by the dioxolane linker in the SS channel. In Cs(+) solutions, the SS had frequent closures. By contrast, in Na(+) solutions the synthetic dimer remained essentially in the open state. The mean open times of SS channels in different solutions (T(open, Na) > T(open,Cs) > T(open,H)) were inversely proportional to the single channel conductances (g(H) > g(Cs) > g(Na)). This suggests that ion occupancy inside the pore stabilizes the open configuration of the gA dimer. The mean closed time of the SS dimer was longer in Cs(+) than in H(+) solutions. Possible mechanisms for these effects are discussed.

Two different stereoisomers of the dioxolane-linked gramicidin A (gA) channels were individually synthesized (the SS and RR dimers;. Science. 244:813-817). The structural differences between these dimers arise from different chiralities within the dioxolane linker. The SS dimer mimics the helicity and the inter- and intramolecular hydrogen bonding of the monomer-monomer association of gA's. In contrast, there is a significant disruption of the helicity and hydrogen bonding pattern of the ion channel in the RR dimer. Single ion channels formed by the SS and RR dimers in planar lipid bilayers have different proton transport properties. The lipid environment in which the different dimers are reconstituted also has significant effects on single-channel proton conductance (g(H)). g(H) in the SS dimer is about 2-4 times as large as in the RR. In phospholipid bilayers with 1 M [H(+)](bulk), the current-voltage (I-V) relationship of the SS dimer is sublinear. Under identical experimental conditions, the I-V plot of the RR dimer is supralinear (S-shaped). In glycerylmonooleate bilayers with 1 M [H(+)](bulk), both the SS and RR dimers have a supralinear I-V plot. Consistent with results previously published (. Biophys. J. 73:2489-2502), the SS dimer is stable in lipid bilayers and has fast closures. In contrast, the open state of the RR channel has closed states that can last a few seconds, and the channel eventually inactivates into a closed state in either phospholipid or glycerylmonooleate bilayers. It is concluded that the water dynamics inside the pore as related to proton wire transfer is significantly different in the RR and SS dimers. Different physical mechanisms that could account for this hypothesis are discussed. The gating of the synthetic gA dimers seems to depend on the conformation of the dioxolane link between gA's. The experimental results provide an important framework for a detailed investigation at the atomic level of proton conduction in different and relatively simple ion channel structures.

The mobility of protons in a dioxolane-linked gramicidin A channel (D1) is comparable to the mobility of protons in aqueous solutions (Cukierman, S., E. P. Quigley, and D. S. Crumrine. 1997. Biophys. J. 73:2489-2502). Aliphatic alcohols decrease the mobility of H+ in aqueous solutions. In this study, the effects of methanol on proton conduction through D1 channels were investigated in different lipid bilayers and at different HCl concentrations. Methanol attenuated H+ currents in a voltage-independent manner. Attenuation of proton currents was also independent of H+ concentrations in solution. In phospholipid bilayers, methanol decreased the single channel conductance to protons without affecting the binding affinity of protons to bilayers. In glycerylmonooleate membranes, the attenuation of single channel proton conductances qualitatively resembled the decrease of conductivities of HCl solutions by methanol. However, in both types of lipid bilayers, single channel proton conductances through D1 channels were considerably more attenuated than the conductivities of different HCl solutions. This suggests that methanol modulates single proton currents through D1 channels. It is proposed that, on average, one methanol molecule binds to a D1 channel, and attenuates H+ conductance. The Gibbs free energy of this process (DeltaG0) is approximately 1.2 kcal/mol, which is comparable to the free energy of decrease of HCl conductivity in methanol solutions (1.6 kcal/mol). Apolar substances like urea and glucose that do not transport protons in HCl solutions and do not permeate D1 channels decreased solution conductivity and single channel conductance by a considerably larger proportion than methanol. Cs+ currents through D1 channels were considerably less (fivefold) attenuated by methanol than proton currents. It is proposed that methanol partitions inside the pore of gramicidin channels and delays the transfer of protons between water and methanol molecules, causing a significant attenuation of the single channel proton conductance. Gramicidin channels offer an interesting experimental model to study proton hopping along a single chain of water molecules interrupted by a single methanol molecule.

Gramicidin A (gA) molecules were covalently linked with a dioxolane ring. Dioxolane-linked gA dimers formed ion channels, selective for monovalent cations, in planar lipid bilayers. The main goal of this study was to compare the functional single ion channel properties of natural gA and its covalently linked dimer in two different lipid bilayers and HCl concentrations (10-8000 mM). Two ion channels with different gating and conductance properties were identified in bilayers from the product of dimerization reaction. The most commonly observed and most stable gramicidin A dimer is the main object of this study. This gramicidin dimer remained in the open state most of the time, with brief closing flickers (tau(closed) approximately 30 micros). The frequency of closing flickers increased with transmembrane potential, making the mean open time moderately voltage dependent (tau(open) changed approximately 1.43-fold/100 mV). Such gating behavior is markedly different from what is seen in natural gA channels. In PEPC (phosphatidylethanolamine-phosphatidylcholine) bilayers, single-channel current-voltage relationships had an ohmic behavior at low voltages, and a marked sublinearity at relatively higher voltages. This behavior contrasts with what was previously described in GMO (glycerylmonooleate) bilayers. In PEPC bilayers, the linear conductance of single-channel proton currents at different proton concentrations was essentially the same for both natural and gA dimers. g(max) and K(D), obtained from fitting experimental points to a Langmuir adsorption isotherm, were approximately 1500 pS and 300 mM, respectively, for both the natural gA and its dimer. In GMO bilayers, however, proton affinities of gA and the dioxolane-dimer were significantly lower (K(D) of approximately 1 and 1.5 M, respectively), and the g(max) higher (approximately 1750 and 2150 pS, respectively) than in PEPC bilayers. Furthermore, the relationship between single-channel conductance and proton concentration was linear at low bulk concentrations of H+ (0.01-2 M) and saturated at concentrations of more than 3 M. It is concluded that 1) The mobility of protons in gramicidin A channels in different lipid bilayers is remarkably similar to proton mobilities in aqueous solutions. In particular, at high concentrations of HCl, proton mobilities in gramicidin A channel and in solution differ by only 25%. 2) Differences between proton conductances in gramicidin A channels in GMO and PEPC cannot be explained by surface charge effects on PEPC membranes. It is proposed that protonated phospholipids adjacent to the mouth of the pore act as an additional source of protons for conduction through gA channels in relation to GMO bilayers. 3) Some experimental results cannot be reconciled with simple alterations in access resistance to proton flow in gA channels. Said differences could be explained if the structure and/or dynamics of water molecules inside gramicidin A channels is modulated by the lipid environment and by modifications in the structure of gA channels. 4) The dioxolane ring is probably responsible for the closing flickers seen in the dimer channel. However, other factors can also influence closing flickers.