Catheter Trajectory Research Articles

SURG-28. THE IMPACT OF PERILESIONAL HEATSINK STRUCTURES ON ABLATION VOLUMES AND SYMMETRY IN LASER INTERSTITIAL THERMAL THERAPY FOR THE TREATMENT OF PRIMARY CENTRAL NERVOUS SYSTEM TUMORS

Abstract BACKGROUND Laser Interstitial Thermal Therapy (LITT) has emerged as a minimally invasive treatment for primary CNS tumors. While LITT offers advantages over traditional approaches, perilesional intracranial heatsinks can lead to asymmetric ablation, impacting patient outcomes. Understanding heatsink effects is crucial for optimizing LITT efficacy. METHODS We retrospectively analyzed primary CNS tumors treated with LITT at a single tertiary care center. Ablation outcomes were quantified using the Heatsink Effect Index (HEI) measured on a scale of 0-1 (0=total symmetry; 1=complete asymmetry), and extent of ablation (EOA). Heatsink types evaluated were sulci, meninges, vasculature, and cerebrospinal fluid (CSF) spaces, inclusive of ventricles, surgical resection cavities, and CSF cisterns. Statistical analyses assessed the relationship between heatsink proximity and ablation outcomes. RESULTS A total of 99 patients satisfied all selection criteria. The cohort was 53% female, with a mean age of 61 years. Glioblastoma was the most predominant tumor type (78%), followed by low grade gliomas (15%), and meningiomas (4%). Heatsink proximity significantly correlated with ablation asymmetry (HEI) (p < 0.001), particularly at the midpoint of the catheter trajectory. The correlation between closest heatsink distance and HEI varied across the different heatsink types, with distance to vasculature and CSF spaces correlating the strongest with ablation asymmetry. When assessing the relationship between EOA and medial HEI during suboptimal ablations (EOA < 100%), we demonstrated a negative correlation showing improved EOA as HEI was reduced. Optimal cutoff catheter-heatsink distances for predicting ablation asymmetry ranged from 6.6-13.0 mm, emphasizing the impact of heatsink proximity on LITT efficacy. CONCLUSION We show that proximity to heatsinks, especially within a threshold distance of 13.0mm from the laser catheter, significantly predicts ablation asymmetry and volume in the setting of primary CNS tumors. Neurosurgeons should consider heatsink effects in pre- and intraoperative planning to optimize LITT outcomes and preserve normal brain tissue.

High-fidelity pose estimation for real-time extended reality (XR) visualization for cardiac catheterization

Extended reality (XR) technologies are emerging as promising platforms for medical training and procedural guidance, particularly in complex cardiac interventions. This paper presents a high-fidelity methodology to perform real-time 3D catheter tracking and visualization during simulated cardiac interventions. A custom 3D-printed setup with mounted cameras enables biplane video capture of a catheter. A computer vision algorithm processes the biplane images in real-time to reconstruct the 3D catheter trajectory represented by any designated number of points along its length. This method accurately localizes the catheter tip within 1 mm and can reconstruct any arbitrary catheter configuration. The tracked catheter data is integrated into an interactive Unity-based scene rendered on the Meta Quest 3 headset. The visualization seamlessly combines a reconstructed 3D patient-specific heart model with the dynamically tracked catheter, creating an immersive extended reality training environment. Our experimental study, involving six participants, demonstrated that the 3D visualization provided by the proposed XR system significantly outperformed 2D visualization in terms of speed and user experience. This suggests that the XR system has the potential to enhance catheterization training by improving spatial comprehension and procedural skills. The proposed system demonstrates the potential of XR technologies to transform percutaneous cardiac interventions through improved visualization and interactivity.

PO0110: Treatment Planning with Clinically Feasible Curved Catheter Trajectory Prediction for HDR Prostate Brachytherapy

PO0110: Treatment Planning with Clinically Feasible Curved Catheter Trajectory Prediction for HDR Prostate Brachytherapy

Intraventricular baclofen for intractable spasticity and secondary dystonia: a frame-based stereotactic approach and case series

ObjectiveIntraventricular baclofen has been reported as an alternative to intrathecal baclofen for managing refractory spasticity and dystonia in some circumstances. In this report, we described a frame-based stereotactic approach for precisely positioning of the infusion catheter into the third ventricle.Material and methodsHigh resolution contrast-enhanced anatomical MR sequences was acquired prior to surgery for pre-planning. Catheter trajectory was planned to pass from the lateral ventricle to the third ventricle through the Foramen of Monro. The surgical procedure was adapted from the frame-based deep brain stimulation surgery. The Touch-Loc kit (SceneRay, China) was used to temporarily secure the catheter in place during the surgery. From July 2022 to December 2022, three patients suffering from intractable spasticity and/or secondary dystonia received IVB successfully using the described technique.ResultsNo severe adverse events, including death, intracranial hemorrhage, infection, catheter migration or fracture, were documented at the last follow-up (range: 12‒24 months). Transient side effects included mild nausea following the initiation of infusion or the increase in infusion rate. All three patients responded to the IVB.ConclusionsThe described frame-based stereotactic technique for IVB catheter implant is feasible and could be quickly mastered by neurosurgeons in related fields. Larger prospective cohorts with longer follow-up periods are necessary to further evaluate the long-term safety and efficacy of this procedure.

Neural network reconstruction of the left atrium using sparse catheter paths.

Catheter-based radiofrequency ablation for pulmonary vein isolation has become the first line of treatment for atrial fibrillation in recent years. This requires a rather accurate map of the left atrial sub-endocardial surface including the ostia of the pulmonary veins, which requires dense sampling of the surface and currently takes more than 10min. The focus of this work is to provide left atrial visualization early in the procedure to ease procedure complexity and enable further workflows, such as using catheters that have difficulty sampling the surface. We propose a dense encoder-decoder network with a novel regularization term to reconstruct the shape of the left atrium from partial data which is derived from simple catheter maneuvers. To train the network, we acquire a large dataset of 3D atria shapes and generate corresponding catheter trajectories, from which traversed point clouds are obtained. Once trained, we show that the suggested network can sufficiently approximate the atrium shape based on a given trajectory. We compare several network solutions for the 3D atrium reconstruction. We demonstrate that the solution proposed produces realistic visualization using partial acquisition within a 3-min time interval using human clinical cases.

Intraoperative cone-beam computed tomography for catheter placement verification in pediatric hydrocephalus: technical note.

Ventriculoperitoneal (VP) shunt placement, essential for managing hydrocephalus, often risks catheter malpositioning, especially in patients with small ventricles. We present a novel technique combining neuronavigation with intraoperative cone-beam computed tomography using the BrainLab system and Loop-X mobile imaging unit. This approach enables real-time verification of catheter placement by integrating preoperative MRI data with intraoperative CT imaging. In a 12-year-old boy with therapy-refractory idiopathic intracranial hypertension, neuronavigation was guided by the BrainLab Skull Fix and Cushing canula, ensuring precise catheter insertion into the right frontal horn. Post-placement, Loop-X facilitated immediate verification of the catheter's trajectory and positioning, corroborated by postoperative MRI. This technique demonstrated high precision and minimized radiation exposure, emphasizing its utility in reducing revision rates due to suboptimal catheter placement.

Flow reduction due to arterial catheterization during stroke treatment - A computational study using a distributed compartment model.

The effectiveness of various stroke treatments depends on the anatomical variability of the cerebral vasculature, particularly the collateral blood vessel network. Collaterals at the level of the Circle of Willis and distal collaterals, such as the leptomeningeal arteries, serve as alternative avenues of flow when the primary pathway is obstructed during an ischemic stroke. Stroke treatment typically involves catheterization of the primary pathway, and the potential risk of further flow reduction to the affected brain area during this treatment has not been previously investigated. To address this clinical question, we derived the lumped parameters for catheterized blood vessels and implemented a corresponding distributed compartment (0D) model. This 0D model was validated against an experimental model and benchmark test cases solved using a 1D model. Additionally, we compared various off-center catheter trajectories modeled using a 3D solver to this 0D model. The differences between them were minimal, validating the simplifying assumption of the central catheter placement in the 0D model. The 0D model was then used to simulate blood flows in realistic cerebral arterial networks with different collateralization characteristics. Ischemic strokes were modeled by occlusion of the M1 segment of the middle cerebral artery in these networks. Catheters of different diameters were inserted up to the obstructed segment and flow alterations in the network were calculated. Results showed up to 45% maximum blood flow reduction in the affected brain region. These findings suggest that catheterization during stroke treatment may have a further detrimental effect for some patients with poor collateralization.

SURG-06. FRAMELESS STEREOTACTIC INTRACRANIAL CATHETER PLACEMENT FOR DELIVERY OF INTRATUMORAL CELLULAR THERAPIES

Abstract BACKGROUND As the leading disease-related cause of death in children, pediatric brain tumors, and in particular diffuse midline glioma, require novel treatment approaches. Cellular-based therapies offer promise, but challenges still exist in defining their optimal delivery route. Emerging data from our group suggest there may be a role for intratumoral injection in treatment algorithms. We here describe a surgical workflow for intratumoral injection of cellular therapies that utilizes existing and widely used neurosurgical technologies that can be incorporated into future clinical trials. METHODS Infusion target and catheter trajectory was planned using standard pre-operative MRI. Components from an FDA-approved frameless stereotactic intracranial biopsy system were chosen such that they would accept and guide an FDA-approved rigid intracranial catheter system intended for MR-guided procedures. Following catheter insertion, an intraoperative CT was used to determine accuracy of catheter placement by merging the image with the pre-operative MRI. RESULTS The proposed system was tested in a simulated fashion using a phantom cranial model registered to an accompanying brain MRI. The stereotactic biopsy mount was affixed to the skull at the planned entry site for a posterior fossa approach to the pons. Catheter insertion depth was determined using the stereotactic system and the catheter was inserted to this depth through the biopsy mount. Intraoperative CT confirmed the catheter tip location which correlated with the planned infusion target with sub-millimetric accuracy. CONCLUSION Our proposed intratumoral delivery method using frameless stereotaxy shows promise for use in future clinical trials that require intratumoral delivery of cellular therapies. Utilizing FDA-approved devices allows for quick integration into protocols and their wide-spread use makes the approach generalizable. This approach also eliminates the need for MR-guided procedures which can increase cost and require significant hospital resources to perform. Future work will be aimed at streamlining the intraoperative workflow.

Augmented Reality-based Contextual Guidance through Surgical Tool Tracking in Neurosurgery.

External ventricular drain (EVD) is a common, yet challenging neurosurgical procedure of placing a catheter into the brain ventricular system that requires prolonged training for surgeons to improve the catheter placement accuracy. In this paper, we introduce NeuroLens, an Augmented Reality (AR) system that provides neurosurgeons with guidance that aides them in completing an EVD catheter placement. NeuroLens builds on prior work in AR-assisted EVD to present a registered hologram of a patient's ventricles to the surgeons, and uniquely incorporates guidance on the EVD catheter's trajectory, angle of insertion, and distance to the target. The guidance is enabled by tracking the EVD catheter. We evaluate NeuroLens via a study with 33 medical students and 9 neurosurgeons, in which we analyzed participants' EVD catheter insertion accuracy and completion time, eye gaze patterns, and qualitative responses. Our study, in which NeuroLens was used to aid students and surgeons in inserting an EVD catheter into a realistic phantom model of a human head, demonstrated the potential of NeuroLens as a tool that will aid and educate novice neurosurgeons. On average, the use of NeuroLens improved the EVD placement accuracy of the year 1 students by 39.4%, of the year 2 -4 students by 45.7%, and of the neurosurgeons by 16.7%. Furthermore, students who focused more on NeuroLens-provided contextual guidance achieved better results, and novice surgeons improved more than the expert surgeons with NeuroLens's assistance.

Establishment of new transurethral catheterization methods for male mice.

Transurethral catheterization in mice is multifaceted, serving essential functions such as perfusion and drug delivery, and is critical in the development of various urological animal disease models. The complex anatomy of the male mouse urethra presents significant challenges in transurethral catheterization, leading to a predominance of research focused on female specimens. This bias limits the utilization of male mice in lower urinary tract disease studies. Our research aims to develop new reliable methods for transurethral catheterization in adult male mice, thereby expanding their use in relevant disease research. Experiments were conducted on adult male C57BL/6J mice. Utilizing a PE10 catheter measuring 4.5-5 cm in length, the catheter was inserted into the bladder via the mouse's urethra under anesthesia. The intubation technique entailed regulating the insertion force, ensuring the catheter's lubrication, using a trocar catheter, modifying the catheter's trajectory, and accommodating the curvature of the bladder neck. Post-catheter insertion, ultrasound imaging was employed to confirm the catheter's accurate positioning within the bladder. Subsequent to catheterization, the bladder was perfused using trypan blue. This method was further validated through its successful application in establishing an acute urinary retention (AUR) model, where the mouse bladder was infused with saline to a pressure of 50 or 80 cm H2O, maintained steadily for 30 min. A thorough morphological assessment of the mouse bladder was conducted after the infusion. Our study successfully pioneered methods for transurethral catheterization in male mice. This technique not only facilitates precise transurethral catheterization but also proves applicable to male mouse models for lower urinary tract diseases, such as AUR.

Left Transradial Access Using a Radial-Specific Neurointerventional Guiding Sheath for Coil Embolization of Anterior Circulation Aneurysm Associated With the Aberrant Right Subclavian Artery: Technical Note and Literature Review

Aberrant right subclavian artery (ARSA) is a rare condition, but the most common anomaly of the aortic arch. Although neurointerventions via transradial access (TRA) are becoming increasingly popular worldwide, transradial carotid cannulation has been extremely challenging in patients with an ARSA. Herein, we present a case of ARSA-associated anterior communicating artery (ACoA) aneurysm that was successfully treated with a radial-specific 6F Simmons guiding sheath via left TRA. We also review the relevant literature. A 68-year-old-woman who was diagnosed as having an ARSA-associated ACoA aneurysm underwent simple coiling via left TRA. After the 6F Simmons guiding sheath was engaged into the right common carotid artery using the pull-back-technique, transradial quadraxial system (6F Simmons guiding sheath/6F intermediate catheter/3.2F intermediate catheter/coil-delivery microcatheter) was implemented. Simple coiling of the aneurysm was successfully achieved without catheter kinking or system instability. The postprocedural course was uneventful. A follow-up magnetic resonance angiography showed no evidence of recanalization 1 years 9 months after the procedure. Transradial anterior circulation intervention has been rarely used for patients with an ARSA due to unfavorable catheter trajectory. Left TRA using the 6F Simmons guiding sheath is a useful treatment option to address anterior circulation interventions for patients with an ARSA. Preoperative diagnosis of ARSA is necessary for the application of our method.

Letter: Transradial Flow-Diverting Stent Placement Through an Arteria Lusoria: 2-Dimensional Operative Video.

To the Editor: We read with great interest the article “Transradial Flow-Diverting Stent Placement Through an Arteria Lusoria: 2-Dimensional Operative Video” by Hackett et al.1 The authors present a case of a patient with an arteria lusoria who received effective flow-diverting stent therapy for a large left internal carotid artery (ICA) aneurysm using a large bore guide catheter through right transradial access (TRA). Diagnostic angiography showed that the left ICA could be accessed through the right TRA. A 6F radial sheath was introduced into the right radial artery, and the sheath was then exchanged over a 0.035″ guidewire for an 8F 90-cm guide catheter (Infinity; Stryker Neurovascular). After navigating a 5F 130-cm Simmons catheter into the left common carotid artery through the arteria lusoria, the 8F guide catheter was delivered into the left ICA using the telescoping technique. The large left ICA-ophthalmic artery aneurysm was successfully treated with a pipeline embolization device (Medtronic). The importance of evaluating transradial diagnostic angiography to determine whether a catheter system can safely track into the target supra-aortic vessels is critical for successful transradial neurointervention in patients with arteria lusoria, and we wholeheartedly concur with the authors' conclusion on this point. Cannulation into the supra-aortic vessels through right TRA can be extremely challenging in patients with arteria lusoria because of unfavorable catheter trajectory.2 In addition, the right TRA can cause fatal arteria lusoria dissection.3 Therefore, transfemoral access is frequently employed as first-line access if neurointerventionalists encounter arteria lusoria.2 Previous study reported that left TRA is a technically feasible alternative in neurointerventions for patients with arteria lusoria.4 Nevertheless, a guide catheter may result in a failed TRA that necessitates a crossover to transfemoral access because of a failed cannulation, a kinked catheter, or an unstable system. We have used transradial access as the first-line access for neurointerventions.5-18 The first-line TRA using a 6F preshaped Simmons guiding sheath (outer diameter, 2.70 mm; inner diameter, 0.088″; usable length, 90 cm; 6F Axcelguide Stiff-J; Medikit) offers a large bore working channel and a high procedural success rate without catheter kinking or system instability even in patients with an unfavorable steep supra-aortic take-off.5-7,13 The 6F Simmons guiding sheath is fully engaged into the target common carotid artery with a pull-back maneuver (the pull-back technique) after reforming the Simmons curve within the ascending aorta. The Simmons curve can be reformed by anchoring the 6F Simmons guiding sheath to the descending aorta (the descending aorta anchoring technique) or contralateral subclavian artery (the subclavian artery anchoring technique) through the left TRA. Transradial carotid cannulation with the pull-back technique is technically simple and promising. As a result, left TRA with the 6F Simmons guiding sheath can be a beneficial treatment choice for performing anterior circulation procedures in patients with arteria lusoria. Finally, we would like to express our appreciation to the authors for their interesting article that advances the transradial neurointerventional method.

MO-0297 Fast catheter trajectory planning for patient-tailored cervical cancer brachytherapy applicators

MO-0297 Fast catheter trajectory planning for patient-tailored cervical cancer brachytherapy applicators

Free-hand bedside catheter evacuation without 3D reconstruction for extensive revascularization-associated hemorrhage after ischemic stroke

ObjectiveTo evaluate the feasibility of free-hand bedside catheterization using axial computed tomography (CT) in patients with brain hemorrhage after ischemic revascularization. MethodsPatients who received revascularization therapy and underwent bedside catheterization were consecutively screened from December 2020 to July 2022. Revascularization included intravenous thrombolysis with or without mechanical thrombectomy, balloon angioplasty, and stenting. The catheter trajectory was designed according to the axial CT along the long axis of the hematoma body and projected onto the scalp at the calculated distance and angle. Urokinase was used locally to drain the hematoma. ResultsIn 12 patients (mean age 66 ± 8 years), an 86% reduction in hematoma volume was found after catheter drainage, from 48.6 ± 20.4 ml to 6.7 ± 5.7 ml (P＜0.001). In accordance with the reduction of the hematoma volume, the Glasgow Coma Scale improved from 7 (6.5–8) to 10 (7–10.5) (P = 0.031). Four patients (33.3%) achieved good outcomes (modified Rankin Scale 0–3) at the 180-day follow-up. All-cause mortality was 25%. One patient experienced active hemorrhage. No bacterial brain infections were observed. ConclusionsFree-hand bedside catheterization according to axial CT localization is feasible for treating extensive revascularization-related hematoma after ischemic stroke.

An Artificial Intelligence-Aided Robotic Platform for Ultrasound-Guided Transcarotid Revascularization

Transcarotid Artery Revascularization (TCAR) is typically performed by manual catheter insertion and implies radiation exposure for both the patient and the surgeon. Taking advantage from robotics and artificial intelligence (AI), this letter presents a robotic ultrasound (RUS) platform for improving the procedure. To this purpose, ultrasound (US) imaging is considered both in the pre-operative stage for procedure planning and in the intra-operative stage to track a catheter. 3D vascular volumes can be precisely reconstructed from sequences of 2D images exploiting robotic probe manipulation and AI-based image analysis. The method proved a median reconstruction error lower than 1 mm. Pre-operative information are mapped to the intra-operative scenario thanks to a US-based registration routine. The automatic probe alignment on the target vessel demonstrated to be as precise as 0.84°. The reconstructed 3D model can be exploited to automatically generate a catheter trajectory based on user inputs. Such trajectory enabled automatic insertion of a magnetic catheter steered by an external permanent magnet actuated by the RUS platform. Our results demonstrate a catheter tip target reaching error of 3.3 mm. We believe that these results can open the way for the introduction of robotics and AI in TCAR procedures enabling precise and automatic small-scale intravascular devices control.

Inadvertent through-and-through internal jugular vein penetration and intracarotid placement of a central venous catheter: Microsurgical retrieval technique and operative video

Inadvertent carotid cannulation is a rare complication of internal jugular vein (IJV) catheterization, occurring in less than 1% of cases. Given the significant risk of embolic stroke, urgent catheter removal is indicated. In this technical report and operative video, we present our microsurgical technique for the retrieval and removal of an inadvertently placed, transjugular intracarotid central venous catheter (CVC). A 52-year old man presented with sepsis and hemodynamic lability. An attempt to catheterize the left IJV resulted in inadvertent intracarotid CVC placement, following a through-and-through transjugular path. An open microsurgical approach was used to retrieve the CVC and secure local hemostasis, resulting in excellent outcome. Though generally more invasive than percutaneous and endovascular approaches, open surgical retrieval of misplaced intracarotid CVC leads to consistently excellent outcomes, rendering it the preferred approach in the setting of complex catheter trajectories. The technical note and surgical video presented here can serve as a step-by-step guide for performing this procedure, both safely and effectively.

Development and validation of a rapidly deployable CT-guided stereotactic system for external ventricular drainage: preclinical study

External ventricular drainage (EVD) is an emergency neurosurgical procedure to decrease intracranial pressure through a catheter mediated drainage of cerebrospinal fluid. Most EVD catheters are placed using free hands without direct visualization of the target and catheter trajectory, leading to a high rate of complications- hemorrhage, brain injury and suboptimal catheter placement. Use of stereotactic systems can prevent these complications. However, they have found limited application for this procedure due to their long set-up time and expensive hardware. Therefore, we have developed and pre-clinically validated a novel 3D printed stereotactic system for rapid and accurate implantation of EVD catheters. Its mechanical and imaging accuracies were found to be at par with clinical stereotactic systems. Preclinical trial in human cadaver specimens revealed improved targeting accuracy achieved within an acceptable time frame compared to the free hand technique. CT angiography emulated using cadaver specimen with radio-opaque vascular contrast showed vessel free catheter trajectory. This could potentially translate to reduced hemorrhage rate. Thus, our 3D printed stereotactic system offers the potential to improve the accuracy and safety of EVD catheter placement for patients without significantly increasing the procedure time.

Intraparenchymal hematoma and intraventricular catheter placement using robotic stereotactic assistance (ROSA): A single center preliminary experience

BackgroundLarge supratentorial intraparenchymal hemorrhages are managed emergently with image-guided catheters that aim to minimize injury to surrounding parenchyma. Robotic assistance may offer advantages for stereotactic guidance and placement of such catheters. We describe our center’s experience with minimally invasive ROSA-assisted intraventricular and intraparenchymal hemorrhage catheter placement and delineate its safety and outcomes. MethodsA retrospective analysis was performed including all patients with intraparenchymal hematoma that underwent ROSA-assisted intraparenchymal and intraventricular catheter placement at the University of Pittsburgh Medical Center between 2017 and 2019. All patients received tissue plasminogen activator (tPA) through the intraparenchymal catheter. We performed a manual chart review of these patients. Pertinent clinical and radiological characteristics and patient outcomes were recorded and analyzed. Catheter trajectory was independently quantified and analyzed by two independent reviewers. Error between the planned trajectory and final position was calculated and analyzed. ResultsFour patients (2 males and 2 females, mean age of 64 years) with deep brain large volume intraparenchymal hemorrhages were treated with catheter evacuation with robotic assistance. For 2 of the 4 patients, thin-cut CT imaging allowed for the real trajectory of the catheter to be compared to the targeted trajectory to calculate error. The mean error of catheter placement was 3.48 mm. ROSA-assisted catheter placement achieved up to 95% reduction of intraparenchymal hematoma volume with a statistically significant decrease following catheter drainage (pre- 51.8 ± 19.1 cc vs. post- 13.0 ± 14.4; p < 0.01). ConclusionRobotic stereotactic assistance offers a safe and sufficiently accurate technique for intraparenchymal hematoma and intraventricular catheter placement.

A Novel Transforaminal Approach to Presacral Abscess

Presacral abscess is a common disease in the developing countries. Treatments include minimally invasive percutaneous drainage and open surgical debridement. Percutaneous drainage under computed tomography (CT) guidance has been recommended by the American College of Radiology as a good alternative to surgical drainage before elective surgical treatment. Because of the many anatomic obstacles, the presacral space can be one of the most difficult locations to access. There are several reported access routes like transabdominal, transgluteal, transvaginal, transperineal, transanal, precoccygeal, transpedicular, and so on. We introduce a novel approach, the trans-sacral-foramen approach, to drain presacral abscess under CT guidance. A 47-year-old woman who had lumbar laminectomy debridement for epidural abscess was diagnosed with residual presacral abscess. She was placed in the prone position. One-step technique was applied. Intermittent CT scans were obtained during drainage catheter (8F) advancement into the sacral posterior foramen. The stylet was withdrawn and an approximately 60° angle for catheter trajectory was used to best reach the sacral anterior foramen due to the inherent pelvic tilt. When the catheter tip reached the presacral abscess, the abscess cavity was aspirated with a syringe, pus was drained, and catheter was fixed to skin. Sensitive antibiotics were administered. After 2 weeks magnetic resonance imaging (MRI) showed significant reduced abscess and the catheters were removed. At 18-month follow-up, MRI showed intervertebral fusion at the lumbosacral segment. Trans-sacral-foramen approach is the shortest path to reach the presacral abscess. The approach is easier and safer than the others for patients with indication.

Evaluation of a patient-specific algorithm for predicting distribution for convection-enhanced drug delivery into the brainstem of patients with diffuse intrinsic pontine glioma.

With increasing use of convection-enhanced delivery (CED) of drugs, the need for software that can predict infusion distribution has grown. In the context of a phase I clinical trial for pediatric diffuse intrinsic pontine glioma (DIPG), CED was used to administer an anti-B7H3 radiolabeled monoclonal antibody, iodine-124-labeled omburtamab. In this study, the authors retrospectively evaluated a software algorithm (iPlan Flow) for the estimation of infusate distribution based on the planned catheter trajectory, infusion parameters, and patient-specific MRI. The actual infusate distribution, as determined on MRI and PET imaging, was compared to the distribution estimated by the software algorithm. Similarity metrics were used to quantify the agreement between predicted and actual distributions. Ten pediatric patients treated at the same dose level in the NCT01502917 trial conducted at Memorial Sloan Kettering Cancer Center were considered for this retrospective analysis. T2-weighted MRI in combination with PET imaging was used to determine the distribution of infusate in this study. The software algorithm was applied for the generation of estimated fluid distribution maps. Similarity measures included object volumes, intersection volume, union volume, Dice coefficient, volume difference, and the center and average surface distances. Acceptable similarity was defined as a simulated distribution volume (Vd Sim) object that had a Dice coefficient higher than or equal to 0.7, a false-negative rate (FNR) lower than 50%, and a positive predictive value (PPV) higher than 50% compared to the actual Vd (Vd PET). Data for 10 patients with a mean infusion volume of 4.29 ml (range 3.84-4.48 ml) were available for software evaluation. The mean Vd Sim found to be covered by the actual PET distribution (PPV) was 77% ± 8%. The mean percentage of PET volume found to be outside the simulated volume (FNR) was 34% ± 10%. The mean Dice coefficient was 0.7 ± 0.05. In 8 out of 10 patients, the simulation algorithm fulfilled the combined acceptance criteria for similarity. iPlan Flow software can be useful to support planning of trajectories that produce intraparenchymal convection. The simulation algorithm is able to model the likely infusate distribution for a CED treatment in DIPG patients. The combination of trajectory planning guidelines and infusion simulation in the software can be used prospectively to optimize personalized CED treatment.