Feasibility and Accuracy of a Novel Hands-Free Robotic System for Percutaneous Needle Insertion and Steering.

PURPOSE: To assess the performance and accuracy of CT-guided needle insertion for clinical biopsies using a novel, hands-free robotic system that balances accuracy with the duration of the procedure and radiation dose. MATERIALS AND METHODS: A prospective, multi-center study was conducted on 60 clinically indicated biopsies of abdominal lesions at two centers (Center 1, n=26; Center 2, n=34). CT datasets were obtained for planning and controlled placement of 17g and 18g needles using a patient-mounted, CT-guided robotic system with 5 degrees of freedom. Planning included target selection, skin entry point, and predetermined checkpoints where additional imaging was performed to permit stepwise correction of the needle trajectory. Success rate, needle tip-to-target distance, number of checkpoints used, number of trajectory corrections, procedure duration, and effective radiation dose were recorded and compared between centers. RESULTS: In 55 of 60 procedures (91.7%), the robot positioned the trocar needle successfully on target. In the remaining 5 patients, the procedure was manually performed by the operator due to technical failure (n=3) or patient-related factors (n=2). The average lesion size was 2.8 ± 1.7cm with a lesion depth from the skin of 8.7 ± 2.6cm, and there was no difference between centers. The overall accuracy (needle tip-to-target distance) was 1.71 ± 1.49 (range 0.05-7.20mm), with an accuracy of 2.06 ± 1.45 mm at Center 1 and 1.45 ± 1.52 mm at Center 2 (p=0.1358). Center 1 used significantly more checkpoints (4.96 ± 1.08) and performed target adjustments in 20 of 24 (83%) cases compared to Center 2 (2.77 ± 0.6 checkpoints and target adjustments in 13 of 31 cases, 42%) (p=0.0024). Accordingly, the steering duration from skin entry to the target varied between Centers 1 and 2; 13.1min ± 4.25min vs. 5.7min ± 2.7min, respectively (p <0.001). The average DLP for the entire procedure was 1147 ± 820 mGycm, with a slightly lower average at Center 2 (1031 ± 724 mGycm) compared to Center 1 (1297 ± 925 mGycm) (p=0.236). CONCLUSION: Accurate needle-targeting within an error of 2mm can be achieved in patients using a CT-guided robotic system. The variation in the number of checkpoints did not affect system accuracy but was related to shorter steering times and may contribute to a lower radiation dose. Accurate needle insertion using a hands-free CT-guided robotic system may facilitate difficult needle placement and enhance the performance of less-experienced interventionalists.

Identifying Areas for Operational Improvement and Growth in IR Workflow Using Workflow Modeling, Simulation, and Optimization Techniques.

Identifying areas for workflow improvement and growth is essential for an interventional radiology (IR) department to stay competitive. Deployment of traditional methods such as Lean and Six Sigma helped in reducing the waste in workflows at a strategic level. However, achieving efficient workflow needs both strategic and tactical approaches. Uncertainties about patient arrivals, staff availability, and variability in procedure durations pose hindrances to efficient workflow and lead to delayed patient care and staff overtime. We present an alternative approach to address both tactical and strategic needs using discrete event simulation (DES) and simulation based optimization methods. A comprehensive digital model of the patient workflow in a hospital-based IR department was modeled based on expert interviews with the incumbent personnel and analysis of 192 days' worth of electronic medical record (EMR) data. Patient arrival patterns and process times were derived from 4393 individual patient appointments. Exactly 196 unique procedures were modeled, each with its own process time distribution and rule-based procedure-room mapping. Dynamic staff schedules for interventional radiologists, technologists, and nurses were incorporated in the model. Stochastic model simulation runs revealed the resource "computed tomography (CT) suite" as the major workflow bottleneck during the morning hours. This insight compelled the radiology department leadership to re-assign time blocks on a diagnostic CT scanner to the IR group. Moreover, this approach helped identify opportunities for additional appointments at times of lower diagnostic scanner utilization. Demand for interventional service from Outpatients during late hours of the day required the facility to extend hours of operations. Simulation-based optimization methods were used to model a new staff schedule, stretching the existing pool of resources to support the additional 2.5 h of daily operation. In conclusion, this study illustrates that the combination of workflow modeling, stochastic simulations, and optimization techniques is a viable and effective approach for identifying workflow inefficiencies and discovering and validating improvement options through what-if scenario testing.

The Use of Penile Computed Tomography Cavernosogram in the Evaluation of Peyronie's Disease: A Pilot Study.

BACKGROUND: Clinical assessment of Peyronie disease (PD) is unreliable and difficult to reproduce. AIM: To assess the utility of the computed tomography cavernosography (CTC) in evaluating the penile functional abnormalities of PD. METHODS: Men were placed in the Philips IQon Spectral CT scanner (Phillips, Cambridge, MA, USA) in the supine position. The penis was injected with trimix (papaverine 30 mg/cc, phentolamine 2 mg/cc, and prostaglandin 20 mcg/cc) in the left proximal base using a 27-gauge syringe. Clinical effect was assessed after 5 minutes. If penile erection was less rigid than adequate for penetration, the dose was repeated until a satisfactory result was achieved. A subcutaneous injection of 1% lidocaine for local analgesia was then injected into the left subcoronal corpora. After the maximum erection was obtained, a 20-gauge angiocatheter was inserted into the anesthetized area. The angiocatheter was connected via intravenous tubing to a 60-cc luer lock syringe of 50% mixture of iodinated contrast in normal saline. The penis was manually inflated until maximum erection was achieved as per the patient's report. The patient then underwent computed tomography scan. Upon completion, a reversal dose of phenylephrine was administered through the angiocatheter. The angiocatheter was then removed, and a penile compression dressing was applied. OUTCOMES: Images were assessed for degree of curvature, presence of corporal involvement, and location of corporal involvement. RESULTS: 63 men underwent CTC. The average age was 57 years (95% confidence interval [CI]: 54, 60). Duration of PD was 5.2 years (95% CI: 3, 7). Diabetes and hypogonadism were found in 15% and 50% of men, respectively. The primary angulation was 52° (95% CI: 40, 60). Multiple angulations were found in 80% of men with 3 or more degrees of angulation in 14%. Bilateral corporal involvement was found in 87%, and proximal involvement was found in 64%. Dorsal/dorsolateral, ventral/ventrolateral, lateral, and hourglass/corkscrew deformities were seen in 58%, 23%, 12%, and 7%, respectively. Average dose of trimix (mg-papaverine + mg-phentolamine + mcg-PGE-1), contrast dose, and radiation dose per scan were 26 (22, 31), 55 cc (47, 63), and 770 mGy∗cm (902, 638), respectively. CLINICAL IMPLICATIONS: CTC may reveal additional information regarding the anatomy of the penis in men with PD which is not readily available by existing methods of evaluation. STRENGTHS & LIMITATIONS: We evaluated a small cohort of men with CTC which allowed for detailed visualization and assessment of their PD. This study is limited by the small sample of patients, retrospective nature, and absence of clinical outcomes which will require further study in the future. CONCLUSION: The CTC may be useful in clearly defining the corporal abnormalities in men with PD. McCullough AR, Trussler J, Alnammi M, et al. The Use of Penile Computed Tomography Cavernosogram in the Evaluation of Peyronie's Disease: A Pilot Study. J Sex Med 2020;17:1041-1043.

Percutaneous Transjejunal Biliary Access in 60 Patients with Bilioenteric Anastomoses.

PURPOSE: To determine success and complication rates of percutaneous transjejunal biliary access (PTJBA) in patients with bilioenteric anastomoses. MATERIALS AND METHODS: In a single-center, retrospective study, 169 PTJBA procedures were performed over a 13.8-y period in 60 subjects (47 male; mean age, 54.5 y). Indications for biliary interventions were cholangitis (137 cases, 45 subjects) or hyperbilirubinemia (32 cases, 18 subjects). All patients had antecolic bilioenteric anastomoses without surgical fixation to the peritoneum (liver transplantation with hepaticojejunostomy, n = 37; hepatectomy with hepaticojejunostomy, n = 8; hepaticojejunostomy only, n = 12; pancreaticoduodenectomy, n = 3). RESULTS: Initial PTJBA was successful in 140 cases (82.8%) in 35 subjects (58.3%). Twenty-one additional PTJBAs (12.4%) in 18 subjects (30.0%) were performed secondarily following a conventional transhepatic approach. Radiographic markers on the Roux-en-Y limb (P = .14, odds ratio [OR] = 2.98) or preprocedural imaging (P = .13, OR = 10.00) did not increase the odds of successful PTJBA. There were 7 major complications (4.3%) in 6 patients (10.0%) requiring hospitalization longer than 5 d, and 37 minor complications (23.0%) in 19 patients (31.7%). No procedure-related mortality was observed. Minor and major complication rates were not affected by time between bilioenteric anastomosis creation and PTJBA (P = .70, OR = 1.00; P = .62, OR = 1.00), longer dwell time of a transjejunal drain (P = .68, OR = 1.02; P = .49, OR = 0.71), or access size (P = .40, OR = 0.85; P = .23, OR = 0.59). CONCLUSIONS: PTJBA is a relatively safe technique with a high success rate in patients with bilioenteric loops that are not surgically fixed to the peritoneum.

Inpatient Complexity in Radiology-a Practical Application of the Case Mix Index Metric.

With ongoing healthcare payment reforms in the USA, radiology is moving from its current state of a revenue generating department to a new reality of a cost-center. Under bundled payment methods, radiology does not get reimbursed for each and every inpatient procedure, but rather, the hospital gets reimbursed for the entire hospital stay under an applicable diagnosis-related group code. The hospital case mix index (CMI) metric, as defined by the Centers for Medicare and Medicaid Services, has a significant impact on how much hospitals get reimbursed for an inpatient stay. Oftentimes, patients with the highest disease acuity are treated in tertiary care radiology departments. Therefore, the average hospital CMI based on the entire inpatient population may not be adequate to determine department-level resource utilization, such as the number of technologists and nurses, as case length and staffing intensity gets quite high for sicker patients. In this study, we determine CMI for the overall radiology department in a tertiary care setting based on inpatients undergoing radiology procedures. Between April and September 2015, CMI for radiology was 1.93. With an average of 2.81, interventional neuroradiology had the highest CMI out of the ten radiology sections. CMI was consistently higher across seven of the radiology sections than the average hospital CMI of 1.81. Our results suggest that inpatients undergoing radiology procedures were on average more complex in this hospital setting during the time period considered. This finding is relevant for accurate calculation of labor analytics and other predictive resource utilization tools.

Purposeful creation of a pneumothorax and chest tube placement to facilitate CT-guided coil localization of lung nodules before video-assisted thoracoscopic surgical wedge resection.

PURPOSE: To evaluate the feasibility and efficacy of pneumothorax creation and chest tube insertion before computed tomography (CT)-guided coil localization of small peripheral lung nodules for video-assisted thoracoscopic surgical (VATS) wedge resection. MATERIALS AND METHODS: From May 2011 to October 2013, 21 consecutive patients (seven men; mean age, 62 y; range, 42-76 y) scheduled for VATS wedge resection required CT-guided coil localization for small, likely nonpalpable peripheral lung lesions at a single institution. Outcomes were evaluated retrospectively for technical success and complications. RESULTS: There were 12 nodules and nine ground-glass opacities. Mean lesion distance from the pleural surface was 15 mm (range, 5-35 mm), and average size was 13 mm (range, 7-30 mm). A pneumothorax was successfully created in all patients with a Veress needle, and a chest tube was inserted. All target lesions were marked successfully, leaving one end of the coil within/beyond the lesion and the other end of the coil in the pleural space. The inserted chest tube was used to insufflate air to widen the pleural space during coil positioning and to aspirate any residual air before transfer of the patient to the operating room holding area. Intraparenchymal hemorrhages smaller than 7 cm in diameter developed in two patients during coil placement. All lesions were successfully resected with VATS. Histologic examinaiton revealed 13 primary adenocarcinomas, four metastases, and four benign lesions. CONCLUSIONS: Pneumothorax creation and chest tube placement before CT-guided coil localization of peripheral lung nodules for VATS wedge resection facilitates the deployment of the peripheral end of the coil in the pleural space and provides effective management of procedure-related pneumothorax until surgery.

Dynamic and simultaneous MR measurement of R1 and R2* changes during respiratory challenges for the assessment of blood and tissue oxygenation.

This work presents a novel method for the rapid and simultaneous measurement of R1 and R2* relaxation rates. It is based on a dynamic short repetition time steady-state spoiled multigradient-echo sequence and baseline R1 and B1 measurements. The accuracy of the approach was evaluated in simulations and a phantom experiment. The sensitivity and specificity of the method were demonstrated in one volunteer and in four patients with intracranial tumors during carbogen inhalation. We utilized (ΔR2*, ΔR1) scatter plots to analyze the multiparametric response amplitude of each voxel within an area of interest. In normal tissue R2* decreased and R1 increased moderately in response to the elevated blood and tissue oxygenation. A strong negative ΔR2* and ΔR1 response was observed in veins and some tumor areas. Moderate positive ΔR2* and ΔR1 response amplitudes were found in fluid-rich tissue as in cerebrospinal fluid, peritumoral edema, and necrotic areas. The multiparametric approach was shown to increase the specificity and sensitivity of oxygen-enhanced MRI compared to measuring ΔR2* or ΔR1 alone. It is thus expected to provide an optimal tool for the identification of tissue areas with low oxygenation, e.g., in tumors with compromised oxygen supply.

Percutaneous Robotics in Interventional Radiology.

The accuracy of the robotic device not only relies on a reproducible needle advancement, but also on the possibility to correct target movement at chosen checkpoints and to deviate from a linear to a nonlinear trajectory. We report our experience in using the robotic device for the insertion of trocar needles in CT guided procedures. The majority of procedures were targeted organ biopsies in the chest abdomen or pelvis. The accuracy of needle placement after target adjustments did not significantly differ from those patients where a linear trajectory could be used. The steering capabilities of the robot allow correction of target movement of the fly.

Temporary targeted renal blood flow interruption using a reverse thermosensitive polymer to facilitate bloodless partial nephrectomy: a swine survival study.

UNLABELLED: What's known on the subject? and What does the study add? Lumagel™ is a reverse thermosensitive polymer (RTP) that has previously been described in the literature as providing temporary vascular occlusion to allow for bloodless partial nephrectomy (PN) while maintaining blood flow to the untargeted portion of the kidney. At body temperature, Lumagel™ has the consistency of a viscous gel but upon cooling rapidly converts to a liquid state and does not reconstitute thereafter. This property has allowed for it to be used in situations requiring temporary vascular occlusion. Previous experience with similar RTPs in coronary arteries proved successful, with no detectable adverse events. We have previously described our technique for temporary vascular occlusion of the main renal artery, as well as segmental and sub-segmental renal branches, to allow for bloodless PN in either an open or minimally invasive approach. These experiments were performed in the acute setting. This study is a two-armed survival trial to assess whether this RTP is as safe as hilar clamping for bloodless PN. Surviving animals showed normal growth after using the RTP, absence of toxicity, no organ dysfunction, and no pathological changes attributable to the RTP. We conclude that Lumagel™ is as safe as conventional PN with hilar clamping, while adding the advantage of uninterrupted perfusion during renal resection. OBJECTIVE: To examine whether randomly selected regions of the kidney could undergo temporary flow interruption with a reverse thermosensitive polymer (RTP), Lumagel™ (Pluromed, Inc., Woburn, MA, USA), followed by partial nephrectomy (PN), without adding risks beyond those encountered in the same procedure with the use of hilar clamping. MATERIALS AND METHODS: A two-armed (RTP vs hilar clamp), 6-week swine survival study was performed. Four swine underwent PN using hilar clamps, while six underwent PN with flow interruption using the RTP. The RTP, administered angiographically, was used for intraluminal occlusion of segmental or subsegmental arteries and was compared with main renal artery clamping with hilar clamps. The resection site was randomized for each swine. Laboratory studies were performed preoperatively, and at weeks 1, 3 and 6. Before killing the swine, repeat angiography was performed with emphasis on the site of previous flow interruption. Gross and microscopic examination of kidney, liver, lung, heart, skeletal muscle was later performed, and the vessel that had supported the previous plug was examined. RESULTS: All animals survived. No abnormal chemistry or haematology results were encountered over the 6 weeks. There were no surgical complications in either group. Using angiography we found 100% patency of vessels that had been occluded with the polymer 6 weeks previously for PN. The only gross or microscopic abnormalities were related to the renal resection and scar formation, and were similar in the two groups. CONCLUSION: Targeted flow interruption with the RTP added no additional risk to PN while allowing bloodless resection and uninterrupted flow to untargeted renal tissue.

Feasibility of bloodless liver resection using Lumagel, a reverse thermoplastic polymer, to produce temporary, targeted hepatic blood flow interruption.

BACKGROUND: Lumagel, a reverse thermosensitive polymer (RTP), provides targeted flow interruption to the kidney by reversibly plugging segmental branches of the renal artery, allowing blood-free partial nephrectomy. Extending this technology to the liver requires the development of techniques for temporary occlusion of the hepatic artery and selected portal vein branches. METHODS: A three-phased, 15 swine study was performed to determine feasibility, techniques and survival implications of using Lumagel for occlusion of inflow vessels to targeted portions of the liver. Lumagel was delivered using angiographic techniques to sites determined by pre-operative 3-D vascular reconstructions of arterial and venous branches. During resection, the targeted liver mass was resected without vascular clamping. Three survival swine were sacrificed at 3 weeks; the remainder at 6 weeks for pathological studies. RESULTS: Six animals (100%) survived, with normal growth, blood tests and no adverse events. Three left lateral lobe resections encountered no bleeding during resection; one right median resection bled; two control animals bled significantly. Pre-terminal angiography and autopsy showed no local pathology and no remote organ damage. CONCLUSIONS: Targeted flow interruption to the left lateral lobe of the swine liver is feasible and allows resection without bleeding, toxicity or pathological sequelae. Targeting the remaining liver will require more elaborate plug deposition owing to the extensive collateral venous network.

Noninvasive imaging after stent-assisted coiling of intracranial aneurysms: comparison of 3-T magnetic resonance imaging and 64-row multidetector computed tomography--a pilot study.

BACKGROUND AND PURPOSE: Follow-up imaging after stent-assisted coiling of intracranial aneurysms is limited by signal loss in the stented vessel segment using magnetic resonance imaging or by streak artifacts caused by aneurysm coils using multidetector computed tomography. In the search for a noninvasive surveillance in this condition, we propose a technique to minimize streak artifacts in multidetector computed tomography by gated data reconstruction and shifting the reconstruction window. METHODS: The effect of the gated data acquisition in 64-row computed tomographic angiography (gCTA) on artifact reduction was evaluated in a preliminary phantom study and compared with nongated CTA, time-of-flight magnetic resonance angiography (TOF-MRA), and digital subtraction angiography (DSA). Scans were also obtained from 5 patients treated with stent-assisted coiling as part of their follow-up protocol. The length of impaired vessel segments (LIVS) in TOF-MRA and gCTA was compared and correlated with the stent's length, the number of coils, and the packing density. The assessment of treatment outcome in TOF-MRA and gCTA was compared with DSA as the standard of reference. RESULTS: The phantom study revealed 2 aspects: first, a distinct reduction of streak artifacts caused by coils using gated data acquisition; and second, because artifact orientation could be rotated systematically by shifting the reconstruction window, visualization of treated vessel segments was significantly superior in gCTA. In magnetic resonance imaging, all stented vessel segments were characterized by signal loss in both phantom and patients. The LIVS was 78% shorter in gCTA (4.86 ± 6.93 mm) compared with that in TOF-MRA (21.82 ± 7.47 mm, P < 0.01). In TOF-MRA, the LIVS correlated with the stent's length, in gCTA with the number of coils. With regard to assessment of treatment outcome, gCTA and TOF-MRA correlated with DSA in 3 and in none of 5 patients, respectively. CONCLUSIONS: Gated CTA is a promising technique to reduce the amount of artifacts induced by stent-assisted intracranial coils. Image quality and assessment of treatment outcome in patients with stent-assisted coiling is superior compared with TOF-MRA.

Clinical evaluation of a robotic system for precise CT-guided percutaneous procedures.

PURPOSE: To assess accuracy and compare protocols for CT-guided needle insertion for clinical biopsies using a hands-free robotic system, balancing system accuracy with duration of procedure and radiation dose. METHODS: Thirty-two percutaneous abdominal and pelvic biopsies were performed and analyzed at two centers (Center 1 n = 11; Center 2 n = 21) as part of an ongoing prospective, multi-center study. CT datasets were obtained for planning and controlled placement of 17 g needles using a patient-mounted, CT-guided robotic system. Planning included target selection, skin entry point, and predetermined checkpoints. Additional CT imaging was performed at checkpoints to confirm needle location and permit stepwise correction of the trajectory. Center 1 used a more conservative approach with multiple checkpoints, whereas Center 2 used fewer checkpoints. Scanning and needle advancement were performed under respiratory gating. Accuracy, radiation dose, and steering duration were compared. RESULTS: Overall accuracy was 1.6 ± 1.5 mm (1.9 ± 1.2 mm Center 1; 1.5 ± 1.6 mm Center 2; p = 0.55). Mean distance to target was 86.2 ± 27.1 mm (p = 0.18 between centers). Center 1 used 4.6 ± 0.8 checkpoints, whereas Center 2 used 1.8 ± 0.6 checkpoints (p < 0.001). Effective radiation doses were lower for Center 1 than for Center 2 (22.2 ± 12.6 mSv vs. 11.7 ± 4.3 mSv; p = 0.002). Likewise, steering duration (from planning to target) was significantly reduced in relation to the number of checkpoints from 43.8 ± 15.9 min for Center 1 to 30.5 ± 10.2 min for Center 2 (p = 0.008). CONCLUSIONS: Accurate needle targeting with < 2 mm error can be achieved in patients when using a CT-guided robotic system. Judicious selection of the number of checkpoints may substantially reduce procedure time and radiation dose without sacrificing accuracy.

External Fixation Devices Within the Magnetic Resonance Imaging Bore: A Safety and Radiologic Analysis.

OBJECTIVES: To (1) report the thermal changes encountered at the pin/skin interface in a cadaver with a knee-spanning external fixator inside the magnetic resonance imaging (MRI) bore and (2) report on the quality of the MRI sequences collected. METHODS: Three commonly used external fixation systems were placed on cadaveric lower extremities to simulate knee external fixation. Fiber optic thermal probes were placed at the pin/skin interface of a femoral and tibial pin. A control probe was embedded in the soft tissues of the thigh. Full knee MRI scans were performed using a 1.5-Tesla magnet. Real-time thermal data were collected. A clinically significant increase in temperature compared with the control was defined as 2°C. Two blinded radiologists evaluated the images for image quality and overall diagnostic utility using a standardized 5-point grading scale. RESULTS: There were statistically significant differences in the temperature changes between the femoral/tibial pin sites and the control probe sites during each phase of the MRI scan. However, there was only one clinically significant difference in temperature change during a single sequence of one MRI scan of one of the external fixator devices. Overall image quality was graded as a 4 for each image set with 100% interobserver agreement (k = 1.0). CONCLUSIONS: Despite significant differences in temperature changes between the pin sites and controls over multiple MRI sequences in commonly used external fixator devices, the differences in temperature change are likely not clinically relevant. Overall image quality and interpretability of the images were excellent.

Towards radiologist-level cancer risk assessment in CT lung screening using deep learning.

PURPOSE: Lung cancer is the leading cause of cancer mortality in the US, responsible for more deaths than breast, prostate, colon and pancreas cancer combined and large population studies have indicated that low-dose computed tomography (CT) screening of the chest can significantly reduce this death rate. Recently, the usefulness of Deep Learning (DL) models for lung cancer risk assessment has been demonstrated. However, in many cases model performances are evaluated on small/medium size test sets, thus not providing strong model generalization and stability guarantees which are necessary for clinical adoption. In this work, our goal is to contribute towards clinical adoption by investigating a deep learning framework on larger and heterogeneous datasets while also comparing to state-of-the-art models. METHODS: Three low-dose CT lung cancer screening datasets were used: National Lung Screening Trial (NLST, n = 3410), Lahey Hospital and Medical Center (LHMC, n = 3154) data, Kaggle competition data (from both stages, n = 1397 + 505) and the University of Chicago data (UCM, a subset of NLST, annotated by radiologists, n = 132). At the first stage, our framework employs a nodule detector; while in the second stage, we use both the image context around the nodules and nodule features as inputs to a neural network that estimates the malignancy risk for the entire CT scan. We trained our algorithm on a part of the NLST dataset, and validated it on the other datasets. Special care was taken to ensure there was no patient overlap between the train and validation sets. RESULTS AND CONCLUSIONS: The proposed deep learning model is shown to: (a) generalize well across all three data sets, achieving AUC between 86% to 94%, with our external test-set (LHMC) being at least twice as large compared to other works; (b) have better performance than the widely accepted PanCan Risk Model, achieving 6 and 9% better AUC score in our two test sets; (c) have improved performance compared to the state-of-the-art represented by the winners of the Kaggle Data Science Bowl 2017 competition on lung cancer screening; (d) have comparable performance to radiologists in estimating cancer risk at a patient level.

Changes in the MR relaxation rate R(2)* induced by respiratory challenges at 3.0 T: a comparison of two quantification methods.

The consistent determination of changes in the transverse relaxation rate R(2)* (ΔR(2)*) is essential for the mapping of the effect of hyperoxic and hypercapnic respiratory challenges, which enables the noninvasive assessment of blood oxygenation changes and vasoreactivity by MRI. The purpose of this study was to compare the performance of two different methods of ΔR(2)* quantification from dynamic multigradient-echo data: (A) subtraction of R(2)* values calculated from monoexponential decay functions; and (B) computation of ΔR(2)* echo-wise from signal intensity ratios. A group of healthy volunteers (n = 12) was investigated at 3.0 T, and the brain tissue response to carbogen and CO(2)-air inhalation was registered using a dynamic multigradient-echo sequence with high temporal and spatial resolution. Results of the ΔR(2)* quantification obtained by the two methods were compared with respect to the quality of the voxel-wise ΔR(2)* response, the number of responding voxels and the behaviour of the 'global' response of all voxels with significant R(2)* changes. For the two ΔR(2)* quantification methods, we found no differences in the temporal variation of the voxel-wise ΔR(2)* responses or in the detection sensitivity. The maximum change in the 'global' response was slightly smaller when ΔR(2)* was derived from signal intensity ratios. In conclusion, this first methodological comparison shows that both ΔR(2)* quantifications, from monoexponential approximation as well as from signal intensity ratios, are applicable for the monitoring of R(2)* changes during respiratory challenges.

Intracranial tumor response to respiratory challenges at 3.0 T: impact of different methods to quantify changes in the MR relaxation rate R2*.

PURPOSE: To compare two DeltaR2* quantification methods for analyzing the response of intracranial tumors to different breathing gases. The determination of changes in the magnetic resonance imaging (MRI) relaxation rate R2* (DeltaR2*), induced by hyperoxic and hypercapnic respiratory challenges, enables the noninvasive assessment of blood oxygenation changes and vasoreactivity. MATERIALS AND METHODS: Sixteen patients with various intracranial tumors were examined at 3.0 T. The response to respiratory challenges was registered using a dynamic multigradient-echo sequence with high temporal and spatial resolution. At each dynamic step, DeltaR2* was derived in two different ways: 1) by subtraction of R2* values obtained from monoexponential decay functions, 2) by computing DeltaR2* echo-wise from signal intensity ratios. The sensitivity for detection of responding voxels and the behavior of the "global" response were investigated. RESULTS: Significantly more responding voxels (about 4%) were found for method (1). The "global" response was independent from the chosen quantification method but showed slightly larger changes (about 6%) when DeltaR2* was derived from method (1). CONCLUSION: Similar results were observed for the two methods, with a slightly higher detection sensitivity of responding voxels when DeltaR2* was obtained from monoexponential approximation.

Quantification of the magnetic resonance signal response to dynamic (C)O(2)-enhanced imaging in the brain at 3 T: R*(2) BOLD vs. balanced SSFP.

PURPOSE: To compare two magnetic resonance (MR) contrast mechanisms, R*(2) BOLD and balanced SSFP, for the dynamic monitoring of the cerebral response to (C)O(2) respiratory challenges. MATERIALS AND METHODS: Carbogen and CO(2)-enriched air were delivered to 9 healthy volunteers and 1 glioblastoma patient. The cerebral response was recorded by two-dimensional (2D) dynamic multi-gradient-echo and passband-balanced steady-state free precession (bSSFP) sequences, and local changes of R*(2) and signal intensity were investigated. Detection sensitivity was analyzed by statistical tests. An exponential signal model was fitted to the global response function delivered by each sequence, enabling quantitative comparison of the amplitude and temporal behavior. RESULTS: The bSSFP signal changes during carbogen and CO(2)/air inhalation were lower compared with R*(2) BOLD (ca. 5% as opposed to 8-13%). The blood-oxygen-level-dependent (BOLD) response amplitude enabled differentiation between carbogen and CO(2)/air by a factor of 1.4-1.6, in contrast to bSSFP, where differentiation was not possible. Furthermore, motion robustness and detection sensitivity were higher for R*(2) BOLD. CONCLUSION: Both contrast mechanisms are well suited to dynamic (C)O(2)-enhanced MR imaging, although the R*(2) BOLD mechanism was demonstrated to be superior in several respects for the chosen application. This study suggests that the R*(2) BOLD and bSSFP-response characteristics are related to different physiologic mechanisms.

Endovascular temporary vessel occlusion with a reverse-thermosensitive polymer for bloodless minimally invasive renal surgery.

PURPOSE: To demonstrate the feasibility of reversible vessel embolization with angiographic guidance for delivery of a rapid reverse-thermosensitive polymer to provide hemostasis as an aid for minimally invasive renal surgery in a porcine model. MATERIALS AND METHODS: After isolation of the left kidney of seven anesthetized pigs (50-70 kg) with a surgical robot, a renal angiogram of both kidneys was obtained. A 5-F angiographic catheter was used to selectively embolize a lower-pole segmental artery of the right and left kidney with a thermosensitive polymer (LeGoo-XL). Distal and proximal embolization of the target vessel was compared. Degree and duration of hemostasis and reversibility was determined. After complete hemostasis was obtained angiographically, a partial robotic lower-pole nephrectomy was performed on the left kidney only. RESULTS: Only proximal embolization provided controllable hemostasis. A 20% polymer concentration in a buffer solution of 40% saline solution and 40% iodine contrast medium by weight injected at room temperature resulted in a reproducible embolus for more than 30 minutes, the time needed to perform a partial nephrectomy. The radiographic appearance of the embolus was used to determine the total amount of polymer needed. Cold saline solution completely dissolved any residual polymer at the end of surgery. CONCLUSIONS: Proximal arterial occlusion with a thermosensitive polymer can be rapidly reversed with selective intraarterial infusion of chilled saline solution. Preceding nephron-sparing surgery with transcatheter embolization of the relevant branch of the renal artery with the polymer can facilitate the procedure and ought to be investigated further.