A low-cost tracked C-arm (TC-arm) upgrade system for versatile quantitative intraoperative imaging

Purpose

   C-arm fluoroscopy is frequently used in clinical applications as a low-cost and mobile real-time qualitative assessment tool. C-arms, however, are not widely accepted for applications involving quantitative assessments, mainly due to the lack of reliable and low-cost position tracking methods, as well as adequate calibration and registration techniques. The solution suggested in this work is a tracked C-arm (TC-arm) which employs a low-cost sensor tracking module that can be retrofitted to any conventional C-arm for tracking the individual joints of the device.

Methods

   Registration and offline calibration methods were developed that allow accurate tracking of the gantry and determination of the exact intrinsic and extrinsic parameters of the imaging system for any acquired fluoroscopic image. The performance of the system was evaluated in comparison to an Optotrak \(^\mathrm{TM}\) motion tracking system and by a series of experiments on accurately built ball-bearing phantoms. Accuracies of the system were determined for 2D–3D registration, three-dimensional landmark localization, and for generating panoramic stitched views in simulated intraoperative applications.

Results

   The system was able to track the center point of the gantry with an accuracy of \(1.5 \pm 1.2\)  mm or better. Accuracies of 2D–3D registrations were \(2.3 \pm 1.1\)  mm and \(0.2 \pm 0.2^{\circ }\) . Three-dimensional landmark localization had an accuracy of \(3.1 \pm 1.3\%\) of the length (or \(4.4 \pm 1.9\)  mm) on average, depending on whether the landmarks were located along, above, or across the table. The overall accuracies of the two-dimensional measurements conducted on stitched panoramic images of the femur and lumbar spine were 2.5 \(\pm \) 2.0 % \((3.1 \pm 2.5 \hbox { mm})\) and \(0.3 \pm 0.2^{\circ }\) , respectively.

Conclusion

   The TC-arm system has the potential to achieve sophisticated quantitative fluoroscopy assessment capabilities using an existing C-arm imaging system. This technology may be useful to improve the quality of orthopedic surgery and interventional radiology.     

Usability of unbiased nonlocal means for de-noising intraoperative magnetic resonance images in neurosurgery

Purpose

   Intraoperative magnetic resonance imaging (iMRI) is a powerful tool that allows real-time image-guided excision of brain tumors. However, low magnetic field iMRI devices may produce low-quality images due to nonideal imaging conditions in the operating room and additional noise of unknown origin. The purpose of this study was to evaluate a three-dimensional unbiased nonlocal means filter for iMRI (UNLM-i) that we developed in order to enhance image quality and increase the diagnostic value of iMRI.

Methods

   We first evaluated the effect of UNLM by assessing the modulation transfer function (MTF) and Weiner spectrum (WS) of UNLM in simulated imaging. We then tested the diagnostic value of UNLM-i de-noising by applying it to a series of randomly chosen iMR images that were assessed by 4 neurosurgeons and 4 radiological technologists using a 5-point rating scale to compare 13 parameters, including tumor visibility, edema, and sulci, before and after de-noising.

Results

   Unbiased nonlocal means provided better MTF in comparison with other filters, and the WS for UNLM de-noising was reduced for all spatial frequencies. Postprocessing UNLM-i allowed de-noising with preserved edges and \(>\) twofold improvement in the signal-to-noise ratio without extending the MRI scanning time ( \(p < 0.001\) ). The diagnostic value of UNLM-i de-noising was rated as “superior” or “better” in \(>\) 80 % of cases in terms of contrast between white and gray matter and visibility of sulci, tumor, and edema ( \(p < 0.001\) ).

Conclusions

   Unbiased nonlocal means filter for iMRI de-noising proved very useful for image quality enhancement and assistance in the interpretation of iMR images.     

Design and initial evaluation of a treatment planning software system for MRI-guided laser ablation in the brain

Purpose

   An open-source software system for planning magnetic resonance (MR)-guided laser-induced thermal therapy (MRgLITT) in brain is presented. The system was designed to provide a streamlined and operator-friendly graphical user interface (GUI) for simulating and visualizing potential outcomes of various treatment scenarios to aid in decisions on treatment approach or feasibility.

Methods

   A portable software module was developed on the 3D Slicer platform, an open-source medical imaging and visualization framework. The module introduces an interactive GUI for investigating different laser positions and power settings as well as the influence of patient-specific tissue properties for quickly creating and evaluating custom treatment options. It also provides a common treatment planning interface for use by both open-source and commercial finite element solvers. In this study, an open-source finite element solver for Pennes’ bioheat equation is interfaced to the module to provide rapid 3D estimates of the steady-state temperature distribution and potential tissue damage in the presence of patient-specific tissue boundary conditions identified on segmented MR images.

Results

   The total time to initialize and simulate an MRgLITT procedure using the GUI was \(<\) 5 min. Each independent simulation took \(<\) 30 s, including the time to visualize the results fused with the planning MRI. For demonstration purposes, a simulated steady-state isotherm contour \((57\,^{\circ }\hbox {C})\) was correlated with MR temperature imaging (N = 5). The mean Hausdorff distance between simulated and actual contours was 2.0 mm \((\sigma \,=\,0.4\,\hbox {mm})\) , whereas the mean Dice similarity coefficient was 0.93 \((\sigma =0.026)\) .

Conclusions

   We have designed, implemented, and conducted initial feasibility evaluations of a software tool for intuitive and rapid planning of MRgLITT in brain. The retrospective in vivo dataset presented herein illustrates the feasibility and potential of incorporating fast, image-based bioheat predictions into an interactive virtual planning environment for such procedures.     

Optimal setting of image bounding box can improve registration accuracy of diffusion tensor tractography

Purpose

When we register diffusion tensor tractography (DTT) to anatomical images such as fast imaging employing steady-state acquisition (FIESTA), we register the B0 image to FIESTA. Precise registration of the DTT B0 image to FIESTA is possible with non-rigid registration compared to rigid registration, although the non-rigid methods lack convenience. We report the effect of image data bounding box settings on registration accuracy using a normalized mutual information (NMI) method

Methods

MRI scans of 10 patients were used in this study. Registration was performed without modification of the bounding box in the control group, and the results were compared with groups re-registered using multiple bounding boxes limited to the region of interest (ROI). The distance of misalignment after registration at 3 anatomical characteristic points that are common to both FIESTA and B0 images was used as an index of accuracy.

Results

Mean ( $\pm $ SD) misalignment at the 3 anatomical points decreased significantly from $5.99\pm 1.58$ to $2.21\pm 1.24$  mm, $p<0.0001$ ), $4.36\pm 1.58$ to $1.48\pm 0.58$  mm, ( $p<0.0001)$ , and $5.21\pm 1.76$ to $1.20\pm 0.74$  mm, ( $p<0.0001)$ , each showing improvement compared to the control group

Conclusion

Narrowing the image data bounding box to the ROI improves the accuracy of registering B0 images to FIESTA by NMI method. With our proposed methodology, accuracy can be improved in extremely easy steps, and this methodology may prove useful for DTT registration to anatomical image     

Three-dimensional prediction of free-flap volume in autologous breast reconstruction by CT angiography imaging

Purpose

   The diagnostic use of computer tomography angiography (CTA) to identify perforating blood vessels for abdominal free-flap breast reconstruction was extended to estimate the three-dimensional (3D) preoperative flap volume and to compare it with the real intraoperative flap weights in order to (1) evaluate the accuracy of CTA-based 3D flap volume prediction, and (2) to analyze abdominal tissue estimation for required breast volume reconstruction.

Methods

   Preoperative CTA was performed in 54 patients undergoing unilateral breast reconstruction with a free, deep, inferior epigastric artery perforator flap. 3D flap volumes ( \(\hbox {cm}^{3}\) ) based on CTA data were calculated and compared with the actual intraoperative flap weight (g). In addition, a breast volume to flap volume ratio was calculated to analyze whether the estimated 3D abdominal flap volume would match that of the breast to be removed.

Results

   40 CTA data sets (74.1 %) fulfilled the technical requirements for a reliable determination of flap volume. 3D CTA flap volume prediction showed no relevant differences to the actual flap weight (p = 0.44) and high correlations (r = 0.998, \(p < 0.001\) ), allowing a prediction accuracy within 0.29 \(\pm \) 3.0 % (range: from \(-\) 8.77 to 5.67 %) of the real flap weight. Significantly larger flap volumes were harvested compared with the actually required breast volumes ( \(p < 0.001\) ), leading to an average of 21 % of the remnant flap tissue potentially being discarded.

Conclusions

   CTA-based 3D flap volume prediction provides accurate preoperative guidelines concerning the needed amount of abdominal tissue that can be harvested to achieve acceptable symmetry.     

Simultaneous extraction of carotid artery intima-media interfaces in ultrasound images: assessment of wall thickness temporal variation during the cardiac cycle

Objectives

   The aim of this work is to present and evaluate a novel segmentation method for localizing the contours of the intima-media complex in the carotid artery wall through longitudinal ultrasound B-mode imaging. The method is used to investigate the association between atherosclerosis risk factors and the cyclic variation of the intima-media thickness during the heart beat.

Methods

   The framework introduced is based on two main features. The first is a simultaneous extraction of both the lumen-intima and the media-adventitia interfaces, using the combination of an original shape-adapted filter bank and a specific dynamic programming scheme. The second is an innovative spatial transformation that eases the extraction of skewed and curved contours, and exploits the result from the previous image as a priori information, when processing the current image. The intima-media thickness is automatically derived from the estimated contours for each time step during the cardiac cycle. Our method was evaluated in vivo on 57 healthy volunteers and 25 patients at high cardiovascular risk. Reference contours were generated for each subject by averaging the tracings performed by three experienced observers.

Results

   Segmentation errors were \(29 \pm 27\,\upmu \hbox {m}\) for the lumen-intima interface, \(42 \pm 38\,\upmu \hbox {m}\) for the media-adventitia interface, and \(22 \pm 16\,\upmu \hbox {m}\) for the intima-media thickness. This uncertainty was similar to inter- and intra-observer variability. Furthermore, the amplitude of the temporal variation in thickness of the intima-media layers during the cardiac cycle was significantly higher in at-risk patients compared to healthy volunteers \((79 \pm 36\) vs. \(64 \pm 26\,\upmu \hbox {m},\, p=0.032)\) .

Conclusion

   The method proposed may provide a relevant diagnostic aid for atherosclerosis screening in clinical studies.     

Mesh-based method for measuring intracranial volume in patients with craniosynostosis

Purpose

   Craniosynostosis may lead to reduced intracranial volume (ICV) and disturb normal brain growth and development. Thus, ICV is an important parameter with respect to the surgical outcome. Current methods for ICV determination from computed tomography (CT) images have drawbacks. The aim of this study was to investigate the performance of the novel mesh-based method (MBM) for ICV determination with craniosynostosis patients.

Methods

   Twenty-two patients operated on for scaphocephaly were included in this study. ICVs from preoperative, one-week postoperative, and one-year postoperative CT images were measured with MBM. The level of agreement with the manual segmentation method (MSM) was determined for the measurements of preoperative and one-year postoperative datasets. Repeatability was determined with re-measurements of six datasets. Measurement time was recorded for MBM.

Results

   Mean $(\pm \text{ SD})$ preoperative ICV values were 895.0 $\pm $ 153.1 $\text{ cm}^{3}$ and 896.4 $\pm $ 147.2 $\text{ cm}^{3}$ as measured with MBM and MSM, respectively. Corresponding one-year postoperative values were 1,238.3 $\pm $ 118.7 $\text{ cm}^{3}$ and 1,250.1 $\pm $ 117.5 $\text{ cm}^{3}$ . The MBM allowed ICV determination from one-week postoperative datasets. Measurement time with MBM was 4

Conclusions

   MBM is an efficient method for determining the ICV of craniosynostosis patients, allowing the measurement of skulls with bony defects. The repeatability and short measurement time of MBM are attributable to the user interference and assessment of the measurement process.     

Automated implant segmentation in cone-beam CT using edge detection and particle counting

Purpose

To develop a fully automated, accurate and robust segmentation technique for dental implants on cone-beam CT (CBCT) images.

Methods

A head-size cylindrical polymethyl methacrylate phantom was used, containing titanium rods of 5.15 mm diameter. The phantom was scanned on 17 CBCT devices, using a total of 39 exposure protocols. Images were manually thresholded to verify the applicability of adaptive thresholding and to determine a minimum threshold value \(({T}_{\mathrm{min}})\) . A three-step automatic segmentation technique was developed. Firstly, images were pre-thresholded using \({T}_{\mathrm{min}}\) . Next, edge enhancement was performed by filtering the image with a Sobel operator. The filtered image was thresholded using an iteratively determined fixed threshold \(({T}_{\mathrm{edge}})\) and converted to binary. Finally, a particle counting method was used to delineate the rods. The segmented area of the titanium rods was compared to the actual area, which was corrected for phantom tilting.

Results

Manual thresholding resulted in large variation in threshold values between CBCTs. After applying the edge-enhancing filter, a stable \({T}_{\mathrm{edge}}\) value of 7.5 % was found. Particle counting successfully detected the rods for all but one device. Deviations between the segmented and real area ranged between \(-\) 2.7 and + \(14.4\,\hbox {mm}^{2}\) with an average absolute error of \(2.8\,\hbox {mm}^{2}\) . Considering the diameter of the segmented area, submillimeter accuracy was seen for all but two data sets.

Conclusion

A segmentation technique was defined which can be applied to CBCT data for an accurate and fully automatic delineation of titanium rods. The technique was validated in vitro and will be further tested and refined on patient data.     

A morphological study of anatomical plates for acetabular posterior column

Purposes

   The objective of this work is to explore the morphological characteristics of the acetabular posterior column using digital technology, in order to develop anatomical plates for internal fixation of acetabular posterior column fractures.

Materials and methods

   Three-dimensional reconstruction models of the pelvis were developed from computed tomography scan data of 111 adult patients. From them, the diameter (D) of the femoral head, three approximate arcs along the acetabular posterior column plate path with corresponding radius of curvature \(\hbox {R}_{1}, \hbox {R}_{2}\) and \(\hbox {R}_{3}\) , as well as an angle \(\alpha \) were measured. A statistical analysis was used to determine the most feasible method of designing anatomical plates according to the data.

Results

   The statistical analysis results showed that \(\hbox {R}_{1}, \hbox {R}_{2}\) and \(\hbox {R}_{3}\) had no correlations with D, and they also exhibited no statistically significant differences between genders. By examining the correlations between four morphological parameters of the acetabular posterior column, the results showed \(\hbox {R}_{2}\) increased along with \(\hbox {R}_{1}, \alpha \) was inversely proportional to \(\hbox {R}_{1}\) and \(\hbox {R}_{2}\) , and \(\hbox {R}_{3}\) was independent with little variation. Taking \(\hbox {R}_{1}\) as the reference, the data were divided into three groups and three types of anatomical plates were designed according to the three groups of data.

Conclusion

   The anatomical structure of the acetabular posterior column exhibits great individual differences. Anatomical plates designed in this study have higher accuracy than those conventional ones, which is helpful to the quality of fracture reduction and reduce the operation difficult. Meanwhile, they also can be conveniently used in clinic.     

Intraoperative detection and localization of cylindrical implants in cone-beam CT image data

Purpose

Orthopedic fractures are often fixed using metal implants. The correct positioning of cylindrical implants such as surgical screws, rods and guide wires is highly important. Intraoperative 3D imaging is often used to ensure proper implant placement. However, 3D image interaction is time-consuming and requires experience. We developed an automatic method that simplifies and accelerates location assessment of cylindrical implants in 3D images.

Methods

Our approach is composed of three major steps. At first, cylindrical characteristics are detected by analyzing image gradients in small image regions. Next, these characteristics are grouped in a cluster analysis. The clusters represent cylindrical implants and are used to initialize a cylinder-to-image registration. Finally, the two end points are optimized regarding image contrast along the cylinder axis.

Results

A total of 67 images containing 420 cylindrical implants were used for testing. Different anatomical regions (calcaneus, spine) and various image sources (two mobile devices, three reconstruction methods) were investigated. Depending on the evaluation set, the detection performance was between 91.7 and 96.1 % true- positive rate with a false-positive rate between 2.0 and 3.2 %. The end point distance errors ranged from \(1.0 \pm 1.2\) to \(4.3 \pm 2.9\)  mm and the orientation errors from \(1.6 \pm 2.2\) to \(2.3 \pm 2.2\) degrees. The average computation time was less than 5 seconds.

Conclusions

An automatic method was developed and tested that obviates the need for 3D image interaction during intraoperative assessment of cylindrical orthopedic implants. The required time for working with the viewing software of cone-beam CT device is drastically reduced and leads to a shorter time under anesthesia for the patient.     

Correlation of thermodilution-derived extravascular lung water and ventilation/perfusion-compartments in a porcine model

Purpose

This study examines the correlation between the transpulmonary thermodilution derived extravascular lung water content (EVLW) and the ventilation/perfusion-distribution ( $ \dot{V}/\dot{Q} $ ) measured by multiple inert gas elimination (MIGET) in a porcine model.

Methods

$ \dot{V}/\dot{Q} $ measured by micropore membrane inlet mass spectrometry-MIGET (MMIMS-MIGET) and EVLW were simultaneously measured in twelve pigs in the heathy state, with impaired gas exchange from repetitive lung lavage and after 3 h of ventilation. The relationship between $ \dot{V}/\dot{Q} $ compartments and EVLW was analysed by linear correlation and regression.

Results

Considerable increases in EVLW and $ \dot{V}/\dot{Q} $ mismatching were induced through the lavage procedure. Significant correlations between the EVLW and the $ \dot{V}/\dot{Q} $ fractions representing pulmonary shunt and low $ \dot{V}/\dot{Q} $ were found. Perfusion to the normal $ \dot{V}/\dot{Q} $ regions was inversely correlated to the EVLW.

Conclusions

Increased EVLW is associated with increased low $ \dot{V}/\dot{Q} $ and shunt, but not equal to pulmonary shunt alone. Beneath true shunt EVLW can also be associated with low $ \dot{V}/\dot{Q} $ regions.     

Experimental evaluation of ultrasound-guided 3D needle steering in biological tissue

Purpose

In this paper, we present a system capable of automatically steering bevel tip flexible needles under ultrasound guidance toward stationary and moving targets in gelatin phantoms and biological tissue while avoiding stationary and moving obstacles. We use three-dimensional (3D) ultrasound to track the needle tip during the procedure.

Methods

Our system uses a fast sampling-based path planner to compute and periodically update a feasible path to the target that avoids obstacles. We then use a novel control algorithm to steer the needle along the path in a manner that reduces the number of needle rotations, thus reducing tissue damage. We present experimental results for needle insertion procedures for both stationary and moving targets and obstacles for up to 90 mm of needle insertion.

Results

We obtained a mean targeting error of \(0.32\pm 0.10\) and \(0.38\,\pm \,0.19\)  mm in gelatin-based phantom and biological tissue, respectively.

Conclusions

The achieved submillimeter accuracy suggests that our approach is sufficient to target the smallest lesions ( \(\phi \)  2 mm) that can be detected using state-of-the-art ultrasound imaging systems.     

C-arm angle measurement with accelerometer for brachytherapy: an accuracy study

Purpose

 X-ray fluoroscopy guidance is frequently used in medical interventions. Image-guided interventional procedures that employ localization for registration require accurate information about the C-arm’s rotation angle that provides the data externally in real time. Optical, electromagnetic, and image-based pose tracking systems have limited convenience and accuracy. An alternative method to recover C-arm orientation was developed using an accelerometer as tilt sensor.

Methods

    The fluoroscopic C-arm’s orientation was estimated using a tri-axial acceleration sensor mounted on the X-ray detector as a tilt sensor. When the C-arm is stationary, the measured acceleration direction corresponds to the gravitational force direction. The accelerometer was calibrated with respect to the C-arm’s rotation along its two axes, using a high-accuracy optical tracker as a reference. The scaling and offset error of the sensor was compensated using polynomial fitting. The system was evaluated on a GE OEC 9800 C-arm. Results obtained by accelerometer, built-in sensor, and image-based tracking were compared, using optical tracking as ground truth data.

Results

The accelerometer-based orientation measurement error for primary angle rotation was $-0.1\pm 0.0^{\circ }$ and for secondary angle rotation it was $0.1\pm 0.0^{\circ }$ . The built-in sensor orientation measurement error for primary angle rotation was $-0.1\pm 0.2^{\circ }$ , and for secondary angle rotation it was $0.1\pm 0.2^{\circ }$ . The image-based orientation measurement error for primary angle rotation was $-0.1\pm 1.3^{\circ }$ , and for secondary angle rotation it was $-1.3\pm 0.3^{\circ }$ .

Conclusion

The accelerometer provided better results than the built-in sensor and image-based tracking. The accelerometer sensor is small, inexpensive, covers the full rotation range of the C-arm, does not require line of sight, and can be easily installed to any mobile X-ray machine. Therefore, accelerometer tilt sensing is a very promising applicant for orientation angle tracking of C-arm fluoroscopes.     

Clinical testing of an alternate method of inserting bone-implanted fiducial markers

Background

   Deep brain stimulation (DBS) surgery utilizes image guidance via bone-implanted fiducial markers to achieve the desired submillimetric accuracy and to provide means for attaching microstereotactic frames. For maximal benefit, the markers must be inserted to the correct depth since over-insertion leads to stripping and under-insertion leads to instability.

Purpose

   The purpose of the study was to test clinically a depth-release drive system, the PosiSeat \(^{\mathrm{TM}}\) , versus manual insertion (pilot hole followed by manual screwing until tactile determined correct seating) for implanting fiducial markers into the bone.

Methods

   With institutional review board approval, the PosiSeat \(^{\mathrm{TM}}\) was used to implant markers in 15 DBS patients (57 fiducials). On post-insertion CT scans, the depth of the gap between the shoulder of the fiducial markers and the closest bone surface was measured. Similar depth measurements were performed on the CT scans of 64 DBS patients (250 fiducials), who underwent manual fiducial insertion.

Results

   Median of shoulder-to-bone distance for PosiSeat \(^{\mathrm{TM}}\) and manual insertion group were 0.03 and 1.06 mm, respectively. Fifty percent of the fiducials had the shoulder-to-bone distances within 0.01–0.09 mm range for the PosiSeat group and 0.04–1.45 mm range for the manual insertion group. These differences were statistically significant.

Conclusions

   A depth-release drive system achieves more consistent placement of bone-implanted fiducial markers than manual insertion.     

A pilot study on magnetic navigation for transcatheter aortic valve implantation using dynamic aortic model and US image guidance

Purpose   In this paper, we propose a pilot study for transcatheter aortic valve implantation guided by an augmented magnetic tracking system (MTS) with a dynamic aortic model and intra-operative ultrasound (US) images. Methods    The dynamic 3D aortic model is constructed from the preoperative 4D computed tomography, which is animated according to the real-time electrocardiograph (ECG) input of patient. Before the procedure, the US probe calibration is performed to map the US image coordinate to the tracked device coordinate. A temporal alignment is performed to synchronize the ECG signals, the intra-operative US image and the tracking information. Thereafter, with the assistance of synchronized ECG signals, the spatial registration is performed by using a feature-based registration. Then the augmented MTS guides the surgeon to confidently position and deploy the transcatheter aortic valve prosthesis to the target. Results   The approach was validated by US probe calibration evaluation and animal study. The US calibration accuracy achieved $1.37\pm 0.43\, \text{ mm}$ , whereas in the animal study on three porcine subjects, fiducial, target, deployment distance and tilting errors reached $3.16\pm 0.55\,\text{ mm}$ , $3.80\pm 1.83\,\text{ mm}$ , $3.13\pm 1.12\,\text{ mm}$ and $5.87\pm 2.35^{\circ }$ , respectively. Conclusion   Our pilot study has revealed that the proposed approach is feasible and accurate for delivery and deployment of transcatheter aortic valve prosthesis.     

Stent graft visualization and planning tool for endovascular surgery using finite element analysis

Purpose

A new approach to optimize stent graft selection for endovascular aortic repair is the use of finite element analysis. Once the finite element model is created and solved, a software module is needed to view the simulation results in the clinical work environment. A new tool for interpretation of simulation results, named Medical Postprocessor, that enables comparison of different stent graft configurations and products was designed, implemented and tested.

Methods

 Aortic endovascular stent graft ring forces and sealing states in the vessel landing zone of three different configurations were provided in a surgical planning software using the Medical Imaging Interaction Tool Kit (MITK) software system. For data interpretation, software modules for 2D and 3D presentations were implemented. Ten surgeons evaluated the software features of the Medical Postprocessor. These surgeons performed usability tests and answered questionnaires based on their experience with the system.

Results

The Medical Postprocessor visualization system enabled vascular surgeons to determine the configuration with the highest overall fixation force in \(16 \pm 6\)  s, best proximal sealing in \(56 \pm 24\)  s and highest proximal fixation force in \(38\pm 12\)  s. The majority considered the multiformat data provided helpful and found the Medical Postprocessor to be an efficient decision support system for stent graft selection. The evaluation of the user interface results in an ISONORM-conform user interface (113.5 points).

Conclusion

The Medical Postprocessor visualization software tool for analyzing stent graft properties was evaluated by vascular surgeons. The results show that the software can assist the interpretation of simulation results to optimize stent graft configuration and sizing.     

Early intermittent noninvasive ventilation for acute chest syndrome in adults with sickle cell disease: a pilot study

Purpose

Alveolar hypoxia and hypoxic vasoconstriction lead to trapping of sickle cells within the pulmonary vasculature. Improving alveolar ventilation and oxygenation may improve the outcome of acute chest syndrome (ACS).

Methods

Prospective randomized single-center open study from November 1998 to February 2002 to test whether noninvasive ventilation (NIV) was more effective than oxygen alone in improving oxygenation on day 3 in adults with ACS and to evaluate the effects on pain, transfusion requirements, and length of stay.

Results

Seventy-one consecutive ACS episodes in 67 patients were randomly allocated to oxygen (n = 36) or NIV (n = 35) for 3 days in a medical step-down unit. Baseline respiratory rate and pain score were higher in the NIV group. NIV promptly lowered the respiratory rate, raised $ {\text{Pa}}_{{\text{O}_{2}}} $ , and decreased alveolar–arterial oxygen gradient $ (({\text{A}} - {\text{a}})_{{{\text{O}}_{ 2} }} ) $ , which remained unchanged with oxygen alone. $ {\text{Pa}}_{{{\text{CO}}_{ 2} }} $ significantly worsened only in the oxygen group. On day 3, the groups did not differ regarding the proportion of episodes with normal $ {\text{Pa}}_{{{\text{O}}_{ 2} }} $ (35% with NIV and 25% with oxygen; P = 0.5) or $ (({\text{A}} - {\text{a}})_{{{\text{O}}_{ 2} }} ) $ . Patient satisfaction and compliance were lower with NIV. No differences were noted in pain relief, transfusions, or length of stay. In the subgroup of patients with severe hypoxemia $ ( {\text{Pa}}_{{{\text{O}}_{ 2} }} \le 6 5\,{\text{mmHg)}} $ , physiological variables also improved faster with NIV, the differences being slightly more pronounced.

Conclusions

Respiratory rate and gas exchange improved faster with NIV. However, NIV failed to significantly reduce the number of patients remaining hypoxemic at day 3, and was associated with greater patient discomfort.     

Percutaneous lung biopsy: comparison between an augmented reality CT navigation system and standard CT-guided technique

Purpose

Percutaneous lung biopsies (PLBs) performed for the evaluation of pulmonary masses require image guidance to avoid critical structures. A new CT navigation system (SIRIO, “Sistema robotizzato assistito per il puntamento intraoperatorio”) for PLBs was validated.

Methods

The local Institutional Review Board approved this retrospective study. Image-guided PLBs in 197 patients were performed with a CT navigation system (SIRIO). The procedures were reviewed based on the number of CT scans, patients’ radiation exposure and procedural time recorded. Comparison was performed with a group of 72 patients undergoing standard CT-guided PLBs. Sensitivity, specificity and overall diagnostic accuracy were assessed in both groups.

Results

SIRIO-guided PLBs showed a significant reduction in procedure time, number of required CT scans and the radiation dose administered to patients ( $p<0.001$ ). In terms of diagnostic accuracy, SIRIO proved to be more accurate for small-sized lesions ( $<$ 20 mm) than standard CT-guidance.

Conclusion

SIRIO proved to be a reliable and effective tool when performing CT-guided PLBs and was especially useful for sampling small ( $<$ 20 mm) lesions.     

A novel four-wire-driven robotic catheter for radio-frequency ablation treatment

Purpose

   Robotic catheters have been proposed to increase the efficacy and safety of the radio-frequency ablation treatment. The robotized motion of current robotic catheters mimics the motion of manual ones—namely, deflection in one direction and rotation around the catheter. With the expectation that the higher dexterity may achieve further efficacy and safety of the robotically driven treatment, we prototyped a four-wire-driven robotic catheter with the ability to deflect in two- degree-of-freedom motions in addition to rotation.

Methods

   A novel quad-directional structure with two wires was designed and developed to attain yaw and pitch motion in the robotic catheter. We performed a mechanical evaluation of the bendability and maneuverability of the robotic catheter and compared it with current manual catheters.

Results

   We found that the four-wire-driven robotic catheter can achieve a pitching angle of 184.7 \(^{\circ }\) at a pulling distance of wire for 11 mm, while the yawing angle was 170.4 \(^{\circ }\) at 11 mm. The robotic catheter could attain the simultaneous two- degree-of-freedom motions in a simulated cardiac chamber.

Conclusion

   The results indicate that the four-wire-driven robotic catheter may offer physicians the opportunity to intuitively control a catheter and smoothly approach the focus position that they aim to ablate.     

Using the low-pass monogenic signal framework for cell/background classification on multiple cell lines in bright-field microscope images

Purpose

   Several cell detection approaches which deal with bright-field microscope images utilize defocusing to increase image contrast. The latter is related to the physical light phase through the transport of intensity equation (TIE). Recently, it was shown that it is possible to approximate the solution of the TIE using a low-pass monogenic signal framework. The purpose of this paper is to show that using the local phase of the aforementioned monogenic signal instead of the defocused image improves the cell/background classification accuracy.

Materials and methods

   The paper statement was tested on an image database composed of three cell lines: adherent CHO, adherent L929, and Sf21 in suspension. Local phase and local energy images were generated using the low-pass monogenic signal framework with axial derivative images as input. Machine learning was then employed to investigate the discriminative power of the local phase. Three classifier models were utilized: random forest (RF), support vector machine (SVM) with a linear kernel, and SVM with a radial basis function (RBF) kernel.

Results

   The improvement, averaged over cell lines, of classifying $5 \times 5$ sized patches extracted from the local phase image instead of the defocused image was $7.3$  % using the RF, $11.6$  % using the linear SVM, and $10.2$  % when a RBF kernel was employed instead of the linear one. Furthermore, the feature images can be sorted by increasing discriminative power as follows: at-focus signal, local energy, defocused signal, local phase. The only exception to this order was the superiority of local energy over defocused signal for suspended cells.

Conclusions

   Local phase computed using the low-pass monogenic signal framework considerably outperforms the defocused image for the purpose of pixel-patch cell/background classification in bright-field microscopy.