Image-guided Interventions Research Articles

Image-Guided Biliary Interventions: How to Recognize, Avoid, or Get Out of Trouble

Percutaneous biliary interventions have a well-established role in the management of hepatobiliary diseases. Good outcomes include recognizing and avoiding complications. This section will cover the "standard" technique of percutaneous biliary drainage, pearls to decrease the risk of problems, and approaches to treat those complications in patients undergoing percutaneous transhepatic cholangiography and percutaneous transhepatic biliary drainage.

Image-Guided Nephrostomy Interventions: How to Recognize, Avoid, or Get Out of Trouble

Image-guided percutaneous nephrostomy is a relatively safe and successful procedure for access to the renal collecting system for multiple purposes including relief of urinary obstruction, urinary diversion, access for endourologic procedures, and diagnostic testing. Although placing a percutaneous nephrostomy catheter is most times straightforward, providing immediate benefit for the patient and satisfaction for the practitioner, there can be situations that make the procedure more difficult or risky. A thorough review of the patient's imaging and medical record will help to set a path for success. However, there may be innuendos and unforeseen circumstances that occur. Having knowledge of most of these "stumbling blocks" and how to deal with them will keep you on the path. This paper serves to fill some of that mental file with the aim to increase clinical success.

Teaching Radiologists Who Perform Image-Guided Interventions Effective Communication Skills Through Simulation

Teaching Radiologists Who Perform Image-Guided Interventions Effective Communication Skills Through Simulation

Additional lesions seen in magnetic resonance imaging of breast cancer patients: the role of second-look ultrasound and imaging-guided interventions.

PurposeThe purpose of this study was to investigate the final outcomes of magnetic resonance imaging (MRI)-identified additional lesions (MRALs) in breast cancer patients and the role of second-look ultrasound (SLUS) and imaging-guided interventions.MethodsWe analyzed breast cancer patients with MRALs on preoperative MRI between January and June 2012. MRALs were defined as additional lesions suspected on MRI but not suspected on mammograms or ultrasound. The malignancy rate of MRALs, MRI-based Breast Imaging Reporting and Database System (BI-RADS) category, positional relationship with the index cancer, MRI-concordant lesion visibility on SLUS, performance of imaging-guided interventions, and total mastectomy (TM) rates were evaluated for the confirmed lesions.ResultsAmong the 119 confirmed lesions, SLUS and imaging-guided interventions were performed in 94 (79.0%) and 82 cases (68.9%), respectively. The malignancy rate was 68.1% (81 of 119), and was significantly higher in BI-RADS 4C-5 lesions than in 4A-4B lesions (94.6% vs. 56.1%, P<0.01) and in ipsilateral same-quadrant lesions than in contralateral lesions (84.2% vs. 33.3%, P<0.01). The lesion visibility rate on SLUS was 90.4%. The malignancy rate was not significantly different according to lesion visibility on SLUS. The TM rate in the 98 cases with ipsilateral MRALs was 37.8%, while it was significantly lower in patients who underwent an imaging-guided intervention than in those who did not (27.9% vs. 54.1%, P=0.017).ConclusionMRALs show a high probability of malignancy, especially if they are ipsilateral. SLUS and imaging-guided interventions can eliminate many unnecessary TMs.

Assessment of the Inferior Petrosal Sinus on T1-Weighted Contrast-Enhanced Magnetic Resonance Imaging.

Context:Skull base venous anatomy.Aims:While prior studies have focused on the efficacy of conventional fluoroscopic venography and multidetector computed tomography venography to evaluate the inferior petrosal sinus (IPS) before image-guided intervention (such as dural venous sinus sampling), we believe that routine magnetic resonance imaging (MRI) may provide reliable structural information helpful for planning without the need for further imaging.Settings and Design:Retrospective review of brain MRI.Materials and Methods:Retrospective analysis was carried out on IPSs on contrast-enhanced T1-weighted MR images. Qualitative measurements were made regarding the grade of patency of the IPS, variation in IPS drainage pattern, and grading of the ipsilateral transverse and sigmoid sinuses (TS and SS).Statistical Analysis Used:Pearson's product-moment correlation.Results:Evaluation of a total of 148 IPSs revealed that 91% of cases were grade 3 or grade 2 (either fully or mostly visualized), with 65% of cases demonstrating “typical” (type A) drainage directly into the internal jugular vein and no statistically significant correlation between the patency of the IPS and the dominance of the ipsilateral TS/SS. A bilateral concordance rate of 77% was also observed.Conclusions:Our analysis indicates that routine thin-slice contrast-enhanced T1-weighted MRI can provide sufficient anatomic detail to identify typical drainage pattern of the IPS in a majority of cases. In cases where routine drainage was not identified, spatial resolution was not sufficient to further delineate complex drainage anatomy. No correlation was observed between the TS/SS dominance and patency of the ipsilateral IPS.

Technical challenges of imaging & image-guided interventions in obese patients.

Obese patients challenge imaging departments in their ability to obtain diagnostic quality images and to perform image-guided interventions. These technical challenges include properly accommodating large patients on imaging equipment, adjusting equipment settings to address imaging limitations, and pre-planning and preparation for image-guided interventions to insure safe and successful outcomes. Knowing and addressing these challenges can result in successfully addressing the imaging and image-guided interventions needs of obese patients.

MRI-Guided Interventions in Musculoskeletal System.

Image-guided interventions in the musculoskeletal system require accurate detection and characterization of lesions involving bone and soft tissues. Magnetic resonance imaging (MRI) has superior soft tissue contrast resolution particularly in bone and soft tissues where computed tomography and ultrasonography have significant limitations. In addition, the multiplanar imaging capabilities of MRI facilitate targeting lesions and tracking interventional devices. Although conventional diagnostic MRI sequences suffer from motion sensitivity and prolonged imaging time, recently developed fast imaging sequences allow for rapid acquisition of high-quality images, rendering MRI more suitable for image-guided interventions. Although computed tomography and ultrasonography still dominate the spectrum of image-guided interventions in the musculoskeletal system, many MRI-guided procedures have been developed and are well established in routine clinical work. In addition, new techniques and novel MRI-guided applications are being developed to address complex clinical problems in a minimally invasive fashion.

MITT: Medical Image Tracking Toolbox.

Over the years, medical image tracking has gained considerable attention from both medical and research communities due to its widespread utility in a multitude of clinical applications, from functional assessment during diagnosis and therapy planning to structure tracking or image fusion during image-guided interventions. Despite the ever-increasing number of image tracking methods available, most still consist of independent implementations with specific target applications, lacking the versatility to deal with distinct end-goals without the need for methodological tailoring and/or exhaustive tuning of numerous parameters. With this in mind, we have developed the medical image tracking toolbox (MITT)-a software package designed to ease customization of image tracking solutions in the medical field. While its workflow principles make it suitable to work with 2-D or 3-D image sequences, its modules offer versatility to set up computationally efficient tracking solutions, even for users with limited programming skills. MITT is implemented in both C/C++ and MATLAB, including several variants of an object-based image tracking algorithm and allowing to track multiple types of objects (i.e., contours, multi-contours, surfaces, and multi-surfaces) with several customization features. In this paper, the toolbox is presented, its features discussed, and illustrative examples of its usage in the cardiology field provided, demonstrating its versatility, simplicity, and time efficiency.

Model-Based Sparse-to-Dense Image Registration for Realtime Respiratory Motion Estimation in Image-Guided Interventions.

Intra-interventional respiratory motion estimation is becoming a vital component in modern radiation therapy delivery or high intensity focused ultrasound systems. The treatment quality could tremendously benefit from more accurate dose delivery using real-time motion tracking based on magnetic-resonance (MR) or ultrasound (US) imaging techniques. However, current practice often relies on indirect measurements of external breathing indicators, which has an inherently limited accuracy. In this work, we present a new approach that is applicable to challenging real-time capable imaging modalities like MR-Linac scanners and 3D-US by employing contrast-invariant feature descriptors. We combine GPU-accelerated image-based realtime tracking of sparsely distributed feature points and a dense patient-specific motion-model for regularisation and sparse-to-dense interpolation within a unified optimization framework. We achieve highly accurate motion predictions with landmark errors of ≈ 1 mm for MRI (and ≈ 2 mm for US) and substantial improvements over classical template tracking strategies. Our technique can model physiological respiratory motion more realistically and deals particularly well with the sliding of lungs against the rib cage. Our model-based sparse-to-dense image registration approach allows for accurate and realtime respiratory motion tracking in image-guided interventions.

3D/2D model-to-image registration by imitation learning for cardiac procedures

PurposeIn cardiac interventions, such as cardiac resynchronization therapy (CRT), image guidance can be enhanced by involving preoperative models. Multimodality 3D/2D registration for image guidance, however, remains a significant research challenge for fundamentally different image data, i.e., MR to X-ray. Registration methods must account for differences in intensity, contrast levels, resolution, dimensionality, field of view. Furthermore, same anatomical structures may not be visible in both modalities. Current approaches have focused on developing modality-specific solutions for individual clinical use cases, by introducing constraints, or identifying cross-modality information manually. Machine learning approaches have the potential to create more general registration platforms. However, training image to image methods would require large multimodal datasets and ground truth for each target application.MethodsThis paper proposes a model-to-image registration approach instead, because it is common in image-guided interventions to create anatomical models for diagnosis, planning or guidance prior to procedures. An imitation learning-based method, trained on 702 datasets, is used to register preoperative models to intraoperative X-ray images.ResultsAccuracy is demonstrated on cardiac models and artificial X-rays generated from CTs. The registration error was 2.92pm 2.22,hbox { mm} on 1000 test cases, superior to that of manual (6.48pm 5.6,hbox { mm}) and gradient-based (6.79pm 4.75,hbox { mm}) registration. High robustness is shown in 19 clinical CRT cases.ConclusionBesides the proposed methods feasibility in a clinical environment, evaluation has shown good accuracy and high robustness indicating that it could be applied in image-guided interventions.

18F-Positron Emitting/Trimethine Cyanine-Fluorescent Contrast for Image-Guided Prostate Cancer Management.

[18/19F]-4, an anionic GCPII/PSMA inhibitor for image-guided intervention in prostate cancer, is described. [19F]-4 is radiolabeled with a radiochemical yield that is ≥27% and a molar activity of 190 ± 50 mCi/μmol in a <1 h, one-step, aqueous isotopic exchange reaction. [19F]-4 allows PSMA expression to be imaged by fluorescence (FL) and [18F]-PET. PC3-PIP (PSMA-positive, EC50 = 6.74 ± 1.33 nM) cancers are specifically delineated in mice that bear 3 million (18 mg) PC3-PIP and PC3 (control, PSMA-negative) cells. Colocalization of [18/19F]-4 PET, fluorescence, scintillated biodistribution, and PSMA expression are observed.

Patient Complaints in Image-Guided Interventions: Evaluation of Multifactorial Issues Using a Coding Taxonomy.

The purpose of this article is to classify complaints from patients undergoing image-guided interventions using a coding taxonomy and to test whether single-coded complaints were resolved satisfactorily compared with multifactorial (multiple codes) complaints. In this retrospective study, patients' complaint narratives between April 1999 and December 2012 were reviewed and categorized according to a three-level taxonomy into domains and codes. Resolutions were categorized as satisfactory or unsatisfactory to the patient and were classified as follows: clarification, apology, manager notification, change of provider, reimbursement, and quality review. Complaints were classified as single coded (only one code identified in the patients' description) and multifactorial (multiple codes identified). Statistical analysis was performed with the Fisher test, with the significance level set at 0.05. A run chart with the distribution of complaints by domains (relationships, management, and clinical) by year was performed. A total of 146 codes were extracted from 71 narratives (2.06 codes/complaint) and were classified into the following domains: clinical (52%; n = 76), management (24%; n = 35), and relationships (24%; n = 35). The most common codes included quality of care, safety, and communication breakdown issues. A run chart found a decline in absolute numbers of complaints over the years in the domains studied. The frequency of satisfactory resolution was 86% for multifactorial versus 81% for single-coded complaints with no statistically significant differences observed (p = 0.72). Over 50% of complaints were resolved by providing clarification to patients (n = 36). There were no statistically significant differences between multifactorial and single-coded complaints. Clinical codes and communication breakdown were the most common reasons for patient-reported complaint, with most complaints successfully resolved with clarification.

Advanced Image Registration and Reconstruction using the O-Arm System: Dose Reduction, Image Quality, and Guidance using Known-Component Models.

Model-based image registration and reconstruction offer strong potential for improved safety and precision in image-guided interventions. Advantages include reduced radiation dose, improved soft-tissue visibility (detection of complications), and accurate guidance with/without a dedicated navigation system. This work reports the development and performance of such methods on an O-arm system for intraoperative imaging and translates them to first clinical studies. Two novel methodologies predicate the work: (1) Known-Component Registration (KC-Reg) for 3D localization of the patient and interventional devices from 2D radiographs; and (2) Penalized-Likelihood reconstruction (PLH) for improved 3D image quality and dose reduction. A thorough assessment of geometric stability, dosimetry, and image quality was performed to define algorithm parameters for imaging and guidance protocols. Laboratory studies included: evaluation of KC-Reg in localization of spine screws delivered in cadaver; and PLH performance in contrast, noise, and resolution in phantoms/cadaver compared to filtered backprojection (FBP). KC-Reg was shown to successfully register screw implants within ~1 mm based on as few as 3 radiographs. PLH was shown to improve soft-tissue visibility (61% improvement in CNR) compared to FBP at matched resolution. Cadaver studies verified the selection of algorithm parameters and the methods were successfully translated to clinical studies under an IRB protocol. Model-based registration and reconstruction approaches were shown to reduce dose and provide improved visualization of anatomy and surgical instrumentation. Immediate future work will focus on further integration of KC-Reg and PLH for Known-Component Reconstruction (KC-Recon) to provide high-quality intraoperative imaging in the presence of dense instrumentation.

Gantry rotational motion-induced blur in cone-beam computed tomography.

As neuro-endovascular image-guided interventions (EIGIs) make use of higher resolution detectors, gantry rotational motion-induced blur becomes more noticeable in acquired projections as well as reconstructed images by reducing the visibility of vascular and device features whose visualization could be critical in the treatment of vascular pathology. Motion-induced blur in projections views is a function of an object's position in the field-of-view (FOV), gantry rotational speed, and frame capture or exposure time. In this work different frame rates were used to investigate the effects of blurring from individual projections on the reconstructed image. To test the effects of these parameters on reconstructed images, a regular pattern phantom of small objects was simulated and projection views were generated at various different frame rates for a given simulated rotational velocity. The reconstruction was made using a linear interpolation of filtered backprojections. Images reconstructed from lower frame rates showed significant blurring in the azimuthal direction, increasingly worse towards the periphery of the image. However, those reconstructed from higher frame rates showed significantly less blur throughout the entire FOV. While lower frame rates could be used with slower gantry speeds this would increase the risk of voluntary or involuntary patient motion contributing to blur over the entire FOV. A high frame rate used with high gantry speeds could reliable provide images without gantry-motion blur while reducing the risk of patient-motion blur. Frame rates exceeding 2000 fps available with photon counting detectors such as the X-counter Actaeon1 are available.

High-Frequency Jet Ventilation During Cryoablation of Small Renal Tumours

AimTo evaluate the effect of high-frequency jet ventilation (HFJV) in place of standard intermittent positive-pressure ventilation (IPPV) on procedure duration, patient radiation dose, complication rates, and outcomes during CT-guided cryoablation of small renal tumours.Materials and MethodsOne hundred consecutive CT-guided cryoablation procedures to treat small renal tumours under general anaesthesia were evaluated—50 with standard IPPV and 50 after the introduction of HFJV as standard practice. Anaesthesia and procedural times, ionising radiation dose, complications, and 1-month post-treatment outcomes were collected.ResultsHFJV was feasible and safe in all cases. Mean procedure time and total anaesthetic time were shorter with HFJV (p = <0.0001). The number of required CT acquisitions (p = 0.0002) and total procedure patient radiation dose (p = 0.0027) were also lower in the HFJV group compared with the IPPV group. There were a total of four complications of Clavien–Dindo classification 3 or above—three in the IPPV group and one in the HFJV group. At 1-month follow-up, two cases (both in the IPPV group) demonstrated subtotal treatment. Both cases were subsequently successfully retreated with cryoablation.ConclusionBy reducing target tumour motion during CT-guided renal cryoablation, HFJV can reduce procedure times and exposure to ionising radiation. HFJV provides an important adjunct to complex image-guided interventions, with potential to improve safety and treatment outcomes.

Colour for Behavioural Success.

Colour information not only helps sustain the survival of animal species by guiding sexual selection and foraging behaviour but also is an important factor in the cultural and technological development of our own species. This is illustrated by examples from the visual arts and from state-of-the-art imaging technology, where the strategic use of colour has become a powerful tool for guiding the planning and execution of interventional procedures. The functional role of colour information in terms of its potential benefits to behavioural success across the species is addressed in the introduction here to clarify why colour perception may have evolved to generate behavioural success. It is argued that evolutionary and environmental pressures influence not only colour trait production in the different species but also their ability to process and exploit colour information for goal-specific purposes. We then leap straight to the human primate with insight from current research on the facilitating role of colour cues on performance training with precision technology for image-guided surgical planning and intervention. It is shown that local colour cues in two-dimensional images generated by a surgical fisheye camera help individuals become more precise rapidly across a limited number of trial sets in simulator training for specific manual gestures with a tool. This facilitating effect of a local colour cue on performance evolution in a video-controlled simulator (pick-and-place) task can be explained in terms of colour-based figure-ground segregation facilitating attention to local image parts when more than two layers of subjective surface depth are present, as in all natural and surgical images.

3:36 PM Abstract No. 215 Patient-specific needle guidance templates manufactured intraprocedurally for image-guided intervention

Multifocal or large tumors can be treated effectively using multiple ablation needles, but it is time consuming and difficult to perform accurately without frequent re-scanning or use of navigation systems. A new targeting method was developed using a custom patient-specific needle guide template, fabricated intraoperatively. In an IACUC approved study, a 78kg pig was studied under general anesthesia. Steel balls (1.5 mm) were implanted into the liver to serve as targets. Fiducial markers were affixed to the abdomen. A custom 150 × 220 mm plastic frame designed to hold two parallel plates was fixed over the abdomen using a rigid mounting arm. The frame and subject underwent CT scan with breath-hold. The targets, fiducial and frame were identified in the images. A preprocedure needle trajectory plan was created for each target, with defined skin entry sites and a path that avoided critical structures. The plan that included all needle paths was converted into a drilling program for an inexpensive numerical-controlled table-top milling machine, and the hole pattern corresponding to the planned trajectories was drilled into two plates. The plates were attached to the frame and needles were passed through the drilled holes toward the targets. After each needle placement, the animal was re-scanned to determine the accuracy of needle placement by determining the distance from needle tip to target. The system was also studied in similar fashion in static phantom experiments. The needle to target error distance for four live animal insertions was 3.2 (standard deviation, 1.8 mm) and ranged between 1.5 and 5.2 mm. The needle delivery technique was feasible for targeting multiple liver locations and facilitated complex oblique paths to the target. The planning step required approximately 5 minutes. The template was manufactured at bedside in 7.5 minutes. Accurate placement of multiple needles using a custom-drilled, patient-specific template (based on a preprocedure CT) is possible and can be performed in the scan room immediately prior to insertion. The system is similar in performance to more complex systems that require tracking.

Enabling Technology for MRI-Guided Intervention.

The use of magnetic resonance imaging (MRI) for image-guided intervention poses both great opportunity and challenges. Although MRI is distinguished by its excellent contrast resolution and lack of ionizing radiation, it was not till the 1990s that technologic innovations allowed for adoption of MRI as a guidance modality for intervention. With advances in magnet, protocol, coil, biopsy needle, and ablation probe design, MRI has emerged as a viable, and increasingly, preferable alternative to other image guidance modalities. With the development of targeting software, augmented reality, robotic assist devices, and MR thermometry, the future of MRI-guided interventions remains promising.

Sparse Ultrasound Image Reconstruction From a Shape-Sensing Single-Element Forward-Looking Catheter.

Minimally invasive procedures, such as intravascular and intracardiac interventions, may benefit from guidance with forward-looking (FL) ultrasound. In this work, we investigate FL ultrasound imaging using a single-element transducer integrated in a steerable catheter, together with an optical shape sensing (OSS) system. We tested the feasibility of the proposed device by imaging the surface of a tissue-mimicking (TM) phantom and an ex vivo human carotid plaque. While manually steering the catheter tip, ultrasound A-lines are acquired at 60 Hz together with the catheter shape from the OSS system, resulting in a two-dimensional sparse and irregularly sampled data set. We implemented an adaptive Normalized Convolution (NC) algorithm to interpolate the sparse data set by applying an anisotropic Gaussian kernel that is rotated according to the local direction of the catheter scanning pattern. To choose the Gaussian widths tangential ( ${\sigma _t}$) and normal ( ${\sigma _n}$) to the scanning pattern, an exhaustive search was implemented based on RMSE computation on simulated data. Simulations showed that the sparse data set contains only 5% of the original information. The chosen widths, ${\sigma _n} = \text{250}\;\mu {\textrm{m}}$ and ${\sigma _t} = \text{100}\;\mu{\textrm{m}}$, are used to successfully reconstruct the surface of the phantom with a contrast ratio of 0.9. The same kernel is applied successfully to the carotid plaque data. The proposed approach enables FL imaging with a single ultrasound element, mounted on a steerable device. This principle may find application in a variety of image-guided interventions, such as chronic total occlusion (CTO) recanalization.

Using optical tracking for kinematic testing of medical robots.

In image-guided robotic interventions, an error component is related to the positioning error of the manipulator. Therefore, measuring the kinematic error is required during robot development. However, no specialized measurement device exists for this task. This study explores the possibility of using optical tracking for robot measurement. A CNC machine is used to position an optical marker, generating a gold standard reference. Repeated position measurements are acquired with an NDI Polaris Hybrid® optical tracker at each static location, and averaged. These measurements are compared to the reference set. Averaging repeated static position measurements improves precision (200-500 samples). Measurement accuracy ranges between 44μm and 137μm in close proximity of the tracker. Repeated static position measurements in the near field of view enable the optical tracker to outperform its general-purpose accuracy specification. Optical tracking may be used to test robot kinematics with a high degree of accuracy.