Cone beam computed tomography improves the detection of injured vessels and involved vascular territories in patients with bleeding of uncertain origin

Deformable motion compensation in interventional cone-beam CT with a context-aware learned autofocus metric

PURPOSE

Interventional Cone-Beam CT (CBCT) offers 3D visualization of soft-tissue and vascular anatomy, enabling 3D guidance of abdominal interventions. However, its long acquisition time makes CBCT susceptible to patient motion. Image-based autofocus offers a suitable platform for compensation of deformable motion in CBCT, but it relies on handcrafted motion metrics based on first-order image properties and that lack awareness of the underlying anatomy. This work proposes a data-driven approach to motion quantification via a learned, context-aware, deformable metric,VI F D L ${\bm{VI}}{{\bm{F}}}_{DL}$ , that quantifies the amount of motion degradation as well as the realism of the structural anatomical content in the image.

METHODS

The proposedVI F D L ${\bm{VI}}{{\bm{F}}}_{DL}$ was modeled as a deep convolutional neural network (CNN) trained to recreate a reference-based structural similarity metric-visual information fidelity (VIF). The deep CNN acted on motion-corrupted images, providing an estimation of the spatial VIF map that would be obtained against a motion-free reference, capturing motion distortion, and anatomic plausibility. The deep CNN featured a multi-branch architecture with a high-resolution branch for estimation of voxel-wise VIF on a small volume of interest. A second contextual, low-resolution branch provided features associated to anatomical context for disentanglement of motion effects and anatomical appearance. The deep CNN was trained on paired motion-free and motion-corrupted data obtained with a high-fidelity forward projection model for a protocol involving 120 kV and 9.90 mGy. The performance ofVI F D L ${\bm{VI}}{{\bm{F}}}_{DL}$ was evaluated via metrics of correlation with ground truth VIF ${\bm{VIF}}$ and with the underlying deformable motion field in simulated data with deformable motion fields with amplitude ranging from 5 to 20 mm and frequency from 2.4 up to 4 cycles/scan. Robustness to variation in tissue contrast and noise levels was assessed in simulation studies with varying beam energy (90-120 kV) and dose (1.19-39.59 mGy). Further validation was obtained on experimental studies with a deformable phantom. Final validation was obtained via integration ofVI F D L ${\bm{VI}}{{\bm{F}}}_{DL}$ on an autofocus compensation framework, applied to motion compensation on experimental datasets and evaluated via metric of spatial resolution on soft-tissue boundaries and sharpness of contrast-enhanced vascularity.

RESULTS

The magnitude and spatial map ofVI F D L ${\bm{VI}}{{\bm{F}}}_{DL}$ showed consistent and high correlation levels with the ground truth in both simulation and real data, yielding average normalized cross correlation (NCC) values of 0.95 and 0.88, respectively. Similarly,VI F D L ${\bm{VI}}{{\bm{F}}}_{DL}$ achieved good correlation values with the underlying motion field, with average NCC of 0.90. In experimental phantom studies,VI F D L ${\bm{VI}}{{\bm{F}}}_{DL}$ properly reflects the change in motion amplitudes and frequencies: voxel-wise averaging of the localVI F D L ${\bm{VI}}{{\bm{F}}}_{DL}$ across the full reconstructed volume yielded an average value of 0.69 for the case with mild motion (2 mm, 12 cycles/scan) and 0.29 for the case with severe motion (12 mm, 6 cycles/scan). Autofocus motion compensation usingVI F D L ${\bm{VI}}{{\bm{F}}}_{DL}$ resulted in noticeable mitigation of motion artifacts and improved spatial resolution of soft tissue and high-contrast structures, resulting in reduction of edge spread function width of 8.78% and 9.20%, respectively. Motion compensation also increased the conspicuity of contrast-enhanced vascularity, reflected in an increase of 9.64% in vessel sharpness.

CONCLUSION

The proposedVI F D L ${\bm{VI}}{{\bm{F}}}_{DL}$ , featuring a novel context-aware architecture, demonstrated its capacity as a reference-free surrogate of structural similarity to quantify motion-induced degradation of image quality and anatomical plausibility of image content. The validation studies showed robust performance across motion patterns, x-ray techniques, and anatomical instances. The proposed anatomy- and context-aware metric poses a powerful alternative to conventional motion estimation metrics, and a step forward for application of deep autofocus motion compensation for guidance in clinical interventional procedures.

Danger Zones of the Gluteal Anatomy: Improving the Safety Profile of the Gluteal Fat Grafting

INTRODUCTION

Knowledge of the vascular anatomy is critical to performing safe gluteal surgery. To date, only the course of the main blood vessels within the muscles has been outlined. These findings are based on MRI and CTA images that do not conform to a topographically standardized and normalized probability distribution.

OBJECTIVES

The aim of this study was to develop a three-dimensional mapping of the gluteal zones of high vascular density in relation to anatomical landmarks.

MATERIALS AND METHODS

This single-center retrospective cohort analysis comprised all consecutive patients who underwent cone-beam computed tomography (CBCT) scans between January 2016 and October 2021. The location of blood vessels in the gluteal region was allometrically normalized in relation to anatomical landmarks. Moreover, the caliber and area of the blood vessels were assessed.

RESULTS

CBCT scans of 32 patients with an average age of 64 ± 12 years (range 34-87 years) were included. Fifty-three percent were female. The median [IQR] caliber of the intramuscular gluteal vessels was 1.47 [1.15-1.88] mm, significantly greater than that of the subcutaneous vessels 1.09 [0.72-1.44] mm (p < 0.001). Vascular density was higher intramuscularly, as 4.5% of the area of the muscle was occupied by blood vessels, as opposed to 0.3% in the adipose tissue.

CONCLUSION

The analysis of the CBCT scans showed a higher vascular density and larger vessels intramuscularly. We, therefore, recommend the injection of autologous fat merely to the subcutaneous plane.

LEVEL OF EVIDENCE II

This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

Cone-Beam CT-assisted navigation for endovascular treatment of erection-related artery stenosis in patients with erectile dysfunction

Background

Angioplasty and stenting have emerged as endovascular treatment options for arteriogenic erectile dysfunction over the past few years. Considerable anatomical variation of the erection related pelvic arteries can be challenging during these procedures, leading to time-consuming repetitive super-selective angiograms for navigation.

Technique

We report a novel technique of using C-arm Cone-Beam CT and vessel navigation software to facilitate super-selective catheterization.

Conclusion

Cone-Beam CT-guided navigation for vascular assessment of arteriogenic ED is an optional approach compared to exclusive angiographic assessment. Compared to CT angiography, C-arm Cone-Beam CT offers benefits regarding usage of contrast media and radiation exposure. It has the advantage to combine imaging with endovascular procedures in a single session, reduces time to target navigation in complex pelvic arteries anatomy and may increase therapy safety in endovascular treatment of ED.

Reference-free learning-based similarity metric for motion compensation in cone-beam CT

Purpose. Patient motion artifacts present a prevalent challenge to image quality in interventional cone-beam CT (CBCT). We propose a novel reference-free similarity metric (DL-VIF) that leverages the capability of deep convolutional neural networks (CNN) to learn features associated with motion artifacts within realistic anatomical features. DL-VIF aims to address shortcomings of conventional metrics of motion-induced image quality degradation that favor characteristics associated with motion-free images, such as sharpness or piecewise constancy, but lack any awareness of the underlying anatomy, potentially promoting images depicting unrealistic image content. DL-VIF was integrated in an autofocus motion compensation framework to test its performance for motion estimation in interventional CBCT.Methods. DL-VIF is a reference-free surrogate for the previously reported visual image fidelity (VIF) metric, computed against a motion-free reference, generated using a CNN trained using simulated motion-corrupted and motion-free CBCT data. Relatively shallow (2-ResBlock) and deep (3-Resblock) CNN architectures were trained and tested to assess sensitivity to motion artifacts and generalizability to unseen anatomy and motion patterns. DL-VIF was integrated into an autofocus framework for rigid motion compensation in head/brain CBCT and assessed in simulation and cadaver studies in comparison to a conventional gradient entropy metric.Results. The 2-ResBlock architecture better reflected motion severity and extrapolated to unseen data, whereas 3-ResBlock was found more susceptible to overfitting, limiting its generalizability to unseen scenarios. DL-VIF outperformed gradient entropy in simulation studies yielding average multi-resolution structural similarity index (SSIM) improvement over uncompensated image of 0.068 and 0.034, respectively, referenced to motion-free images. DL-VIF was also more robust in motion compensation, evidenced by reduced variance in SSIM for various motion patterns (σ_DL-VIF = 0.008 versusσ_{gradient entropy} = 0.019). Similarly, in cadaver studies, DL-VIF demonstrated superior motion compensation compared to gradient entropy (an average SSIM improvement of 0.043 (5%) versus little improvement and even degradation in SSIM, respectively) and visually improved image quality even in severely motion-corrupted images.Conclusion: The studies demonstrated the feasibility of building reference-free similarity metrics for quantification of motion-induced image quality degradation and distortion of anatomical structures in CBCT. DL-VIF provides a reliable surrogate for motion severity, penalizes unrealistic distortions, and presents a valuable new objective function for autofocus motion compensation in CBCT.

The utility of using TACE-assisted software with CBCT in colonic diverticular bleeding without extravascular leakage

The utility of three-dimensional (3D) imaging with cone-beam computed tomography (CBCT) during interventional radiology (IVR) in colonic diverticular bleeding was compared to that of contrast-enhanced computed tomography (CECT). Additionally, to identify the responsible vessels in the absence of extravascular leakage using digital subtraction angiography, we examined the detection rate using software conventionally applied to transcatheter arterial chemoembolization (TACE). The 3D images obtained by CECT before IVR did not clearly show the destroyed vessels, whereas the 3D images obtained by CBCT during IVR clearly depicted the peripheral vessels. The TACE-assisted software identified the responsible vessels with a high probability, even in cases without extravascular leakage. CBCT could delineate vascular positions more accurately than CECT. Moreover, 80% of the responsible vessels could be delineated using the software; however, caution should be exercised as results may differ depending on the positioning of the region of interest.

Endovascular Rescue for Renal Artery Pseudoaneurysms following Minimally Invasive Robot-Assisted Partial Nephrectomy—A Case Series

Nephron sparing surgery or partial nephrectomy has been employed ever since in cases of renal tumors with an aim to preserve the function of residual kidney. Lately, there has been increasing adoption in robot-assisted techniques for partial nephrectomy. However, renal surgeries of any kind have always been a hazard for postoperative vascular complications owing to high vascularity of the renal tissues, of which renal artery pseudoaneurysm is one of the most fatal complications. We present a case series where highly super-selective embolization rescues the patient and augments the nephron sparing nature of the precise robot-assisted partial nephrectomy.

Central Retinal Artery Visualization with Cone-Beam CT Angiography

Background There are multiple tools available to visualize the retinal and choroidal vasculature of the posterior globe. However, there are currently no reliable in vivo imaging techniques that can visualize the entire retrobulbar course of the retinal and ciliary vessels. Purpose To identify and characterize the central retinal artery (CRA) using cone-beam CT (CBCT) images obtained as part of diagnostic cerebral angiography. Materials and Methods In this retrospective study, patients with catheter DSA performed between October 2019 and October 2020 were included if CBCT angiography included the orbit in the field of view. The CBCT angiography data sets were postprocessed with a small field-of-view volume centered in the posterior globe to a maximum resolution of 0.2 mm. The following were evaluated: CRA origin, CRA course, CRA point of penetration into the optic nerve sheath, bifurcation of the CRA at the papilla, visualization of anatomic variants, and visualization of the central retinal vein. Descriptive statistical analysis was performed. Results Twenty-one patients with 24 visualized orbits were included in the analysis (mean age, 55 years ± 15; 14 women). Indications for angiography were as follows: diagnostic angiography (n = 8), aneurysm treatment (n = 6), or other (n = 7). The CRA was identified in all orbits; the origin, course, point of penetration of the CRA into the optic nerve sheath, and termination in the papilla were visualized in all orbits. The average length of the intraneural segment was 10.6 mm (range, 7-18 mm). The central retinal vein was identified in six of 24 orbits. Conclusion Cone-beam CT, performed during diagnostic angiography, consistently demonstrated the in vivo central retinal artery, demonstrating excellent potential for multiple diagnostic and therapeutic applications. © RSNA, 2021 Online supplemental material is available for this article.

Cone Beam CT Guidance Improves Transbronchial Lung Cryobiopsy Safety

INTRODUCTION

Determining the cause of diffuse parenchymal lung disease (DPLD) is challenging. While surgical lung biopsy has been the standard approach, transbronchial lung cryobiopsy (TBLC) represents a minimally invasive alternative with an acceptable safety profile and reasonable accuracy. In this study, we prospectively assessed whether the use of cone beam CT (CBCT) coupled with a novel bronchoscope holder and prophylactic administration of vasoconstricting medications decreases potential complications and improves diagnostic accuracy when performing TBLC.

METHODS

33 patients presenting for evaluation of newly diagnosed DPLD were enrolled. Demographic data, pulmonary function values, chest imaging pattern, procedural information, and diagnosis were recorded.

RESULTS

Mean patient age was 67, with the majority Caucasian (n = 26, 79%) and male (n = 20, 61%). Mean pulmonary function values revealed restrictive lung disease (76 ± 14% predicted) and diffusing capacity impairment (52 ± 16%). A non-usual interstitial pneumonia imaging pattern was commonly seen (n = 20, 61%). CBCT guided TBLC was performed in one lobe (n = 29, 88%) or two lobes (n = 4, 12%) with mean probe-to-pleura distance of 4.2 ± 1.3 mm. No peri or post procedural complications occurred. 32 patients (97%) received a histological diagnosis with a final multidisciplinary conference diagnosis possible for 32 (97%).

CONCLUSION

CBCT guided TBLC coupled with a novel articulating scope holder and prophylactic phenylephrine administration has the potential to increase safety and diagnostic yield for patients with newly identified DPLD. Future studies comparing different aspects of this approach in isolation and with other modalities have the potential to refine this procedure to improve patient care.

Extrahepatic Clinical Application of Vessel Tracking Software and 3D Roadmapping Tools: Preliminary Experience

This article demonstrates the use of a representative commercially available automated vessel-tracking software originally intended for liver-only application (Vessel Assist Flight Plan for Liver; GE) in 4 patients. Treatment settings included embolization of small bowel hemorrhage source, treatment of renal cell carcinoma, management of symptomatic benign prostate hypertrophy, and detection with subsequent closure of a mesenteric pseudoaneurysm. All patients were treated successfully.