Three-dimensional CT with a modified C-arm image intensifier: feasibility

Cone beam versus conventional computed tomography angiography volume measurement in partial splenic embolization

When performing partial splenic arterial embolization (PSE), it can be difficult to determine the embolization ratio based on 2-dimensional digital subtraction angiography (DSA) image diagnosis alone. Therefore, at our department, we conduct computed tomography (CT) imaging intraoperatively and postoperatively to determine whether the planned embolization has been achieved. In recent years, developments in interventional radiology devices have enabled diagnostic imaging using cone beam CT. Here, we investigated whether the embolization ratio could be predicted from volume measurement with cone beam CT in PSE.We investigated correlations between volume measurement with conventional CT angiography (CTA) and volume measurement with cone beam CTA in 11 cases that underwent PSE with cone beam CT guidance (Allura Clarity FD20; Phillips, Amsterdam, The Netherlands) between December 2013 and May 2018.The mean subject age was 65.0 ± 5.8 years (6 men, 5 women). The subjects had underlying liver disorders of hepatitis C virus infection (4 cases), nonalcoholic steatohepatitis (4 cases), and alcohol-related disease (3 cases). A positive correlation was noted between conventional CTA and cone beam CTA, with infarction rates of 61.28 ± 9.31% and 64.04 ± 9.24%, respectively. The correlation coefficient between the 2 variables was .772.Because blood washout occurs rapidly in the spleen, contrast medium had to be continuously injected during imaging to enable dual-phase imaging with cone beam CT. However, we successfully performed imaging up to the second phase and volume measurement for the embolization ratio by inserting a catheter into the splenic artery and confirming the cone beam CT arrival time from the DSA images. The results were almost identical to those obtained from volume measurement with conventional CT based on CTA imaging. Thus, our results suggest that the splenic embolization ratio measurement obtained via cone beam CTA can be used to assess PSE treatment endpoints.

3D Ultrasound for Orthopedic Interventions

Ultrasound is a real-time, non-radiation-based imaging modality with an ability to acquire two-dimensional (2D) and three-dimensional (3D) data. Due to these capabilities, research has been carried out in order to incorporate it as an intraoperative imaging modality for various orthopedic surgery procedures. However, high levels of noise, different imaging artifacts, and bone surfaces appearing blurred with several mm in thickness have prohibited the widespread use of ultrasound as a standard of care imaging modality in orthopedics. In this chapter, we provided a detailed overview of numerous applications of 3D ultrasound in the domain of orthopedic surgery. Specifically, we discuss the advantages and disadvantages of methods proposed for segmentation and enhancement of bone ultrasound data and the successful application of these methods in clinical domain. Finally, a number of challenges are identified which need to be overcome in order for ultrasound to become a preferred imaging modality in orthopedics.

Arms Down Cone Beam CT Hepatic Angiography Performance Assessment: Vascular Imaging Quality and Imaging Artifacts

INTRODUCTION

The practice of positioning patients' arms above the head during catheter-injected hepatic arterial phase cone beam CT (A-CBCT) imaging has been inherited from standard CT imaging due to image quality concerns, but interrupts workflow and extends procedure time. We sought to assess A-CBCT image quality and artifacts with arms extended above the head versus down by the side.

METHODS

We performed an IRB approved retrospective evaluation of reformatted and 3D-volume rendered images from 91 consecutive A-CBCTs (43 arms up, 48 arms down) acquired during hepatic tumor arterial embolization procedures. Two interventional radiologists reviewed all A-CBCT imaging and assigned vessel visualization scores (VVS) from 1 to 5, ranging from non-diagnostic to optimal visualization. Streak artifacts across axial images were rated from 1 to 3 based on resulting image quality (none to significant). Presence of respiratory or cardiac motion during acquisition, body mass index and radiation dose area product (DAP) were also recorded and analyzed. Univariate and multivariate analyses were used to assess the impact of arm position on VVS and imaging artifacts.

RESULTS

VVS were not significantly associated with arm position during A-CBCT imaging. One reader reported more streak artifacts across axial images in the arms down group (p = 0.005). DAP was not statistically different between the groups (23.9 Gy cm² [6.1-73.4] arms up, 26.1 Gy cm² [4.2-102.6] arms down, p = 0.54).

CONCLUSION

A-CBCT angiography performed with the arms above the head is not superior for clinically relevant hepatic vascular visualization compared to imaging performed with the arms by the patient's side.

Ultrasound imaging and segmentation of bone surfaces: A review

Due to its real-time, non-radiation based three-dimensional (3D) imaging capabilities, ultrasound (US) has been incorporated into various orthopedic procedures. However, imaging artifacts, low signal-to-noise ratio (SNR) and bone boundaries appearing several mm in thickness make the analysis of US data difficult. This paper provides a review about the state-of-the-art bone segmentation and enhancement methods developed for two-dimensional (2D) and 3D US data. First, an overview for the appearance of bone surface response in B-mode data is presented. Then, classification of the proposed techniques in terms of the image information being used is provided. Specifically, the focus is given on segmentation and enhancement of B-mode US data. The review is concluded by discussing future directions of research and additional challenges which need to be overcome in order to make this imaging modality more successful in orthopedics.

[Intraoperative 3D imaging : Diagnostic accuracy and therapeutic benefits]

Intraoperative 3D imaging has a marked impact on the surgical treatment of articular fractures. In theory, insufficient reduction of fracture fragments and malpositioning of implants can be corrected in the same session so that unnecessary secondary imaging and revision surgery can be avoided. Current evidence on the accuracy of 3D scans, however, relies on heterogeneous preclinical data and must be interpreted with caution. Every fourth 3D scan seems to lead to a repositioning of fracture fragments or implants, despite unproven sensitivity and specificity. The interaction between diagnostic accuracy and therapeutic consequences needs exploration before any conclusions on the (additional) benefits of intraoperative 3D imaging can be drawn.

Enhancement of bone shadow region using local phase-based ultrasound transmission maps

PURPOSE

Ultrasound is increasingly being employed in different orthopedic procedures as an imaging modality for real-time guidance. Nevertheless, low signal-to-noise-ratio and different imaging artifacts continue to hamper the success of ultrasound-based procedures. Bone shadow region is an important feature indicating the presence of bone/tissue interface in the acquired ultrasound data. Enhancement and automatic detection of this region could improve the sensitivity of ultrasound for imaging bone and result in improved guidance for various orthopedic procedures.

METHODS

In this work, a method is introduced for the enhancement of bone shadow regions from B-mode ultrasound data. The method is based on the combination of three different image phase features: local phase tensor, local weighted mean phase angle, and local phase energy. The combined local phase image features are used as an input to an [Formula: see text] norm-based contextual regularization method which emphasizes uncertainty in the shadow regions. The enhanced bone shadow images are automatically segmented and compared against expert segmentation.

RESULTS

Qualitative and quantitative validation was performed on 100 in vivo US scans obtained from five subjects by scanning femur and vertebrae bones. Validation against expert segmentation achieved a mean dice similarity coefficient of 0.88.

CONCLUSIONS

The encouraging results obtained in this initial study suggest that the proposed method is promising enough for further evaluation. The calculated bone shadow maps could be incorporated into different ultrasound bone segmentation and registration approaches as an additional feature.

A novel method of micro-tomography geometric angle calibration with random phantom

The objective of this study is to develop and test the feasibility of applying a machine learning method for geometry calibration of angles in micro-tomography systems. Increasing importance of micro-tomography systems are manifested with escalating applications in various scenarios including but not limited to oral and maxillofacial surgery, vascular and intervention radiology, among other specific applications for purposes of diagnosis and treatments planning. There is possibility, however, actual pathology is confused by artifact of tissue structures after volume reconstruction as a result of CT construction errors. A Kernel Ridge Regression algorithm for micro-tomography geometry estimation and its corresponding phantom is developed and tested in this study. Several projection images of a rotating Random Phantom of some steel ball bearings in an unknown geometry with gantry angle information were utilized to calibrate both in-plane and out-plane rotation of the detector. The described method can also be expanded to calibrate other parameters of CT construction effortlessly. Using computer simulation, the study results validated that geometry parameters of micro-tomography system were accurately calibrated.

C-Arm Cone Beam Computed Tomography Guidance for Radiofrequency Ablation in Hepatocellular Carcinoma

OBJECTIVE

To assess the usefulness of C-arm cone beam computed tomography (CBCT) combined with ultrasound for the treatment of hepatocellular carcinoma (HCC) by radiofrequency ablation (RFA).

METHODS

Patients underwent RFA following transcatheter arterial chemoembolization (TACE) or RFA alone under ultrasound or CBCT guidance combined with ultrasound-based techniques. They were divided into 2 groups based on the use (C group) and nonuse (NC group) of CBCT guidance. The technical success of RFA and local tumor progression after the first RFA session were evaluated by dynamic contrast-enhanced imaging methods. Between-group differences were assessed retrospectively.

RESULTS

We enrolled 198 patients with 260 HCC nodules. The complete ablation rates were 63.0 and 89.4% in the NC and C groups, respectively. In log-rank testing, local tumor progression occurred significantly more often in the NC group when RFA was used without TACE, in males when des-gamma-carboxy prothrombin was ≥29 mAU/mL, and when the diameter of a nodule was ≥18 mm. On Cox proportional-hazards regression analysis, the NC group, RFA alone without TACE, and male gender were significant independent variables.

CONCLUSION

TACE followed by RFA under CBCT and ultrasound guidance improves the reliability of ablation of target HCC nodules, reduces the need for additional treatment sessions, and prevents local tumor progression.

Investigation of cone-beam CT image quality trade-off for image-guided radiation therapy

It is well-known that projections acquired over an angular range slightly over 180° (so-called short scan) are sufficient for fan-beam reconstruction. However, due to practical imaging conditions (projection data and reconstruction image discretization, physical factors, and data noise), the short-scan reconstructions may have different appearances and properties from the full-scan (scans over 360°) reconstructions. Nevertheless, short-scan configurations have been used in applications such as cone-beam CT (CBCT) for head-neck-cancer image-guided radiation therapy (IGRT) that only requires a small field of view due to the potential reduced imaging time and dose. In this work, we studied the image quality trade-off for full, short, and full/short scan configurations with both conventional filtered-backprojection (FBP) reconstruction and iterative reconstruction algorithms based on total-variation (TV) minimization for head-neck-cancer IGRT. Anthropomorphic and Catphan phantoms were scanned at different exposure levels with a clinical scanner used in IGRT. Both visualization- and numerical-metric-based evaluation studies were performed. The results indicate that the optimal exposure level and number of views are in the middle range for both FBP and TV-based iterative algorithms and the optimization is object-dependent and task-dependent. The optimal view numbers decrease with the total exposure levels for both FBP and TV-based algorithms. The results also indicate there are slight differences between FBP and TV-based iterative algorithms for the image quality trade-off: FBP seems to be more in favor of larger number of views while the TV-based algorithm is more robust to different data conditions (number of views and exposure levels) than the FBP algorithm. The studies can provide a general guideline for image-quality optimization for CBCT used in IGRT and other applications.

Three-dimensional C-arm computed tomography combined with fluoroscopic guided pediculoplasty for treatment of vertebral body metastasis with lytic pedicle

The aim of this retrospective study was to evaluate a percutaneous pediculoplasty (PP) technique, using 3-dimensional C-arm CT reformation combined with fluoroscopic guidance for patients presented vertebral body metastasis with lytic pedicle. Thirteen patients (average age 57.8 years) were treated through lytic pedicle approach in our study. Subjective good and partial pain relief was reported with Visual Analogue Scale reduction ≥ 4 in 11/13 patients at 1 month after procedure, two patients with insufficient pain relief died from clinical complications unrelated with PP at 3 month follow-up. Pain relief was maintained in 10 patients at 6 month post-procedural follow-up. One patient died from underlying disease unrelated with the procedure at 5 month follow-up. PP through the lytic pedicle approach under 3-dimensional C-arm CT reformation combined with fluoroscopic guidance was a feasible, safe, and minimally invasive procedure that could provide both the precise control of needle placement and cement injection with one imaging system.

Intraoperative 3-dimensional imaging of scaphoid fracture reduction and fixation

INTRODUCTION

We examined the clinical benefit of two intraoperative three-dimensional imaging modalities for reduction and fixation of scaphoid fractures.

HYPOTHESIS

Our hypothesis was that three dimensional imaging will aid in operative care in comparison with standard fluoroscopy.

METHODS

In 25 consecutive patients treated for fractures, after satisfactory reduction and fixation was obtained with a single Kirschner wire using fluoroscopy, intraoperative three-dimensional visualization was performed. The quality of fracture reduction, wire position and extrusion of the wire were examined.

RESULTS

In two of the 25 cases, after three-dimensional visualization, malreduction of the fracture was seen and the reduction revised. Artifact and the dependency on technologist performance, limited the use of these modalities to locate the wire accurately.

DISCUSSION

Diagnosis of malreduction of a scaphoid fracture is possible with 3-dimensional modalities. Utilization of these systems is still limited by technical factors.

Evaluation of intensity of artefacts in CBCT by radio-opacity of composite simulation models of implants in vitro

OBJECTIVES

The aim was to compare the intensity of artefacts in CBCT images caused by different percentages of radio-opacifying material in composite simulation models of implants. Titanium and zirconia models of implants were used as a reference for the evaluation of the intensity of artefacts.

METHODS

Seven different percentages of radio-opacifying BaAlSiO2 fillers were added to composite resin to fabricate seven step wedges and simulation models of implants. Titanium and zirconia simulation models of implants were also fabricated. Aluminium step wedge was used as a reference for the measurement of grey values in intraoral radiographs. Step wedges were exposed with a Planmeca Intra X-ray machine (Planmeca Oy, Helsinki, Finland). All composite, titanium and zirconia simulation models of implants were exposed with a SCANORA(®) 3D dental X-ray machine (Soredex, Tuusula, Finland). Images and grey values were analysed with ImageJ software (National Institutes of Health, Bethesda, MD). To demonstrate possible artefacts between all the simulation models of implants, the images were also visually compared with each other using ImageJ software.

RESULTS

Artefacts were clearly present in CBCT images caused by titanium and zirconia and when the composite material consisted at least 20% BaAlSiO2. The intensity of artefacts increased when the radio-opacity of the composite material increased.

CONCLUSIONS

Materials containing less radio-opacity produce less pronounced artefacts. The cut-off point for artefacts is at 20% radio-opaque filling material in composite material.

Can C-arm cone-beam CT detect a micro-embolic effect after TheraSphere radioembolization of neuroendocrine and carcinoid liver metastasis?

RATIONAL AND OBJECTIVE

Radioembolization with yttrium-90 microspheres is a therapy that is used for hepatic tumors. 20-30 μm microspheres loaded with Y90 are supposedly occluding tumor vessels at the capillary level. Then, these spheres deliver high-dose radiation to the tumor. However, this theoretical embolic effect has never been appreciated in imaging. Dual-Phase cone-beam computed tomography (DPCBCT) is a multi-phasic intra-procedural scan that uses only one contrast media injection to visualize early (feeding vessel) and delayed (capillary level) tumor enhancement. The purpose of this study was to determine whether there is a micro-embolic effect induced by TheraSpheres® (MDS Nordion, Ottawa, Ontario, Canada) at the capillary level by using DPCBCT imaging.

MATERIALS AND METHODS

14 patients with 72 carcinoid or neuroendocrine tumors were treated with radioembolization, and all underwent DPCBCT (Allura Xper, Philips Healthcare) imaging before and immediately after radioembolization with TheraSpheres®. Tumor enhancement was measured in each phase by drawing a region of interest within the tumors.

RESULTS

72 tumors were evaluated: average tumor density in the early arterial phase was 241 and 230 Hounsfield units (HU) (p<0.001) before and after radioembolization, respectively; the average density in the delayed arterial phase was 226 and 161 HU (p<0.001) before and after radioembolization, respectively. Average difference in tumor attenuation before and after radioembolization in early arterial and delayed phase was 11 HU and 64 HU (p<0.001), respectively.

CONCLUSION

The significant decrease in tumor enhancement in the DPCBCT delayed phase after TheraSpheres® injection indicates that there is an appreciable microembolic effect at the tumor capillary bed level.

Accuracy of 3D fluoroscopy in cranial stereotactic surgery: a comparative study in phantoms and patients

BACKGROUND

To assess the precision and accuracy of 3D fluoroscopy (XT) in phantoms and patients compared to computed tomography (CT) in localizing stereotactic probes.

METHODS

Approval was obtained from the institutional research ethics board. The prospective phantom study was compared to a retrospective patient cohort. Accuracy was assessed by the mean error and precision by the mean dispersion between XT and CT with a cubic or a skull phantom containing metallic spheres installed on plates or along trajectories. Significance was assessed by Friedman's and Levene's test. Secondary endpoints were Euclidean error, other influences e.g. installed frame and radiation exposure.

RESULTS

A total of 3,342 distances were assessed in 17 XT and 13 CT phantom scans. The cubic phantom showed mean distance errors of 0.33 mm (SD + -0.46 mm) for XT compared to 0.19 mm (SD + -0.83 mm) for CT scans (p = 0.0004) and a dispersion of 0.22 mm (XT) and 0.70 mm (CT). The dispersion was 0.36 mm with and 0.63 mm without a stereotactic frame (p < 0.0001). The mean Euclidean error was 0.72 mm (SD + -0.59 mm) in the skull phantom and 1.34 mm (SD + -0.82 mm) in the patient cohort. The effective dose was 0.65 mSv for the XT and 1.12 mSv for the CT.

CONCLUSIONS

The accuracy of XT imaging in phantoms revealed a slightly lower accuracy but higher precision than the CT. The overall accuracy of XT was higher than that of the stereotactic frame allowing stereotactic localization with about half of the effective dose of a CT-scan.

Intraoperative C-arm CT imaging in angular stable plate osteosynthesis of distal radius fractures

The purpose of this study was to analyze the practicability and benefit of intraoperative C-arm computed tomography (CT) imaging in volar plate osteosynthesis of unstable distal radius fractures. During a 1 year period, intraoperative three dimensional (3D) imaging with the ARCADIS Orbic 3D was performed in addition to standard fluoroscopy in 51 cases. The volar angular stable plate oesteosyntheses were analyzed intraoperatively and, if necessary, improved immediately. The duration of the scan and radiation exposure dose were measured. On average, performance of the scan and analysis of the CT dataset took 6.7 minutes. In 31.3% of the surgeries a misplacement of screws was detected and correction was done immediately. C-arm CT imaging can easily be integrated in the normal course of surgery. As a complement to the standard 2D-fluoroscopy, the C-arm CT is a useful tool to evaluate the quality of osteosynthesis.

Toward the era of a one-stop imaging service using an angiography suite for neurovascular disorders

Transportation of patients requiring multiple diagnostic and imaging-guided therapeutic modalities is unavoidable in current radiological practice. This clinical scenario causes time delays and increased risk in the management of stroke and other neurovascular emergencies. Since the emergence of flat-detector technology in imaging practice in recent decades, studies have proven that flat-detector X-ray angiography in conjunction with contrast medium injection and specialized reconstruction algorithms can provide not only high-quality and high-resolution CT-like images but also functional information. This improvement in imaging technology allows quantitative assessment of intracranial hemodynamics and, subsequently in the same imaging session, provides treatment guidance for patients with neurovascular disorders by using only a flat-detector angiographic suite-a so-called one-stop quantitative imaging service (OSIS). In this paper, we review the recent developments in the field of flat-detector imaging and share our experience of applying this technology in neurovascular disorders such as acute ischemic stroke, cerebral aneurysm, and stenoocclusive carotid diseases.

A multiplanar radiography method for assessing cup orientation in total hip arthroplasty

Correct orientation of the acetabular cup considering patient-specific functional pelvic angles is an important factor for improving outcomes and avoiding complications after total hip arthroplasty. This study introduces a new, noninvasive radiographic tool for accurately determining a patient's specific pelvic tilt angle preoperatively, as well as accurately assessing acetabular cup orientation with respect to bony landmarks intraoperatively and postoperatively. The method was validated by imaging a bone replica model of the pelvis with implanted hip components, in comparison to digitized references, and verified with a cadaveric specimen. Pelvic tilt was measured with an accuracy of 0.1 deg and SD of 0.4 deg. Operative cup inclination and anteversion showed accuracies of 0.6 deg and 2.5 deg, with SD of 0.4 deg and 0.6 deg, respectively; these could be improved further by subtracting systematic bias. The method shows accuracy advantages over existing radiographic and fluoroscopic methods and exposes the subjects to a lower radiation dose compared to the similar computed tomography methods. These results suggest that the proposed method is feasible for assessing cup placement with reference to the functional and anatomical references. Furthermore, the ability to reference the same bony landmarks preoperatively, intraoperatively, and postoperatively has important research and clinical advantages.

Isocentric 3-dimensional C-arm imaging of component alignments in total knee arthroplasty with potential intraoperative and postoperative applications

An intraoperative imaging tool for total knee arthroplasty could help avoid poor clinical outcomes related to malalignment. We investigated the feasibility of using isocentric (ISO-C) fluoroscopic imaging for this purpose. Three-dimensional ISO-C and computed tomographic (CT) images were acquired from 6 cadaveric specimens implanted with standard knee arthroplasty components and analyzed to determine rotational alignments. In comparison with standard CT measures, the ISO-C-based measures had overall accuracies (determined as root mean square error) of 0.8° and 1.3° and corresponding SDs of 1.3° and 1.4° for the femoral and tibial components, respectively. With ISO-C imaging, it is possible to measure rotational alignment in knee arthroplasty with accuracy and repeatability comparable with CT. Isocentric imaging has strong potential as an intraoperative tool to accurately align arthroplasty components.

Radiation dose and image quality of X-ray volume imaging systems: cone-beam computed tomography, digital subtraction angiography and digital fluoroscopy

OBJECTIVE

Radiation dose and image quality estimation of three X-ray volume imaging (XVI) systems.

METHODS

A total of 126 patients were examined using three XVI systems (groups 1-3) and their data were retrospectively analysed from 2007 to 2012. Each group consisted of 42 patients and each patient was examined using cone-beam computed tomography (CBCT), digital subtraction angiography (DSA) and digital fluoroscopy (DF). Dose parameters such as dose-area product (DAP), skin entry dose (SED) and image quality parameters such as Hounsfield unit (HU), noise, signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were estimated and compared using appropriate statistical tests.

RESULTS

Mean DAP and SED were lower in recent XVI than its previous counterparts in CBCT, DSA and DF. HU of all measured locations was non-significant between the groups except the hepatic artery. Noise showed significant difference among groups (P < 0.05). Regarding CNR and SNR, the recent XVI showed a higher and significant difference compared to its previous versions. Qualitatively, CBCT showed significance between versions unlike the DSA and DF which showed non-significance.

CONCLUSION

A reduction of radiation dose was obtained for the recent-generation XVI system in CBCT, DSA and DF. Image noise was significantly lower; SNR and CNR were higher than in previous versions. The technological advancements and the reduction in the number of frames led to a significant dose reduction and improved image quality with the recent-generation XVI system.

KEY POINTS

• X-ray volume imaging (XVI) systems are increasingly used for interventional radiological procedures. • More modern XVI systems use lower radiation doses compared with earlier counterparts. • Furthermore more modern XVI systems provide higher image quality. • Technological advances reduce radiation dose and improve image quality.

Emerging technologies for image guidance and device navigation in interventional radiology

Recent developments in image-guidance and device navigation, along with emerging robotic technologies, are rapidly transforming the landscape of interventional radiology (IR). Future state-of-the-art IR procedures may include real-time three-dimensional imaging that is capable of visualizing the target organ, interventional tools, and surrounding anatomy with high spatial and temporal resolution. Remote device actuation is becoming a reality with the introduction of novel magnetic-field enabled instruments and remote robotic steering systems. Robots offer several degrees of freedom and unprecedented accuracy, stability, and dexterity during device navigation, propulsion, and actuation. Optimization of tracking and navigation of interventional tools inside the human body will be critical in converting IR suites into the minimally invasive operating theaters of the future with increased safety and unsurpassed therapeutic efficacy. In the not too distant future, individual image guidance modalities and device tracking methods could merge into autonomous, multimodality, multiparametric platforms that offer real-time data of anatomy, morphology, function, and metabolism along with on-the-fly computational modeling and remote robotic actuation. The authors provide a concise overview of the latest developments in image guidance and device navigation, while critically envisioning what the future might hold for 2020 IR procedures.

Preliminary report of three-dimensional reconstructive intraoperative C-arm in percutaneous vertebroplasty

OBJECTIVE

Percutaneous vertebroplasty (PVP) is usually carried out under three-dimensional (2D) fluoroscopic guidance. However, operative complications or bone cement distribution might be difficult to assess on the basis of only 2D radiographic projection images. We evaluated the feasibility of performing an intraoperative and postoperative examination in patients undergoing PVP by using three-dimensional (3D) reconstructive C-arm.

METHODS

Standard PVP procedures were performed on 14 consecutive patients by using a Siremobil Iso-C(3D) and a multidetector computed tomography machine. Post-processing of acquired volumetric datasets included multiplanar reconstruction (MPR) and surface shaded display (SSD). We analyzed intraoperative and immediate postoperative evaluation of the needle trajectory and bone cement distribution.

RESULTS

THE MALE : female ratio was 2 : 12; mean age of patients, 70 (range, 77-54) years; and mean T score, -3.4. The mean operation time was 52.14 min, but the time required to perform and post-process the rotational acquisitions was 7.76 min. The detection of bone cement distribution and leakage after PVP by using MPR and SSD was possible in all patients. However, detection of the safe trajectory for needle insertion was not possible.

CONCLUSION

3D rotational image acquisition can enable intra- or post-procedural assessment of vertebroplasty procedures for the detection of bone cement distribution and leakage. However, it is difficult to assess the safe trajectory for needle insertion.

Ablation margin assessment of liver tumors with intravenous contrast-enhanced C-arm computed tomography

AIM: To evaluate the feasibility of intravenous contrast-enhanced C-arm computed tomography (CT) for assessing ablative areas and margins of liver tumors.

METHODS: Twelve patients (5 men, 7 women; mean age, 69.5 years) who had liver tumors (8 hepatocellular carcinomas, 4 metastatic liver tumors; mean size, 16.3 mm; size range, 8-20 mm) and who underwent percutaneous radiofrequency ablations (RFAs) with a flat-detector C-arm system were retrospectively reviewed. Intravenously enhanced C-arm CT and multidetector computed tomography (MDCT) images were obtained at the end of the RFA sessions and 3-7 d after RFA to evaluate the ablative areas and margins. The ablated areas and margins were measured using axial plane images acquired by both imaging techniques, with prior contrast-enhanced MDCT images as the reference. The sensitivity, specificity, and positive and negative predictive values of C-arm CT for detecting insufficient ablative margins (< 5 mm) were calculated. Statistical differences in the ablative areas and margins evaluated with both imaging techniques were compared using a paired t-test.

RESULTS: All RFA procedures were technically successful. Of 48 total ablative margins, 19 (39.6%) and 20 (41.6%) margins were found to be insufficient with C-arm CT and MDCT, respectively. Moreover, there were no significant differences between these 2 imaging techniques in the detection of these insufficient ablative margins. The sensitivity, specificity, and positive and negative predictive values for detecting insufficient margins by C-arm CT were 90.0%, 96.4%, 94.7% and 93.1%, respectively. The mean estimated ablative areas calculated from C-arm CT (462.5 ± 202.1 mm²) and from MDCT (441.2 ± 212.5 mm²) were not significantly different. The mean ablative margins evaluated by C-arm CT (6.4 ± 2.2 mm) and by MDCT (6.0 ± 2.4 mm) were also not significantly different.

CONCLUSION: The efficacy of intravenous contrast-enhanced C-arm CT in assessing the ablative areas and margins after RFA of liver tumors is nearly equivalent to that of MDCT.

Laparoscopic radical nephrectomy under near real-time three-dimensional surgical navigation with C-arm cone beam computed tomography

OBJECTIVE

The aim of this study was to demonstrate the advantages of C-arm cone beam computed tomography for imaging guidance of laparoscopic radical nephrectomy (LRN).

METHODS

Four patients referred to the authors' institution for LRN were included in this study. To visualize the renal vascular anatomy, the Iopamiron 300 contrast agent was injected intravenously. The surgeon could adjust the viewing angle of the images and rotate the reconstructed three-dimensional (3D) image manually by using a mouse-like controller. Using the near real-time 3D navigation images, the surgeon was able to recognize the renal vascular anatomy, and more easily perform the LRN.

RESULTS

All procedures were successfully performed with a satisfactory diagnostic yield or therapeutic effect without procedure-related complications.

CONCLUSION

This novel technology has great potential for application in LRN because it enables accurate depiction of the renal vessels and increases surgeon confidence.

Automatic bone localization and fracture detection from volumetric ultrasound images using 3-D local phase features

This article presents a novel method for bone segmentation from three-dimensional (3-D) ultrasound images that derives intensity-invariant 3-D local image phase measures that are then employed for extracting ridge-like features similar to those that occur at soft tissue/bone interfaces. The main contributions in this article include: (1) the extension of our previously proposed phase-symmetry-based bone surface extraction from two-dimensional (2-D) to 3-D images using 3-D Log-Gabor filters; (2) the design of a new framework for accuracy evaluation based on using computed tomography as a gold standard that allows the assessment of surface localization accuracy across the entire 3-D surface; (3) the quantitative validation of accuracy of our 3-D phase-processing approach on both intact and fractured bone surfaces using phantoms and ex vivo 3-D ultrasound scans; and (4) the qualitative validation obtained by scanning emergency room patients with distal radius and pelvis fractures. We show a 41% improvement in surface localization error over the previous 2-D phase symmetry method. The results demonstrate clearly visible segmentations of bone surfaces with a localization accuracy of <0.6 mm and mean errors in estimating fracture displacements below 0.6 mm. The results show that the proposed method is successful even for situations when the bone surface response is weak due to shadowing from muscle and fascia interfaces above the bone, which is a situation where the 2-D method fails.

Three-dimensional C-arm computed tomography reformation combined with fluoroscopic-guided sacroplasty for sacral metastases

The aim of this retrospective study was to evaluate a sacroplasty technique, using three-dimensional C-arm CT reformation combined with fluoroscopic guidance for patients with severe painful sacral metastases. We studied the data of seven patients (average age 55.7 years) treated through trans-sacroiliac joint approach with the technique. Patients with additional thoracolumbar osteolytic metastases (five out of seven) also received concomitant vertebroplasty accordingly. Subjective significant pain relief was reported with visual analogue scale reduction ≥4 in all seven patients at 1 month after procedure, six out of seven at 3 months, and five out of six at 6 months. Pain recurrence was reported in two patients at 3 and 6 months follow-up, respectively, associated with their clinical evidence of tumor progression. One patient died from underlying disease unrelated with the procedure. Sacroplasty under three-dimensional C-arm CT reformation combined with fluoroscopic guidance was a feasible, safe, and minimally invasive procedure that could provide both the precise control of needle placement and cement injection with one imaging system.

Use of cone beam computed tomography in otolaryngologic treatments

Cone beam computed tomography (CBCT) allows us to evaluate 3-dimensional (3D) morphology of the maxillofacial skeleton and also used in dentomaxillofacial imaging to solve complex diagnostic and treatment planning problems such as craniofacial fractures, temporamandibular dysfunctions or sinus imaging. CBCT uses a rectangular or round 2D detector, which allows a single rotation of the gantry to generate a scan of the entire region of interest. Technological and application-specific factors such as development of compact, relatively low-cost, high-quality, large, flat-panel detector arrays; the availability of low-cost computers with processing power sufficient for cone beam image reconstruction; the fabrication of highly efficient radiograph tubes capable of multiple exposures necessary for cone beam scanning at prices lower than those currently used for fan beam CT; and limited volume scanning (e.g., head and neck) eliminating the need for subsecond gantry rotation speeds make this possible. The objective of this study is to review published evidence for CBCT having an important role in ORL treatments. We aimed to review all the available literature about the CBCT imagination in ORL treatments. Systematic literature search was performed using PubMed and Ovid. Additional literature was retrieved from reference lists in the articles. Systematic analysis of the literature from 1998 to 2010 was performed. A total of 40 abstracts were evaluated independently by two members of the project group, and 38 articles were included in the review.

Assessment of two 3-D fluoroscopic systems for articular fracture reduction: a cadaver study

OBJECTIVE

The most commonly used imaging device for assessment of fracture reduction is the two-dimensional X-ray fluoroscope. Two recently introduced 3D fluoroscopic devices, the Siremobil ISO-C3D (Siemens) and the C-InSight (Mazor Surgical Technologies), enable the surgeon to obtain spatial information for the assessment of articular reduction and hardware placement. The purpose of this study was to assess the reliability and accuracy of these two 3D fluoroscopic systems in measuring articular reduction in a cadaveric tibial plateau fracture.

METHODS

Six cadaveric knee specimens were osteotomized at the lateral tibial plateau and fixed with a maximal articular step-off of 0, 1, 2.5, 5 and 7.5 mm. Each specimen was scanned 10 times with two 3D fluoroscopes, the Siremobil ISO-C3D and the C-InSight. The resulting images were reformatted and interpreted for articular displacements at four different locations at the plateau level and were compared with high-resolution CT scans by an independent observer.

RESULTS

For the non-displaced fracture, no displacement (mean < 0.1 mm) was observed in either modality. The mean scanning time for the ISO-C3D was 2 min, while each C-InSight scan took 20 s. The readings at four different points along the malreduced fractures were similar for most measurements with either of the two modalities. The C-InSight readings were less accurate than those of the ISO-C3D, relative to the CT scan, but most errors were within clinically acceptable limits (< 2 mm) and used less radiation.

CONCLUSIONS

Intraoperative 3D fluoroscopes can detect clinically significant intra-articular step-off with acceptable measurement errors, using newer devices that enable the use of a conventional C-arm and reduced radiation.

[Radiological procedures in the traumatised wrist]

Injuries of the wrist are difficult to diagnose because of the complex and narrow anatomic structures. On the basis of precise clinical examination, X-rays, CT and MRI are valuable additional tools that can be used. In the case of bone injury, spiral computer tomography with multiplanar reformatting is currently the method of choice. MRI is indicated for the identification of soft tissue or ligamentous injury and avital fragments or necrosis. Other diagnostic tools for the wrist are currently of minor importance. Technical and methodological innovations allow ever better visualisation and classification of lesions, as well as their extent, thus enabling more targeted therapy. However, prerequisites of effective use include differential assessment and precise knowledge of the procedures.

C-arm cone beam CT for hepatic tumor ablation under real-time 3D imaging

OBJECTIVE

We describe our experience with the application of a novel technology in which fluoroscopy and 3D imaging from C-arm cone beam CT systems are combined with integrated navigation software.

CONCLUSION

We applied this technology to five cases in which radiofrequency ablation was performed for hepatocellular carcinoma. Technical success was achieved without treatment-related complications in all cases. We conclude that this novel technology is potentially useful for targeting hepatic lesions.

C-arm-based mobile computed tomography: a comparison with established imaging on the basis of simulated treatments of talus neck fractures in a cadaveric study

OBJECTIVE

To analyse the image quality and diagnostic effectiveness of a new C-arm-based 3D imaging method (C-arm-CT) for intraoperative evaluation of screw osteosyntheses adjacent to a peripheral joint.

MATERIALS AND METHODS

Insertion of screws into four cadaveric specimens simulated the surgical treatment of talus neck fractures. Ten orthopedic surgeons and 10 radiologists evaluated X-ray, C-arm fluoroscopy, C-arm-CT and CT images.

RESULTS

The best image quality was obtained with X-rays (p < 0.001), followed by C-arm fluoroscopy (2D) and CT, with the C-arm-CT (3D) being rated lowest (p < 0.001). The most correct diagnoses were obtained with CT and C-arm-CT (with no statistical difference between them), while C-arm-fluoroscopy was inferior (p < 0.001) and X-rays were the worst (p < 0.05).

CONCLUSIONS

Even if the image quality of C-arm-CT is definitely inferior to that of CT, screw misplacements can be reliably detected using C-arm-CT. As compared to the current standard procedures (intraoperative fluoroscopy and postoperative radiography), C-arm-CT performed better. C-arm-CT is ideally suited to the intraoperative diagnosis of high-contrast inquiries like bone fragments and OS material, especially at the extremities. Coupling of the new 3D imaging to existing navigation systems is possible. C-arm-CT will support the further development and implementation of open and minimally invasive surgical procedures.

Dosimetry and image quality of four dental cone beam computed tomography scanners compared with multislice computed tomography scanners

OBJECTIVES

The aim of this study was to evaluate the radiation dose and image quality of four dental cone beam CT (CBCT) scanners, and to compare them with those of two multislice CT (MSCT) scanners.

METHODS

Tissue doses were measured using a tissue-equivalent anthropomorphic RANDO Head Phantom((R)) with thermoluminescence dosemeters (TLD). An RSVP Head Phantom(TM) with a specially designed cylindrical insert was used for comparison of image quality and absorbed dose. Image quality was evaluated in the form of contrast-to-noise ratio (CNR) and modulation transfer function (MTF).

RESULTS

Using standard imaging parameters, the effective doses varied between 14 microSv and 269 microSv (International Commission on Radiation Protection (ICRP) 1990) and 27 microSv and 674 microSv (ICRP 2008) with the CBCT scanners, and between 350 microSv and 742 microSv (ICRP 1990) and 685 microSv and 1410 microSv (ICRP 2008) with the MSCT scanners. The CNR of the CBCT and MSCT scanners were 8.2-18.8 and 13.6-20.7, respectively. Low-dose MSCT protocols provided CNRs comparable with those from CBCT scanners. The 10% MTF of the CBCT scanners varied between 0.1 mm(-1) and 0.8 mm(-1), and was 0.5 mm(-1) for all the MSCT protocols examined.

CONCLUSIONS

CBCT scanners provide adequate image quality for dentomaxillofacial examinations while delivering considerably smaller effective doses to the patient. Large variations in patient dose and image quality emphasize the importance of optimizing imaging parameters in both CBCT and MSCT examinations.

Detection of hepatocellular carcinoma by CT during arterial portography using a cone-beam CT technology: comparison with conventional CTAP

BACKGROUND

To evaluate the detectability of hepatocellular carcinoma (HCC) by computed tomography during arterial portography (CTAP) using cone-beam CT technology (CBCTAP) by comparing it with conventional CTAP.

METHODS

Forty-four HCC lesions (mean diameter 1.9 +/- 1.1 cm) of 24 patients who sequentially underwent conventional CTAP and CBCTAP during the same angiography session were evaluated. CBCTAP findings of each tumor were classed into three grades as compared to conventional CTAP: optimal; suboptimal; and nondiagnostic.

RESULTS

All CBCTAP images had image artifacts from the catheter placed in the superior mesenteric artery and enhanced portal veins. Additionally, the contrast between HCC lesion and surrounding liver parenchyma of CBCTAP images was less than that of CTAP images. Of the 44 tumors, findings of 31 nodules (mean 2.2 +/- 1.2 cm) (70.5%) were classed as optimal. Eight nodules (mean 1.4 +/- 0.8 cm) (18.2%) were classed as suboptimal. Five nodules (mean 1.0 +/- 0.1 cm) (11.4%) including two located in the outside of field of view were classed as nondiagnostic.

CONCLUSION

CBCTAP had sufficient image quality to detect almost all small HCC lesions compared to conventional CTAP and could depict approximately 89% of HCC nodules, including eight suboptimal lesions.

Three-dimensional C-arm cone-beam CT: applications in the interventional suite

C-arm cone-beam computed tomography (CT) with a flat-panel detector represents the next generation of imaging technology available in the interventional radiology suite and is predicted to be the platform for many of the three-dimensional (3D) roadmapping and navigational tools that will emerge in parallel with its integration. The combination of current and unappreciated capabilities may be the foundation on which improvements in both safety and effectiveness of complex vascular and nonvascular interventional procedures become possible. These improvements include multiplanar soft tissue imaging, enhanced pretreatment target lesion roadmapping and guidance, and the ability for immediate multiplanar posttreatment assessment. These key features alone may translate to a reduction in the use of iodinated contrast media, a decrease in the radiation dose to the patient and operator, and an increase in the therapeutic index (increase in safety-vs-benefit ratio). In routine practice, imaging information obtained with C-arm cone-beam CT provides a subjective level of confidence factor to the operator that has not yet been thoroughly quantified.

X-ray based imaging for computer-assisted surgery

X-ray based imaging is routinely used for preoperative diagnosis and planning, for intraoperative guidance and control, and for the postoperative evaluation of computer-assisted surgery (CAS) in the majority of its applications. Standard radiography, fluoroscopy and computed tomography (CT) are the modalities of outstanding importance. In this report we will review the state of the art in fluoroscopy and in CT with respect to technology and physics, but -- except for detector technology -- we will neglect standard radiography. Recent technical developments which aim at providing CT capabilities for standard fluoroscopy equipment are of particular topical importance; they can significantly improve workflow in the operating room (OR). Considerations regarding x-ray doses are of high concern. Our analysis indicates that most types of applications, including CT, do not bear considerable risks. However, fluoroscopic interventions with long exposure times have to be carefully monitored.

[Radiological procedures in the traumatised wrist]

Injuries of the wrist are difficult to diagnose because of the complex and narrow anatomic structures. On the basis of precise clinical examination, X-rays, CT and MRI are valuable additional tools that can be used. In the case of bone injury, spiral computer tomography with multiplanar reformatting is currently the method of choice. MRI is indicated for the identification of soft tissue or ligamentous injury and avital fragments or necrosis. Other diagnostic tools for the wrist are currently of minor importance. Technical and methodological innovations allow ever better visualisation and classification of lesions, as well as their extent, thus enabling more targeted therapy. However, prerequisites of effective use include differential assessment and precise knowledge of the procedures.

Three-dimensional C-arm computed tomography-guided sacroplasty for the treatment of sacral body fracture

STUDY DESIGN

Case report.

OBJECTIVE

To report our results of a sacroplasty technique, using 3-dimensional C-arm CT for the treatment of sacral body fracture.

SUMMARY OF BACKGROUND DATA

Sacroplasty may provide symptomatic relief and hasten recovery in the treatment of sacral insufficiency fractures. To our knowledge, there is no case report in the literature describing the application of sacroplasty for the treatment of sacral body fracture. We present a case of patient who had percutaneous sacroplasty for sacral body fracture and sacral alar fracture under 3-dimensional C-arm CT guidance and discuss the clinical results and technical considerations.

METHODS

The procedure included a standard prone positioning of the patient and the area to be treated was prepared in a strictly sterile manner, and a local anesthesia was used. After a small skin incision, an 11-gauge vertebroplasty needle was positioned at the entry point in the sacrum. Then, the needle was inclined, directed, and advanced from the posterior aspect to the anterior aspect of the sacral vertebral body. PMMA cement was incrementally introduced in 0.5 mL aliquots and the volume of PMMA cement injected was total 4 mL. Precise needle placement and PMMA cement injection was performed under the 3-dimensional C-arm CT system and the right sacral alar region was performed in a similar manner.

RESULTS

There were no peri-procedural complications occurred and the patient experienced an immediate and substantial pain relief that was persistent during a 12-month follow-up.

CONCLUSIONS

3-dimensional C-arm CT-guided sacroplasty is a safe, practical, and effective solution to treatment of sacral body fracture.

Intraoperative cone-beam computed tomography in oral and maxillofacial surgery using a C-arm prototype: first clinical experiences after treatment of zygomaticomaxillary complex fractures

PURPOSE

To describe the first clinical applications of intraoperative cone-beam computed tomography with an integrated flat-panel detector in oral and maxillofacial surgery after surgical treatment of zygomaticomaxillary complex fractures

PATIENTS AND METHODS

Nine cone-beam computed tomography datasets of patients with zygomaticomaxillary complex fractures were intraoperatively acquired using a mobile isocentric C-arm (PowerMobil; Siemens Medical Solutions, Erlangen, Germany), including a flat-panel detector. Datasets based on 400, 200, and 100 fluoroscopic images were performed with different tube currents (4.6 mA, 3.3 mA, 2.3 mA, 1.2 mA, and 0.5 mA) and a current tube voltage of 100 kV. Postprocessing resulted in 15 different datasets available for comparison with corresponding preoperative computed tomography datasets. Four oral and maxillofacial surgeons and 2 experienced radiologists evaluated each dataset regarding noise, transition, and the delimitation of landmarks.

RESULTS

All examinations were successfully performed. Reconstructed datasets showed high-resolution images of all midfacial osseous structures in near-computed tomography quality. Regarding high-contrast structures, detailed analyses of datasets acquired in this study suggest that the parameters 400 projections, 1.2 mA, and 100 kV are sufficient. In terms of soft-tissue visualization, a higher level of mA seems preferable.

CONCLUSIONS

The tested prototype predicts a new era in cone-beam computed tomography imaging. The integration of a flat-panel detector will overcome the limitations of current available systems. The size of the field of view is increased allowing regularly the visualization of the whole facial skeleton. Particularly in cases of open reduction of unilateral fractures, the assessment of symmetry is of clinical value.

Usefulness of cone-beam computed tomography during ultraselective transcatheter arterial chemoembolization for small hepatocellular carcinomas that cannot be demonstrated on angiography

This study evaluated the usefulness of cone-beam computed tomography (CBCT) during ultraselective transcatheter arterial chemoembolization (TACE) for hepatocellular carcinomas (HCC) that could not be demonstrated on angiography. Twenty-eight patients with 33 angiographically occult tumors (mean diameter 1.3 +/- 0.3 cm) were enrolled in the study. The ability of CBCT during arterial portography (CBCTAP), during hepatic arteriography (CBCTHA), and after iodized oil injection (LipCBCT) to detect HCC lesions was retrospectively analyzed. The technical success of TACE was divided into three grades: complete (the embolized area included the entire tumor with at least a 5-mm wide margin), adequate (the embolized area included the entire tumor but without a 5-mm wide margin in parts), and incomplete (the embolized area did not include the entire tumor) according to computed axial tomographic (CAT) images obtained 1 week after TACE. Local tumor progression was also evaluated. CBCTAP, CBCTHA, and LipCBCT detected HCC lesions in 93.9% (31 of 33), 96.7% (29 of 30), and 100% (29 of 29) of patients, respectively. A single branch was embolized in 28 tumors, and 2 branches were embolized in five tumors. Twenty-seven tumors (81.8%) were classed as complete, and 6 (18.2%) were classed as adequate. None of the tumors were classed as incomplete. Twenty-five tumors (75.8%) had not recurred during 12.0 +/- 6.2 months. Eight tumors (24.2%), 5 (18.5%) of 27 complete success and 3 (50%) of 6 adequate success, recurred during 10.1 +/- 6.2 months. CBCT during TACE is useful in detecting and treating small HCC lesions that cannot not be demonstrated on angiography.

Three-dimensional C-arm cone-beam CT: applications in the interventional suite

C-arm cone-beam computed tomography (CT) with a flat-panel detector represents the next generation of imaging technology available in the interventional radiology suite and is predicted to be the platform for many of the three-dimensional (3D) roadmapping and navigational tools that will emerge in parallel with its integration. The combination of current and unappreciated capabilities may be the foundation on which improvements in both safety and effectiveness of complex vascular and nonvascular interventional procedures become possible. These improvements include multiplanar soft tissue imaging, enhanced pretreatment target lesion roadmapping and guidance, and the ability for immediate multiplanar posttreatment assessment. These key features alone may translate to a reduction in the use of iodinated contrast media, a decrease in the radiation dose to the patient and operator, and an increase in the therapeutic index (increase in the safety-vs-benefit ratio). In routine practice, imaging information obtained with C-arm cone-beam CT provides a subjective level of confidence factor to the operator that has not yet been thoroughly quantified.