Diagnostic Accuracy of Cone-Beam CT for Acute Intracranial Hemorrhage: A Systematic Review and Meta-Analysis

OBJECTIVE

Our purpose was to synthesize evidence in the literature to determine the diagnostic accuracy of cone-beam CT (CBCT) for the detection of intracranial hemorrhage (ICH) and hemorrhage types, including intraparenchymal hemorrhage (IPH), subarachnoid hemorrhage (SAH), and intraventricular hemorrhage (IVH).

METHODS

We performed a meta-analysis following the Preferred Reporting Items for Systematic Review and Meta-Analyses guidelines. Our protocol was registered with International Prospective Register of Systematic Reviews (PROSPERO-CRD42021261915). Systematic searches were last performed on April 30, 2024, in EMBASE, PubMed, Web-of-Science, Scopus, and Cumulative Index to Nursing and Allied Health Literature databases. Inclusion criteria were (1) studies reporting diagnostic metrics of CBCT for ICH and (2) studies using a reference standard to determine ICH. Exclusion criteria were (1) case reports, abstracts, reviews and (2) studies without patient-level data. Pooled estimates and 95% confidence intervals (CIs) were calculated for diagnostic odds ratios (DORs), sensitivity, and specificity using random-effects and common-effects models. Mixed methods appraisal tool was used to evaluate risk of bias.

RESULTS

Seven studies were included in the meta-analysis yielding 466 patients. Mean or median age ranged from 54 to 75 years. Female patients represented 51.4% (222 of 432) in reported studies. Multidetector CT was the reference standard in all studies. DOR, pooled sensitivity, and pooled specificity for ICH were 5.28 (95% CI: 4.11-6.46), 0.88 (95% CI: 0.79-0.97), and 0.99 (95% CI: 0.98-1.0). Pooled sensitivity for IPH, SAH, and IVH was 0.98 (95% CI: 0.95-1.0), 0.82 (95% CI: 0.57-1.0), and 0.78 (95% CI: 0.55-1.0). Pooled specificity for IPH, SAH, and IVH was 0.99 (95% CI: 0.98-1.0), 0.99 (95% CI: 0.97-1.0), and 1.0 (95% CI: 0.98-1.0).

DISCUSSION

CBCT had moderate DOR and high pooled specificity for ICH and hemorrhage types. However, pooled sensitivity varied by hemorrhage type, with the highest sensitivity for IPH, followed by SAH and IVH.

Radiation Detectors and Sensors in Medical Imaging

Medical imaging instrumentation design and construction is based on radiation sources and radiation detectors/sensors. This review focuses on the detectors and sensors of medical imaging systems. These systems are subdivided into various categories depending on their structure, the type of radiation they capture, how the radiation is measured, how the images are formed, and the medical goals they serve. Related to medical goals, detectors fall into two major areas: (i) anatomical imaging, which mainly concerns the techniques of diagnostic radiology, and (ii) functional-molecular imaging, which mainly concerns nuclear medicine. An important parameter in the evaluation of the detectors is the combination of the quality of the diagnostic result they offer and the burden of the patient with radiation dose. The latter has to be minimized; thus, the input signal (radiation photon flux) must be kept at low levels. For this reason, the detective quantum efficiency (DQE), expressing signal-to-noise ratio transfer through an imaging system, is of primary importance. In diagnostic radiology, image quality is better than in nuclear medicine; however, in most cases, the dose is higher. On the other hand, nuclear medicine focuses on the detection of functional findings and not on the accurate spatial determination of anatomical data. Detectors are integrated into projection or tomographic imaging systems and are based on the use of scintillators with optical sensors, photoconductors, or semiconductors. Analysis and modeling of such systems can be performed employing theoretical models developed in the framework of cascaded linear systems analysis (LCSA), as well as within the signal detection theory (SDT) and information theory.

Effect of Matrix Size and Acquisition Mode on Image Quality and Radiation Dose of Ultra-High-Resolution CT of the Temporal Bone: An Anatomical Study

Purpose: To compare image quality and radiation exposure between super- and ultra-high-resolution helical and super-high-resolution volumetric CT of the temporal bone. Methods: Six cadaveric temporal bone specimens were used to evaluate key temporal bone structures using the following CT reconstruction and acquisition modes: helical and single-volume acquisition modes in super-high resolution (0.25-mm slice thickness, 10242 matrix), and helical mode in ultra-high resolution (0.25-mm slice thickness, 20482 matrix). Two observers performed 5 previously described preoperative measurements, measured noise and signal-to-noise ratios for air, and noise for bone, and rated the visualization of 5 anatomical structures on a 4-point scale, for each reconstruction mode. Radiation dose exposure was recorded for each examination. Results: There was no significant difference between any of the quantitative or qualitative measurements in any of the reconstruction and acquisition modes. There was a slight increase in noise and a decrease in signal-to-noise ratio in the air using the single-volume mode (115 ± 13.1 HU and 8.37 ± 0.91, respectively) compared to the helicoidal super-high-resolution (92.4 ± 11.8 HU and 10.8 ± 1.26, respectively) and helicoidal ultra-high-resolution (91.1 ± 10.7 HU and 10.9 ± 1.39, respectively) modes (P < .002). The volumic CT dose index was 50.9 mGy with helical acquisition and 29.8 mGy with single-volume acquisition mode (P < .0001). Conclusion: The single-volume super-high-resolution acquisition mode allows a reduction in radiation dose exposure without compromising image quality compared to helical scanning, but with a slightly lower signal-to-noise ratio in air with the single-volume mode, while there was no difference in image quality between the helical super- and ultra-high-resolution modes.

Evaluation of a prototype metal artifact reduction algorithm for cone beam CT in patients undergoing radioembolization

Metal artifacts notoriously pose significant challenge in computed tomography (CT), leading to inaccuracies in image formation and interpretation. Artifact reduction tools have been designed to improve cone beam computed tomography (CBCT) image quality by reducing artifacts caused by certain high-density materials. Metal artifact reduction (MAR) tools are specific algorithms that are applied during image reconstruction to minimize or eliminate artifacts degrading CBCT images. The purpose of the study is to evaluate the effect of a MAR algorithm on image quality in CBCT performed for evaluating patients before transarterial radioembolization (TARE). We retrospectively included 40 consecutive patients (aged 65 ± 13 years; 23 males) who underwent 45 CBCT examinations (Allura FD 20, XperCT Roll protocol, Philips Healthcare, Best, The Netherlands) in the setting of evaluation for TARE between January 2017 and December 2018. Artifacts caused by coils, catheters, and surgical clips were scored subjectively by four readers on a 5-point scale (1 = artifacts affecting diagnostic information to 5 = no artifacts) using a side-by-side display of uncorrected and MAR-corrected images. In addition, readers scored tumor visibility and vessel discrimination. MAR-corrected images were assigned higher scores, indicating better image quality. The differences between the measurements with and without MAR were most impressive for coils with a mean improvement of 1.6 points (95%CI [1.5 1.8]) on the 5-point likert scale, followed by catheters 1.4 points (95%CI [1.3 1.5]) and clips 0.7 points (95%CI [0.3 1.1]). Improvements for other artifact sources were consistent but relatively small (below 0.25 points on average). Interrater agreement was good to perfect (Kendall's W coefficient = 0.68-0.95) and was higher for MAR-corrected images, indicating that MAR improves diagnostic accuracy. A metal artifact reduction algorithm can improve diagnostic and interventional accuracy of cone beam CT in patients undergoing radioembolization by reducing artifacts caused by diagnostic catheters and coils, lowering interference of metal artifacts with adjacent major structures, and improving tumor visibility.

The Photon-Counting CT Enters the Field of Cochlear Implantation: Comparison to Angiography DynaCT and Conventional Multislice CT

INTRODUCTION

Cochlear duct length (CDL) measurement plays a role in the context of individualized cochlear implant (CI) surgery regarding an individualized selection and implantation of the CI electrode carrier and an efficient postoperative anatomy-based fitting process. The level of detail of the preoperative temporal bone CT scan depends on the imaging modality with major impact on CDL measurements and CI electrode contact position determination. The aim of this study was to evaluate the accuracy of perioperative CDL measurements and electrode contact determination in photon-counting CT (PCCT).

METHODS

Ten human fresh-frozen petrous bone specimens were examined with a first-generation PCCT. A clinically applicable radiation dose of 27.1 mGy was used. Scans were acquired before and after CI insertion. Postoperative measurement of the CDL was conducted using an otological planning software and 3D-curved multiplanar reconstruction. Investigation of electrode contact position was performed by two respective observers. Measurements were compared with a conventional multislice CT and to a high-resolution flat-panel volume CT with secondary reconstructions.

RESULTS

Pre- and postoperative CDL measurements in PCCT images showed no significant difference to high-resolution flat-panel volume CT. Postoperative CI electrode contact determination was also as precise as the flat-panel CT-based assessment. PCCT and flat-panel volume CT were equivalent concerning interobserver variability.

CONCLUSION

CDL measurement with PCCT was equivalent to flat-panel volume CT with secondary reconstructions. PCCT enabled highly precise postoperative CI electrode contact determination with substantial advantages over conventional multislice CT scanners.

Applications of Tissue Clearing in Central and Peripheral Nerves

The techniques of tissue clearing have been proposed and applied in anatomical and biomedical research since the 19th century. As we all know, the original study of the nervous system relied on serial ultrathin sections and stereoscopic techniques. The 3D visualization of the nervous system was established by software splicing and reconstruction. With the development of science and technology, microscope equipment had constantly been upgraded. Despite the great progress that has been made in this field, the workload is too complex, and it needs high technical requirements. Abundant mistakes due to manual sections were inescapable and structural integrity remained questionable. According to the classification of tissue transparency methods, we introduced the latest application of transparency methods in central and peripheral nerve research from optical imaging, molecular markers and data analysis. This review summarizes the application of transparent technology in neural pathways. We hope to provide some inspiration for the continuous optimization of tissue clearing methods.

Robotic-assisted versus manual Uro Dyna-CT-guided puncture in an ex-vivo kidney phantom

INTRODUCTION AND OBJECTIVES

Challenging percutaneous renal punctures to gain access to the kidney requiring guidance by cross-sectional imaging. To test the feasibility of robotic-assisted CT-guided punctures (RP) and compare them with manual laser-guided punctures (MP) with Uro Dyna-CT (Siemens Healthcare Solutions, Erlangen, Germany).

MATERIAL AND METHODS

The silicon kidney phantom contained target lesions of three sizes. RP were performed using a robotic assistance system (guidoo, BEC GmbH, Pfullingen, Germany) with a robotic arm (LBR med R800, KUKA AG, Augsburg, Germany) and a navigation software with a cone-beam-CT Artis zeego (Siemens Healthcare GmbH, Erlangen, Germany). MP were performed using the syngo iGuide Uro-Dyna Artis Zee Ceiling CT (Siemens Healthcare Solutions). Three urologists with varying experience performed 20 punctures each. Success rate, puncture accuracy, puncture planning time (PPT), and needle placement time (NPT) were measured and compared with ANOVA and Chi-Square Test.

RESULTS

One hundred eighteen punctures with a success rate of 100% for RP and 78% for MP were included. Puncture accuracy was significantly higher for RP. PPT (RP: 238 ± 90s, MP: 104 ± 21s) and NPT (RP: 128 ± 40s, MP: 81 ± 18s) were significantly longer for RP. The outcome variables did not differ significantly with regard to levels of investigators' experience.

CONCLUSION

The accuracy of RP was superior to that of MP. This study paves the way for first in-human application of this robotic puncture system.

Dependence of Cochlear Duct Length Measurement on the Resolution of the Imaging Dataset

HYPOTHESIS

Measurements of the cochlear duct length (CDL) are dependent on the resolution of the imaging dataset.

BACKGROUND

Previous research has shown highly precise cochlear measurements using 3D-curved multiplanar reconstruction (MPR) and flat-panel volume computed tomography (fpVCT). Thus far, however, there has been no systematic evaluation of the imaging dataset resolution required for optimal CDL measurement. Therefore, the aim of this study was to evaluate the dependence of CDL measurement on the resolution of the imaging dataset to establish a benchmark for future CDL measurements.

METHODS

fpVCT scans of 10 human petrous bone specimens were performed. CDL was measured using 3D-curved MPR with secondary reconstruction of the fpVCT scans (fpVCT SECO ) and increasing resolution from 466 to 99 μm. In addition, intraobserver variability was evaluated. A best-fit function for calculation of the CDL was developed to provide a valid tool when there are no measurements done with high-resolution imaging datasets.

RESULTS

Comparison of different imaging resolution settings showed significant differences for CDL measurement in most of the tested groups ( p < 0.05), except for the two groups with the highest resolution. Imaging datasets with a resolution lower than 200 μm showed lower intraobserver variability than the other resolution settings, although there were no clinically unacceptable errors with respect to the Bland-Altman plots. The developed best-fit function showed high accuracy for CDL calculation using resolution imaging datasets of 300 μm or lower.

CONCLUSION

3D-curved MPR in fpVCT with a resolution of the imaging dataset of 200 μm or higher revealed the most precise CDL measurement. There was no benefit of using a resolution higher than 200 μm with regard to the accuracy of the CDL measurement.

Flat panel CT versus multidetector CT in skull base imaging: are there differences in image quality?

BACKGROUND

Purpose of this study was to compare image quality of the skull base in standard 20s protocol flat panel computed tomography (FPCT) with the new time and dose improved 10s protocol as well as with 128 slice multidetector computed tomography (MDCT).

METHODS

10 whole skull preparations were scanned with either 128 slice MDCT(SOMATOM Definition AS+, Siemens, Erlangen) or FPCT (AXIOM-Artis, Siemens, Erlangen) using 10s or 20s protocol.

RESULTS

FPCT provides significantly better image quality and improved delimitation of clinically relevant structures in the anterior, temporal and posterior skull base compared to 128 slice MDCT. The 20s FPCT protocol yielded best delimitability of evaluated skull base structures. However, the shorter, dose saving 10s FPCT protocol was still significantly superior to 128 slice MDCT regarding delimitability of skull base structures and additionally showed no significant inferiority compared with the 20s FPCT protocol.

CONCLUSIONS

The 10s FPCT protocol yields a significantly better image quality at a comparable radiation dose exposure in imaging skull base structures compared to MDCT.

TRIAL REGISTRATION

371/2017BO2.

Accuracy of radiological prediction of electrode position with otological planning software and implications of high-resolution imaging

OBJECTIVES

In cochlear implantation, preoperative prediction of electrode position has recently gained increasing attention. Currently, planning is usually done by multislice CT (MSCT). However, flat-panel volume CT (fpVCT) and its secondary reconstructions (fpVCTSECO) allow for more precise visualization of the cochlea. Combined with a newly developed otological planning software, the position of every single contact can be effectively predicted. In this study it was investigated how accurately radiological prediction forecasts the postoperative electrode localization and whether higher image resolution is advantageous.

METHODS

Utilizing otological planning software (OTOPLAN®) and different clinical imaging modalities (MSCT, fpVCT and fpVCTSECO) the electrode localization [angular insertion depth (AID)] and respective contact frequencies were predicted preoperatively and examined postoperatively. Furthermore, inter-electrode-distance (IED) and inter-electrode-frequency difference (IEFD) were evaluated postoperatively.

RESULTS

Measurements revealed a preoperative overestimation of AID. Corresponding frequencies were also miscalculated. Determination of IED and IEFD revealed discrepancies at the transition from the basal to the middle turn and round window to the basal turn. All predictions and discrepancies were lowest when using fpVCTSECO.

CONCLUSION

The postoperative electrode position can be predicted quite accurately using otological planning software. However, because of several potential misjudgments, high-resolution imaging, such as offered by fpVCTSECO, should be used pre- and postoperatively.

Intraoperative Computed Tomography in Orthopaedic Trauma Surgery

BACKGROUND

When using mobile 3D C-arms, impairments in image quality occur due to artefacts caused by metal implants as well as to the limited field of view. To avoid these restrictions, special computed tomography devices were designed, in order to improve image quality and to meet requirements for intraoperative usage.

OBJECTIVES

To analyse practicability and benefits of a mobile intraoperative CT device (Airo, Brainlab, Munich, Germany) on the basis of several parameters that were obtained during a 40-month period.

MATERIALS AND METHODS

All procedures that were performed with usage of intraoperative CT between January 2017 and April 2020 were analysed with respect to anatomical region, count of scans, duration of scans, consequences drawn from the scans and use of navigation.

RESULTS

354 CT-scans were performed in 171 patients (mean 2.07 [1 - 6] scans per procedure). 47.81% of the procedures were spinal, 52.19% affected the pelvis. 83% of the procedures were navigated. In 22% of patients, improvement in implant placement or reduction was achieved; in most patients (55%), a guidewire for pedicle screws was corrected. The mean scan duration was 10.33 s (3.54 - 21.72).

CONCLUSIONS

Use of intraoperative CT was reliable and helpful. Integration in OR standards requires more effort than mobile 3D C-arms. Image quality was outstanding for intraoperative conditions and allowed proper assessment of implant placement and reduction in all cases. Due to the high financial outlay of the system and the good image quality of 3D C-arms in the extremities, we assume that this procedure can be applied in intraoperative CT in traumatological cases in spinal and pelvic surgery in high-level trauma centres.

Technical assessment of 2D and 3D imaging performance of an IGZO-based flat-panel X-ray detector

BACKGROUND

Indirect detection flat-panel detectors (FPDs) consisting of hydrogenated amorphous silicon (a-Si:H) thin-film transistors (TFTs) are a prevalent technology for digital x-ray imaging. However, their performance is challenged in applications requiring low exposure levels, high spatial resolution, and high frame rate. Emerging FPD designs using metal oxide TFTs may offer potential performance improvements compared to FPDs based on a-Si:H TFTs.

PURPOSE

This work investigates the imaging performance of a new indium gallium zinc oxide (IGZO) TFT-based detector in 2D fluoroscopy and 3D cone-beam CT (CBCT).

METHODS

The new FPD consists of a sensor array combining IGZO TFTs with a-Si:H photodiodes and a 0.7-mm thick CsI:Tl scintillator. The FPD was implemented on an x-ray imaging bench with system geometry emulating intraoperative CBCT. A conventional FPD with a-Si:H TFTs and a 0.6-mm thick CsI:Tl scintillator was similarly implemented as a basis of comparison. 2D imaging performance was characterized in terms of electronic noise, sensitivity, linearity, lag, spatial resolution (modulation transfer function, MTF), image noise (noise-power spectrum, NPS), and detective quantum efficiency (DQE) with entrance air kerma (EAK) ranging from 0.3 to 1.2 μGy. 3D imaging performance was evaluated in terms of the 3D MTF and noise-equivalent quanta (NEQ), soft-tissue contrast-to-noise ratio (CNR), and image quality evident in anthropomorphic phantoms for a range of anatomical sites and dose, with weighted air kerma, K w ${K_w}$ , ranging from 0.8 to 4.9 mGy.

RESULTS

The 2D imaging performance of the IGZO-based FPD exhibited up to ∼1.7× lower electronic noise than the a-Si:H FPD at matched pixel pitch. Furthermore, the IGZO FPD exhibited ∼27% increase in mid-frequency DQE (1 mm^-1 ) at matched pixel size and dose (EAK ≈ 1.0 μGy) and ∼11% increase after adjusting for differences in scintillator thickness. 2D spatial resolution was limited by the scintillator for each FPD. The IGZO-based FPD demonstrated improved 3D NEQ at all spatial frequencies in both head (≥25% increase for all dose levels) and body (≥10% increase for K w ${K_w}$ ≤2 mGy) imaging scenarios. These characteristics translated to improved low-contrast visualization in anthropomorphic phantoms, demonstrating ≥10% improvement in CNR and extension of the low-dose range for which the detector is input-quantum limited.

CONCLUSION

The IGZO-based FPD demonstrated improvements in electronic noise, image lag, and NEQ that translated to measurable improvements in 2D and 3D imaging performance compared to a conventional FPD based on a-Si:H TFTs. The improvements are most beneficial for 2D or 3D imaging scenarios involving low-dose and/or high-frame rate.

High-Resolution CT Imaging of the Temporal Bone: A Cadaveric Specimen Study

Objective  Super-high and ultra-high spatial resolution computed tomography (CT) imaging can be advantageous for detecting temporal bone pathology and guiding treatment strategies. Methods  Six temporal bone cadaveric specimens were used to evaluate the temporal bone microanatomic structures utilizing the following CT reconstruction modes: normal resolution (NR, 0.5-mm slice thickness, 512 ² matrix), high resolution (HR, 0.5-mm slice thickness, 1,024 ² matrix), super-high resolution (SHR, 0.25-mm slice thickness, 1,024 ² matrix), and ultra-high resolution (UHR, 0.25-mm slice thickness, 2,048 ² matrix). Noise and signal-to-noise ratio (SNR) for bone and air were measured at each reconstruction mode. Two observers assessed visualization of seven small anatomic structures using a 4-point scale at each reconstruction mode. Results  Noise was significantly higher and SNR significantly lower with increases in spatial resolution (NR, HR, and SHR). There was no statistical difference between SHR and UHR imaging with regard to noise and SNR. There was significantly improved visibility of all temporal bone osseous structures of interest with SHR and UHR imaging relative to NR imaging ( p  < 0.001) and most of the temporal bone osseous structures relative to HR imaging. There was no statistical difference in the subjective image quality between SHR and UHR imaging of the temporal bone ( p  ≥ 0.085). Conclusion  Super-high-resolution and ultra-high-resolution CT imaging results in significant improvement in image quality compared with normal-resolution and high-resolution CT imaging of the temporal bone. This preliminary study also demonstrates equivalency between super-high and ultra-high spatial resolution temporal bone CT imaging protocols for clinical use.

Distribution of symptomatic cerebral vasospasm following subarachnoid hemorrhage assessed using cone-beam CT angiography

BACKGROUND AND PURPOSE

Cone-beam CT angiography (CB-CTA) provides a three-dimensional spatial resolution which is, so far, unmatched in clinical practice compared with other conventional techniques such as two-dimensional digital subtracted angiography. We aimed to assess the distribution of symptomatic cerebral vasospasm following aneurysmal subarachnoid hemorrhage (aSAH) using CB-CTA.

METHODS

30 consecutive patients with aSAH undergoing vasospasm percutaneous balloon angioplasty (PBA) were recruited and underwent CB-CTA in this single-center prospective cohort series. Intracranial arteries were systematically analyzed by two independent observers from the large trunks to the distal cortical branches and perforators using a high-resolution reconstruction protocol. Intermediate and severe cerebral vasospasm was defined as 30-50% and >50% narrowing in the diameter of the vessel, respectively.

RESULTS

35 arterial cervical artery territories were analyzed, of which 80% were associated with clinical or radiological signs of delayed cerebral ischemia. The median spatial resolution was 150 µm (range 100-250 µm). Intermediate or severe vasospasm was observed in the proximal (86%, 95% CI 74% to 97%), middle (89%, 95% CI 78% to 99%), and distal (60%, 95% CI 44% to 76%) segments of the large trunks, as well as the cortical branches (11%, 95% CI 1% to 22%). No vasospasm was observed in basal ganglia or cortical perforators, or in arteries smaller than 900 µm. Vasospasm was more severe in middle or distal segments compared with proximal segments in 43% (95% CI 26% to 59%) of cases.

CONCLUSIONS

Our study demonstrated that symptomatic cerebral vasospasm following aSAH did not involve arteries smaller than 900 µm, and frequently predominated in middle or distal segments. These results offer new insights into the potential management options for vasospasm using PBA.

Precise evaluation of the postoperative cochlear duct length by flat-panel volume computed tomography - Application of secondary reconstructions

OBJECTIVE

There is still a lack in precise postoperative evaluation of the cochlea because of strong artifacts. This study aimed to improve accuracy of postoperative two-turn (2TL) and cochlear duct length (CDL) measurements by applying flat-panel volume computed tomography (fpVCT), secondary reconstruction (fpVCT_SECO) and three-dimensional curved multiplanar reconstruction.

METHODS

First, 10 temporal bone specimens with or without electrode were measured in multi-slice computed tomography (MSCT), fpVCT and fpVCT_SECO and compared to high-resolution micro-CT scans. Later, pre- and postoperative scans of 10 patients were analyzed in a clinical setting.

RESULTS

Concerning 2TL, no statistically significant difference was observed between implanted fpVCT_SECO and nonimplanted micro-CT in 10 temporal bone specimens. In contrast, there was a significant discrepancy for CDL (difference: -0.7 mm, P = 0.004). Nevertheless, there were no clinically unacceptable errors (±1.5 mm). These results could be confirmed in a clinical setting. Using fpVCT_SECO, CDL was slightly underestimated postoperatively (difference: -0.5 mm, P = 0.002) but without any clinically unacceptable errors.

CONCLUSION

fpVCT_SECO can be successfully applied for a precise measurement of the cochlear lengths pre- and postoperatively. However, users must be aware of a slight systematic underestimation of CDL postoperatively. These results may help to refine electrode selection and frequency mapping.

Prediction of treatment response to transarterial radioembolization of liver metastases: Radiomics analysis of pre-treatment cone-beam CT: A proof of concept study

Purpose

To investigate the potential of texture analysis and machine learning to predict treatment response to transarterial radioembolization (TARE) on pre-interventional cone-beam computed tomography (CBCT) images in patients with liver metastases.

Materials and Methods

In this IRB-approved retrospective single-center study 36 patients with a total of 104 liver metastases (56 % male, mean age 61.1 ± 13 years) underwent CBCT prior to TARE and follow-up imaging 6 months after therapy. Treatment response was evaluated according to RECIST version 1.1 and dichotomized into disease control (partial response/stable disease) versus disease progression (progressive disease). After target lesion segmentation, 104 radiomics features corresponding to seven different feature classes were extracted with the pyRadiomics package. After dimension reduction machine learning classifications were performed on a custom artificial neural network (ANN). Ten-fold cross validation on a previously unseen test data set was performed.

Results

The average administered cumulative activity from TARE was 1.6 Gbq (± 0.5 Gbq). At a mean follow-up of 5.9 ± 0.8 months disease control was achieved in 82 % of metastases. After dimension reduction, 15 of 104 (15 %) texture analysis features remained for further analysis. On a previously unseen set of liver metastases the Multilayer Perceptron ANN yielded a sensitivity of 94.2 %, specificity of 67.7 % and an area-under-the receiver operating characteristics curve of 0.85.

Conclusion

Our study indicates that texture analysis-based machine learning may has potential to predict treatment response to TARE using pre-treatment CBCT images of patients with liver metastases with high accuracy.

Robotic Assistance System for Cone-Beam Computed Tomography-Guided Percutaneous Needle Placement

Purpose

The study aimed to evaluate a new robotic assistance system (RAS) for needle placement in combination with a multi-axis C-arm angiography system for cone-beam computed tomography (CBCT) in a phantom setting.

Materials and Methods

The RAS consisted of a tool holder, dedicated planning software, and a mobile platform with a lightweight robotic arm to enable image-guided needle placement in conjunction with CBCT imaging. A CBCT scan of the phantom was performed to calibrate the robotic arm in the scan volume and to plan the different needle trajectories. The trajectory data were sent to the robot, which then positioned the tool holder along the trajectory. A 19G needle was then manually inserted into the phantom. During the control CBCT scan, the exact needle position was evaluated and any possible deviation from the target lesion measured.

Results

In total, 16 needle insertions targeting eight in- and out-of-plane sites were performed. Mean angular deviation from planned trajectory to actual needle trajectory was 1.12°. Mean deviation from target point and actual needle tip position was 2.74 mm, and mean deviation depth from the target lesion to the actual needle tip position was 2.14 mm. Mean time for needle placement was 361 s. Only differences in time required for needle placement between in- and out-of-plane trajectories (337 s vs. 380 s) were statistically significant (p = 0.0214).

Conclusion

Using this RAS for image-guided percutaneous needle placement with CBCT was precise and efficient in the phantom setting.

New Navigation Approaches for Endoscopic Lateral Skull Base Surgery

Image-guided navigation is well established for surgery of the brain and anterior skull base. Although navigation workstations have been used widely by neurosurgeons and rhinologists for decades, utilization in the lateral skull base (LSB) has been less due to stricter requirements for overall accuracy less than 1 mm in this region. Endoscopic approaches to the LSB facilitate minimally invasive surgeries with less morbidity, yet there are risks of injury to critical structures. With improvements in technology over the years, image-guided navigation for endoscopic LSB surgery can reduce operative time, optimize exposure for surgical corridors, and increase safety in difficult cases.

Highly precise navigation at the lateral skull base by the combination of flat-panel volume CT and electromagnetic navigation

This study aimed to evaluate the feasibility and accuracy of electromagnetic navigation at the lateral skull base in combination with flat panel volume computed tomography (fpVCT) datasets. A mastoidectomy and a posterior tympanotomy were performed on 10 samples of fresh frozen temporal bones. For registration, four self-drilling titanium screws were applied as fiducial markers. Multi-slice computed tomography (MSCT; 600 µm), conventional flat panel volume computed tomography (fpVCT; 466 µm), micro-fpVCT (197 µm) and secondary reconstructed fpVCT (100 µM) scans were performed and data were loaded into the navigation system. The resulting fiducial registration error (FRE) was analysed, and control of the navigation accuracy was performed. The registration process was very quick and reliable with the screws as fiducials. Compared to using the MSCT data, the micro-fpVCT data led to significantly lower FRE values, whereas conventional fpVCT and secondary reconstructed fpVCT data had no advantage in terms of accuracy. For all imaging modalities, there was no relevant visual deviation when targeting defined anatomical points with a navigation probe. fpVCT data are very well suited for electromagnetic navigation at the lateral skull base. The use of titanium screws as fiducial markers turned out to be ideal for comparing different imaging methods. A further evaluation of this approach by a clinical trial is required.

Implementation of secondary reconstructions of flat-panel volume computed tomography (fpVCT) and otological planning software for anatomically based cochlear implantation

Purpose

For further improvements in cochlear implantation, the measurement of the cochlear duct length (CDL) and the determination of the electrode contact position (ECP) are increasingly in the focus of clinical research. Usually, these items were investigated by multislice computed tomography (MSCT). The determination of ECP was only possible by research programs so far. Flat-panel volume computed tomography (fpVCT) and its secondary reconstructions (fpVCT_SECO) allow for high spatial resolution for the visualization of the temporal bone structures. Using a newly developed surgical planning software that enables the evaluation of CDL and the determination of postoperative ECP, this study aimed to investigate the combination of fpVCT and otological planning software to improve the implementation of an anatomically based cochlear implantation.

Methods

Cochlear measurements were performed utilizing surgical planning software in imaging data (MSCT, fpVCT and fpVCT_SECO) of patients with and without implanted electrodes.

Results

Measurement of the CDL by the use of an otological planning software was highly reliable using fpVCT_SECO with a lower variance between the respective measurements compared to MSCT. The determination of the inter-electrode-distance (IED) between the ECP was improved in fpVCT_SECO compared to MSCT.

Conclusion

The combination of fpVCT_SECO and otological planning software permits a simplified and more reliable analysis of the cochlea in the pre- and postoperative setting. The combination of both systems will enable further progress in the development of an anatomically based cochlear implantation.

MONTE CARLO DOSE ASSESSMENT IN DENTAL CONE-BEAM COMPUTED TOMOGRAPHY

Most dental cone-beam computed tomography (CBCT) uses an x-ray beam field covering the maxillomandibular region and the width-truncated detector geometry. The spatial dose distribution in dental CBCT is analyzed in terms of local primary and remote secondary doses by using a list-mode analysis of x-ray interactions obtained from the Monte Carlo simulations. The patient-dose benefit due to the width-truncated detector geometry is also investigated for a wide range of detector offsets. The developed dose estimation agrees with the measurement in a relative error of 7.7%. The secondary dose outside of the irradiation field becomes larger with increasing tube voltage. The dose benefit with the width-truncated geometry linearly increases as the detector-offset width is decreased. Leaving the CT image quality out of the account, the MC results reveal that the operation of dental CBCT with a lower tube voltage and a smaller detector-offset width is beneficial to the patient dose.

Precise Evaluation of the Cochlear Duct Length by Flat-panel Volume Computed Tomography (fpVCT)-Implication of Secondary Reconstructions

HYPOTHESIS

Flat-panel volume computed tomography (fpVCT) and secondary reconstruction allow for more accurate measurements of two-turn length (2TL), cochlear duct length (CDL), and angular length (AL).

BACKGROUND

Cochlear geometry is a controversially debated topic. In the meantime, there are many different studies partly reporting highly divergent values. Our aim is to discuss the differences and to propose a radiological possibility to improve cochlear measurements using 3D-curved multiplanar reconstruction and fpVCT.

METHODS

Performing different image modalities and settings, we tried to find a clinically usable option that allows for a high degree of accuracy. Therefore, we tested them against reference values of high-definition micro-computed tomography.

RESULTS

Comparison of 99 μm slice thickness secondary reconstruction of fpVCT and reference showed no significant differences for 2TL and CDL (p ≥ 0.05). Accordingly, ICC (intraclass correlation) values were excellent (ICC ≥ 0.75; lower limit of confidence interval [CI] ≥ 0.75; Cronbach's alpha [α] ≥ 0.9). Evaluating AL, there was a significant difference (difference: -17.27°; p = 0.002). The lower limit of the CI of the ICC was unacceptable (ICC = 0.944; lower limit of CI = 0.248; α = 0.990). Regarding the Bland-Altman plots, there were no clinically unacceptable errors, but a systematic underestimation of AL.

CONCLUSION

Secondary reconstruction is a suitable tool for producing reliable data that allow the accurate measurement of 2TL and CDL. The option of generating these reconstructions from raw data limits the need for higher radiation doses. Nevertheless, there is an underestimation of AL using secondary reconstructions.

Novel flat-panel cone-beam CT compared to multi-detector CT for assessment of acute ischemic stroke: A prospective study

PURPOSE

Cone beam CT (CBCT) imaging assessment of acute ischemic stroke (AIS) patients with large-vessel occlusion (LVO) in the angiosuite may improve stroke workflow and decrease time to recanalization. In order for this workflow to gain widespread acceptance, current CBCT imaging needs further development to improve image quality. Our study aimed to compare the image quality of a new CBCT protocol performed directly in the angiosuite with imaging from multidetector CT as a gold standard.

METHODS

AIS patients with an LVO who were candidates for endovascular treatment were prospectively included in this study. Following conventional multidetector CT (MDCT), patients underwent unenhanced cone beam CT (XperCT, Philips) imaging in the angiosuite, using two different protocols: a standard 20.8 s XperCT and/or an improved 10.4 s XperCT protocol. Images were evaluated using both qualitative and quantitative methods.

RESULTS

We included 65 patients in the study. Patients received CBCT imaging prior to endovascular treatment; 18 patients were assessed with a standard 20.8 s protocol scans and 47 with a newer 10.4 s scan. The quantitative analysis showed that the mean contrast-to-noise ratio (CNR) was significantly higher for the newer 10.4 s protocol compared with the 20.8 s protocol (2.08 +/- 0.64 vs. 1.15 +/- 0.27, p < 0.004) and the mean image noise was significantly lower for the 10.4 s XperCTs when compared with the 20.8 s XperCTs (6.30 +/- 1.34 vs. 7.82 +/- 2.03, p=<0.003). Qualitative analysis, including 6 measures of image quality, demonstrated that 74.1 % of the 10.4 s XperCT scans were ranked as 'Acceptable' for assessing parenchymal imaging in AIS patients(scoring 3-5 points on a 5-point Likert-scale), compared with 32.4 % of the standard 20.8 s XperCT and 100 % of the MDCT scans. Compared to the MDCT studies, 83 % of the 10.4 s XperCT scans were deemed sufficient image quality for a direct-to-angiosuite selection, compared to only 11 % for the standard 20.8 s scans. The largest image quality improvements included grey/white matter differentiation (59 % improvement), and reduction of image noise and artefacts (63 % & 50 % improvement, respectively).

CONCLUSIONS

Continued advances in cone-beam CT allow marked improvements in image quality for the assessment of brain parenchyma, which supports a direct-to-angiosuite approach for AIS patients eligible for thrombectomy treatment.

Cone-Beam CT-Guided Lung Biopsies: Results in 94 Patients

BACKGROUND

The aim of this study was to evaluate the diagnostic capacity of Cone-Beam computed tomography (CT)-guided transthoracic percutaneous biopsies on lung lesions in our setting and to detect risk factors for possible complications.

METHODS

Retrospective study of 98 biopsies in 94 patients, performed between May 2017 and January 2020. To obtain them, a 17G coaxial puncture system and a Siemens Artis Zee Floor vc21 archwire were used. Descriptive data of the patients, their position at the time of puncture, location and size of the lesions, number of cylinders extracted, and complications were recorded. Additionally, the fluoroscopy time used in each case, the doses/area and the estimated total doses received by the patients were recorded.

RESULTS

Technical success was 96.8%. A total of 87 (92.5%) malignant lesions and 3 (3.1%) benign lesions were diagnosed. The sensitivity was 91.5% and the specificity was 100%. We registered three technical failures and three false negatives initially. Complications included 38 (38.8%) pneumothorax and 2 (2%) hemoptysis cases. Fluoroscopy time used in each case was 4.99 min and the product of the dose area is 11,722.4 microGy/m².

CONCLUSION

The transthoracic biopsy performed with Cone-Beam CT is accurate and safe in expert hands for the diagnosis of lung lesions. Complications are rare and the radiation dose used was not excessive.

A comparative study of trabecular bone micro-structural measurements using different CT modalities

Osteoporosis, characterized by reduced bone mineral density and micro-architectural degeneration, significantly enhances fracture-risk. There are several viable methods for trabecular bone micro-imaging, which widely vary in terms of technology, reconstruction principle, spatial resolution, and acquisition time. We have performed an excised cadaveric bone specimen study to evaluate different computed tomography (CT)-imaging modalities for trabecular bone micro-structural analysis. Excised cadaveric bone specimens from the distal radius were scanned using micro-CT and fourin vivoCT imaging modalities: high-resolution peripheral quantitative computed tomography (HR-pQCT), dental cone beam CT (CBCT), whole-body multi-row detector CT (MDCT), and extremity CBCT. A new algorithm was developed to optimize soft thresholding parameters for individualin vivoCT modalities for computing quantitative bone volume fraction maps. Finally, agreement of trabecular bone micro-structural measures, derived from differentin vivoCT imaging, with reference measures from micro-CT imaging was examined. Observed values of most trabecular measures, including trabecular bone volume, network area, transverse and plate-rod micro-structure, thickness, and spacing, forin vivoCT modalities were higher than their micro-CT-based reference values. In general, HR-pQCT-based trabecular bone measures were closer to their reference values as compared to otherin vivoCT modalities. Despite large differences in observed values of measures among modalities, high linear correlation (rε [0.94 0.99]) was found between micro-CT andin vivoCT-derived measures of trabecular bone volume, transverse and plate micro-structural volume, and network area. All HR-pQCT-derived trabecular measures, except the erosion index, showed high correlation (rε [0.91 0.99]). The plate-width measure showed a higher correlation (rε [0.72 0.91]) amongin vivoand micro-CT modalities than its counterpart binary plate-rod characterization-based measure erosion index (rε [0.65 0.81]). Although a strong correlation was observed between micro-structural measures fromin vivoand micro-CT imaging, large shifts in their values forin vivomodalities warrant proper scanner calibration prior to adopting in multi-site and longitudinal studies.

Value of Performing Routine Vascular Mapping Synchronous with Radiographic Assessment of Endodontic Lesions: Case Series

With the adoption of limited-volume cone beam computed tomographic (CBCT) imaging in dentistry, high resolution of the maxillomandibular complex has led to the recognition of numerous accessory neurovascular canals. The preoperative identification of these structures is essential to facilitate the safe performance of an assortment of invasive dental procedures; however, there is limited information in the endodontic literature regarding mapping of these neurovascular canals and their anatomic variants. To emphasize the utility of accessory neurovascular channel mapping in conjunction with endodontic therapy, we have presented the clinical findings of 4 diverse cases. Comprehensive evaluation of the CBCT scans showed relevant underlying etiopathologies, prompting clinical modifications that led to enhanced patient outcomes.

Low-cost and portable MRI

Research in MRI technology has traditionally expanded diagnostic benefit by developing acquisition techniques and instrumentation to enable MRI scanners to "see more." This typically focuses on improving MRI's sensitivity and spatiotemporal resolution, or expanding its range of biological contrasts and targets. In complement to the clear benefits achieved in this direction, extending the reach of MRI by reducing its cost, siting, and operational burdens also directly benefits healthcare by increasing the number of patients with access to MRI examinations and tilting its cost-benefit equation to allow more frequent and varied use. The introduction of low-cost, and/or truly portable scanners, could also enable new point-of-care and monitoring applications not feasible for today's scanners in centralized settings. While cost and accessibility have always been considered, we have seen tremendous advances in the speed and spatial-temporal capabilities of general-purpose MRI scanners and quantum leaps in patient comfort (such as magnet length and bore diameter), but only modest success in the reduction of cost and siting constraints. The introduction of specialty scanners (eg, extremity, brain-only, or breast-only scanners) have not been commercially successful enough to tilt the balance away from the prevailing model: a general-purpose scanner in a centralized healthcare location. Portable MRI scanners equivalent to their counterparts in ultrasound or even computed tomography have not emerged and MR monitoring devices exist only in research laboratories. Nonetheless, recent advances in hardware and computational technology as well as burgeoning markets for MRI in the developing world has created a resurgence of interest in the topic of low-cost and accessible MRI. This review examines the technical forces and trade-offs that might facilitate a large step forward in the push to "jail-break" MRI from its centralized location in healthcare and allow it to reach larger patient populations and achieve new uses. Level of Evidence: 5 Technical Efficacy Stage: 6 J. Magn. Reson. Imaging 2019. J. Magn. Reson. Imaging 2020;52:686-696.

Flat-panel CT arthrography for cartilage defect detection in the ankle joint: first results in vivo

OBJECTIVES

The purpose of this study was to compare the diagnostic performance of flat-panel computed tomography (FPCT) arthrography for cartilage defect detection in the ankle joint to direct magnetic resonance (MR) arthrography using multidetector computed tomography (MDCT) arthrography as the reference standard.

METHODS

Twenty-seven patients with specific suspicion of articular cartilage lesion underwent ankle arthrography with injection of a mixture of diluted gadolinium and iobitridol and were examined consecutively with the use of FPCT, MDCT, and 1.5 T MR imaging. FPCT, MDCT, and MR arthrography examinations were blinded and randomly evaluated by two musculoskeletal radiologists in consensus. In each ankle, eight articular cartilage areas were assessed separately: medial talar surface, medial talar trochlea, lateral talar trochlea, lateral talar surface, tibial malleolus, medial tibial plafond, lateral tibial plafond, and fibular malleolus. Findings at FPCT and MR were compared with MDCT assessments in 216 cartilage areas.

RESULTS

For the detection of cartilage defects, FPCT demonstrated a sensitivity of 97%, specificity of 95%, and accuracy of 96%; and MR arthrography showed a sensitivity of 69%, specificity of 94%, and accuracy of 87%. FPCT and MR arthrography presented almost perfect agreement (κ = 0.87) and moderate agreement (κ = 0.60), respectively, with MDCT arthrography. Mean diagnostic confidence was higher for FPCT (2.9/3) than for MR (2.3/3) and MDCT (2.7/3) arthrography.

CONCLUSIONS

FPCT demonstrated better accuracy than did 1.5 T MR arthrography for cartilage defect detection in the ankle joint. Therefore, FPCT should be considered in patients scheduled for dedicated imaging of ankle articular cartilage.

Physical evaluation of an ultra-high-resolution CT scanner

OBJECTIVES

To evaluate the technical performance of an ultra-high-resolution CT (UHRCT) system.

METHODS

The physico-technical capabilities of a novel commercial UHRCT system were assessed and compared with those of a current-generation multi-detector (MDCT) system. The super-high-resolution (SHR) mode of the system uses 0.25 mm (at isocentre) detector elements (dels) in the in-plane and longitudinal directions, while the high-resolution (HR) mode bins two dels in the longitudinal direction. The normal-resolution (NR) mode bins dels 2 × 2, resulting in a del-size equivalent to that of the MDCT system. In general, standard procedures and phantoms were used to perform these assessments.

RESULTS

The UHRCT MTF (10% MTF 4.1 lp/mm) is twice as high as that of the MDCT (10% MTF 1.9 lp/mm), which is comparable to the MTF in the NR mode (10% MTF 1.7 lp/mm). The width of the slice sensitivity profile in the SHR mode (FWHM 0.45 mm) is about 60% of that of the MDCT (FWHM 0.77 mm). Uniformity and CT numbers are within the expected range. Noise in the high-resolution modes has a higher magnitude and higher frequency components compared with MDCT. Low-contrast visibility is lower for the NR, HR and SHR modes compared with MDCT, but about a 14%, for NR, and 23%, for HR and SHR, dose increase gives the same results.

CONCLUSIONS

HR and SHR mode scanning results in double the spatial resolution, with about a 23% increase in dose required to achieve the same low-contrast detectability.

KEY POINTS

• Resolution on UHRCT is up to twice as high as for the tested MDCT. • With abdominal settings, UHRCT needs higher dose for the same low-contrast detectability as MDCT, but dose is still below achievable levels as defined by current diagnostic reference levels. • The UHRCT system used in normal-resolution mode yields comparable resolution and noise characteristics as the MDCT system.

Flat Panel Computed Tomography in the Diagnosis of Superior Semicircular Canal Dehiscence Syndrome

HYPOTHESIS

Flat panel computed tomography (FPCT) provides more accurate measurements of dimensions for superior semicircular canal dehiscence (SCD) than multislice CT (MSCT).

BACKGROUND

SCD syndrome occurs when a bony defect of the superior semicircular canal causes vestibular and auditory symptoms. MSCT can overestimate the size of the canal defect, with possible over-diagnosis of SCD and suboptimal selection of surgical approach. The higher resolution of FPCT should afford more accurate measurements of these defects.

METHODS

Radiographic and surgical measurements were compared in 22 patients (mean age 49.4) with clinical SCD syndrome and canal defects confirmed at surgery. Twenty second FPCT scans were acquired before surgery with parameters: 109Kv, small focus, 200 degrees rotation angle, and 0.4 degree per frame angulation step. Dehiscence dimensions were measured from orthogonal multiplanar reconstructions on a high-resolution liquid crystal display monitor and compared with actual measurements recorded during microsurgery.

RESULTS

SCD dimensions by FPCT (x) were 2.8 ± 1.6 mm for length and 0.72 ± 0.28 mm for width. The surgical measurements (y) were 2.8 ± 1.7 mm for length and 0.72 ± 0.34 mm for width. Linear fits between x and y yielded R values of 0.93 (length) and 0.66 (width). Our previous study using MSCT had R values of 0.28 (length) and 0.48 (width). The average difference between each FPCT and corresponding surgical measurement was not significantly different from zero, whereas the results for MSCT were significantly different.

CONCLUSION

FPCT can provide more accurate measurements of SCD than MSCT. Clinicians should consider using FPCT for imaging suspected SCD.

Role of the weight-bearing cone-beam CT in evaluation of flatfoot deformity

Introduction:

Till date, weight-bearing radiographs have been the cornerstone for planning surgeries on flatfoot. The technique, however, has limitations due to the superimposition of the bones and the lack of reproducibility. Weight-bearing CT with its unique design overcomes these limitations and enables cross-sectional imaging of the foot to be done in the natural weight-bearing position. In this paper, we report our initial experience in weight-bearing cross-sectional imaging of the foot for assessment of flatfoot deformity.

Materials and Methods:

Around 19 known cases of flatfoot were scanned on the weight-bearing CT. Each foot was then assessed for the various angles and also for the presence/absence of extra-articular talocalcaneal impingement and subfibular impingement. Other associated abnormalities like secondary osteoarthritic changes, were also noted.

Results:

The Meary, as well as the calcaneal angles, were abnormal, in all but one separate foot. Forefoot abduction was seen in 7 of the 19 feet. The hind foot valgus angle was greater than 10° in all patients. Extra-articular talocalcaneal impingement was seen in 13 of 19 feet. Secondary osteoarthritic changes were seen in 14 feet.

Conclusion:

Weight-bearing CT scan is a very useful technique for evaluation of flatfoot and associated complications. It overcomes the limitations of the radiographs by providing multiplanar three-dimensional assessment of the foot in the natural weight-bearing position and at the same time being easily reproducible and consistent for the measurements around the foot. The definite advantage over the conventional cross-sectional scanners is the weight-bearing capability.

MDCT-QCT, QUS, and DXA in healthy adults: An intermodality comparison

Background: Cortical deceleration is the main reason for bone loss at peripheral sites. It was suggested that when peripheral bones were assessed for osteoporosis, management and therapy can be administered early. The main aim of this study was to assess the relationships between the central and peripheral measurements at different skeleton bone sites (spine, femur, forearm, tibia, and calcaneus) with available modalities: DXA, QUS, and MDCT-QCT. Methods: The volunteers recruited in this study did not have any history or evidence of metabolic bone disease. Blood test and DXA measurements were used as inclusion criteria to select 40 healthy participants. The selected volunteers underwent 3 imaging modalities: QCT, DXA, and QUS. DXA-based measurements were made on 3 sites, including spine, femur, and forearm. QCT and QUS measurements were done for distal of tibia and calcaneus bones, respectively. The extracted parameters from the 3 modalities were analyzed using a bivariate (Pearson) correlation (r) in statistical software. Results: The results showed moderate to good correlations between spongy bones in central and peripheral sites from all the modalities. However, there was no correlation between MDCT measures and central bone values. According to correlations between different peripheral sits, aBMD of 33% radius and trabecular vBMD in 38% distal tibia showed weak but significant relationship between peripheral bones (r=-0.342, p=0.044). Conclusion: The findings demonstrated how bones in central and peripheral sites were correlated. Multimodality imaging was used in this group of healthy volunteers. Also, it was found that QCT-based MDCT needs more optimization and requires further investigations.

Image quality of flat-panel computed tomography using 2 different acquisition times versus multidetector computed tomography in whole-head temporal bone specimen

PURPOSE

Imaging of temporal bone and skull base acquire high resolution due to the small anatomic structures with high clinical relevance. The purpose of this study was to compare image quality of the temporal bone in standard 20 s protocol flat-panel computed tomography (FPCT) with the new time- and dose improved 10 s protocol as well as with 128 slice multidetector computed tomography (MDCT). The aim was to evaluate the new time- and dose improved 10 s protocol.

METHODS

10 whole-skull preparations-20 temporal bones-were scanned with either 128 slice MDCT CT (SOMATOM Definition AS + , Siemens, Erlangen) or FPCT (AXIOM-Artis, Siemens, Erlangen) using 10 s or 20 s protocol.

RESULTS

We show here that overall FPCT provides significantly better image quality and improved delimitation of clinically relevant structures in the temporal bone compared to 128 slice MDCT. Especially the shorter, dose saving 10 s protocol of the FPCT is still superior to 128 slice MDCT. The 20 s FPCT protocol was only significantly superior in identification of the cochlear apical turn and can thereby be used specifically in clinical cases with pathologies in this area.

CONCLUSIONS

The 10 s FPCT protocol yields a significantly better image quality than MDCT in imaging finer structures of the temporal bone.

Facial soft tissue thicknesses in craniofacial identification: Data collection protocols and associated measurement errors

Facial soft tissue thicknesses (FSTT) form a key component of craniofacial identification methods, but as for any data, embedded measurement errors are highly pertinent. These in part dictate the effective resolution of the measurements. As herein reviewed, measurement methods are highly varied in FSTT studies and associated measurement errors have generally not been paid much attention. Less than half (44%) of 95 FSTT studies comment on measurement error and not all of these provide specific quantification. Where informative error measurement protocols are employed (5% of studies), the mean error magnitudes range from 3% to 45% rTEM and are typically in the order of 10-20%. These values demonstrate that FSTT measurement errors are similar in size to (and likely larger than) the magnitudes of many biological effects being chased. As a result, the attribution of small millimeter or submillimeter differences in FSTT to biological variables must be undertaken with caution, especially where they have not been repeated across different studies/samples. To improve the integrity of FSTT studies and the reporting of FSTT measurement errors, we propose the following standard: (1) calculate the technical error of measurement (TEM or rTEM) in any FSTT research work; (2) assess the error embedded in the full data collection procedure; and (3) conduct validation testing of FSTT means proposed for point estimation prior to publication to ensure newly calculated FSTT means provide improvements. In order to facilitate the latter, a freely available R tool TDValidator that uses the C-Table data for validation testing is provided.

Diagnostic accuracy of flat-panel computed tomography in assessing cerebral perfusion in comparison with perfusion computed tomography and perfusion magnetic resonance: a systematic review

Purpose

Flat-panel computed tomography (FP-CT) is increasingly available in angiographic rooms and hybrid OR’s. Considering its easy access, cerebral imaging using FP-CT is an appealing modality for intra-procedural applications. The purpose of this systematic review is to assess the diagnostic accuracy of FP-CT compared with perfusion computed tomography (CTP) and perfusion magnetic resonance (MRP) in cerebral perfusion imaging.

Methods

We performed a systematic literature search in the Cochrane Library, MEDLINE, Embase, and Web of Science up to June 2019 for studies directly comparing FP-CT with either CTP or MRP in vivo. Methodological quality was assessed using the QUADAS-2 tool. Data on diagnostic accuracy was extracted and pooled if possible.

Results

We found 11 studies comparing FP-CT with CTP and 5 studies comparing FP-CT with MRP. Most articles were pilot or feasibility studies, focusing on scanning and contrast protocols. All patients studied showed signs of cerebrovascular disease. Half of the studies were animal trials. Quality assessment showed unclear to high risks of bias and low concerns regarding applicability. Five studies reported on diagnostic accuracy; FP-CT shows good sensitivity (range 0.84–1.00) and moderate specificity (range 0.63–0.88) in detecting cerebral blood volume (CBV) lesions.

Conclusions

Even though FP-CT provides similar CBV values and reconstructed blood volume maps as CTP in cerebrovascular disease, additional studies are required in order to reliably compare its diagnostic accuracy with cerebral perfusion imaging.

Electronic supplementary material

The online version of this article (10.1007/s00234-019-02285-y) contains supplementary material, which is available to authorized users.

Multi-pass approach to reduce cone-beam artifacts in a circular orbit cone-beam CT system

We propose a multi-pass approach to reduce cone-beam artifacts in a circular orbit cone-beam computed tomography (CT) system. Employing a large 2D detector array reduces the scan time but produces cone-beam artifacts in the Feldkamp, Davis, and Kress (FDK) reconstruction because of insufficient sampling for exact reconstruction. While the two-pass algorithm proposed by Hsieh is effective at reducing cone-beam artifacts, the correction performance is degraded when the bone density is moderate and the cone angle is large. In this work, we treated the cone-beam artifacts generated from bone and soft tissue as if they were from less dense bone objects and corrected them iteratively. The proposed method was validated using a numerical Defrise phantom, XCAT phantom data, and experimental data from a pediatric phantom followed by image quality assessment for FDK, the two-pass algorithm, the proposed method, and the total variation minimization-based iterative reconstruction (TV-IR). The results show that the proposed method was superior to the two-pass algorithm in cone-beam artifact reduction and effectively reduced the overcorrection by the two-pass algorithm near bone regions. It can also be observed that the proposed method produced better correction performance with fewer iterations than the TV-IR algorithm. A qualitative evaluation with mean-squared error, structural similarity, and structural dissimilarity demonstrated the effectiveness of the proposed method.

First experiences with the Airo mobile intraoperative CT scanner in acetabular surgery-An analysis of 10 cases

BACKGROUND

Being a proven method in trauma and spine surgery, intraoperative 3D imaging (CBCT) has intrinsic deficits in difficult anatomy and with artifacts because of metal implants. The purpose of this study was to evaluate the use of intraoperative computed tomography (iCT) in acetabular surgery.

METHODS

Ten cases of acetabular fractures that were operated with intraoperative use of the mobile CT scanner Brainlab Airo were analyzed. Data were compared with a historical group of 17 patients.

RESULTS

Additional fluoroscopy time was 24.2 seconds (6-91), which was significantly lower than in the control group where it was 211.4 seconds (77-446; P < 0.000). Operation time did not differ significantly (iCT group 196.8 min [122-288], control group 240.8 min [71-411], P = 0.234).

CONCLUSION

iCT provides images of a reliable high quality and assessability. Radiation exposure to the staff is reduced while surgery time is not altered significantly. Quality of intraoperative imaging and thus patient care can substantially improve patient outcome.

[Design and optimization of a cone-beam CT system for extremity imaging]

OBJECTIVE

To establish a cone beam computed tomography (ECBCT) system for high-resolution imaging of the extremities.

METHODS

Based on three-dimensional X-Ray CT imaging and high-resolution flat plate detector technique, we constructed a physical model and a geometric model for ECBCT imaging, optimized the geometric calibration and image reconstruction methods, and established the scanner system. In the experiments, the pencil vase phantom, image quality (IQ) phantom and a swine feet were scanned using this imaging system to evaluate its effectiveness and stability.

RESULTS

On the reconstructed image of the pencil vase phantom, the edges were well preserved with geometric calibrated parameters and no aliasing artifacts were observed. The reconstructed images of the IQ phantom showed a uniform distribution of the CT number, and the noise power spectra were stable in multiple scanning under the same condition. The reconstructed images of the swine feet had clearly displayed the bones with a good resolution.

CONCLUSIONS

The ECBCT system can be used for highresolution imaging of the extremities to provide important imaging information to assist in the diagnosis of bone diseases.

Intraoperative Imaging and Image Fusion for Venous Interventions

Advanced imaging for intraoperative evaluation of venous pathologies has played an increasingly significant role in this era of evolving minimally invasive surgical and interventional therapies. The evolution of dedicated venous stents and other novel interventional devices has mandated the need for advanced imaging tools to optimize safe and accurate device deployment. Most venous interventions are typically performed using a combination of standard 2-dimensional (2D) fluoroscopy, digital-subtraction angiography, and intravascular ultrasound imaging techniques. Latest generation computer tomography (CT) and magnetic resonance imaging (MRI) scanners have been shown to provide high-resolution 3D and 4D information about venous vasculature. In addition to morphological imaging, novel MRI techniques such as 3D time-resolved MR venography and 4D flow sequences can provide quantitative information and help visualize intricate flow patterns to better understand complex venous pathologies. Moreover, the high-fidelity information from multiple imaging techniques can be integrated using image fusion to overcome the limitations of current intraoperative imaging techniques. For example, the limitations of standard 2D fluoroscopy and luminal angiography can be compensated for by perivascular and soft-tissue information from MRI during complex venous interventions using image fusion techniques. Intraoperative dynamic evaluation of devices such as venous stents and real-time understanding of changes in flow patterns during venous interventions may be routinely available in future interventional suites with integrated multimodality CT or MR imaging capabilities. The purpose of this review is to discuss the outlook for intraoperative imaging and multimodality image fusion techniques and highlight their value during complex venous interventions.

Evaluation of Bone Mineral Density Using DXA and cQCT in Postmenopausal Patients Under Thyrotropin Suppressive Therapy

PURPOSE

This study aimed to examine the discrepancy in osteoporosis diagnoses between central quantitative computed tomography (cQCT) and dual-energy X-ray absorptiometry (DXA) and evaluated correlations among volumetric bone mineral density (vBMD), areal bone mineral density (aBMD), and trabecular bone score(TBS) in postmenopausal women who were undergoing TSH suppressive therapy.

METHODS

We enrolled a total of 81 postmenopausal patients [median age: 58 years; interquartile range (IQR): 57 to 60 years] receiving TSH suppressive therapy with levothyroxine after undergoing total thyroidectomy for papillary thyroid cancer. Patients were diagnosed by their bone mineral density (BMD) T-score and categorized according to a vBMD threshold of 120 mg/cm3 for osteopenia and a threshold of 80 mg/cm3 for osteoporosis.

RESULTS

When DXA and cQCT were compared, the BMD evaluation results differed in 76% of patients (n = 62; P < 0.001), and the detection rate of osteoporosis was 30.9% for cQCT and 21.0% for DXA. Sixty-two patients had discordant results; in 46 of these patients (74%) whose DXA T-scores were normal, the diagnosis shifted to osteopenia (n = 35) and osteoporosis (n = 11) according to the vBMD on cQCT (P < 0.001), and their vBMD values were significantly correlated with TBS (r = 0.293; P = 0.008). However, aBMD was not significantly correlated with TBS (r = 0.080; P = 0.480). TBS was significantly lower in patients with osteopenia (median: 1.35; IQR: 1.18 to 1.47) and osteoporosis (median: 1.28; IQR: 1.07 to 1.47) than in those with a normal BMD value (median: 1.37; IQR: 1.25 to 1.49; P = 0.041) on cQCT. There was no significant difference in TBS according to DXA BMD status (P = 0.200).

CONCLUSIONS

DXA and cQCT yielded inconsistent results, and detection of osteopenia and osteoporosis was higher using cQCT. TBS showed a more significant correlation with vBMD than with aBMD.

Relating the mechanical properties of atherosclerotic calcification to radiographic density: A nanoindentation approach

Calcification morphology can determine atherosclerotic plaque stability and is associated with increased failures rates for endovascular interventions. Computational efforts have sought to elucidate the relationship between calcification and plaque rupture in addition to predicting tissue response during aggressive revascularisation techniques. However, calcified material properties are currently estimated and may not reflect real tissue conditions. The objective of this study is to correlate calcification mechanical properties with three radiographic density groups obtained from corresponding Computed Tomography (CT) images. Seventeen human plaques extracted from carotid (n = 10) and peripheral lower limb (n = 7) arteries were examined using micro-computed tomography (µCT), simultaneously locating the calcified deposits within their internal structure and quantifying their densities. Three radiographic density groups were defined based on the sample density distribution: (A) 130-299.99 Hounsfield Units (HU), (B) 300-449.99 HU and (C) >450 HU. Nanoindentation was employed to determine the Elastic Modulus (E) and Hardness (H) values within the three density groups. Results reveal a clear distinction between mechanical properties with respect to radiographic density groups (p < 0.0005). No significant differences exist in the density-specific behaviours observed between carotid and peripheral samples. Previously defined calcification classifications indicate an association with specific radiographic density patterns. Scanning Electron Microscopy (SEM) examination revealed that density group A regions consist of both calcified and non-calcified tissues. Further research is required to define the radiographic thresholds which identify varying degrees of tissue calcification. This study demonstrates that the mechanical properties of fully mineralised atherosclerotic calcification emulate that of bone tissues (17-25 GPa), affording computational models with accurate material parameters. STATEMENT OF SIGNIFICANCE: Global mechanical characterisation techniques disregard the heterogeneous nature of atherosclerotic lesions. Previous nanoindentation results for carotid calcifications have displayed a wide range. This study evaluates calcification properties with respect to radiographic density obtained from Micro-CT images. This is the first work to characterise calcifications from peripheral lower limb arteries using nanoindentation. Results demonstrate a strong positive correlation between radiographic density and calcification mechanical properties. Characterising calcifications using their density values provides clarity on the variation in published properties for calcified tissues. Furthermore, this study confirms the hypothesis that fully calcified plaque tissue behaviour similar to that of bone. Appropriate material parameters for calcified tissues can now be employed in computational simulations.

Image quality and dose characteristics for an O-arm intraoperative imaging system with model-based image reconstruction

PURPOSE

To assess the imaging performance and radiation dose characteristics of the O-arm CBCT imaging system (Medtronic Inc., Littleton MA) and demonstrate the potential for improved image quality and reduced dose via model-based image reconstruction (MBIR).

METHODS

Two main studies were performed to investigate previously unreported characteristics of the O-arm system. First is an investigation of dose and 3D image quality achieved with filtered back-projection (FBP) - including enhancements in geometric calibration, handling of lateral truncation and detector saturation, and incorporation of an isotropic apodization filter. Second is implementation of an MBIR algorithm based on Huber-penalized likelihood estimation (PLH) and investigation of image quality improvement at reduced dose. Each study involved measurements in quantitative phantoms as a basis for analysis of contrast-to-noise ratio and spatial resolution as well as imaging of a human cadaver to test the findings under realistic imaging conditions.

RESULTS

View-dependent calibration of system geometry improved the accuracy of reconstruction as quantified by the full-width at half maximum of the point-spread function - from 0.80 to 0.65 mm - and yielded subtle but perceptible improvement in high-contrast detail of bone (e.g., temporal bone). Standard technique protocols for the head and body imparted absorbed dose of 16 and 18 mGy, respectively. For low-to-medium contrast (<100 HU) imaging at fixed spatial resolution (1.3 mm edge-spread function) and fixed dose (6.7 mGy), PLH improved CNR over FBP by +48% in the head and +35% in the body. Evaluation at different dose levels demonstrated 30% increase in CNR at 62% of the dose in the head and 90% increase in CNR at 50% dose in the body.

CONCLUSIONS

A variety of improvements in FBP implementation (geometric calibration, truncation and saturation effects, and isotropic apodization) offer the potential for improved image quality and reduced radiation dose on the O-arm system. Further gains are possible with MBIR, including improved soft-tissue visualization, low-dose imaging protocols, and extension to methods that naturally incorporate prior information of patient anatomy and/or surgical instrumentation.

Lower Spine Volumetric Bone Density in Patients With a History of Epidural Steroid Injections

CONTEXT

Epidural steroid injections (ESIs) are a common, effective treatment of lumbar radiculopathy and sciatica. Although the negative skeletal effects of oral glucocorticoids are well established, little is known about the impact of ESI on bone quality.

OBJECTIVE

To investigate the relationship between ESI exposure and volumetric bone mineral density (vBMD) at the lumbar spine (LS) using central quantitative CT.

DESIGN

Retrospective study.

SETTING

University hospital outpatient facility.

PATIENTS

All patients had CT scans of the LS between 2011 and 2016. Cases received at least three ESIs prior to the date of CT (n = 121). Controls were matched for age and sex (n = 121).

MAIN OUTCOME MEASURES

Cumulative ESI dose was calculated. vBMD was measured at T12 through L5 using QCT Pro phantomless software (MindWays).

RESULTS

Mean age of subjects was 65 ± 14 years, and 49% were women. Median number of ESIs was 4 (range: 3 to 16). Median cumulative ESI dosage was 340 mg of triamcinolone or equivalent (range: 150 to 1400 mg). Compared with controls, ESI subjects had lower vBMD at each vertebral level. Higher cumulative dose was associated with lower mean vBMD at T12 to L5 (r = -0.22, P = 0.02).

CONCLUSIONS

Greater cumulative ESI dose was related to lower vBMD at the LS. To our knowledge, this is the first study to measure vBMD in patients treated with ESIs. Prospective studies are needed to confirm these findings and to help identify the best strategies for preventing bone loss in this population.