Dose and image quality of cone-beam computed tomography as compared with conventional multislice computed tomography in abdominal imaging. Invest Radiol. 2014;49:675-684. [PMID: 24853071 DOI: 10.1097/RLI.0000000000000069]

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.

Postoperative computed tomography imaging of pediatric patients with craniosynostosis: radiation dose and image quality comparison between multi-slice computed tomography and O-arm cone-beam computed tomography

BACKGROUND

When postoperative multi-slice computed tomography (MSCT) imaging of patients with craniosynostosis is used, it is usually performed a few days after surgery in a radiology department. This requires additional anesthesia for the patient. Recently, intraoperative mobile cone-beam CT (CBCT) devices have gained popularity for orthopedic and neurosurgical procedures, which allows postoperative CT imaging in the operating room.

OBJECTIVE

This single-center retrospective study compared radiation dose and image quality of postoperative imaging performed using conventional MSCT scanners and O-arm CBCT.

MATERIALS AND METHODS

A total of 104 pediatric syndromic and non-syndromic patients who were operated on because of single- or multiple-suture craniosynostosis were included in this study. The mean volumetric CT dose index (CTDIvol) and dose-length product (DLP) values of optimized craniosynostosis CT examinations (58 MSCT and 46 CBCT) were compared. Two surgeons evaluated the subjective image quality.

RESULTS

CBCT resulted in significantly lower CTDIvol (up to 14%) and DLP (up to 33%) compared to MSCT. Multi-slice CT image quality was considered superior to CBCT scans. However, all scans were considered to be of sufficient quality for diagnosis.

CONCLUSION

The O-arm device allowed for an immediate postoperative CBCT examination in the operating theater using the same anesthesia induction. Radiation exposure was lower in CBCT compared to MSCT scans, thus further encouraging the use of O-arms. Cone-beam CT imaging with an O-arm is a feasible method for postoperative craniosynostosis imaging, yielding less anesthesia to patients, lower health costs and the possibility to immediately evaluate results of the surgical operation.

1.5 T MR-Guided Daily Adapted SBRT on Lymph Node Oligometastases from Prostate Cancer

Introduction: The aim of our study was to evaluate the efficacy and toxicity of a daily adaptive MR-guided SBRT on 1.5 T MR-linac in patients affected by lymph node oligometastases from PCa. Materials and Methods: The present study is a prospective observational study conducted in a single institution (protocol n°: MRI/LINAC n. 23748). Patients with oligometastatic lymph nodes from PCa treated with daily adaptive MR-guided SBRT on 1.5 T MR-linac were included in the study. There was a minimum required follow-up of 3 months after SBRT. The primary end-point was local progression-free survival (LPFS). The secondary end-points were: nodal progression-free survival (NPFS), progression-free survival (PFS), and toxicity. Results: A total of 118 lymph node oligometastases from PCa were treated with daily adaptive 1.5 T MR-guided SBRT in 63 oligometastatic patients. Of the patients, 63.5% were oligorecurrent and 36.5% were oligoprogressive. The two-year LPFS was 90.7%. The median NPFS was 22.3 months and the 2-year NPFS was 46.5%. Receiving hormone therapy before SBRT was correlated with a lower NPFS at the multivariate analysis (1 y NPFS 87.1% versus 42.8%; p = 0.002-HR 0.199, 95% CI 0.073-0.549). Furthermore, the oligorecurrent state during ADT was correlated with a lower NPFS than was the oligoprogressive state. The median PFS was 10.3 months and the 2-year PFS was 32.4%. Patients treated with hormone therapy before SBRT had a significantly lower 1-year PFS the others (28% versus 70.4%; p = 0.01-HR 0.259, 95% CI 0.117-0.574). No acute and late toxicities occurred during treatment. Conclusions: The present study is the largest prospective study of 1.5 T lymph node SBRT on MR-linac in patients with PCa. Lymph node SBRT by 1.5 T MR-linac provides high local control rates with an excellent toxicity profile.

Evaluation of Ultra-High-Resolution Cone-Beam CT Prototype of Twin Robotic Radiography System for Cadaveric Wrist Imaging

RATIONALE AND OBJECTIVES

Cone-beam CT (CBCT) applications possess potential for dose reduction in musculoskeletal imaging. This study evaluates the ultra-high-resolution CBCT prototype of a twin robotic X-ray system in wrist examinations compared to high-resolution multidetector CT (MDCT).

MATERIALS AND METHODS

Sixteen wrists of body donors were examined with the CBCT scan mode and a 384 slice MDCT system. Radiation-equivalent low-dose (CTDI_vol(16cm)  = 3.3 mGy) and full-dose protocols (CTDI_vol(16cm)  = 13.8 mGy) were used for both systems. Two observers assessed image quality on a seven-point Likert scale. In addition, software-assisted quantification of signal intensity fractions in cancellous bone was performed. Fewer pixels with intermediate signal intensity were considered to indicate superior depiction of bone microarchitecture.

RESULTS

Subjective image quality in CBCT was superior to dose equivalent MDCT with p ≤ 0.03 for full-dose and p < 0.001 for low-dose scans, respectively. Median Likert values were 7/7 (reader 1 / reader 2) in full-dose CBCT, 6/6 in full-dose MDCT, 5/6 in low-dose CBCT and 3/3 in low-dose MDCT. Intraclass correlation coefficient was 0.936 (95% confidence interval, 0.897-0.961; p < 0.001), indicating excellent reliability. Objective analysis displayed smaller fractions of "indecisive" pixels with intermediate signal intensity for full-dose CBCT (0.57 [interquartile range 0.13]) compared to full-dose MDCT (0.68 [0.21]), low-dose CBCT (0.72 [0.19]), and low-dose MDCT (0.80 [0.15]) studies. No significant difference was observed between low-dose CBCT and full-dose MDCT.

CONCLUSION

The new CBCT prototype provides superior image quality for trabecula and bone marrow in cadaveric wrist studies and enables dose reduction up to 75% compared to high-resolution MDCT.

Lesion Detectability and Radiation Dose in Spiral Breast CT With Photon-Counting Detector Technology: A Phantom Study

OBJECTIVES

The aim of the article was to evaluate the lesion detectability, image quality, and radiation dose of a dedicated clinical spiral breast computed tomography (CT) system equipped with a photon-counting detector, and to propose optimal scan parameter settings to achieve low patient dose levels and optimal image quality.

METHODS

A breast phantom containing inserts mimicking microcalcifications (diameters 196, 290, and 400 μm) and masses (diameters 1.8, 3.18, 4.76, and 6.32 mm) was examined in a spiral breast CT system with systematic variations of x-ray tube currents between 5 and 125 mA, using 2 slabs of 100 and 160 mm. Signal-to-noise ratio and contrast-to-noise ratio measurements were performed by region of interest analysis. Two experienced radiologists assessed the detectability of the inserts. The average absorbed dose was calculated in Monte Carlo simulations.

RESULTS

Microcalcifications in diameters of 290 and 400 μm and masses in diameters of 3.18, 4.76, and 6.32 mm were visible for all tube currents between 5 and 125 mA. Soft tissue masses in a diameter of 1.8 mm were visible at tube currents of 25 mA and higher. Microcalcifications with a diameter of 196 μm were detectable at a tube current of 25 mA and higher in the small, and at a tube current of 40 mA and higher in the large slab. For the small and large breast, at a tube current of 25 and 40 mA, an average dose value of 4.30 ± 0.01 and 5.70 ± 0.02 mGy was calculated, respectively.

CONCLUSIONS

Optimizing tube current of spiral breast CT according to the breast size enables the visualization of microcalcifications as small as 196 μm while keeping dose values in the range of conventional mammography.

Short-term outcomes of radiofrequency ablation for hepatocellular carcinoma using cone-beam computed tomography for planning and image guidance

BACKGROUND

Percutaneous radiofrequency ablation (RFA) is an effective treatment for unresectable hepatocellular carcinoma (HCC) and a minimally invasive alternative to hepatectomy for treating tumour recurrence. RFA is often performed using contrast-enhanced computed tomography (CECT) and/or ultrasonography. In recent years, angiographic systems with flat panel image detectors and advanced image reconstruction algorithms have broadened the clinical applications of cone-beam computed tomography (CBCT), including RFA. Several studies have shown the effectiveness of using CBCT for immediate treatment assessments and follow-ups.

AIM

To assess the treatment response to RFA for HCC using CBCT.

METHODS

Forty-eight patients (44 men; aged 37-89 years) with solitary HCC [median size: 3.2 (1.2-6.6) cm] underwent RFA and were followed for 25.6 (median; 13.5-35.2) mo. Image fusion of CBCT and pre-operative CECT or magnetic resonance imaging (MRI) was used for tumour segmentation and needle path and ablation zone planning. Real-time image guidance was provided by overlaying the three-dimensional image of the tumour and needle path on the fluoroscopy image. Treatment response was categorized as complete response (CR), partial response (PR), stable disease (SD), or progressive disease (PD). Disease progression, death, time to progression (TTP), and overall survival (OS) were recorded. Kaplan-Meier and Cox regression analyses were performed.

RESULTS

Initial post-RFA CECT/MRI showed 38 cases of CR (79.2%), 10 of PR (20.8%), 0 of SD, and 0 of PD, which strongly correlated with the planning estimation (42 CR, 87.5%; 6 PR, 12.5%; 0 SD; and 0 PD; accuracy: 91.7%, P < 0.01). Ten (20.8%) patients died, and disease progression occurred in 31 (35.4%, median TTP: 12.8 mo) patients, resulting in 12-, 24-, and 35-mo OS rates of 100%, 81.2%, and 72.2%, respectively, and progression-free survival (PFS) rates of 54.2%, 37.1%, and 37.1%, respectively. The median dose-area product of the procedures was 79.05 Gy*cm² (range 40.95-146.24 Gy*cm²), and the median effective dose was 10.27 mSv (range 5.32-19.01 mSv). Tumour size < 2 cm (P = 0.008) was a significant factor for OS, while age (P = 0.001), tumour size < 2 cm (P < 0.001), tumour stage (P = 0.010), and initial treatment response (P = 0.003) were significant factors for PFS.

CONCLUSION

Reliable RFA treatment planning and satisfactory outcomes can be achieved with CBCT.

Cone-beam computed tomography for trauma

Radiographic imaging is critical in helping guide treatment of critically injured patients. Cone-beam computed tomography is an axial imaging technique available from fixed imaging systems found in hybrid operating rooms. It can be used to provide focused studies of specific anatomical regions, where patients cannot undergo conventional multidetector computed tomography. This includes non-contrast-enhanced evaluation of the intracranial contents and vascular imaging throughout the body. There are a number of advantages and disadvantages to cone-beam computed tomography, but these are not widely discussed within the trauma literature. This narrative review article presents the initial practical experience of this novel imaging modality. LEVEL OF EVIDENCE: Review article, level III.

Comparison of 3D X-ray tomography with computed tomography in patients with distal extremity fractures

OBJECTIVE

To compare fracture detection, image quality, and radiation dose in patients with distal extremity fractures using 3D tomography and computed tomography (CT).

MATERIALS AND METHODS

IRB approval was obtained including informed consent for this prospective study from June to December 2016. Patients diagnosed with an acute fracture at CT were consecutively scanned on the same day using 3D tomography. Anatomical location (effected bone and location within the bone) and morphological characteristics of fractures (avulsion, articular involvement, mono- vs. multifragmented, displacement), visibility of bone/soft tissue structures, and image quality were assessed independently by two blinded readers on a 5-point Likert scale. Dose-length-product (DLP; mGy*cm) was compared between both modalities. Descriptive statistics, Wilcoxon signed rank test (P < 0.05), Student's t test (P < 0.05), and Cohen's kappa (κ) for interreader reliability were calculated.

RESULTS

In 46 patients (28 males; 18 females; mean age, 53 ± 20 years) with 28 hand/wrist and 18 foot/ankle examinations, 86 out of 92 fractures were diagnosed with 3D tomography compared with CT. No false-positive finding occurred at 3D tomography. The six missed fractures on 3D tomography were five avulsion fractures of the carpals/metacarpals or tarsals/metatarsals, respectively, and one nondisplaced fracture of the capitate. Interreader agreement of anatomical location and morphological characteristics was substantial to almost perfect for upper (κ = 0.80-0.96) and lower (κ = 0.70-0.97) extremity fractures. Visibility of bone and soft tissue structures and image quality were slightly inferior using 3D tomography compared with CT (upper extremity P < 0.001-0.038 and lower extremity P < 0.001-0.035). DLP of a comparable scan coverage was significantly lower for 3D tomography (P < 0.001) for both upper (3D mean, 19.4 ± 5.9 mGy*cm; estimated CT mean, 336.5 ± 52.2 mGy*cm) and lower extremities (3D mean, 24.1 ± 11.1 mGy*cm; estimated CT mean, 182.9 ± 6.5 mGy*cm). Even the highest DLP with 3D tomography was < 30% of the mean estimated CT dose of a comparable area of coverage.

CONCLUSION

Fracture assessment of peripheral extremities is reliable utilizing a low-dose 3D tomography X-ray system, with slightly reduced image quality.

Impact of Patient Alignment on Image Quality in C-Arm Computed Tomography - Evaluation Using an ACR Phantom

PURPOSE

 To evaluate the influence of patient alignment and thereby heel effect on the image quality (IQ) of C-arm flat-panel detector computed tomography (CACT).

MATERIALS AND METHODS

 An ACR phantom placed in opposite directions along the z-axis (setup A and B) on the patient support was imaged using CACT. Image acquisition was performed with three different image acquisition protocols. The images were reconstructed with four convolution kernels. IQ was assessed in terms of high contrast using the modulation transfer function (MTF) and low contrast by assessing the image noise, signal-to-noise ratio (SNR) and contrast-to-noise ratios (CNR) as well as the reliability of density measurements. Furthermore, the dose intensity profiles were measured free-in-air.

RESULTS

 The MTF in setup B is higher than the MTF measured in setup A (p < 0.01). The image noises measured in setup A for the air and bone inserts were higher compared to those measured in setup B (p > 0.05). Opposite behavior has been observed for the polyethylene, water-equivalent and acrylic inserts. The SNR for all inserts is inversely related to the image noise. A systematically increasing or decreasing trend of CNR could not be observed (p > 0.05). The intensity profile measured by the detector system free-in-air showed that the anode heel effect is perpendicular to the z-axis.

CONCLUSION

 The patient alignment has a minor influence on the IQ of CACT. This effect is not based on the X-ray anode heel effect but is caused mainly by the non-symmetrical rotation of CACT.

KEY POINTS

  · The impact of patient alignment and thereby the heel effect on the image quality of CACT was analyzed.. · The patient alignment has a minor influence on the physical parameters related to image quality, such as noise, SNR, and MTF.. · This effect is based mainly on the non-symmetrical rotation of CACT..

CITATION FORMAT

· Alikhani B, Renne J, Maschke S et al. Impact of Patient Alignment on Image Quality in C-Arm Computed Tomography - Evaluation Using an ACR Phantom. Fortschr Röntgenstr 2021; 193: 417 - 426.

Cone-Beam CT-Assisted Ablation of Renal Tumors: Preliminary Results

INTRODUCTION

Renal ablation is a recognized treatment modality for small renal masses. Cone-beam CT (CBCT) has been recently used in interventional oncology as a promising new guidance device, but this technology still needs to be validated for renal ablations. We aimed to assess the technical success of CBCT applications in renal ablative treatments.

MATERIALS AND METHODS

Between March 2016 and June 2018, 14 patients (mean age 69, range 54-83, 7F, 7M) underwent 21 renal ablations for histologically proven renal cell carcinoma (RCC). All treatments were performed with ultrasound (US) and CBCT guidance under general anesthesia in a dedicated angiography room setting. CBCT was mainly used to assess needle placement and to exclude complications at the end of the procedure. In two small lesions (< 1 cm), pre-acquired CBCT was co-registered with real-time US to obtain a US-CBCT fusion image guidance for tumor ablation.

RESULTS

Whether used alone or in combination with other imaging modalities, CBCT was proven to be technically successful in all 21 procedures to guide or assist tumor ablation. A primary technical efficacy of thermal ablation was achieved in 19/21 ablations (90.1%) at 1 month. Mean procedure duration was 100.2 min (range 160-64). Mean length of hospital stay was 2 days (range 1-10 days). All patients are still under active surveillance for a mean follow-up of 14.5 months (range 4-26 months).

CONCLUSIONS

CBCT for renal ablation guidance is a viable tool. Larger series are needed to compare it to MDCT.

CT-Guided Percutaneous Transthoracic Needle Biopsy Using the Additional Laser Guidance System by a Pulmonologist with 2 Years of Experience in CT-Guided Percutaneous Transthoracic Needle Biopsy

BACKGROUND

We developed an additional laser guidance system to improve the efficacy and safety of conventional computed tomography (CT)-guided percutaneous transthoracic needle biopsy (PTNB), and we conducted this study to evaluate the efficacy and safety of our system.

METHODS

We retrospectively analyzed the medical records of 244 patients who underwent CT-guided PTNB using our additional laser guidance system from July 1, 2015, to January 20, 2016.

RESULTS

There were nine false-negative results among the 238 total cases. The sensitivity, specificity, positive predictive value, negative predictive value, and diagnostic accuracy of our system for diagnosing malignancy were 94.4% (152/161), 100% (77/77), 100% (152/152), 89.5% (77/86), and 96.2% (229/238), respectively. The results of univariate analysis showed that the risk factors for a false-negative result were male sex (p=0.029), a final diagnosis of malignancy (p=0.033), a lesion in the lower lobe (p=0.035), shorter distance from the skin to the target lesion (p=0.003), and shorter distance from the pleura to the target lesion (p=0.006). The overall complication rate was 30.5% (74/243). Pneumothorax, hemoptysis, and hemothorax occurred in 21.8% (53/243), 9.1% (22/243), and 1.6% (4/243) of cases, respectively.

CONCLUSION

The additional laser guidance system might be a highly economical and efficient method to improve the diagnostic efficacy and safety of conventional CT-guided PTNB even if performed by inexperienced pulmonologists.

Initial evaluation of image performance of a 3-D x-ray system: phantom-based comparison of 3-D tomography with conventional computed tomography

Phantom-based initial performance assessment of a prototype three-dimensional (3-D) x-ray system and comparison of 3-D tomography with computed tomography (CT) were proposed. A 3-D image quality phantom was scanned with a prototype version of 3-D cone-beam CT imaging implemented on a twin robotic x-ray system using three trajectories (163 deg = table, 188 deg = upright, and 200 deg = side), six tube voltages (60, 70, 81, 90, 100, and 121 kV), and four detector doses (0.348, 0.696, 1.740, and [Formula: see text]). CT was obtained with a clinical protocol. Spatial resolution (line pairs/cm) and soft-tissue-contrast resolution were assessed by two independent readers. Radiation dose was assessed. Descriptive and analysis of variance (ANOVA) ([Formula: see text]) were performed. With 3-D tomography, a maximum of 16 lp/cm was visible and best soft-tissue-contrast resolution was 2 mm at 30 Hounsfield units (HU) for 160 projections. With CT, 10 lp/cm was visible and soft-tissue-contrast resolution was 4 mm at 20 HU. The upright trajectory yielded significantly better spatial resolution and soft tissue contrast, and the side trajectory yielded significantly higher soft tissue contrast than the table trajectory ([Formula: see text]). Radiation dose was higher in 3-D tomography (45 to 704 mGycm) than CT (44 mGycm). Three-dimensional tomography renders overall equal or higher spatial resolution and comparable soft tissue contrast to CT for medium- and high-dose protocols in the side and upright trajectories, but with higher radiation doses.

Computed Tomography-Assisted Thoracoscopic Surgery: A Novel, Innovative Approach in Patients With Deep Intrapulmonary Lesions of Unknown Malignant Status

OBJECTIVES

Minimally invasive resection of small, deep intrapulmonary lesions can be challenging due to the difficulty of localizing them during video-assisted thoracoscopic surgery (VATS). We report our preliminary results evaluating the feasibility of an image-guided, minimally invasive, 1-stop-shop approach for the resection of small, deep intrapulmonary lesions in a hybrid operating room (OR).

MATERIALS AND METHODS

Fifteen patients (5 men, 10 women; mean age, 63 years) with a total of 16 solitary, deep intrapulmonary nodules of unknown malignant status were identified for intraoperative wire marking. Patients were placed on the operating table for resection by VATS. A marking wire was placed within the lesion under 3D laser and fluoroscopic guidance using a cone beam computed tomography system. Then, wedge resection by VATS was performed in the same setting without repositioning the patient.

RESULTS

Complete resection with adequate safety margins was confirmed for all lesions. Marking wire placement facilitated resection in 15 of 16 lesions. Eleven lesions proved to be malignant, either primary or secondary; 5 were benign. Mean lesion size was 7.7 mm; mean distance to the pleural surface was 15.1 mm (mean lesion depth-diameter ratio, 2.2). Mean procedural time for marking wire placement was 35 minutes; mean VATS duration was 36 minutes.

CONCLUSIONS

Computed tomography-assisted thoracoscopic surgery is a new, safe, and effective procedure for minimally invasive resection of small, deeply localized intrapulmonary lesions. The benefits of computed tomography-assisted thoracoscopic surgery are 1. One-stop-shop procedure, 2. Lower risk for the patient (no patient relocation, no marking wire loss), and 3. No need to coordinate scheduling between the CT room and OR.

Interventional Oncology in Hepatocellular Carcinoma: Progress Through Innovation

The clinical management of hepatocellular carcinoma has evolved greatly in the last decade mostly through recent technical innovations. In particular, the application of cutting-edge image guidance has led to minimally invasive solutions for complex clinical problems and rapid advances in the field of interventional oncology. Many image-guided therapies, such as transarterial chemoembolization and radiofrequency ablation, have meanwhile been fully integrated into interdisciplinary clinical practice, whereas others are currently being investigated. This review summarizes and evaluates the most relevant completed and ongoing clinical trials, provides a synopsis of recent innovations in the field of intraprocedural imaging and tumor response assessment, and offers an outlook on new technologies, such as radiopaque embolic materials. In addition, combination therapies consisting of locoregional therapies and systemic molecular targeted agents (e.g., sorafenib) remain of major interest to the field and are also discussed. Finally, we address the many substantial advances in immune response pathways that have been related to the systemic effects of locoregional therapies. Knowledge of these new developments is crucial as they continue to shape the future of cancer treatment, further establishing interventional oncology along with surgical, medical, and radiation oncology as the fourth pillar of cancer care.

3D CACT-assisted Radiofrequency Ablation Following Transarterial Chemoembolization for Hepatocellular Carcinoma: Early Experience

BACKGROUND

To explored the value of 3D C-arm CT (CACT) guidance system in performing radiofrequency ablation (RFA) following transarterial chemoembolizationon (TACE) for hepatocellular carcinomas.

MATERIALS AND METHODS

RFA of hepatocellular carcinomas (HCC) were performed on 15 patients (21 lesions) with the assistance of CACT guidance system. Technical success, procedure time, complications and patient radiation exposure were investigated. The puncture performance level was evaluated on a five-point scale (5-1: excellent- poor). Complete ablation rate was evaluated after two months follow-up using enhanced CT scans.

RESULTS

The technical success rate of RFA procedure under CACT navigation system was 100%. Mean total procedure time was 24.24 ± 6.53 min, resulting in a mean effective exposure dose of 15.4 ± 5.1 mSv. The mean puncture performance level rated for CACT guided RFA procedure was 4.87 ± 0.35. Complete ablation (CA) was achieved in 20 (95.2%) of the treated 21 tumors after the first RFA session. None of patients developed intra-procedural complications.

CONCLUSIONS

3D CACT guidance system enables reliable and efficient needle positioning by providing real-time intraoperative guidance for performing RFA on HCCs.

Collimation and Image Quality of C-Arm Computed Tomography: Potential of Radiation Dose Reduction While Maintaining Equal Image Quality

OBJECTIVES

The aim of this study was to assess the potential for radiation dose reduction in collimated C-arm computed tomography (CACT) while maintaining the image quality of the full field of view (FFOV) acquisition.

MATERIAL AND METHODS

A whole-body anthropomorphic phantom representing a 70-kg male was used in this study. The upper abdomen of the phantom was imaged using an angiographic system (Artis Zeego Q; Siemens Healthcare, Germany) with either the standard detector radiation dose level (RDL; D100, 360 nGy) or 14 experimental reduced RDLs ranging from 95% (D95, 342 nGy) to 30% D100 (D30, 108 nGy). Either the FFOV (craniocaudal coverage, 18 cm) or a collimated field of view (CFOV; craniocaudal coverage, 6 cm) was applied. The organ dose was measured using thermoluminescence detector dosimetry, and the mean effective dose was computed according to the recommendations by the International Commission on Radiological Protection Publication 103. To compare the CFOV and the FFOV data sets, image quality was assessed in terms of high- and low-contrast resolution by calculating the modulation transfer function using the wire method as well as the image noise, signal-to-noise ratio, and contrast-to-noise ratio using a low-contrast insert placed in the upper abdomen (Δ50 HU).

RESULTS

Collimated imaging (CFOV) covering 33% of the FFOV led to an increase in the x-ray tube output of 152% for CFOV (D100; FFOV, 95.5 mGy; CFOV, 147.7 mGy) to maintain the detector dose. The mean effective dose of D100 was 6.0 mSv (male) and 6.2 mSv (female) for the FFOV and 3.7 mSv (male) and 4.1 mSv (female) for the CFOV. High-contrast resolution was comparable for all acquisition protocols (mean 10% modulation transfer function ± 95% confidence interval; FFOV, 8.8 ± 0.1 line pairs/cm; CFOV, 8.8 ± 0.1 line pairs/cm). Low-contrast resolution was superior for the CFOV compared with that for the FFOV for each RDL (D100; image noise: FFOV, 34 ± 2 HU; CFOV, 22 ± 1 HU; contrast-to-noise ratio: FFOV, 1.3 ± 0.2; CFOV, 1.8 ± 0.3). Low-contrast resolution of the standard (D100) FFOV acquisition was achieved for the CFOV at 84% D100 of the FFOV and 54% D100 of the CFOV. Therefore, collimation up to 33% of the FFOV combined with the lower detector dose allows overall reduction of a patient's radiation exposure to 33% × 84% = 28% compared with FFOV acquisition. In the upper abdomen, this results in a nearly 50% reduction of the mean effective radiation dose (male, 2.0 mSv; female, 2.2 mSv) without loss of image quality compared with the standard FFOV acquisition.

CONCLUSIONS

Craniocaudal collimation in CACT should be used whenever possible to increase the image quality and reduce the patient's overall radiation exposure. Therefore, new smart acquisition protocols are required for collimated CACT to improve the trade-off between radiation exposure and image quality requirements considering the collimation used.

Balloon pulmonary angioplasty: applicability of C-Arm CT for procedure guidance

PURPOSE

To investigate the feasibility of and compare two C-Arm CT (CACT) guidance methods during balloon pulmonary angioplasty (BPA).

MATERIAL AND METHODS

Forty-two BPAs [27 CTEPH patients (nine males, 70 ± 14y)] targeting 143 pulmonary arteries were included. Twenty-two BPAs were guided by contrast-enhanced CACT acquired immediately before BPA (G3D). In another 20 BPAs (G2D), two orthogonal fluoroscopy images of the chest where acquired to compute a registration of a previously acquired CACT. Volume rendering-based graphic representations (VRT guidance) were generated indicating the origin and course of the vessels. Based on VRT guidance, the intervention was planned. Procedure durations and radiation exposure data were compared between the two groups (Wilcoxon test).

RESULTS

The overall intervention time was approximately 2 h in both groups (p = 0.31). BPA was successfully performed in G3D 91 % and G2D 94 %. No significant difference was found concerning the mean dose area product (DAP) related to fluoroscopy (p = 0.38), while DAP related to DSA was slightly higher in G3D (p = 0.048). Overall, DAP was significantly higher in G3D (p = 0.002).

CONCLUSIONS

The use of CACT for procedure guidance in patients undergoing BPA is feasible and accurate. Image fusion of a pre-acquired CACT can be used to decrease radiation exposure due to multiple BPA sessions.

KEY POINTS

• BPA guidance by CACT overlay is feasible and safe. • 2D3D image fusion for BPA guidance is accurate. • Image fusion can reduce patient radiation dose due to repeated BPA sessions.

Radiation exposure of the interventional radiologist during percutaneous biopsy using a multiaxis interventional C-arm CT system with 3D laser guidance: a phantom study

OBJECTIVE

Evaluation of absolute radiation exposure values for interventional radiologists (IRs) using a multiaxis interventional flat-panel C-arm cone beam CT (CBCT) system with three-dimensional laser guidance for biopsy in a triple-modality, abdominal phantom.

METHODS

In the phantom, eight lesions were punctured in two different angles (in- and out-of-plane) using CBCT. One C-arm CT scan was performed to plan the intervention and one for post-procedural evaluation. Thermoluminescent dosemeters (TLDs) were used for dose measurement at the level of the eye lens, umbilicus and ankles on a pole representing the IRs. All measurements were performed without any lead protection. In addition, the dose-area product (DAP) and air kerma at the skin entrance point was documented.

RESULTS

Mean radiation values of all TLDs were 190 µSv for CBCT (eye lens: 180 µS, umbilicus: 230 µSv, ankle: 150 µSv) without a significant difference (p > 0.005) between in- and out-of-plane biopsies. In terms of radiation exposure of the phantom, the mean DAP was not statistically significantly different (p > 0.05) for in- and out-of-plane biopsies. Fluoroscopy showed a mean DAP of 7 or 6 μGym(2), respectively. C-arm CT showed a mean DAP of 5150 or 5130 μGym(2), respectively.

CONCLUSION

In our setting, the radiation dose to the IR was distinctly high using CBCT. For dose reduction, it is advisable to pay attention to lead shielding, to increase the distance to the X-ray source and to leave the intervention suite for C-arm CT scans.

ADVANCES IN KNOWLEDGE

The results indicate that using modern navigation tools and CBCT can be accompanied with a relative high radiation dose for the IRs since detector angulation can make the use of proper lead shielding difficult.

C-Arm Cone-Beam CT Virtual Navigation-Guided Percutaneous Mediastinal Mass Biopsy: Diagnostic Accuracy and Complications

OBJECTIVES

To assess the usefulness of C-arm cone-beam computed tomography (CBCT) virtual navigation-guided percutaneous mediastinal mass biopsy in terms of diagnostic accuracy and complication rates.

METHODS

Seventy-eight CBCT virtual navigation-guided percutaneous mediastinal mass biopsies were performed in 75 patients (M:F, 38:37; mean age, 48.55 ± 18.76 years). The procedural details, diagnostic sensitivity, specificity, accuracy and complication rate were investigated.

RESULTS

Mean lesion size was 6.80 ± 3.08 cm, skin-to-target distance was 3.67 ± 1.80 cm, core needle biopsy rate was 96.2 % (75/78), needle indwelling time was 9.29 ± 4.34 min, total procedure time was 13.26 ± 5.29 min, number of biopsy specimens obtained was 3.13 ± 1.02, number of CBCTs performed was 3.03 ± 0.68, rate of lesion border discrimination from abutting mediastinal structures on CBCT was 26.9 % (21/78), technical success rate was 100 % (78/78), estimated effective dose was 5.33 ± 4.99 mSv, and the dose area product was 12,723.68 ± 10,665.74 mGy⋅cm(2). Among the 78 biopsies, 69 were malignant, 7 were benign and 2 were indeterminate. Diagnostic sensitivity, specificity and accuracy for the diagnosis of malignancies were 97.1 % (67/69), 100 % (7/7) and 97.4 % (74/76), respectively, with a complication rate of 3.85 % (3/78), all of which were small pneumothoraces.

CONCLUSIONS

CBCT virtual navigation-guided biopsy is a highly accurate and safe procedure for the evaluation of mediastinal lesions.

KEY POINTS

• CBCT virtual navigation-guided percutaneous mediastinal biopsy is highly accurate • CBCT virtual navigation-guided percutaneous mediastinal biopsy is a safe procedure • Mediastinal vascular injury can be avoided under CBCT virtual navigation guidance.