Using cone-beam CT as a low-dose 3D imaging technique for the extremities: initial experience in 50 subjects

Cone beam CT in the imaging of musculoskeletal trauma: a scoping review

INTRODUCTION

Cone beam computed tomography (CBCT) is an emerging technology in musculoskeletal (MSK) imaging. The objective of this scoping review was to provide an overview of the research surrounding CBCT utility in bony injury assessment as an alternative to other imaging modalities and investigate any gaps in the current evidence base.

METHODS

MEDLINE, CINAHL, and PubMed were searched up to January 2025 for articles including CBCT studies on human participants following trauma. An online literature review tool was used to manage and streamline the review process.

RESULTS

The search yielded 23 studies. The image quality and diagnostic accuracy of CBCT were high overall, and a number of studies confirmed the radiation dose to be lower than multislice CT. Studies examined CBCT for extremity trauma, with half the studies focused solely on the wrist. The utility appears greatest in the identification of radiographically occult fractures. Limited cost-effectiveness analysis has been undertaken.

CONCLUSIONS

Overall, the literature suggests CBCT can be an effective tool in the diagnosis of bony injuries with greater sensitivity than radiography at a lower radiation dose than multi-slice computed tomography. However, evaluation of wider patient and economic impacts of adopting CBCT in MSK trauma pathways is recommended.

The Use of Cone-Beam Computed Tomography (CBCT) Arthrography for Wrist Ligamentous Injuries - A Diagnostic Test Accuracy Meta-analysis

Background: Diagnosis of ligamentous wrist injuries can be challenging with the absence of dynamic instability on radiographs. Our aim was to evaluate the accuracy of cone-beam computed tomography (CBCT) arthrography in diagnosing scapholunate ligament (SLL), lunotriquetral ligament (LTL) and triangular fibrocartilage complex (TFCC) injuries. Methods: A systematic review and literature search were conducted in compliance with Preferred Reporting Items for a Systematic Review and Meta-analysis (PRISMA) and registered at the International Prospective Register of Systematic Reviews, PROSPERO (CRD42024517655). A mixed-effects logistic regression bivariate model was used to estimate summary sensitivity and specificity, and hierarchical summary receiver operating characteristic (HSROC) curves were constructed to determine diagnostic accuracy of CBCT arthrography. Results: We identified five studies assessing the accuracy of CBCT arthrography against wrist arthrography or intraoperative findings as reference standard. The pooled estimates for sensitivity and specificity of CBCT arthrography was 93% (95% CI 40-100) and 91% (95% CI 81-96) for SLL injuries, 83% (95% CI 37-98) and 64% (95% CI 42-81) for LTL injuries and 78% (95% CI 57-91) and 80% (95% CI 54-93) for TFCC injuries. The area under the curve was 0.91 (95% CI 0.89-0.94), showing an excellent diagnostic accuracy of CBCT arthrography in SLL injuries. CBCT arthrography had an estimated mean effective dose of 3.2 mSv (2.0-4.8). Conclusions: Our study confirms that CBCT arthrography has an excellent diagnostic accuracy for wrist ligamentous injuries with comparably high sensitivity to conventional arthrography and a better specificity. While further studies with more robust methodology are required to support its implementation in clinical practice, our analysis shows that it is a reliable option and has a promising future. Level of Evidence: Level III (Diagnostic).

Dimensional Accuracy Assessment of Medical Anatomical Models Produced by Hospital-Based Fused Deposition Modeling 3D Printer

As 3D printing technology expands rapidly in medical disciplines, the accuracy evaluation of 3D-printed medical models is required. However, no established guidelines to assess the dimensional error of anatomical models exist. This study aims to evaluate the dimensional accuracy of medical models 3D-printed using a hospital-based Fused Deposition Modeling (FDM) 3D printer. Two dissected cadaveric right hands were marked with Titanium Kirshner wires to identify landmarks on the heads and bases of all metacarpals and proximal and middle phalanges. Both hands were scanned using a Cone Beam Computed Tomography scanner. Image post-processing and segmentation were performed on 3D Slicer software. Hand models were 3D-printed using a professional hospital-based FDM 3D printer. Manual measurements of all landmarks marked on both pairs of cadaveric and 3D-printed hands were taken by two independent observers using a digital caliper. The Mean Absolute Difference (MAD) and Mean Dimensional Error (MDE) were calculated. Our results showed an acceptable level of dimensional accuracy. The overall study's MAD was 0.32 mm (±0.34), and its MDE was 1.03% (±0.83). These values fall within the recommended range of errors. A high level of dimensional accuracy of the 3D-printed anatomical models was achieved, suggesting their reliability and suitability for medical applications.

Analysis of spatial patellofemoral alignment using novel three-dimensional measurements based on weight-bearing cone-beam CT

OBJECTIVES

To propose a reliable and standard 3D assessment method to analyze the effect of weight-bearing (WB) status on the location of patella and clarify the diagnostic performance of 3D parameters for recurrent patellar dislocation (RPD) in WB and non-weight-bearing (NWB) conditions.

METHODS

Sixty-five knees of RPD patients and 99 knees of controls were included. Eight landmarks, two lines and a coordinate system were defined on 3D bone models of knees based on weight-bearing CT and non-weight-bearing CT. The shift and tilt of patella in three orthogonal axes (Xshift, Yshift, Zshift, Xtilt, Ytilt, Ztilt) were evaluated.

RESULTS

Xshift and Yshift were significantly higher, Zshift, Xtilt and Ytilt were significantly lower in WB condition than NWB condition (p < 0.001, p < 0.001, p = 0.001, p = 0.002, p = 0.010). In both WB and NWB conditions, Xshift, Yshift and Ztilt were significantly higher, and Xtilt was significantly lower in the RPD group than the control group (WB/NWB: p < 0.001/p = 0.002, p < 0.001/p = 0.001, p < 0.001/p < 0.001, p < 0.001/p = 0.009). In WB condition, Zshift and Ytilt were significantly higher in the RPD group than the control group (p = 0.011, p < 0.001). Ztilt had the best diagnostic performance for RPD in both WB and NWB conditions, with AUC of 0.887 (95% CI: 0.828, 0.946) and 0.885 (95% CI: 0.822, 0.947), respectively.

CONCLUSIONS

The 3D measurement method reliably and comprehensively reflected the relative spatial position relationship of the patellofemoral joint. It can be applied to the 3D preoperative planning of patellofemoral procedures. In addition, patellofemoral evaluation under the WB condition was essential to detect subtle underlying risk factors for RPD, with axial lateral patellar tilt being the best predictor.

CRITICAL RELEVANCE STATEMENT

This 3D measurement method under weight-bearing conditions contributes to comprehensively describing the relative spatial position of the patellofemoral joint in a standardized way and can be applied to preoperative evaluation for recurrent patellar dislocation.

KEY POINTS

Patellofemoral alignment is a 3D problem, and the accuracy of 2D parameters has been questioned. 3D measurement was reliable and comprehensively reflected relative spatial relationships of the patellofemoral joint. 3D measurements under weight-bearing condition help preoperative evaluation for RPD.

Cone-beam CT volumetry: a new method for evaluating osteotomy healing - a clinical evaluation and MDCT comparison

BACKGROUND

Fracture healing complications remain a major problem in trauma monitoring. An open wedge osteotomy of the distal radius provides a unique way of evaluating fracture healing. Since the introduction of cone-beam computed tomography (CBCT) at our institution, it has become the method of choice for assessing hand and wrist bones. To date, CT volumetry has been validated for multidetector CT (MDCT) but not for CBCT.

PURPOSE

To assess osteotomy healing using CBCT volumetry and to evaluate two different segmentation techniques.

MATERIAL AND METHODS

A total of 36 patients were surgically treated for malunited distal radius fractures with open-wedge osteotomy either leaving the void empty (open wedge empty [OWE]) or filled with bone graft substitutes (BGS). They were scanned using CBCT and MDCT postoperatively and after 3, 6, and 12 months. Segmentation was performed both manually and semi-automatically for volumetric measurement. Inter- and intra-observer reliability were assessed using intraclass correlation (ICC).

RESULTS

The median osteotomy volume in the OWE group postoperatively was 0.87 cm3 (range=0.42-2.72). At 3 months, all but one of the OWE volumes had diminished to half or less of their initial volume. In the BGS group, the median postoperative volume was 1.30 cm3 (range=0.73-1.81) and at 12 months, 76% of the initial volume remained. Reliability between CBCT and MDCT volumetry expressed as ICC was ≥0.96. ICC for the two segmentation techniques was ≥0.99 and ICC for inter-observer reliability ≥0.97.

CONCLUSION

CBCT volumetry is a reliable tool and comparable to MDCT to quantify bone healing of an osteotomy.

Space Radiology: Emerging Nonsonographic Medical Imaging Techniques and the Potential Applications for Human Spaceflight

Space medicine is a multidisciplinary field that requires the integration of medical imaging techniques and expertise in diagnosing and treating a wide range of acute and chronic conditions to maintain astronaut health. Medical imaging within this domain has been viewed historically through the lens of inflight point-of-care ultrasound and predominantly research uses of cross-sectional imaging before and after flight. However, space radiology, a subfield defined here as the applications of imaging before, during, and after spaceflight, will grow to necessitate the involvement of more advanced imaging techniques and subspecialist expertise as missions increase in length and complexity. While the performance of imaging in spaceflight is limited by equipment mass and volume, power supply, radiation exposure, communication delays, and personnel training, recent developments in nonsonographic modalities have opened the door to their potential for in-mission use. Additionally, improved exam protocols and scanner technology in combination with artificial intelligence algorithms have greatly advanced the utility of possible pre- and postflight studies. This article reviews the past and present of space radiology and discusses possible use cases, knowledge gaps, and future research directions for radiography, fluoroscopy, computed tomography, and magnetic resonance imaging within space medicine, including both the performance of new exam types for new indications and the increased extraction of information from exams already routinely obtained. Through thoughtfully augmenting the use of these tools, medical mission risk may be reduced substantially through preflight screening, inflight diagnosis and management, and inflight and postflight surveillance.

Cone-Beam Computed Tomography (CBCT)-Based Diagnosis of Dental Bone Defects

Cone Beam Computed Tomography (CBCT) has completely changed the way that bone disorders are diagnosed and treated, especially in the dental and maxillofacial domains. This article examines the diverse applications of computed tomography (CBCT) in the diagnosis and treatment of facial trauma, including mandibular, dentoalveolar, and other facial fractures, as well as bone abnormalities like dislocations and fractures. CBCT is useful for a wide range of dental conditions and greatly improves diagnostic accuracy in periodontics, orthodontics, endodontics, and dental implantology. Additionally, a comparison between CBCT and conventional imaging methods was conducted, emphasizing the latter's inferior 3D imaging capabilities, allowing for more precise treatment planning and better patient outcomes with CBCT. Although CBCT has many benefits, it also has some drawbacks, such as requiring specific training for accurate interpretation, cost considerations, and a higher radiation exposure than with traditional dental X-rays. In order to optimize benefits and reduce risks, the conclusion highlights CBCT's revolutionary influence on clinical practice while arguing for its prudent and responsible application.

A procedural step analysis of radiation exposure in fenestrated endovascular aortic repair

OBJECTIVE

Radiation exposure during complex endovascular aortic repair may be associated with tangible adverse effects in patients and operators. This study aimed to identify the steps of highest radiation exposure during fenestrated endovascular aortic repair (FEVAR) and to investigate potential intraoperative factors affecting radiation exposure.

METHODS

Prospective data of 31 consecutive patients managed exclusively with four-fenestration endografts between March 1, 2020, and July 1, 2022 were retrospectively analyzed. Leveraging the conformity of the applied technique, every FEVAR operation was considered a combination of six overall stages composed of 28 standardized steps. Intraoperative parameters, including air kerma, dose area product, fluoroscopy time, and number of digital subtraction angiographies (DSAs) and average angulations were collected and analyzed for each step.

RESULTS

The mean procedure duration and fluoroscopy time was 140 minutes (standard deviation [SD], 32 minutes), and 40 minutes (SD, 9.1 minutes), respectively. The mean air kerma was 814 mGy (SD, 498 mGy), and the mean dose area product was 66.8 Gy cm2 (SD, 33 Gy cm2). The percentage of air kerma of the entire procedure was distributed throughout the following procedure stages: preparation (13.9%), main body (9.6%), target vessel cannulation (27.8%), stent deployment (29.1%), distal aortoiliac grafting (14.3%), and completion (5.3%). DSAs represented 23.0% of the total air kerma. Target vessel cannulation and stent deployment presented the highest mean lateral angulation (67 and 63 degrees, respectively). Using linear regression, each minute of continuous fluoroscopy added 18.9 mGy of air kerma (95% confidence interval, 17.6-20.2 mGy), and each DSA series added 21.1 mGy of air kerma (95% confidence interval, 17.9-24.3 mGy). Body mass index and lateral angulation were significantly associated with increased air kerma (P < .001).

CONCLUSIONS

Cannulation of target vessels and bridging stent deployment are the steps requiring the highest radiation exposure during FEVAR cases. Optimized operator protection during these steps is mandatory.

Evaluation of Motion Artifact Correction Technique for Cone-Beam Computed Tomography Image Considering Blood Vessel Geometry

Background: In this study, we present a quantitative method to evaluate the motion artifact correction (MAC) technique through the morphological analysis of blood vessels in the images before and after MAC. Methods: Cone-beam computed tomography (CBCT) scans of 37 patients who underwent transcatheter chemoembolization were obtained, and images were reconstructed with and without the MAC technique. First, two interventional radiologists selected the blood vessels corrected by MAC. We devised a motion-corrected index (MCI) metric that analyzed the morphology of blood vessels in 3D space using information on the centerline of blood vessels, and the blood vessels selected by the interventional radiologists were quantitatively evaluated using MCI. In addition, these blood vessels were qualitatively evaluated by two interventional radiologists. To validate the effectiveness of the devised MCI, we compared the MCI values in a blood vessel corrected by MAC and one non-corrected by MAC. Results: The visual evaluation revealed that motion correction was found in the images of 23 of 37 patients (62.2%), and a performance evaluation of MAC was performed with 54 blood vessels in 23 patients. The visual grading analysis score was 1.56 ± 0.57 (radiologist 1) and 1.56 ± 0.63 (radiologist 2), and the proposed MCI was 0.67 ± 0.11, indicating that the vascular morphology was well corrected by the MAC. Conclusions: We verified that our proposed method is useful for evaluating the MAC technique of CBCT, and the MAC technique can correct the blood vessels distorted by the patient's movement and respiration.

On the use of intraoperative 3D-RX C-arm imaging in orthognathic surgery: a prospective non-consecutive case series study

CONTEXT

Segment and osteosynthesis malposition resulting in patients' complaints (mainly about asymmetries) are encountered in orthofacial/orthognathic surgery.

OBJECTIVE, DESIGN, AND SETTING

We planned to investigate the usefulness of intraoperative three-dimensional (3D) imaging concerning positioning and fixation of bone segments and osteosynthesis in orthognathic/orthofacial surgery. We performed a prospective study of non-consecutive cases. All patients receiving a bimaxillary osteotomy, genioplasty, and their combinations were included in the study from May 2016 to May 2020. Unilateral and bilateral sagittal split osteotomies were excluded. There were no gender and age limitations. All were intraoperatively examined using the BV Pulsera 3D-RX System (Philips Medical, Eindhoven, The Netherlands). The outcome variables were the percentage of revisions of segment positioning and osteosynthesis. Predictor variables were age, gender, type of surgery, timing (pre- and post-imaging), and surgeon experience (senior vs assistant).

RESULTS

Forty female and twenty-two male patients were included (mean age 25.25 years ± 7.52 and 29.1 years ± 12.6 respectively). We evaluated 27 genioplasties and 34 Le Fort "type-I" osteotomies. Indications for segment repositioning and redo-osteosynthesis increased after intraoperative imaging as compared to operator's clinical judgment before intraoperative imaging (95% confidence interval; p < .001 and p = .002 respectively).

CONCLUSION

Suboptimal positioning and fixation of bone segments or osteosynthesis were more apparent with 3D imaging. In addition, some satisfactory cases were also revised for an optimal outcome. As a result, surgeons were prompted to more revisions than judged necessary without intraoperative imaging.

Cone-Beam CT of the Extremities in Clinical Practice

Cone-beam CT (CBCT) is a promising tool with increasing applications in musculoskeletal imaging due to its ability to provide thin-section CT images of the appendicular skeleton and introduce weight bearing, which accounts for loading forces that typically interact with and affect this anatomy. CBCT devices include an x-ray source directly opposite a digital silicon detector panel that performs a single rotation around an object of interest, obtaining thin-section images. Currently, the majority of research has been focused on the utility of CBCT with foot and ankle pathologic abnormalities, due to the complex architectural arrangement of the tarsal bones and weight-bearing nature of the lower extremities. Associated software can provide a variety of options for image reconstruction, including metal artifact reduction, three-dimensional biometric measurements, and digitally reconstructed radiographs. Advancements in this technology have allowed imaging of the knee, hip, hand, and elbow. As more data are published, it is becoming evident that CBCT provides many additional benefits, including fast imaging time, low radiation dose, lower cost, and small equipment footprint. These benefits allow placement of CBCT units outside of the traditional radiology department, including the orthopedic clinic setting. These technologic developments have motivated clinicians to define the scope of CBCT for diagnostics, surgical planning, and longitudinal imaging. As efforts are made to create standardized protocol and measurements, the current understanding and surgical approach for various orthopedic pathologic conditions will continue to shift, with the hope of improving outcomes. ©RSNA, 2024 Test Your Knowledge questions for this article are available in the supplemental material.

The Role of Cone-Beam Computed Tomography CT Extremity Arthrography in the Preoperative Assessment of Osteoarthritis

Osteoarthritis (OA) is a prevalent disease and the leading cause of pain, disability, and quality of life deterioration. Our study sought to evaluate the image quality and dose of cone-beam computed tomography arthrography (CBCT-A) and compare them to digital radiography (DR) for OA diagnoses. Overall, 32 cases of CBCT-A and DR with OA met the inclusion criteria and were prospectively analyzed. The Kellgren and Lawrence classification (KLC) stage, sclerosis, osteophytes, erosions, and mean joint width (MJW) were compared between CBCT-A and DR. Image quality was excellent in all CBCT-A cases, with excellent inter-observer agreement. OA under-classification was noticed with DR for MJW (p = 0.02), osteophyte detection (<0.0001), and KLC (p < 0.0001). The Hounsfield Unit (HU) values obtained for the cone-beam computed tomography CBCT did not correspond to the values for multi-detector computed tomography (MDCT), with a greater mean deviation obtained with the MDCT HU for Modeled Based Iterative Reconstruction 1st (MBIR1) than for the 2nd generation (MBIR2). CBCT-A has been found to be more reliable for OA diagnosis than DR as revealed by our results using a three-point rating scale for the qualitative image analysis, with higher quality and an acceptable dose. Moreover, the use of this imaging technique permits the preoperative assessment of extremities in an OA diagnosis, with the upright position and bone microarchitecture analysis being two other advantages of CBCT-A.

Subchondral bone in knee osteoarthritis: bystander or treatment target?

The subchondral bone is an important structural component of the knee joint relevant for osteoarthritis (OA) incidence and progression once disease is established. Experimental studies have demonstrated that subchondral bone changes are not simply the result of altered biomechanics, i.e., pathologic loading. In fact, subchondral bone alterations have an impact on joint homeostasis leading to articular cartilage loss already early in the disease process. This narrative review aims to summarize the available and emerging imaging techniques used to evaluate knee OA-related subchondral bone changes and their potential role in clinical trials of disease-modifying OA drugs (DMOADs). Radiographic fractal signature analysis has been used to quantify OA-associated changes in subchondral texture and integrity. Cross-sectional modalities such as cone-beam computed tomography (CT), contrast-enhanced cone beam CT, and micro-CT can also provide high-resolution imaging of the subchondral trabecular morphometry. Magnetic resonance imaging (MRI) has been the most commonly used advanced imaging modality to evaluate OA-related subchondral bone changes such as bone marrow lesions and altered trabecular bone texture. Dual-energy X-ray absorptiometry can provide insight into OA-related changes in periarticular subchondral bone mineral density. Positron emission tomography, using physiological biomarkers of subchondral bone regeneration, has provided additional insight into OA pathogenesis. Finally, artificial intelligence algorithms have been developed to automate some of the above subchondral bone measurements. This paper will particularly focus on semiquantitative methods for assessing bone marrow lesions and their utility in identifying subjects at risk of symptomatic and structural OA progression, and evaluating treatment responses in DMOAD clinical trials.

Cone-beam computed tomography in the treatment of distal radius fractures

Cone-beam computed tomography (CBCT) is a relatively new imaging technique in hand surgery. Being the most common fractures in adults, distal radius fractures are of special importance not only to hand surgeons. The quantity alone calls for fast, efficient and reliable diagnostic procedures. Surgical techniques and possibilities are progressing, especially regarding intra-articular fracture patterns. The demand for exact anatomic reduction is high. There is an overall consensus regarding the indication for preoperative three-dimensional imaging and it is frequently used. Typically, it is obtained by multi-detector computed tomography (MDCT). Postoperative diagnostic procedures are usually limited to plain x-rays. Commonly accepted recommendations regarding postoperative 3D imaging are not yet established. There is a lack of relevant literature. In case of an indication for a postoperative CT scan, it is generally also obtained by MDCT. CBCT for the wrist is not widely used as yet. This review focuses on the potential role of CBCT in the perioperative management of distal radius fractures. CBCT allows for high-resolution imaging with a potentially lower radiation dose compared with MDCT, both with and without implants. It is easily available and can be operated independently, thus being time-efficient and making daily practice easier. Due to its many advantages, CBCT is a recommendable alternative to MDCT in the perioperative management of distal radius fractures.

Distance mapping in three-dimensional virtual surgical planning in hand, wrist and forearm surgery: a tool to avoid mistakes

PURPOSE

Three-dimensional planning in corrective surgeries in the hand and wrist has become popular throughout the last 20 years. Imaging technologies and software have improved since their first description in the late 1980s. New imaging technologies, such as distance mapping (DM), improve the safety of virtual surgical planning (VSP) and help to avoid mistakes. We describe the effective use of DM in two representative and frequently performed surgical interventions (radius malunion and scaphoid pseudoarthrosis).

METHODS

We simulated surgical intervention in both cases using DM. Joint spaces were quantitatively and qualitatively displayed in a colour-coded fashion, which allowed the estimation of cartilage thickness and joint space congruency. These parameters are presented in the virtual surgical planning pre- and postoperatively as well as in the actual situation in our cases.

RESULTS

DM had a high impact on the VSP, especially in radius corrective osteotomy, where we changed the surgical plan due to the visualization of the planned postoperative situation. The actual postoperative situation was also documented using DM, which allowed for comparison of the VSP and the achieved postoperative situation. Both patients were successfully treated, and bone healing and clinical improvement were achieved.

CONCLUSION

The use of colour-coded static or dynamic distance mapping is useful for virtual surgical planning of corrective osteotomies of the hand, wrist and forearm. It also allows confirmation of the correct patient treatment and assessment of the follow-up radiological documentation.

Gantry-Free High-Resolution Cone-Beam CT: Efficacy for Distal Radius and Scaphoid Fracture Detection and Characterization

OBJECTIVES

Gantry-free cone-beam CT (CBCT) allows for comfortable patient positioning due to an open scanner architecture. Since CBCT without gantry is not yet established for clinical wrist trauma imaging, this study's aim was to investigate its diagnostic value in the preoperative workup of patients with distal radius and scaphoid fractures.

METHODS

Within a 12-month period, 113 patients with severe wrist trauma underwent both radiography and CBCT with the same gantry-free multi-use scanner before surgery. Two radiologists retrospectively analyzed all datasets for the morphology of distal radius (n = 95) and scaphoid fractures (n = 20). In all 115 wrists (two bilateral injuries), surgical reports served as the standard of reference.

RESULTS

While accuracy for distal radius fractures was comparable among CBCT and radiographs, the former was superior with regard to scaphoid fractures (Reader 1: 100.0% vs. 75.0%; Reader 2: 100.0% vs. 65.0%). Accuracy for multi-fragmentary radius injuries (100.0% vs. 90.5%; 100.0% vs. 93.7%), and articular affliction (99.0% vs. 84.2%; 100.0% vs. 83.2%) was also higher in CBCT. Regarding scaphoid fractures, CBCT proved superior for diagnosis of proximal pole or waist involvement (100.0% vs. 70.0%; 100.0% vs. 65.0%) and comminuted patterns (100.0% vs. 70.0%; 100.0% vs. 75.0%). Median effective dose of CBCT was as low as 3.65 µSv compared with 0.16 µSv for standard radiography.

CONCLUSION

Gantry-free CBCT allows for excellent diagnostic accuracy in the assessment of distal radius and scaphoid fracture morphology. Even in patients with limited mobility, very low radiation dose is sufficient to maintain high image quality.

Weight-Bearing Computed Tomography of the Foot and Ankle in the Pediatric Population

BACKGROUND

Newer cone-beam computed tomography (CT) technology has grown in popularity for evaluation of foot and ankle pathology in the weight-bearing (WB) position. Many studies have demonstrated its benefits within the adult population, but there is a paucity of its use within the pediatric literature. The purpose of this study was to describe the indications and clinical findings of WBCT within a pediatric population.

METHODS

A retrospective cohort of 68 patients (86 extremities) who underwent WBCT for a variety of conditions were compared with 48 patients (59 extremities) who underwent traditional supine nonweight-bearing (NWB) CTs. Clinical indications, demographic data, radiation doses, and cost were obtained from the medical record. WBCTs were obtained in a private outpatient orthopaedic clinic, and the conventional NWBCTs were obtained within a hospital-based system.

RESULTS

The most common indications for obtaining a WBCT and NWBCT in our study were fracture, tarsal coalition, and Lisfranc injury. The average WBCT radiation dose was 0.63 mGy for patients <100 lbs and 1.1 mGy for patients >100 lbs undergoing WBCT. For NWBCTs, the average radiation dose was 7.92 mGy for patients <100 lbs and 10.37 mGy for patients greater than 100 lbs. There was a significant reduction in radiation dose for all patients who underwent WBCT (P<0.0001 vs. 0.002). The average reimbursement for NWBCTs was $505 for unilateral studies and $1451 for bilateral studies. The average reimbursement for the WBCTs was $345 for unilateral studies and $635 for bilateral studies.

CONCLUSIONS

WBCT offers a new modality for studying complex foot and ankle pathoanatomy in the pediatric population at a reduced radiation exposure and reduced cost.

LEVEL OF EVIDENCE

Level III-a retrospective comparative study.

Ultra-low-dose cone-beam CT compared to standard dose in the assessment for acute fractures

PURPOSE

Multi-detector computed tomography (MDCT) is superior in fracture detection than conventional radiography; however, dose is increased. Cone-beam computed tomography (CBCT) offers higher spatial resolution and lower dose than MDCT. Manufacturers offer an ultra-low-dose algorithm. This study compares the diagnostic accuracy of the ultra-low-dose CBCT (ULDCBCT) with that of the standard-dose CBCT (SDCBCT).

MATERIALS AND METHODS

In total, 64 patients were scanned with both the SDCBCT and the ULDCBCT protocols. Both studies were reported by two consultant radiologists with fellowship training in emergency radiology separated in time. The reporter recorded a diagnosis of fracture or normal and diagnostic confidence using a 5-point Likert scale. The gold standard was taken as the SDCBCT. Reporters were blinded to the indication and the SDCBCT report. Cases of discrepancy were resolved by consensus.

RESULTS

There were 34 fractures and 30 cases had no fracture. Several fractures were missed using the UDCBCT, and there were also several cases of overdiagnosis. ULD was inferior to SD for fracture diagnosis (p < 0.00001). The diagnostic accuracy of ULDCBCT was 82.8% (75.1-88.9 CI). The diagnostic accuracy of plain radiograph was 64% (55.1-75.7% CI). Diagnostic confidence was reduced; the mean confidence for SDCBCT was 4.68 vs 4.12 for ULDCBCT (p < 0.001). The Kappa for interobserver agreement was 0.6.

CONCLUSION

ULDCBCT is inferior to SDCBCT in fracture detection and confidence is reduced. For diagnostic studies, the standard dose should be used.

Flat-panel conebeam CT in the clinic: history and current state

Research into conebeam CT concepts began as soon as the first clinical single-slice CT scanner was conceived. Early implementations of conebeam CT in the 1980s focused on high-contrast applications where concurrent high resolution ( < 200    μ m ), for visualization of small contrast-filled vessels, bones, or teeth, was an imaging requirement that could not be met by the contemporaneous CT scanners. However, the use of nonlinear imagers, e.g., x-ray image intensifiers, limited the clinical utility of the earliest diagnostic conebeam CT systems. The development of consumer-electronics large-area displays provided a technical foundation that was leveraged in the 1990s to first produce large-area digital x-ray detectors for use in radiography and then compact flat panels suitable for high-resolution and high-frame-rate conebeam CT. In this review, we show the concurrent evolution of digital flat panel (DFP) technology and clinical conebeam CT. We give a brief summary of conebeam CT reconstruction, followed by a brief review of the correction approaches for DFP-specific artifacts. The historical development and current status of flat-panel conebeam CT in four clinical areas-breast, fixed C-arm, image-guided radiation therapy, and extremity/head-is presented. Advances in DFP technology over the past two decades have led to improved visualization of high-contrast, high-resolution clinical tasks, and image quality now approaches the soft-tissue contrast resolution that is the standard in clinical CT. Future technical developments in DFPs will enable an even broader range of clinical applications; research in the arena of flat-panel CT shows no signs of slowing down.

Cone-beam computed tomography for primary investigation of wrist trauma provides a new map of fractures of carpal bones

In 2016, our primary modality for radiological examination of wrist trauma, was changed from radiography to cone-beam computed tomography (CBCT). This is a retrospective survey of carpal bone fractures detected by CBCT during 6 months in 2016/2017, compared with those found on conventional radiographs during 6 months in 2013/2014. The incidence of carpal fractures was three times higher during the CBCT period (92/100,000 per year) compared with the radiography period (29/100,000 per year) and the spectrum of anatomical locations was different between the two periods, with fractures of the lunate (n = 6), trapezium (n = 9), trapezoid (n = 4) and capitate (n = 1) detected by CBCT, in contrast to no fractures of these bones diagnosed during the 6 months radiography period. We suggest a more liberal use of CBCT for examination of wrist trauma considering the benefits of being able to give patients a correct primary diagnosis, treatment and prognosis.Level of evidence: III.

Comparative dosimetry of radiography device, MSCT device and two CBCT devices in the elbow region

The aim of the study was to estimate and to compare effective doses in the elbow region resulting from four different x-ray imaging modalities. Absorbed organ doses were measured using 11 metal oxide field effect transistor (MOSFET) dosimeters that were placed in a custom-made anthropomorphic elbow RANDO phantom. Examinations were performed using Shimadzu FH-21 HR radiography device, Siemens Sensation Open 24-slice MSCT-device, NewTom 5G CBCT device, and Planmed Verity CBCT device, and the effective doses were calculated according to ICRP 103 recommendations. The effective dose for the conventional radiographic device was 1.5 µSv. The effective dose for the NewTom 5G CBCT ranged between 2.0 and 6.7 µSv, for the Planmed Verity CBCT device 2.6 µSv and for the Siemens Sensation MSCT device 37.4 µSv. Compared with conventional 2D radiography, this study demonstrated a 1.4-4.6 fold increase in effective dose for CBCT and 25-fold dose for standard MSCT protocols. When compared with 3D CBCT protocols, the study showed a 6-19 fold increase in effective dose using a standard MSCT protocol. CBCT devices offer a feasible low-dose alternative for elbow 3D imaging when compared to MSCT.

Application of ultra-low-dose CT in 3D printing of distal radial fractures

PURPOSE

To explore the effect of ultra-low-dose computed tomography (CT) on three-dimensional (3D) printing models and the diagnosis of wrist fractures.

METHOD

This study enrolled 76 patients with distal radial fractures (DRFs). All patients underwent 320-row detector CT and were divided randomly into two groups. In Group A, 38 patients were scanned with the standard-dose protocol using a tube voltage of 120 kV and current of 100 mA. In Group B, 38 patients were scanned with the ultra-low-dose protocol using a tube voltage of 80 kV and current of 10 mA. For objective image quality assessment, the noise, CT number, signal-to-noise ratio (SNR), and contrast-to-noise ratio (CNR) were measured. Subjectively, two experienced orthopaedic surgeons blinded to the scan parameters evaluated the clarity of the 3D printing model and fracture line using a 3-point scale (the diagnosis was considered acceptable with scores ≥2). The mean radiation dose was calculated. The diagnostic performances for the fractures between the two groups were compared.

RESULTS

The effective radiation dose was significantly reduced by 97.1 % in Group B, compared to Group A (0.28 ± 0.05vs. 9.75 ± 2.23 μSv, respectively). Quantitative objective image quality parameters (e.g., CNR, SNR, and CT numbers) were higher in the standard-dose group (p < 0.001). However, there was no difference in subjective scoring of the 3D printing model. Although the fracture line score was higher in Group A (2.92±0.27 vs. 2.16 ± 0.37; p < 0.001), the diagnostic performance of the two groups was consistent (all scores ≥2). There were no statistically significant differences in the sensitivity, specificity or accuracy between standard-dose group and ultra-low-dose group.

CONCLUSIONS

The ultra-low-dose protocol effectively reduced the radiation dose by 97.1 %, while maintaining the image quality for diagnosis of DRFs. Therefore, this protocol can meet the needs of 3D printing models for preoperative assessments.

Twin robotic x-ray system in small bone and joint trauma: impact of cone-beam computed tomography on treatment decisions

Objectives

Trauma evaluation of extremities can be challenging in conventional radiography. A multi-use x-ray system with cone-beam CT (CBCT) option facilitates ancillary 3-D imaging without repositioning. We assessed the clinical value of CBCT scans by analyzing the influence of additional findings on therapy.

Methods

Ninety-two patients underwent radiography and subsequent CBCT imaging with the twin robotic scanner (76 wrist/hand/finger and 16 ankle/foot/toe trauma scans). Reports by on-call radiologists before and after CBCT were compared regarding fracture detection, joint affliction, comminuted injuries, and diagnostic confidence. An orthopedic surgeon recommended therapy based on reported findings. Surgical reports (N = 52) and clinical follow-up (N = 85) were used as reference standard.

Results

CBCT detected more fractures (83/64 of 85), joint involvements (69/53 of 71), and multi-fragment situations (68/50 of 70) than radiography (all p < 0.001). Six fractures suspected in radiographs were ruled out by CBCT. Treatment changes based on additional information from CBCT were recommended in 29 patients (31.5%). While agreement between advised therapy before CBCT and actual treatment was moderate (κ = 0.41 [95% confidence interval 0.35–0.47]; p < 0.001), agreement after CBCT was almost perfect (κ = 0.88 [0.83–0.93]; p < 0.001). Diagnostic confidence increased considerably for CBCT studies (p < 0.001). Median effective dose for CBCT was 4.3 μSv [3.3–5.3 μSv] compared to 0.2 μSv [0.1–0.2 μSv] for radiography.

Conclusions

CBCT provides advantages for the evaluation of acute small bone and joint trauma by detecting and excluding extremity fractures and fracture-related findings more reliably than radiographs. Additional findings induced therapy change in one third of patients, suggesting substantial clinical impact.

Key Points

• With cone-beam CT, extremity fractures and fracture-related findings can be detected and ruled out more reliably than with conventional radiography.

• Additional diagnostic information provided by cone-beam CT scans has substantial impact on therapy in small bone and joint trauma.

• For distal extremity injury assessment, one-stop-shop imaging without repositioning is feasible with the twin robotic x-ray system.

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.

Cost-effectiveness of introducing cone-beam computed tomography (CBCT) in the management of complex phalangeal fractures: economic simulation

Purpose

The purpose of this study was to evaluate the cost-effectiveness of introducing cone-beam computed tomography (CBCT) in the management of the complex finger fractures with articular involvement.

Methods

We created a decision tree model simulating the diagnostic pathway of complex finger fractures, suggesting the use of CBCT as alternative to multi-slice computed tomography (MSCT), and we compared their clinical outcomes, costs, and cost-effectiveness for a hypothetical cohort of 10,000 patients. Measures of effectiveness are analysed by using quality-adjusted life years, incremental cost-effectiveness ratio, and net monetary benefit.

Results

Diagnosis of a complex finger fracture performed with CBCT costed 67.33€ per patient, yielded 9.08 quality-adjusted life years, and gained an incremental cost-effectiveness ratio of 29.94€ and a net monetary benefit of 9.07 € at 30,000€ threshold. Using MSCT for diagnosis costed 106.23 €, yielded 8.18 quality-adjusted life years, and gained an incremental cost-effectiveness ratio of 371.15 € and a net monetary benefit of 8.09 €. CBCT strategy dominated the MSCT strategy. The acceptability curve shows that there is 98% probability of CBCT being the optimal strategy at 30,000€ threshold (1 EUR equal to 1.11 USD; updated on 02/02/2020).

Conclusion

CBCT in complex finger fractures management is cost saving compared with MSCT and may be considered a valuable imaging tool in preoperative assessment, allowing early detection and appropriate treatment. It shortens the time to completion of diagnostic work-up, reduces the number of additional diagnostic procedures, improves quality of life, and may reduce costs in a societal perspective.

Experiences with image quality and radiation dose of cone beam computed tomography (CBCT) and multidetector computed tomography (MDCT) in pediatric extremity trauma

INTRODUCTION

Novel dedicated extremity cone beam computed tomography (CBCT) devices, recently introduced to the market, raised attention as a possible alternative in advanced diagnostic pediatric trauma imaging, today usually performed by multidetector computed tomography (MDCT). This work aimed to compare image quality and radiation dose of CBCT and MDCT.

MATERIALS AND METHODS

Fifty-four CBCT-MDCT examination pairs, containing nine MDCTs acquired in parallel prospectively and 45 MDCTs matched in retrospect, were included in this study. Image quality was analyzed semi-objectively by measuring noise, contrast-to-noise ratio (CNR), and signal-to-noise ratios (SNR) and subjectively by performing image impression ratings. CT dose records were readout.

RESULTS

Image noise was significantly lower in CBCT compared with MDCT, both semi-objectively and subjectively (both p < 0.001). CNR and SNRs were also in favor of CBCT, though CBCT examinations exhibited significantly more beam hardening artifacts that diminished the advantages of the superior semi-objective image quality. These artifacts were believed to occur more often in children due to numerous bone-cartilage transitions in open growth plates and may have led to a better subjective diagnostic certainty rating (p = 0.001). Motion artifacts were infrequently, but exclusively observed in CBCT. CT dose index (CTDI_vol) was substantially lower in CBCT (p < 0.001).

CONCLUSION

Dedicated extremity CBCT could be an alternative low-dose modality in the diagnostic pathway of pediatric fractures. At lower doses compared with MDCT and commonly affected by beam hardening artifacts, semi-objective CBCT image quality parameters were generally better than in MDCT.

Ultra-low-dose CT for extremities in an acute setting: initial experience with 203 subjects

OBJECTIVE

The purpose of this study was to assess if ultra-low-dose CT is a useful clinical alternative to digital radiographs in the evaluation of acute wrist and ankle fractures.

MATERIALS AND METHODS

An ultra-low-dose protocol was designed on a 256-slice multi-detector CT. Patients from the emergency department were evaluated prospectively. After initial digital radiographs, an ultra-low-dose CT was performed. Two readers independently analyzed the images. Also, the radiation dose, examination time, and time to preliminary report was compared between digital radiographs and CT.

RESULTS

In 207 extremities, digital radiography and ultra-low-dose CT detected 73 and 109 fractures, respectively (p < 0.001). The odds ratio for fracture detection with ultra-low-dose CT vs. digital radiography was 2.0 (95% CI, 1.4-3.0). CT detected additional fracture-related findings in 33 cases (15.9%) and confirmed or ruled out suspected fractures in 19 cases (9.2%). The mean effective dose was comparable between ultra-low-dose CT and digital radiography (0.59 ± 0.33 μSv, 95% CI 0.47-0.59 vs. 0.53 ± 0.43 μSv, 95% CI 0.54-0.64). The mean combined examination time plus time to preliminary report was shorter for ultra-low-dose CT compared to digital radiography (7.6 ± 2.5 min, 95% CI 7.1-8.1 vs. 9.8 ± 4.7 min, 95% CI 8.8-10.7) (p = 0.002). The recommended treatment changed in 34 (16.4%) extremities.

CONCLUSIONS

Ultra-low-dose CT is a useful alternative to digital radiography for imaging the peripheral skeleton in the acute setting as it detects significantly more fractures and provides additional clinically important information, at a comparable radiation dose. It also provides faster combined examination and reporting times.

The Role of Cone-Beam Computed Tomography (CBCT) Scan for Detection and Follow-Up of Traumatic Wrist Pathologies

Emergency diagnostics demand fast, easily available, and cost-effective procedures. The higher the accuracy of radiological imaging, the better it supports the surgeon in decision-making for further treatment. Cone-beam computed tomography has been proven to be a reliable tool in diagnosing fractures of the hand and distal forearm. It can be easily installed, has a high spatial resolution, and a potentially lower radiation dose when compared with multislice computed tomography or a series of plain x-rays. This review focuses on the value of conventional radiography, cone-beam computed tomography, and multislice computed tomography for diagnosing traumatic wrist pathologies.

Incorporating Cone-Beam CT Into the Diagnostic Algorithm for Suspected Radiocarpal Fractures: A New Standard of Care?

OBJECTIVE. The purpose of this study was to assess the result of adding cone-beam CT to the standard imaging algorithm for patients with suspected radiographically occult traumatic radiocarpal fractures. SUBJECTS AND METHODS. A prospective review was performed on all patients who had cone-beam CT investigation of acute wrist pain after normal initial radiographs. Patients with no identified fractures were clinically reassessed and referred for MRI if concern for a fracture persisted. RESULTS. In all, 117 patients were assessed; 50.4% had fractures identified with a total of 67 radiographically occult fractures. One fracture was identified on MRI that was not seen on cone-beam CT. Cone-beam CT had sensitivity of 98.3% (95% CI, 91.1-100%), specificity of 100% (95% CI, 93.7-100%), positive predictive value of 100%, and negative predictive value of 98.3% (95% CI, 89.1-100%). Accuracy was 99.1% (95% CI, 95.3-100%). CONCLUSION. Incorporating cone-beam CT into routine clinical practice as part of a standardized diagnostic algorithm yielded a 50% fracture detection rate in patients with negative wrist radiographs but ongoing clinical concern for radiocarpal fracture. Cone-beam CT provides more diagnostic information than radiographs at a lower radiation dose than conventional MDCT. Given the poor accuracy of radiographs for acute radiocarpal fractures and the high fracture prevalence in this cohort, we feel that cone-beam CT should be regarded as the new standard of care in the investigation of these patients.

Trapezium fracture: a common clinical mimic of scaphoid fracture

PURPOSE

Fractures of the trapezium are rarely diagnosed on plain radiographs after acute wrist trauma. High-resolution cross-sectional imaging identifies fractures of the trapezium as the most common radiographically occult carpal bone fracture. We review the fracture frequency, mechanisms and patterns of trapezium fractures.

METHODS

Cone beam CT was performed in patients with suspected radiographically occult radiocarpal fracture following acute injury. The frequency of carpal bone fractures was assessed and compared.

RESULTS

Ninety-three radiographically occult wrist fractures were identified in 166 patients with acute trauma and negative radiographs. The trapezium was the most frequently fractured carpal bone, making up 20.4% of wrist fractures. Seventy-nine percent of trapezium fractures involved the volar ridge. The scaphoid was the clinically suspected fractured bone at initial assessment in 84% of patients with trapezium fractures.

CONCLUSION

Fractures of the trapezium in acute wrist trauma are much more common than described in the literature. If initial radiographs are negative, a fracture of the trapezium is more likely to be present than one of the scaphoid, despite high levels of clinical suspicion for scaphoid injuries. Awareness of the types and mechanisms of trapezium fracture is important. Cross-sectional imaging should be considered in all cases of post-traumatic wrist pain with negative radiographs.

Comparing the diagnostic performance of radiation dose-equivalent radiography, multi-detector computed tomography and cone beam computed tomography for finger fractures - A phantom study

PURPOSE

To compare the diagnostic performance and raters´confidence of radiography, radiography equivalent dose multi-detector computed tomography (RED-MDCT) and radiography equivalent dose cone beam computed tomography (RED-CBCT) for finger fractures.

METHODS

Fractures were inflicted artificially and randomly to 10 cadaveric hands of body donors. Radiography as well as RED-MDCT and RED-CBCT imaging were performed at dose settings equivalent to radiography. Images were de-identified and analyzed by three radiologists regarding finger fractures, joint involvement and confidence with their findings. Reference standard was consensus reading by two radiologists of the fracturing protocol and high-dose multi-detector computed tomography (MDCT) images. Sensitivity and specificity were calculated and compared with Cochrane´s Q and post hoc analysis. Rater´s confidence was calculated with Friedman Test and post hoc Nemenyi Test.

RESULTS

Rater´s confidence, inter-rater correlation, specificity for fractures and joint involvement were higher in RED-MDCT and RED-CBCT compared to radiography. No differences between the modalities were found regarding sensitivity.

CONCLUSION

In this phantom study, radiography equivalent dose computed tomography (RED-CT) demonstrates a partly higher diagnostic accuracy than radiography. Implementing RED-CT in the diagnostic work-up of finger fractures could improve diagnostics, support correct classification and adequate treatment. Clinical studies should be performed to confirm these preliminary results.

Hand-wrist, knee, and foot-ankle dosimetry and image quality measurements of a novel extremity imaging unit providing CBCT and 2D imaging options

PURPOSE

Radiation dose is a general concern in diagnostic imaging and a special concern for children who are at greater risk from radiation effects. This study evaluates effective doses (E) produced during 2D and volume imaging with a novel cone beam computed tomography (CBCT) based extremity imaging device. The device's compact size and protocol options offer image choices that enhance the potential for reduced dose and improved diagnostics when evaluating sports injuries.

METHODS

Hand-wrist, foot-ankle, and knee phantoms were developed for use with optically stimulated luminescent dosimeters (OSL). Dosimetry of transmission radiographs (2D) and CBCT volumes (3D) was assessed for Standard and lowered dose (Lite) exposure protocols. Effective dose was calculated for child and adult age groups. Image quality was assessed with contrast-to-noise ratio (CNR) and modulation transfer function (MTF). A figure of merit was calculated as the square of CNR divided by E.

RESULTS

Standard 2D doses ranged from 0.001-0.06 μSv for adults, 0.001-0.05 μSv for 15-yr olds, 0.003-0.13 μSv for 10-yr olds, and 0.005-0.20 for 5-yr olds. Dose reductions with Lite protocols ranged from 26 to 51%. Standard CBCT doses ranged from 0.3-4.6 μSv for adults, 0.3-4.4 μSv for 15-yr olds, 0.6-9.8 μSv for 10-yr olds, and 1-22.6 μSv for 5-yr olds. For both 2D and 3D a trend of increasing imaging dose with reduced age was present and was statistically significant for children below the age of 10 (P = 0.0009). Lite dose reductions averaged 47%. CNR was statistically reduced in Lite dose scans (P = 0.0384) but was not statistically different using FOM analysis (P = 0.3089). MTF was not significantly affected by the two dose protocols (P = 0.8104).

CONCLUSION

CBCT effective doses calculated from anthropomorphic phantom exposures following manufacturer suggested protocols appear to be substantially less than previously reported doses for similar MDCT extremity examinations. In this study, effective dose from 2D radiographic imaging was approximately two orders of magnitude less than CBCT imaging. Doses were on the order of a few minutes to hours of ubiquitous per-capita background dose for 2D imaging and a few hours to days for 3D imaging. Dose significantly increased for children younger than age 10. Lite protocols resulted in substantial dose reductions and can be recommended for children and those examinations where reduced CNR will not affect diagnosis. Flexibility of 2D and 3D imaging options with low-dose protocols make this technology a promising option for radiographic evaluation of the extremities. Efficacy studies are needed to determine when MDCT, CBCT or Digital Radiography are best used for particular diagnostic tasks.

Cone beam CT of the musculoskeletal system: clinical applications

Objectives

The aim of this pictorial review is to illustrate the use of CBCT in a broad spectrum of musculoskeletal disorders and to compare its diagnostic merit with other imaging modalities, such as conventional radiography (CR), Multidetector Computed Tomography (MDCT) and Magnetic Resonance Imaging.

Background

Cone Beam Computed Tomography (CBCT) has been widely used for dental imaging for over two decades.

Discussion

Current CBCT equipment allows use for imaging of various musculoskeletal applications. Because of its low cost and relatively low irradiation, CBCT may have an emergent role in making a more precise diagnosis, assessment of local extent and follow-up of fractures and dislocations of small bones and joints. Due to its exquisite high spatial resolution, CBCT in combination with arthrography may be the preferred technique for detection and local staging of cartilage lesions in small joints. Evaluation of degenerative joint disorders may be facilitated by CBCT compared to CR, particularly in those anatomical areas in which there is much superposition of adjacent bony structures. The use of CBCT in evaluation of osteomyelitis is restricted to detection of sequestrum formation in chronic osteomyelitis. Miscellaneous applications include assessment of (symptomatic) variants, detection and characterization of tumour and tumour-like conditions of bone.

Teaching Points

• Review the spectrum of MSK disorders in which CBCT may be complementary to other imaging techniques.

• Compare the advantages and drawbacks of CBCT compared to other imaging techniques.

• Define the present and future role of CBCT in musculoskeletal imaging.

Modeling and evaluation of a high-resolution CMOS detector for cone-beam CT of the extremities

PURPOSE

Quantitative assessment of trabecular bone microarchitecture in extremity cone-beam CT (CBCT) would benefit from the high spatial resolution, low electronic noise, and fast scan time provided by complementary metal-oxide semiconductor (CMOS) x-ray detectors. We investigate the performance of CMOS sensors in extremity CBCT, in particular with respect to potential advantages of thin (<0.7 mm) scintillators offering higher spatial resolution.

METHODS

A cascaded systems model of a CMOS x-ray detector incorporating the effects of CsI:Tl scintillator thickness was developed. Simulation studies were performed using nominal extremity CBCT acquisition protocols (90 kVp, 0.126 mAs/projection). A range of scintillator thickness (0.35-0.75 mm), pixel size (0.05-0.4 mm), focal spot size (0.05-0.7 mm), magnification (1.1-2.1), and dose (15-40 mGy) was considered. The detectability index was evaluated for both CMOS and a-Si:H flat-panel detector (FPD) configurations for a range of imaging tasks emphasizing spatial frequencies associated with feature size aobj. Experimental validation was performed on a CBCT test bench in the geometry of a compact orthopedic CBCT system (SAD = 43.1 cm, SDD = 56.0 cm, matching that of the Carestream OnSight 3D system). The test-bench studies involved a 0.3 mm focal spot x-ray source and two CMOS detectors (Dalsa Xineos-3030HR, 0.099 mm pixel pitch) - one with the standard CsI:Tl thickness of 0.7 mm (C700) and one with a custom 0.4 mm thick scintillator (C400). Measurements of modulation transfer function (MTF), detective quantum efficiency (DQE), and CBCT scans of a cadaveric knee (15 mGy) were obtained for each detector.

RESULTS

Optimal detectability for high-frequency tasks (feature size of ~0.06 mm, consistent with the size of trabeculae) was ~4× for the C700 CMOS detector compared to the a-Si:H FPD at nominal system geometry of extremity CBCT. This is due to ~5× lower electronic noise of a CMOS sensor, which enables input quantum-limited imaging at smaller pixel size. Optimal pixel size for high-frequency tasks was <0.1 mm for a CMOS, compared to ~0.14 mm for an a-Si:H FPD. For this fine pixel pitch, detectability of fine features could be improved by using a thinner scintillator to reduce light spread blur. A 22% increase in detectability of 0.06 mm features was found for the C400 configuration compared to C700. An improvement in the frequency at 50% modulation (f50 ) of MTF was measured, increasing from 1.8 lp/mm for C700 to 2.5 lp/mm for C400. The C400 configuration also achieved equivalent or better DQE as C700 for frequencies above ~2 mm-1 . Images of cadaver specimens confirmed improved visualization of trabeculae with the C400 sensor.

CONCLUSIONS

The small pixel size of CMOS detectors yields improved performance in high-resolution extremity CBCT compared to a-Si:H FPDs, particularly when coupled with a custom 0.4 mm thick scintillator. The results indicate that adoption of a CMOS detector in extremity CBCT can benefit applications in quantitative imaging of trabecular microstructure in humans.

Surface radiation dose comparison of a dedicated extremity cone beam computed tomography (CBCT) device and a multidetector computed tomography (MDCT) machine in pediatric ankle and wrist phantoms

Objectives

To evaluate and compare surface doses of a cone beam computed tomography (CBCT) and a multidetector computed tomography (MDCT) device in pediatric ankle and wrist phantoms.

Methods

Thermoluminescent dosimeters (TLD) were used to measure and compare surface doses between CBCT and MDCT in a left ankle and a right wrist pediatric phantom. In both modalities adapted pediatric dose protocols were utilized to achieve realistic imaging conditions. All measurements were repeated three times to prove test-retest reliability. Additionally, objective and subjective image quality parameters were assessed.

Results

Average surface doses were 3.8 ±2.1 mGy for the ankle, and 2.2 ±1.3 mGy for the wrist in CBCT. The corresponding surface doses in optimized MDCT were 4.5 ±1.3 mGy for the ankle, and 3.4 ±0.7 mGy for the wrist. Overall, mean surface dose was significantly lower in CBCT (3.0 ±1.9 mGy vs. 3.9 ±1.2 mGy, p<0.001). Subjectively rated general image quality was not significantly different between the study protocols (p = 0.421), whereas objectively measured image quality parameters were in favor of CBCT (p<0.001).

Conclusions

Adapted extremity CBCT imaging protocols have the potential to fall below optimized pediatric ankle and wrist MDCT doses at comparable image qualities. These possible dose savings warrant further development and research in pediatric extremity CBCT applications.

Motion compensation in extremity cone-beam CT using a penalized image sharpness criterion

Cone-beam CT (CBCT) for musculoskeletal imaging would benefit from a method to reduce the effects of involuntary patient motion. In particular, the continuing improvement in spatial resolution of CBCT may enable tasks such as quantitative assessment of bone microarchitecture (0.1 mm-0.2 mm detail size), where even subtle, sub-mm motion blur might be detrimental. We propose a purely image based motion compensation method that requires no fiducials, tracking hardware or prior images. A statistical optimization algorithm (CMA-ES) is used to estimate a motion trajectory that optimizes an objective function consisting of an image sharpness criterion augmented by a regularization term that encourages smooth motion trajectories. The objective function is evaluated using a volume of interest (VOI, e.g. a single bone and surrounding area) where the motion can be assumed to be rigid. More complex motions can be addressed by using multiple VOIs. Gradient variance was found to be a suitable sharpness metric for this application. The performance of the compensation algorithm was evaluated in simulated and experimental CBCT data, and in a clinical dataset. Motion-induced artifacts and blurring were significantly reduced across a broad range of motion amplitudes, from 0.5 mm to 10 mm. Structure similarity index (SSIM) against a static volume was used in the simulation studies to quantify the performance of the motion compensation. In studies with translational motion, the SSIM improved from 0.86 before compensation to 0.97 after compensation for 0.5 mm motion, from 0.8 to 0.94 for 2 mm motion and from 0.52 to 0.87 for 10 mm motion (~70% increase). Similar reduction of artifacts was observed in a benchtop experiment with controlled translational motion of an anthropomorphic hand phantom, where SSIM (against a reconstruction of a static phantom) improved from 0.3 to 0.8 for 10 mm motion. Application to a clinical dataset of a lower extremity showed dramatic reduction of streaks and improvement in delineation of tissue boundaries and trabecular structures throughout the whole volume. The proposed method will support new applications of extremity CBCT in areas where patient motion may not be sufficiently managed by immobilization, such as imaging under load and quantitative assessment of subchondral bone architecture.

Image quality of cone beam computed tomography for evaluation of extremity fractures in the presence of metal hardware: visual grading characteristics analysis

OBJECTIVE

To evaluate image quality and interobserver reliability of a novel cone-beam CT (CBCT) scanner in comparison with plain radiography for assessment of fracture healing in the presence of metal hardware.

METHODS

In this prospective institutional review board-approved Health Insurance Portability and Accountability Act of 1996-complaint study, written informed consent was obtained from 27 patients (10 females and 17 males; mean age 44 years, age range 21-83 years) with either upper or lower extremity fractures, and with metal hardware, who underwent CBCT scans and had a clinical radiograph of the affected part. Images were assessed by two independent observers for quality and interobserver reliability for seven visualization tasks. Visual grading characteristic (VGC) curve analysis determined the differences in image quality between CBCT and plain radiography. Interobserver agreement was calculated using Pearson's correlation coefficient.

RESULTS

VGC results displayed preference of CBCT images to plain radiographs in terms of visualizing (1) cortical and (2) trabecular bones; (3) fracture line; (4) callus formation; (5) bridging ossification; and (6) screw thread-bone interface and its inferiority to plain radiograph in the visualization of (7) large metallic side plate contour with strong interobserver correlation (p-value < 0.05), except for visualizing large metallic side plate contour.

CONCLUSION

For evaluation of fracture healing in the presence of metal hardware, CBCT image quality is preferable to plain radiograph for all visualization tasks, except for large metallic side plate contours. Advances in knowledge: CBCT has the potential to be a good diagnostic alternative to plain radiographs in evaluation of fracture healing in the presence of metal hardware.

Comparison of Diagnostic Accuracy of Radiation Dose-Equivalent Radiography, Multidetector Computed Tomography and Cone Beam Computed Tomography for Fractures of Adult Cadaveric Wrists

PURPOSE

To compare the diagnostic accuracy of radiography, to radiography equivalent dose multidetector computed tomography (RED-MDCT) and to radiography equivalent dose cone beam computed tomography (RED-CBCT) for wrist fractures.

METHODS

As study subjects we obtained 10 cadaveric human hands from body donors. Distal radius, distal ulna and carpal bones (n = 100) were artificially fractured in random order in a controlled experimental setting. We performed radiation dose equivalent radiography (settings as in standard clinical care), RED-MDCT in a 320 row MDCT with single shot mode and RED-CBCT in a device dedicated to musculoskeletal imaging. Three raters independently evaluated the resulting images for fractures and the level of confidence for each finding. Gold standard was evaluated by consensus reading of a high-dose MDCT.

RESULTS

Pooled sensitivity was higher in RED-MDCT with 0.89 and RED-MDCT with 0.81 compared to radiography with 0.54 (P = < .004). No significant differences were detected concerning the modalities' specificities (with values between P = .98). Raters' confidence was higher in RED-MDCT and RED-CBCT compared to radiography (P < .001).

CONCLUSION

The diagnostic accuracy of RED-MDCT and RED-CBCT for wrist fractures proved to be similar and in some parts even higher compared to radiography. Readers are more confident in their reporting with the cross sectional modalities. Dose equivalent cross sectional computed tomography of the wrist could replace plain radiography for fracture diagnosis in the long run.

Bone strength and management of postmenopausal fracture risk with antiresorptive therapies: considerations for women's health practice

Bone strength – and, hence, fracture risk – reflects the structural and material properties of the skeleton, which changes with bone turnover during aging and following effective pharmacotherapy. A variety of powerful new techniques (quantitative computed tomography, as well as peripheral quantitative computed tomography and high-resolution peripheral quantitative computed tomography) provide precise images of bone structure and can be used to model the response of specific bones to different types of mechanical load. This review explores the various components of bone strength and the clinical significance of measures, such as bone mineral density, bone turnover markers, and modern imaging data, with regard to fracture risk in women with postmenopausal osteoporosis, before and after initiating antiresorptive therapy. These imaging and related techniques offer an ever-clearer picture of the changes in bone structure and bone mineral metabolism during normal aging and in osteoporosis, as well as in response to treatment. However, because the newer techniques are not yet available in routine practice, validated tools for absolute fracture risk assessment remain essential for clinical decision making. These tools, which are tailored to patient risk data in individual countries, are based on bone mineral density and other readily available clinical data. In addition, bone turnover marker measurements can be useful in assessing risk and guiding treatment decisions for women with postmenopausal osteoporosis. Such tests may be used before starting a patient on antiresorptive therapy and for ongoing monitoring of treatment effectiveness.

Scattered image artifacts from cone beam computed tomography and its clinical potential in bone mineral density estimation

Background

Image artifacts affect the quality of medical images and may obscure anatomic structure and pathology. Numerous methods for suppression and correction of scattered image artifacts have been suggested in the past three decades. In this paper, we assessed the feasibility of use of information on scattered artifacts for estimation of bone mineral density (BMD) without dual-energy X-ray absorptiometry (DXA) or quantitative computed tomographic imaging (QCT).

Methods

To investigate the relationship between scattered image artifacts and BMD, we first used a forearm phantom and cone-beam computed tomography. In the phantom, we considered two regions of interest—bone-equivalent solid material containing 50 mg HA per cm⁻³ and water—to represent low- and high-density trabecular bone, respectively. We compared the scattered image artifacts in the high-density material with those in the low-density material. The technique was then applied to osteoporosis patients and healthy subjects to assess its feasibility for BMD estimation.

Results

The high-density material produced a greater number of scattered image artifacts than the low-density material. Moreover, the radius and ulna of healthy subjects produced a greater number of scattered image artifacts than those from osteoporosis patients.

Conclusions

Although other parameters, such as bone thickness and X-ray incidence, should be considered, our technique facilitated BMD estimation directly without DXA or QCT. We believe that BMD estimation based on assessment of scattered image artifacts may benefit the prevention, early treatment and management of osteoporosis.

Radiocarpal Injuries: Cone Beam Computed Tomography Arthrography, Magnetic Resonance Arthrography, and Arthroscopic Correlation among 21 Patients

Background and Aims:

Patients with acute or chronic wrist pain often undergo wrist arthroscopy for evaluation of chondral and ligamentous abnormalities. The purpose of this study was to compare findings of wrist arthroscopy with cone beam computed tomography arthrography and magnetic resonance arthrography.

Materials and Methods:

Altogether, 21 patients with wrist pain underwent cone beam computed tomography arthrography, magnetic resonance arthrography, and wrist arthroscopy. Chondral surfaces of the scaphoid, lunate, and radius facing the scaphoid and lunate were evaluated. The scapholunate ligament, the lunotriquetral ligament, and the triangular fibrocartilage complex were classified as either intact or torn. Sensitivity, specificity, positive and negative predictive values, and accuracy with 95% confidence intervals were assessed.

Results:

For chondral lesions (n = 10), cone beam computed tomography arthrograms showed slightly higher specificity than magnetic resonance arthrography. The sensitivity of cone beam computed tomography arthrography was also better for these lesions, except for those on the chondral surface of the lunate. For triangular fibrocartilage complex injuries (n = 9), cone beam computed tomography arthrography showed a better specificity and sensitivity than magnetic resonance arthrography. For ligamentous injuries (n = 6), cone beam computed tomography arthrograms were more sensitive, but less specific than magnetic resonance arthrography images. However, the number of lesions was very small and the 95% confidence intervals are overlapping.

Conclusion:

Cone beam computed tomography is an emerging imaging modality that offers several advantages over computed tomography and magnetic resonance imaging. Its usefulness particularly in ligamentous injuries should be further explored in a larger study. Cone beam computed tomography arthrography seems to offer similar sensitivity, specificity, and accuracy compared to magnetic resonance arthrography and therefore serves as a valuable option in evaluating patients with wrist pain.

Initial Clinical Experience With Extremity Cone-Beam CT of the Foot and Ankle in Pediatric Patients

OBJECTIVE

Extremity cone-beam CT (CBCT) scanners have become available for clinical use in the United States. The purpose of this study was to review an initial clinical experience with CBCT of the foot and ankle in pediatric patients.

MATERIALS AND METHODS

A retrospective review was conducted of all foot or ankle CBCT examinations performed on patients 18 years old and younger at one institution from August 1, 2013, through February 28, 2015. A t test was used to compare mean effective dose for CBCT with that for MDCT foot or ankle examinations of age-matched control subjects. To assess changes in utilization, a t test also was used to compare the mean numbers of foot or ankle CT examinations per month before and after installation of the CBCT scanner at the institution.

RESULTS

Thirty-four CBCT examinations were performed. The mean effective dose was 0.013 ± 0.003 mSv compared with 0.023 ± 0.020 mSv for MDCT of age-matched control subjects (p < 0.005). The mean numbers of foot or ankle CT examinations per month were 3.4 in the 18 months before and 3.8 in the 18 months after installation of the CBCT scanner (p = 0.28). The mean number of foot or ankle MDCT examinations per month decreased significantly (3.4 vs 1.9, p = 0.03) over the same period. In 56% of patients, CBCT revealed important findings that were not visible on contemporaneous radiographs. In 68% of patients, the CBCT findings affected clinical management.

CONCLUSION

CBCT of the foot or ankle of pediatric patients is a viable lower-dose alternative to MDCT that provides important information that may affect clinical management.