Diagnostic yield of dental radiography and digital tomosynthesis for the identification of anatomic structures in cats

Introduction

Digital tomosynthesis (DT) has emerged as a potential imaging modality for evaluating anatomic structures in veterinary medicine. This study aims to validate the diagnostic yield of DT in identifying predefined anatomic structures in feline cadaver heads, comparing it with conventional intraoral dental radiography (DR).

Methods

A total of 16 feline cadaver heads were utilized to evaluate 19 predefined clinically relevant anatomic structures using both DR and DT. A semi-quantitative scoring system was employed to characterize the ability of each imaging method to identify these structures.

Results

DT demonstrated a significantly higher diagnostic yield compared to DR for all evaluated anatomic structures. Orthogonal DT imaging identified 13 additional anatomic landmarks compared to a standard 10-view feline set obtained via DR. Moreover, DT achieved statistically significant higher scores for each of these landmarks, indicating improved visualization over DR.

Discussion

These findings validate the utility of DT technology in reliably identifying clinically relevant anatomic structures in the cat skull. This validation serves as a foundation for further exploration of DT imaging in detecting dentoalveolar and other maxillofacial bony lesions and pathologies in cats.

The use of digital tomosynthesis in suspected scaphoid fractures

We report a retrospective observational series of patients undergoing digital tomosynthesis (DTS) for suspected scaphoid fractures. With a specificity and sensitivity of 100%, DTS demonstrates the potential to be an excellent tool in the diagnosis of occult scaphoid fractures.

"Tool-in-lesion" Accuracy of Galaxy System-A Robotic Electromagnetic Navigation BroncHoscopy With Integrated Tool-in-lesion-Tomosynthesis Technology: The MATCH Study

BACKGROUND

The Galaxy System (Noah Medical) is a novel robotic endoluminal platform using electromagnetic navigation combined with integrated tomosynthesis technology and augmented fluoroscopy. It provides intraprocedural imaging to correct computerized tomography (CT) to body divergence and novel confirmation of tool-in-lesion (TIL). The primary aim of this study was to assess the TIL accuracy of the robotic bronchoscope with integrated digital tomosynthesis and augmented fluoroscopy.

METHODS

Four operators conducted the experiment using 4 pigs. Each physician performed between 4 and 6 nodule biopsies for 20 simulated lung nodules with purple dye and a radio pacifier. Using Galaxy's "Tool-in-Lesion Tomography (TOMO+)" with augmented fluoroscopy, the physician navigated to the lung nodules, and a tool (needle) was placed into the lesion. TIL was defined by the needle in the lesion determined by cone-beam CT.

RESULTS

The lung nodule's average size was 16.3 ± 0.97 mm and was predominantly in the lower lobes (65%). All 4 operators successfully navigated to all (100%) of the lesions in an average of 3 minutes and 39 seconds. The median number of tomosynthesis sweeps was 3 and augmented fluoroscopy was utilized in most cases (17/20 or 85%). TIL after the final TOMO sweep was 95% (19/20) and tool-touch-lesion was 5% (1/20). Biopsy yielding purple pigmentation was also 100% (20/20).

CONCLUSION

The Galaxy System demonstrated successful digital TOMO confirmed TIL success in 95% (19/20) of lesions and tool-touch-lesion in 5% (1/20) as confirmed by cone-beam CT. Successful diagnostic yield was achieved in 100% (20/20) of lesions as confirmed by intralesional pigment acquisition.

Digital Tomosynthesis: Review of Current Literature and Its Impact on Diagnostic Bronchoscopy

Bronchoscopy has garnered increased popularity in the biopsy of peripheral lung lesions. The development of navigational guided bronchoscopy systems along with radial endobronchial ultrasound (REBUS) allows clinicians to access and sample peripheral lesions. The development of robotic bronchoscopy improved localization of targets and diagnostic accuracy. Despite such technological advancements, published diagnostic yield remains lower compared to computer tomography (CT)-guided biopsy. The discordance between the real-time location of peripheral lesions and anticipated location from preplanned navigation software is often cited as the main variable impacting accurate biopsies. The utilization of cone beam CT (CBCT) with navigation-based bronchoscopy has been shown to assist with localizing targets in real-time and improving biopsy success. The resources, costs, and radiation associated with CBCT remains a hindrance in its wider adoption. Recently, digital tomosynthesis (DT) platforms have been developed as an alternative for real-time imaging guidance in peripheral lung lesions. In North America, there are several commercial platforms with distinct features and adaptation of DT. Early studies show the potential improvement in peripheral lesion sampling with DT. Despite the results of early observational studies, the true impact of DT-based imaging devices for peripheral lesion sampling cannot be determined without further prospective randomized trials and meta-analyses.

Advances in Bone Joint Imaging-Metal Artifact Reduction

Numerous types of metal implants have been introduced in orthopedic surgery and are used in everyday practice. To precisely evaluate the postoperative condition of arthroplasty or trauma surgery, periprosthetic infection, and the loosening of implants, it is important to reduce artifacts induced by metal implants. In this review, we focused on technical advances in metal artifact reduction using digital tomosynthesis, computed tomography, and magnetic resonance imaging. We discussed new developments in diagnostic imaging methods and the continuous introduction of novel technologies to reduce metal artifacts; however, these innovations have not yet completely removed metal artifacts. Different algorithms need to be selected depending on the size, shape, material and implanted body parts of an implant. Future advances in metal artifact reduction algorithms and techniques and the development of new sequences may enable further reductions in metal artifacts even on original images taken previously. Moreover, the combination of different imaging modalities may contribute to further reductions in metal artifacts. Clinicians must constantly update their knowledge and work closely with radiologists to select the best diagnostic imaging method for each metal implant.

Diagnostic Performance and Advanced Imaging Reduction With Digital Tomosynthesis in Scaphoid Fracture Management

BACKGROUND

Management of scaphoid fractures often requires advanced imaging to achieve accurate diagnoses and appropriate treatment. Digital tomosynthesis (DTS) is a cross-sectional imaging modality that may be used to substitute magnetic resonance imaging or computed tomographic scans. The purpose of this study is to: (1) determine the diagnostic accuracy of DTS in occult scaphoid fractures; and (2) report on the reduction of other advanced imaging when using DTS.

METHODS

From May 2014 to October 2017, the charts of all patients who underwent scaphoid tomogram were retrospectively reviewed. The diagnostic accuracy of DTS for occult fracture was compared with 2-week follow-up plain films. To measure the reduction in utilization of advanced imaging, it was determined whether DTS eliminated the need for advanced imaging by providing adequate information regarding the clinical question.

RESULTS

A total of 78 patients underwent scaphoid tomography in this time frame: 39 for occult fracture, 33 for fracture union, 5 for fracture morphology, and 1 for hardware positioning. For the detection of occult fracture, DTS had a sensitivity of 100%, specificity of 83%, positive predictive value of 64%, and negative predictive value of 100%. Advanced imaging was not used in 35 of the remaining 39 patients based on the results obtained by DTS. In patients who did receive advanced imaging, 83% of tomograms provided conclusive diagnostic information.

CONCLUSIONS

Digital tomosynthesis increases the diagnostic sensitivity of occult scaphoid fractures, reducing unnecessary immobilization and advanced imaging. Digital tomosynthesis provides clinical detail beyond plain film, which reduces the need to obtain advanced imaging when assessing union, fracture pattern, and hardware placement.

Shape-Sensing Robotic-Assisted Bronchoscopy vs Digital Tomosynthesis-Corrected Electromagnetic Navigation Bronchoscopy: A Comparative Cohort Study of Diagnostic Performance

BACKGROUND

Electromagnetic navigational bronchoscopy has been the dominant bronchoscopic technology for targeting small peripheral lesions and now includes digital tomosynthesis-electromagnetic navigational bronchoscopy (DT-ENB), allowing near-real-time intraprocedural nodule visualization. Shape-sensing robotic-assisted bronchoscopy (ssRAB), with improved catheter stability and articulation recently became available. Although the diagnostic performance of these two methods seems higher than that of legacy systems, data remain limited. We sought to compare the diagnostic yield of these two novel platforms after their introduction at our institution.

RESEARCH QUESTION

Does the diagnostic yield of ssRAB differ significantly from that of DT-ENB in patients undergoing biopsy of peripheral pulmonary lesions (PPLs)?

STUDY DESIGN AND METHODS

This retrospective comparative cohort study analyzed prospectively collected data on consecutive procedures performed with DT-ENB and ssRAB in their first 6 months of use at our institution. Biopsies were considered diagnostic if histopathologic analysis revealed malignancy or specific benign features that readily explained the presence of a PPL. Nonspecific inflammation, normal lung or airway, and atypia not diagnostic of malignancy were considered nondiagnostic.

RESULTS

SSRAB was used to biopsy 143 PPLs in 133 patients and DT-ENB was used to biopsy 197 PPLs in 170 patients. Diagnostic yield was 77% for ssRAB (110 of 143 PPLs) and 80% (158 of 197 PPLs) for DT-ENB (OR, 0.8; 95% CI, 0.5-1.4; P = .4). Median lesion diameters were 17 and 19 mm, respectively. No difference in diagnostic yield was found after adjustment for lesion size, bronchus sign, peripheral vs middle third location, and sex. Pneumothorax complicated 1.5% of ssRAB and 1.8% of DT-ENB procedures (P = .86).

INTERPRETATION

SSRAB and DT-ENB showed comparable diagnostic yields and safety profiles in this comparative cohort study.

Role of digital tomosynthesis in the context of tuberculosis contact investigation: comparisons with digital radiography

BACKGROUND

Chest radiography value as a screening tool in those exposed to pulmonary tuberculosis (TB) is reduced by its lower sensitivity to detect small intrapulmonary lesions.

PURPOSE

To evaluate the efficacy of digital tomosynthesis (DTS) screening of individuals that had contacted persons with active TB using low-dose computed tomography (CT) as the reference standard methods.

MATERIAL AND METHODS

This retrospective, community-based screening study of 90 adults who had been in close contact with a TB case was undertaken at our institution. All individuals underwent clinical evaluation, digital radiography (DR), DTS, and low-dose chest CT. Observers assessed and classified DR and DTS images using CT as the reference-standard method. Based on clinical and imaging findings, TB status was classified as normal, latent, minimal, subclinical, and active. Diagnostic performances of DTS and DR for the interpretation of correct diagnosis were calculated.

RESULTS

The estimated effective doses for DR, DTS, and low-dose CT were 0.01 mSv, 0.1 mSv, and 0.33 mSv, respectively. TB statuses of the 90 individuals were as follows: 62 latent (68.9%); two subclinical (2.2%); and one minimal (1.1%). The sensitivities, specificities, and accuracies of DTS and DR in the interpretation of correct diagnosis were 75.8%, 100%, 91.1% and 48.5%, 96.5%, 78.9%, respectively.

CONCLUSION

DTS appears to be superior to DR for the detection of lung lesions in individuals with TB contacts. DTS can offer a reasonable option for TB contact investigation.

Digital tomography in the diagnosis of a posterior pneumothorax in the intensive care unit

Portable chest radiography is a valuable tool in the intensive care unit. However, the supine position causes superposition of anatomical structures resulting in less reliable detection of certain abnormalities. Recently, a portable digital tomosynthesis (pDTS) prototype with a modified motorized X-ray device was developed. We aimed to compare the diagnostic value of pDTS to standard bedside chest radiography in the diagnosis of a posterior pneumothorax. A modified motorized X-ray device was developed to perform 15 radiographic projections while translating the X-ray tube 25 cm (10 cm ramp up and 15 cm during X-ray exposure) with a total radiation dose of 0.54 mSv. This new technique of pDTS was performed in addition to standard bedside chest X-ray in a patient with a confirmed posterior hydropneumothorax. The images were compared with the standard bedside chest X-ray and computed tomography (CT) images by two experienced radiologists. The posterior hydropneumothorax previously identified with CT was visible on tomosynthesis images but not with standard bedside imaging. Combining the digital tomosynthesis technique with the portable X-ray machine could increase the diagnostic value of bedside chest radiography for the diagnosis of posterior pneumothoraces while avoiding intrahospital transport and limiting radiation exposure compared to CT.

New Evaluation Method for Bone Formation around a Fully Hydroxyapatite-Coated Stem Using Digital Tomosynthesis: A Retrospective Cross-Sectional Study

Digital tomosynthesis (DTS) is a new imaging technique derived from radiography, and its usefulness has been gradually reported in the field of orthopedic diagnosis in recent years. A fully hydroxyapatite (HA)-coated stem, which is used for total hip arthroplasty (THA), is a type of cementless stem that has been widely used recently and reported to have good results. However, stem loosening on plain radiographs is difficult to determine in some cases due to cancellous condensation around the stem. In this retrospective cross-sectional study, we compared the results of plain radiography versus DTS to evaluate the imaging findings after THA using a fully HA-coated stem. Twenty joints each in the 3 y and 1 y postoperative groups underwent plain radiography and DTS. On DTS, bone formation around the stem was confirmed in all cases; however, this formation was not reproducible on plain radiography, and there were cases in which the reaction could not be confirmed or cases with cancellous condensation resembling reactive lines. This reaction was not reproducible on plain radiographs, and in some cases, the reaction could not be confirmed, or there were cases with cancellous condensation that resembled reactive lines. Therefore, DTS was useful in the diagnosis of bone formation around the implant.

Use of Digital Tomosynthesis in Assessing Accurate Medial Epicondyle Fracture Displacement as Compared With Conventional Radiography and Computed Tomography

INTRODUCTION

Medial epicondyle fracture displacement is notoriously difficult to determine on conventional radiography, and follow-up computed tomography (CT) is often obtained to measure precise displacement. Another option for fracture characterization is digital tomosynthesis (DT), a technology providing high in-plane resolution of bony anatomy by acquiring multiple low-dose images in a linear arc. Advantages of DT include lower radiation exposure and lower cost than CT, rapid image acquisition, and a similar patient experience to conventional radiography. The digital application of tomosynthesis is relatively new and is integrated as an add-on feature with modern radiography equipment. This study compares DT, CT and conventional radiography for measurement accuracy in medial epicondyle fractures with the goal of determining relative accuracy in measuring medial epicondyle fracture displacement.

METHODS

Medial epicondyle fractures were created in 5 cadaveric elbow specimens. Each specimen was imaged with conventional radiography, DT, and CT. True displacement measured by digital calipers was compared with "measured" displacement for each image acquisition. CT images included axial, sagittal, and coronal reformats. DT images of the elbow included anteroposterior (AP) longitudinal and transverse, lateral longitudinal and transverse, and axial longitudinal and transverse. Conventional radiographs included AP, lateral, and axial distal humerus images. Four physicians reviewed all images 3 months later. Each reviewer independently measured maximum apparent fracture displacement to the nearest 0.1 mm. Measurement accuracy was calculated as percent difference [(measured displacement-actual displacement)/actual displacement] for each acquisition. Mean, median, and SD for measurement accuracy were calculated. Two-tailed paired t tests were performed on each acquisition to compare the measurement accuracy.

RESULTS

Compared with conventional radiographs, accuracy of DT was superior in AP longitudinal (P=0.03), AP transverse (P=0.01), axial longitudinal (P=0.0001), and axial transverse projections (P=0.001). Accuracy of CT was superior to conventional radiography in the AP projection (P=0.03), but was equivalent in the axial projection (P=0.9). Accuracy of CT was similar to DT in AP longitudinal (P=0.6), AP transverse (P=0.5), and axial longitudinal projections (P=0.07). Accuracy of DT in the axial transverse projection was superior to CT (P=0.03).

CONCLUSION

DT is more accurate than conventional radiography (both AP and axial views) and as accurate as CT in assessing millimeters of displacement of medial epicondyle fracture fragments.

LEVEL OF EVIDENCE

Level IV-diagnostic study.

Improved detection of solitary pulmonary nodules on radiographs compared with deep bone suppression imaging

Background

The present study aimed to investigate whether deep bone suppression imaging (BSI) could increase the diagnostic performance for solitary pulmonary nodule detection compared with digital tomosynthesis (DTS), dual-energy subtraction (DES) radiography, and conventional chest radiography (CCR).

Methods

A total of 256 patients (123 with a solitary pulmonary nodule, 133 with normal findings) were included in the study. The confidence score of 6 observers determined the presence or absence of pulmonary nodules in each patient. These were first analyzed using a CCR image, then with CCR plus deep BSI, then with CCR plus DES radiography, and finally with DTS images. Receiver-operating characteristic curves were used to evaluate the performance of the 6 observers in the detection of pulmonary nodules.

Results

For the 6 observers, the average area under the curve improved significantly from 0.717 with CCR to 0.848 with CCR plus deep BSI (P<0.01), 0.834 with CCR plus DES radiography (P<0.01), and 0.939 with DTS (P<0.01). Comparisons between CCR and CCR plus deep BSI found that the sensitivities of the assessments by the 3 residents increased from 53.2% to 69.5% (P=0.014) for nodules located in the upper lung field, from 30.6% to 44.6% (P=0.015) for nodules that were partially/completely obscured by the bone, and from 33.2% to 45.8% (P=0.006) for nodules <10 mm.

Conclusions

The deep BSI technique can significantly increase the sensitivity of radiology residents for solitary pulmonary nodules compared with CCR. Increased detection was seen mainly for smaller nodules, nodules with partial/complete obscuration, and nodules located in the upper lung field.

Assessment of Early Biological Fixation of Cementless Tapered-Wedge Stems Using Digital Tomosynthesis

BACKGROUND

We aimed to compare radiographic and digital tomosynthesis assessments of early biological fixation of a cementless stem in primary total hip arthroplasty and to investigate the factors associated with early biological fixation.

METHODS

Seventy-three patients underwent total hip arthroplasty using cementless short tapered-wedge stems. Both radiography and digital tomosynthesis were performed at 6 weeks and 3, 6, 12, and 24 months after surgery. The presence of spot welds (SW) was evaluated at each postoperative period to assess biological fixation between the stem and the femur. The area of contact between the femur and the stem was divided into seven zones based on Gruen's zone classification.

RESULTS

All 73 patients had no SW 6 weeks after surgery on radiography and digital tomosynthesis. Three months postoperatively, there was no SW on radiography; however, digital tomosynthesis revealed SW in 31 (42%) patients. Six months postoperatively, radiography showed 22 SW in 18 (24.7%) patients and digital tomosynthesis showed 94 SW in 48 patients (65.8%).

CONCLUSION

Digital tomosynthesis detected biological fixation between the stem and femur earlier than radiography; biological fixation may appear within 3 months after surgery.

Assessment of Intravertebral Mechanical Strains and Cancellous Bone Texture Under Load Using a Clinically Available Digital Tomosynthesis Modality

Vertebral fractures are the most common osteoporotic fractures, but clinical means for assessment of vertebral bone integrity are limited in accuracy, as they typically use surrogate measures that are indirectly related to mechanics. The objective of this study was to examine the extent to which intravertebral strain distributions and changes in cancellous bone texture generated by a load of physiological magnitude can be characterized using a clinically available imaging modality. We hypothesized that digital tomosynthesis-based digital volume correlation (DTS-DVC) and image texture-based metrics of cancellous bone microstructure can detect development of mechanical strains under load. Isolated cadaveric T11 vertebrae and L2-L4 vertebral segments were DTS imaged in a nonloaded state and under physiological load levels. Axial strain, maximum principal strain, maximum compressive and tensile principal strains, and von Mises equivalent strain were calculated using the DVC technique. The change in textural parameters (line fraction deviation, anisotropy, and fractal parameters) under load was calculated within the cancellous centrum. The effect of load on measured strains and texture variables was tested using mixed model analysis of variance, and relationships of strain and texture variables with donor age, bone density parameters, and bone size were examined using regression models. Magnitudes and heterogeneity of intravertebral strain measures correlated with applied loading and were significantly different from background noise. Image texture parameters were found to change with applied loading, but these changes were not observed in the second experiment testing L2-L4 segments. DTS-DVC-derived strains correlated with age more strongly than did bone mineral density (BMD) for T11.

Atypical ductal hyperplasia on core needle biopsy: Surgical outcomes of 200 consecutive cases from a high-volume breast program

Atypical ductal hyperplasia (ADH) is an indication for excisional biopsy to rule out occult breast cancer. We analyzed pathological findings on excisional biopsy for ADH diagnosed in a high volume breast center equipped with digital tomosynthesis. Two hundred consecutive patients were diagnosed with ADH on core biopsy with radiographic concordance followed by excisional biopsy. On excisional biopsy, 33 patients (16.5%) were diagnosed with DCIS or invasive breast cancer. Patients with a concurrent diagnosis of papilloma had a higher risk of upstaging on both univariate and multivariate analysis (41.7% vs. 14.9%, p=0.015). No other statistically significant predictors of upgrading were identified (p>0.05).

Emphasizing the Diagnostic Value of Digital Tomosynthesis in Detecting Hip Fractures

Our institution recently implemented the use of digital tomosynthesis (DTS) to workup emergency room patients with suspected hip fractures after initial negative or indeterminate radiographs. Our purpose is to evaluate the diagnostic accuracy of DTS for hip fracture detection. We performed a retrospective review of all DTS studies over a 17-month period (July 2017 to November 2018). The results of the radiographs and DTS were recorded as either positive or negative for fracture based on the radiology report. Our reference standard for a fracture was either confirmation on subsequent CT or MRI from the same visit or documentation of clinical findings supportive of a fracture in the patient’s electronic medical record. For patients with negative DTS who did not undergo subsequent cross-sectional imaging, a missed fracture was excluded if they did not return within 30 days with a confirmed fracture. Among 91 patients, there were 34 confirmed fractures—sites including, 7 femoral necks, 10 pubic rami, and 7 greater trochanters. DTS was positive for fracture in 29 patients; 28 of these fractures were true positives, 6 confirmed on cross-sectional imaging, and 22 confirmed clinically. One false positive was observed in a patient with no clinical evidence of a fracture. Six fractures were not detected by tomosynthesis but confirmed on CT/MRI. The sensitivity and specificity of DTS are 82% and 98%, respectively, compared to that of radiographs alone at 47% and 96%, respectively. DTS is a promising adjunct to radiographs for hip fracture detection in an emergency department.

Evaluation of peri-prosthetic radiolucent lines surrounding the cementless femoral stem using digital tomosynthesis with metal artifact reduction: a cadaveric study in comparison with radiography and computed tomography

Background

The traditional criterion for the diagnosis of implant loosening in total hip arthroplasty (THA) was once defined as a radiolucent line of >2 mm in width, based on plain radiography. Recent progress in imaging technology has allowed for the identification of complete radiolucent lines of ≤2 mm around the whole prosthesis as the basis for diagnosing component loosening in the absence of component migration. This study aimed to compare the sensitivity and specificity of digital tomosynthesis with metal artifact reduction with those of radiography and conventional computed tomography (CT) for detecting radiolucent lines of ≤2 mm surrounding cementless femoral stems of different widths.

Methods

The medullary canals of 4 cadaveric femurs were broached to 13 mm in diameter. Cylindrical cementless femoral stems with diameters of 9, 10, 11, 12, and 13 mm were sequentially inserted into each femur, creating 5 groups of radiolucent lines 2.0, 1.5-1.6, 1.1-1.2, 0.5-0.6, and 0 mm in diameter, respectively. Imaging by tomosynthesis, radiography, and CT was conducted for each radiolucent line model. The width information of the radiolucent line models was used as a reference standard for calculating sensitivity and specificity: observations in the group of 0 mm were used for calculating specificity, and those in the other four groups were used for sensitivity. The differences in sensitivity and specificity between the imaging methods were compared with chi-square test, and the 95% confidence intervals of improvements in the sensitivity and specificity of tomosynthesis compared with radiography and CT were calculated using mixed effects models.

Results

The overall sensitivity of tomosynthesis (63.3%) for detecting radiolucent lines ≤2 mm wide was significantly higher (P<0.017) than that of radiography (20.5%) and CT (50.2%), an improvement of 58.2%±3.1% (95% CI, P<0.001) and 21.7%±7.1% (95% CI, P<0.001) compared to radiography and CT, respectively. The sensitivity values for detecting radiolucent lines in all four groups by tomosynthesis and CT were significantly higher than those of radiography (P<0.017). Tomosynthesis also had significantly higher sensitivity than CT (P<0.017) in detecting radiolucent line ≤1.2 mm wide. The specificity of TMAR, radiography, and CT for detecting radiolucent lines was 87.5%, 92.5%, and 82.5%, respectively, with no significant difference (P>0.017).

Conclusions

Digital tomosynthesis with metal artifact reduction had significantly higher sensitivity than radiography for detecting radiolucent lines ≤2 mm wide surrounding cementless femoral stems. It also displayed higher sensitivity than CT for detecting radiolucent lines ≤1.2 mm in width. With a higher rate of detection for radiolucent lines narrower than 2 mm, tomosynthesis has the potential to improve the accuracy of early diagnosis of cementless THA stem loosening in clinical practice.

Identification of aspirated radiolucent foreign bodies in the pediatric airway using digital tomosynthesis: a multireader phantom study

Purpose: Foreign body aspiration is difficult to diagnose because many aspirated foreign bodies are low density or radiolucent. Digital radiographs (DR) are poor at detecting radiolucent foreign bodies. Digital tomosynthesis (DTS) has been shown to be ideally suited for applications where DR is insensitive and the increased dose from computed tomography (CT) is not justified. Our objective was to determine if DTS can be a practical alternative to DR and CT in the diagnosis of foreign body aspiration. Approach: A phantom approximating the densities of a pediatric chest was constructed. Radiolucent foreign bodies were placed in the airways. Seven pediatric radiologists assessed DTS and DR images with and without simulated breathing motion. Two rounds were performed with fixed exposure techniques and then automatic exposure control techniques. Interobserver agreement was evaluated using Fleiss' kappa. Results: DTS and DR images using fixed exposure techniques performed very poorly with accuracies of 42% to 60%. DTS with automatic exposure control techniques increased accuracy to 84% for a stationary phantom, but the accuracy dropped to 70% in a phantom with simulated motion. DTS outperformed DR, with DR accuracies of 60% and 63% for stationary simulations and motion, respectively. Interobserver agreement was poor with Fleiss' kappa of 0.476. Conclusion: DTS is superior to DR for radiolucent foreign body detection. However, the overall accuracy and interobserver agreement are likely too low for this modality to be clinically useful.

Digital tomosynthesis based digital volume correlation: A clinically viable noninvasive method for direct measurement of intravertebral displacements using images of the human spine under physiological load

PURPOSE

We have developed a clinically viable method for measurement of direct, patient-specific intravertebral displacements using a novel digital tomosynthesis based digital volume correlation technique. These displacements may be used to calculate vertebral stiffness under loads induced by a patient's body weight; this is particularly significant because, among biomechanical variables, stiffness is the strongest correlate of bone strength. In this proof of concept study, we assessed the feasibility of the method through a preliminary evaluation of the accuracy and precision of the method, identification of a range of physiological load levels for which displacements are measurable, assessment of the relationship of measured displacements with microcomputed tomography based standards, and demonstration of the in vivo application of the technique.

METHODS

Five cadaveric T11 vertebrae were allocated to three groups in order to study (a) the optimization of digital volume correlation algorithm input parameters, (b) accuracy and precision of the method and the ability to measure displacements at a range of physiological load levels, and (c) the correlation between displacements measured using tomosynthesis based digital volume correlation vs. high resolution microcomputed tomography based digital volume correlation and large scale finite element models. Tomosynthesis images of one patient (Female, 60 yr old) were used to calculate displacement maps, and in turn stiffness, using images acquired in both standing and standing-with-weight (8 kg) configurations.

RESULTS

We found that displacements were accurate (2.28 µm total error) and measurable at physiological load levels (above 267 N) with a linear response to applied load. Calculated stiffness among three tested vertebral bodies was within an acceptable range relative to reported values for vertebral stiffness (5651-13260 N/mm). Displacements were in good qualitative and quantitative agreement with both microcomputed tomography based finite element (r²  = 0.762, P < 0.001) and digital volume correlation (r²  = 0.799, P < 0.001) solutions. For one patient tested twice, once standing and once holding weights, results demonstrated excellent qualitative reproducibility of displacement distributions with superior endplate displacements increasing by 22% with added weight.

CONCLUSIONS

The results of this work collectively suggest the feasibility of the method for in vivo measurement of intravertebral displacements and stiffness in humans. These findings suggest that digital volume correlation using digital tomosynthesis imaging may be useful in understanding the mechanical response of bone to disease and may further enhance our ability to assess fracture risk and treatment efficacy for the spine.

Accuracy of Digital Tomosynthesis With Metal Artifact Reduction for Detecting Osteointegration in Cementless Hip Arthroplasty

BACKGROUND

Cementless hip arthroplasty is increasingly gaining popularity worldwide. Radiologic identification of osteointegration is key to confirming biologic fixation. We conducted the study reported here to determine the sensitivity and specificity of digital tomosynthesis with metal artifact reduction (TMAR), radiography, and conventional computed tomography in detecting osteointegration in cementless hip arthroplasty.

METHODS

We prospectively included data for 24 patients who underwent revision hip arthroplasty in our hospital, with 13 femoral and 14 acetabular cementless components retrieved that contained solid evidence of biologic fixation. All patients underwent 3 examinations before surgery, and evidence of osteointegration on retrieved prostheses was used as the reference standard. Seven orthopedic surgeons evaluated these images independently using uniform criteria.

RESULTS

On the femoral side, the sensitivity and specificity of detecting osteointegration were 73.8% ± 4.6% and 94.3% ± 1.5%, respectively, for TMAR; 50.4% ± 5.3% and 87.8% ± 2.1%, respectively, for radiography; and 36.4% ± 5.1% and 90.9% ± 1.9%, respectively, for CT. On the cup side, the corresponding values were 60.2% ± 8.3% and 86.4% ± 5.7%, respectively, for TMAR; 45.9% ± 8.5% and 66.4% ± 7.8%, respectively, for radiography; and 45.1% ± 8.5% and 73.5% ± 7.3%, respectively, by computed tomography.

CONCLUSION

TMAR significantly improved the accuracy osteointegration detection in cementless hip arthroplasty (P < .017).

The value of X-ray digital tomosynthesis in the diagnosis of urinary calculi

Urinary calculus is a common and recurrent condition that affects kidney function. The present study evaluated the use of digital tomosynthesis (DTS) and Kidneys-Ureters-Bladder (KUB) radiography as methods of diagnosing urinary calculi. Unenhanced multidetector computed tomography (UMDCT) was used in the diagnosis of calculi. KUB radiography and DTS procedures were conducted on patients prior to and following bowel preparation to detect kidney, ureteral and bladder calculi. Differences in diagnostic performance of KUB radiography and DTS imaging on prepared and unprepared bowel were evaluated using the χ² test. The consistency of diagnostic results between two examining physicians was analyzed using the κ test. A total of 138 calculi from 80 patients were detected via UMDCT. The calculi detection rates of KUB prior to and following bowel preparation were 47.8 and 66.7% respectively, and the calculi detection rate of DTS prior to and following bowel preparation were 94.2 and 96.4%, respectively. The detection rates of calculi >5 mm via KUB prior to and following bowel preparation were 56.6 and 73.5% respectively, and in DTS they were 100% prior to and following bowel preparation. Economically, DTS performed on the unprepared bowel was the most cost effective, followed by DTS on the prepared bowel, KUB on the unprepared bowel and KUB on the prepared bowel. Therefore, the current study concluded that DTS may be an appropriate first-line imaging technique in patients with urinary calculi.

[The modern view of the radiodiagnostic methods applied for determining the position of the electrode array in cochlear implantation surgery]

The objective of the present work was to overview the currently available literature publications dealing with the radiodiagnostic techniques applied to evaluate the position of the electrode array used for the purpose of cochlear implantation surgery including both the conventional methods and the recently proposed approaches. It is shown that the intraoperative control guarantees the timely identification of the possible complications and should meet both the safety criteria and the requirements for obtaining high-quality images and intraoperative usability of the surgical instruments being employed. Moreover, the intraoperative monitoring can be exercised under control of fluoroscopy as well as with the use of the portable computed radiography scanners and navigation systems. The postoperative monitoring is carried out with the use of transorbital X ray visualization, multi-slice computed tomography, cone beam computed tomography, and digital tomosynthesis. Each of the listed methods has specific advantages and disadvantages, but there is yet neither a universally recognized systematic approach to the assessment of their effectiveness nor the generally acceptable criteria for the evaluation of the image quality.

Second generation stationary digital breast tomosynthesis system with faster scan time and wider angular span

PURPOSE

The aim of this study was to characterize a new generation stationary digital breast tomosynthesis system with higher tube flux and increased angular span over a first generation system.

METHODS

The linear CNT x-ray source was designed, built, and evaluated to determine its performance parameters. The second generation system was then constructed using the CNT x-ray source and a Hologic gantry. Upon construction, test objects and phantoms were used to characterize system resolution as measured by the modulation transfer function (MTF), and artifact spread function (ASF).

RESULTS

The results indicated that the linear CNT x-ray source was capable of stable operation at a tube potential of 49 kVp, and measured focal spot sizes showed source-to-source consistency with a nominal focal spot size of 1.1 mm. After construction, the second generation (Gen 2) system exhibited entrance surface air kerma rates two times greater the previous s-DBT system. System in-plane resolution as measured by the MTF is 7.7 cycles/mm, compared to 6.7 cycles/mm for the Gen 1 system. As expected, an increase in the z-axis depth resolution was observed, with a decrease in the ASF from 4.30 mm to 2.35 mm moving from the Gen 1 system to the Gen 2 system as result of an increased angular span.

CONCLUSIONS

The results indicate that the Gen 2 stationary digital breast tomosynthesis system, which has a larger angular span, increased entrance surface air kerma, and faster image acquisition time over the Gen 1 s-DBT system, results in higher resolution images. With the detector operating at full resolution, the Gen 2 s-DBT system can achieve an in-plane resolution of 7.7 cycles per mm, which is better than the current commercial DBT systems today, and may potentially result in better patient diagnosis.

Clinical Study of Orthogonal-View Phase-Matched Digital Tomosynthesis for Lung Tumor Localization

Background and Purpose:

Compared to cone-beam computed tomography, digital tomosynthesis imaging has the benefits of shorter scanning time, less imaging dose, and better mechanical clearance for tumor localization in radiation therapy. However, for lung tumors, the localization accuracy of the conventional digital tomosynthesis technique is affected by the lack of depth information and the existence of lung tumor motion. This study investigates the clinical feasibility of using an orthogonal-view phase-matched digital tomosynthesis technique to improve the accuracy of lung tumor localization.

Materials and Methods:

The proposed orthogonal-view phase-matched digital tomosynthesis technique benefits from 2 major features: (1) it acquires orthogonal-view projections to improve the depth information in reconstructed digital tomosynthesis images and (2) it applies respiratory phase-matching to incorporate patient motion information into the synthesized reference digital tomosynthesis sets, which helps to improve the localization accuracy of moving lung tumors. A retrospective study enrolling 14 patients was performed to evaluate the accuracy of the orthogonal-view phase-matched digital tomosynthesis technique. Phantom studies were also performed using an anthropomorphic phantom to investigate the feasibility of using intratreatment aggregated kV and beams’ eye view cine MV projections for orthogonal-view phase-matched digital tomosynthesis imaging. The localization accuracy of the orthogonal-view phase-matched digital tomosynthesis technique was compared to that of the single-view digital tomosynthesis techniques and the digital tomosynthesis techniques without phase-matching.

Results:

The orthogonal-view phase-matched digital tomosynthesis technique outperforms the other digital tomosynthesis techniques in tumor localization accuracy for both the patient study and the phantom study. For the patient study, the orthogonal-view phase-matched digital tomosynthesis technique localizes the tumor to an average (± standard deviation) error of 1.8 (0.7) mm for a 30° total scan angle. For the phantom study using aggregated kV–MV projections, the orthogonal-view phase-matched digital tomosynthesis localizes the tumor to an average error within 1 mm for varying magnitudes of scan angles.

Conclusion:

The pilot clinical study shows that the orthogonal-view phase-matched digital tomosynthesis technique enables fast and accurate localization of moving lung tumors.

Estimating scatter from sparsely measured primary signal

Scatter radiation severely degrades the image quality. Measurement-based scatter correction methods sample the scatter signal at sparsely distributed points, from which the scatter profile is estimated and deterministically removed from the projection image. The estimation of the scatter profile is generally done through a spline interpolation and the resulting scatter profile is quite smooth. Consequently, the noise is intact and the signal-to-noise ratio is reduced in the projection image after scatter correction, leading to image artifacts and increased noise in the reconstruction images. We propose a simple and effective method, referred to as filtered scatter-to-primary ratio ([Formula: see text]-SPR) estimation, to estimate the scatter profile using the sparsely sampled scatter signal. Using the primary sampling device and the stationary digital tomosynthesis systems previously developed in our lab, we evaluated and compared the [Formula: see text]-SPR method in comparison with existing methods in terms of contrast ratio, signal difference-to-noise ratio, and modulation transfer function. A significant improvement in image quality is observed in both the projection and the reconstruction images using the proposed method.

Design and evaluation of a grid reciprocation scheme for use in digital breast tomosynthesis

This work describes a methodology for efficient removal of scatter radiation during digital breast tomosynthesis (DBT). The goal of this approach is to enable grid image obscuration without a large increase in radiation dose by minimizing misalignment of the grid focal point (GFP) and x-ray focal spot (XFS) during grid reciprocation. Hardware for the motion scheme was built and tested on the dual modality breast tomosynthesis (DMT) scanner, which combines DBT and molecular breast tomosynthesis (MBT) on a single gantry. The DMT scanner uses fully isocentric rotation of tube and x-ray detector for maintaining a fixed tube-detector alignment during DBT imaging. A cellular focused copper prototype grid with 80 cm focal length, 3.85 mm height, 0.1 mm thick lamellae, and 1.1 mm hole pitch was tested. Primary transmission of the grid at 28 kV tube voltage was on average 74% with the grid stationary and aligned for maximum transmission. It fell to 72% during grid reciprocation by the proposed method. Residual grid line artifacts (GLAs) in projection views and reconstructed DBT images are characterized and methods for reducing the visibility of GLAs in the reconstructed volume through projection image flat-field correction and spatial frequency-based filtering of the DBT slices are described and evaluated. The software correction methods reduce the visibility of these artifacts in the reconstructed volume, making them imperceptible both in the reconstructed DBT images and their Fourier transforms.

Studies of a prototype linear stationary x-ray source for tomosynthesis imaging

A prototype linear x-ray source to implement stationary source-stationary detector tomosynthesis (TS) imaging has been studied. Potential applications include human breast and small animal imaging. The source is comprised of ten x-ray source elements each consisting of a field emission cathode, electrostatic lens, and target. The electrostatic lens and target are common to all elements. The source elements form x-ray focal spots with minimum diameters of 0.3-0.4 mm at electron beam currents of up to 40 mA with a beam voltage of 40 kV. The x-ray flux versus time was quantified from each source. X-ray bremsstrahlung spectra from tungsten targets were produced using electron beam energies from 35 to 50 keV. The half-value layer was measured to be 0.8, 0.9, and 1.0 mm, respectively, for the 35, 40, and 45 kV tube potentials using the tungsten target. The suppression of voltage breakdown events, particularly during source operation, and the use of a modified form of the standard cold-cathode geometry, enhanced source reliability. The prototype linear source was used to collect tomographic data sets of a mouse phantom using digital TS reconstruction methods and demonstrated a slice-sensitivity profile with a full-width-half-maximum of 1.3 mm. Lastly, preliminary studies of tomographic imaging of flow through the mouse phantom were performed.

Grating-based phase contrast tomosynthesis imaging: proof-of-concept experimental studies

PURPOSE

This paper concerns the feasibility of x-ray differential phase contrast (DPC) tomosynthesis imaging using a grating-based DPC benchtop experimental system, which is equipped with a commercial digital flat-panel detector and a medical-grade rotating-anode x-ray tube. An extensive system characterization was performed to quantify its imaging performance.

METHODS

The major components of the benchtop system include a diagnostic x-ray tube with a 1.0 mm nominal focal spot size, a flat-panel detector with 96 μm pixel pitch, a sample stage that rotates within a limited angular span of ± 30°, and a Talbot-Lau interferometer with three x-ray gratings. A total of 21 projection views acquired with 3° increments were used to reconstruct three sets of tomosynthetic image volumes, including the conventional absorption contrast tomosynthesis image volume (AC-tomo) reconstructed using the filtered-backprojection (FBP) algorithm with the ramp kernel, the phase contrast tomosynthesis image volume (PC-tomo) reconstructed using FBP with a Hilbert kernel, and the differential phase contrast tomosynthesis image volume (DPC-tomo) reconstructed using the shift-and-add algorithm. Three inhouse physical phantoms containing tissue-surrogate materials were used to characterize the signal linearity, the signal difference-to-noise ratio (SDNR), the three-dimensional noise power spectrum (3D NPS), and the through-plane artifact spread function (ASF).

RESULTS

While DPC-tomo highlights edges and interfaces in the image object, PC-tomo removes the differential nature of the DPC projection data and its pixel values are linearly related to the decrement of the real part of the x-ray refractive index. The SDNR values of polyoxymethylene in water and polystyrene in oil are 1.5 and 1.0, respectively, in AC-tomo, and the values were improved to 3.0 and 2.0, respectively, in PC-tomo. PC-tomo and AC-tomo demonstrate equivalent ASF, but their noise characteristics quantified by the 3D NPS were found to be different due to the difference in the tomosynthesis image reconstruction algorithms.

CONCLUSIONS

It is feasible to simultaneously generate x-ray differential phase contrast, phase contrast, and absorption contrast tomosynthesis images using a grating-based data acquisition setup. The method shows promise in improving the visibility of several low-density materials and therefore merits further investigation.

A phantom-based calibration method for digital x-ray tomosynthesis

OBJECTIVE

The purpose of this study was to develop a phantom-based experimental calibration method to minimize the reconstruction artifacts for the geometric misalignments of the digital tomosynthesis prototype.

METHODS

A calibration phantom with ten fiducial markers was designed. Using this calibration phantom, the projection matrices of an experimental digital tomosynthesis prototype were acquired from each projection view under a series of misalignment conditions. The American College of Radiology mammography phantom was imaged and reconstructed with and without using the correction of the corresponding calibration projection matrices. The effectiveness of the calibration technique was then quantitatively analyzed through comparison of the calibrated and uncalibrated images.

RESULTS

As the isocenter horizontal-shift increases, the reconstruction artifacts become clearly distinguishable. Using the calibration technique, the reconstruction artifacts resulting from the isocenter horizontal-shift were effectively minimized for the prototype.

CONCLUSIONS

For the specific experimental conditions utilized in this study, the phantom-based calibration method effectively reduced reconstruction artifacts for the prototype investigated in this study. The calibration method holds potential to benefit other tomosynthesis applications.