Pulmonary mycobacterial disease: diagnostic performance of low-dose digital tomosynthesis as compared with chest radiography

Next-generation digital chest tomosynthesis

The objective of this study was to demonstrate the performance characteristics and potential utility of a novel tomosynthesis device as applied to imaging the chest, specifically relating to lung nodules. The imaging characteristics and quality of a novel digital tomosynthesis prototype system was assessed by scanning, a healthy volunteer, and an andromorphic lung phantom with different configurations of simulated pulmonary nodules. The adequacy of nodule detection on the phantoms was rated by chest radiologists using a standardized scale. Results from using this tomosynthesis device demonstrate in plane resolution of 16lp/cm, with estimated effective radiation doses of 90% less than low dose CT. Nodule detection was adequate across various anatomic locations on a phantom. These proof-of-concept tests showed this novel tomosynthesis device can detect lung nodules with low radiation dose to the patient. This technique has potential as an alternative to low dose chest CT for lung nodule screening and tracking.

AI-based computer-aided diagnostic system of chest digital tomography synthesis: Demonstrating comparative advantage with X-ray-based AI systems

BACKGROUND

Compared with chest X-ray (CXR) imaging, which is a single image projected from the front of the patient, chest digital tomosynthesis (CDTS) imaging can be more advantageous for lung lesion detection because it acquires multiple images projected from multiple angles of the patient. Various clinical comparative analysis and verification studies have been reported to demonstrate this, but there is no artificial intelligence (AI)-based comparative analysis studies. Existing AI-based computer-aided detection (CAD) systems for lung lesion diagnosis have been developed mainly based on CXR images; however, CAD-based on CDTS, which uses multi-angle images of patients in various directions, has not been proposed and verified for its usefulness compared to CXR-based counterparts.

BACKGROUND AND OBJECTIVE

This study develops and tests a CDTS-based AI CAD system to detect lung lesions to demonstrate performance improvements compared to CXR-based AI CAD.

METHODS

We used multiple (e.g., five) projection images as input for the CDTS-based AI model and a single-projection image as input for the CXR-based AI model to compare and evaluate the performance between models. Multiple/single projection input images were obtained by virtual projection on the three-dimensional (3D) stack of computed tomography (CT) slices of each patient's lungs from which the bed area was removed. These multiple images result from shooting from the front and left and right 30/60∘. The projected image captured from the front was used as the input for the CXR-based AI model. The CDTS-based AI model used all five projected images. The proposed CDTS-based AI model consisted of five AI models that received images in each of the five directions, and obtained the final prediction result through an ensemble of five models. Each model used WideResNet-50. To train and evaluate CXR- and CDTS-based AI models, 500 healthy data, 206 tuberculosis data, and 242 pneumonia data were used, and three three-fold cross-validation was applied.

RESULTS

The proposed CDTS-based AI CAD system yielded sensitivities of 0.782 and 0.785 and accuracies of 0.895 and 0.837 for the (binary classification) performance of detecting tuberculosis and pneumonia, respectively, against normal subjects. These results show higher performance than the sensitivity of 0.728 and 0.698 and accuracies of 0.874 and 0.826 for detecting tuberculosis and pneumonia through the CXR-based AI CAD, which only uses a single projection image in the frontal direction. We found that CDTS-based AI CAD improved the sensitivity of tuberculosis and pneumonia by 5.4% and 8.7% respectively, compared to CXR-based AI CAD without loss of accuracy.

CONCLUSIONS

This study comparatively proves that CDTS-based AI CAD technology can improve performance more than CXR. These results suggest that we can enhance the clinical application of CDTS. Our code is available at https://github.com/kskim-phd/CDTS-CAD-P.

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.

Diagnostic performance of digital tomosynthesis to evaluate silicone airway stents and related complications

Background

Digital tomosynthesis (DTS) is an imaging technique with benefits in reconstructing sequential cross-sectional images. We evaluated the diagnostic performance of DTS for silicone airway stents and stent-related complications in patients who underwent bronchoscopic intervention.

Methods

This retrospective study included patients who underwent bronchoscopic intervention after chest radiography (CXR) and DTS examinations from September 2013 to August 2020. The interval between CXR, DTS, and bronchoscopic intervention was a maximum of 10 days. CXR and DTS images were evaluated using a bronchoscopic view as a reference. We calculated the sensitivity, specificity, accuracy, positive predictive value, and negative predictive value for assessing the diagnostic performance.

Results

The total CXR, DTS, and bronchoscopic intervention-matching datasets comprised 213 cases from 119 patients and, silicone stents were present in 167 of them. The ability of DTS to detect silicone stents was better than that of CXR (sensitivity, 92.8% vs. 71.3%, P<0.001). Of the 167 cases with silicone stents, 53 experienced stent migration and 121 experienced stent obstructions due to granulation tissue or fibrosis. The sensitivity for detecting stent migration was also higher with DTS than with CXR (45.3% vs. 24.5%, P=0.025). The sensitivity for detecting the stent obstruction was better with DTS than with CXR (64.5% vs. 19.0%, P<0.001).

Conclusions

DTS was more sensitive and accurate in revealing silicone airway stents and silicone stent-related complications than CXR. However, there were limitations in confirming stent migration and obstruction with DTS due to granulation tissue growth and fibrosis.

The Effect of Dose Reduction on Overall Image Quality in Clinical Chest Tomosynthesis

RATIONALE AND OBJECTIVES

To evaluate the effect of reduction in effective dose on the reproduction of anatomical structures in chest tomosynthesis (CTS).

MATERIALS AND METHODS

Twenty-four CTS examinations acquired at exposure settings resulting in an effective dose of 0.12 mSv for an average sized patient were included in the study. The examinations underwent simulated dose reduction to dose levels corresponding to 32%, 50%, and 70% of the original dose using a previously described and validated method. The image quality was evaluated by five thoracic radiologists who rated the fulfillment of specified image quality criteria in a visual grading study. The ratings for each image quality criterion in the dose-reduced images were compared to the corresponding ratings for the full-dose examinations using visual grading characteristics (VGC) analysis. The area under the resulting VGC curve (AUC_VGC) provides a measure of the difference between the ratings, where an AUC_VGC of 0.5 indicates no difference.

RESULTS

The dose reductions resulted in inferior reproduction of structures compared to the original dose level (AUC_VGC <0.5). Structures in the central region of the lung obtained the lowest AUC_VGC for each dose level whereas the reproduction of structures in the parenchyma was least affected by the dose reduction.

CONCLUSION

Although previous studies have shown that dose reduction in CTS is possible without affecting the performance of certain clinical tasks, the reproduction of normal anatomical structures is significantly degraded even at small reductions. It is therefore important to consider the clinical purpose of the CTS examinations before deciding on a permanent dose reduction.

[Extraction of respiratory signals from chest tomosynthesis]

OBJECTIVE

To analyze the respiratory motion of the scanned object during acquisition of digital chest tomosynthesis (CTS) using a linear model.

OBJECTIVE

Respiratory signals were generated by extracting the motion of the diaphragm from the projection radiographs. The diaphragm trajectory obtained by dynamic programming (DP) was modeled and fitted, and according to the fitting of the data, the base motion curve and respiratory signal curve of the diaphragm were separated. Multipurpose chest phantom data, simulated digital Xcat phantom data and the datasets of 3 clinical patients were used to validate the performance of the proposed method.

OBJECTIVE

The motion trajectory of the diaphragm extracted from multipurpose chest phantom simulation data was linear. The respiratory signals could be effectively extracted from the 3 datasets of clinical patients in different respiratory states. The correlation coefficient between the respiratory signal extracted in Xcat simulation experiment and the original design was 0.9797.

OBJECTIVE

The linear model can effectively obtain the respiratory motion information of patients in real time, thus enabling the physicians to make clinical decisions on a rescan.

Surveillance of small, solid pulmonary nodules at digital chest tomosynthesis: data from a cohort of the pilot Swedish CArdioPulmonary bioImage Study (SCAPIS)

Background

Digital tomosynthesis (DTS) might be a low-dose/low-cost alternative to computed tomography (CT).

Purpose

To investigate DTS relative to CT for surveillance of incidental, solid pulmonary nodules.

Material and Methods

Recruited from a population study, 106 participants with indeterminate solid pulmonary nodules on CT underwent surveillance with concurrently performed CT and DTS. Nodule size on DTS was assessed by manual diameter measurements and semi-automatic nodule segmentations were independently performed on CT. Measurement agreement was analyzed according to Bland–Altman with 95% limits of agreement (LoA). Detection of nodule volume change > 25% by DTS in comparison to CT was evaluated with receiver operating characteristics (ROC).

Results

A total of 81 nodules (76%) were assessed as measurable on DTS by two independent observers. Inter- and intra-observer LoA regarding change in average diameter were ± 2 mm. Calculation of relative volume change on DTS resulted in wide inter- and intra-observer LoA in the order of ± 100% and ± 50%. Comparing relative volume change between DTS and CT resulted in LoA of –58% to 67%. The area under the ROC curve regarding the ability of DTS to detect volumetric changes > 25% on CT was 0.58 (95% confidence interval [CI] = 0.40–0.76) and 0.50 (95% CI = 0.35–0.66) for the two observers.

Conclusion

The results of the present study show that measurement variability limits the agreement between DTS and CT regarding nodule size change for small solid nodules.

Accuracy of Digital Tomosynthesis of the Chest in Detection of Interstitial Lung Disease Comparison With Digital Chest Radiography

PURPOSE

The aim of the study was to assess the ability of chest digital tomosynthesis (DTS) for detection of interstitial lung disease (ILD) compared with conventional chest radiography.

MATERIALS AND METHODS

We retrospectively reviewed 78 patients (60 males, 18 females, mean age = 53.05 years, range, 19-83 years) who underwent chest DTS for a 5-year interval (January 1, 2009-December 31, 2014). Of the 78 patients, 33 (42.3%) carried a diagnosis of ILD and 45 (57.7%) were not ILD. All computed tomography reports and medical records were reviewed. The conventional chest radiography and DTS were separately reviewed by 2 radiologists for the presence of ILD and the confidence in diagnosis.

RESULTS

The diagnostic accuracy of DTS for the detection of ILD was better than conventional chest radiography (P < 0.05). Digital tomosynthesis had a sensitivity of 83.3% and negative predictive value of 89.0% that were statistically significantly better than conventional chest radiography (43.9% and 70.9%, respectively). Confidence in diagnosing ILD at DTS was higher than conventional chest radiography (P < 0.001) and had higher interobserver agreement than conventional chest radiography (P < 0.01).

CONCLUSIONS

Digital tomosynthesis improves diagnostic performance and confidence in diagnosing ILD compared with conventional chest radiography. Digital tomosynthesis can be suggested as the initial diagnostic technique for patients with suspected ILD.

Detection and Characterization of Solid Pulmonary Nodules at Digital Chest Tomosynthesis: Data from a Cohort of the Pilot Swedish Cardiopulmonary Bioimage Study

Purpose To investigate the performance of digital tomosynthesis (DTS) for detection and characterization of incidental solid lung nodules. Materials and Methods This prospective study was based on a population study with 1111 randomly selected participants (age range, 50-64 years) who underwent a medical evaluation that included chest computed tomography (CT). Among these, 125 participants with incidental nodules 5 mm or larger were included in this study, which added DTS in conjunction with the follow-up CT and was performed between March 2012 and October 2014. DTS images were assessed by four thoracic radiologists blinded to the true number of nodules in two separate sessions according to the 5-mm (125 participants) and 6-mm (55 participants) cut-off for follow-up of incidental nodules. Pulmonary nodules were directly marked on the images by the readers and graded regarding confidence of presence and recommendation for follow-up. Statistical analyses included jackknife free-response receiver operating characteristic, receiver operating characteristic, and Cohen κ coefficient. Results Overall detection rate ranges of CT-proven nodules 5 mm or larger and 6 mm or larger were, respectively, 49%-58% and 48%-62%. Jackknife free-response receiver operating characteristics figure of merit for detection of CT-proven nodules 5 mm or larger and 6 mm or larger was 0.47 and 0.51, respectively, and area under the receiver operating characteristic curve regarding recommendation for follow-up was 0.62 and 0.65, respectively. Conclusion Routine use of DTS would result in lower detection rates and reduced number of small nodules recommended for follow-up. ^© RSNA, 2018.

Sin-quadratic model for chest tomosynthesis respiratory signal analysis and its application in four dimensional chest tomosynthesis reconstruction

Chest tomosynthesis (CTS) is a newly developed imaging technique which provides pseudo-3D volume anatomical information of thorax from limited-angle projections and contains much less of superimposed anatomy than the chest X-ray radiography. One of the relatively common problems in CTS is the patient respiratory motion during image acquisition, which negatively impacts the detectability. In this work, we propose a sin-quadratic model to analyze the respiratory motion during CTS scan, which is a real time method where the respiratory signal is generated by extracting the motion of diaphragm from projection radiographs. According to the estimated respiratory signal, the CTS projections were then amplitude-based sorted into four to eight phases, and an iterative reconstruction strategy with total variation regularization was adopted to reconstruct the CTS images at each phase. Simulated digital XCAT phantom data and three sets of patient data were adopted for the experiments to validate the performance of the sin-quadratic model and its application in four dimensional (4D) CTS reconstruction. Results of the XCAT phantom simulation study show that the correlation coefficient between the extracted respiratory signal and the originally designed respiratory signal is 0.9964, which suggests that the proposed model could exactly extract the respiratory signal from CTS projections. The 4D CTS reconstructions of both the phantom data and the patient data show clear reduction of motion-induced blur.

Value of a Computer-aided Detection System Based on Chest Tomosynthesis Imaging for the Detection of Pulmonary Nodules

Purpose To assess the value of a computer-aided detection (CAD) system for the detection of pulmonary nodules on chest tomosynthesis images. Materials and Methods Fifty patients with and 50 without pulmonary nodules underwent both chest tomosynthesis and multidetector computed tomography (CT) on the same day. Fifteen observers (five interns and residents, five chest radiologists, and five abdominal radiologists) independently evaluated tomosynthesis images of 100 patients for the presence of pulmonary nodules in a blinded and randomized manner, first without CAD, then with the inclusion of CAD marks. Multidetector CT images served as the reference standard. Free-response receiver operating characteristic analysis was used for the statistical analysis. Results The pooled diagnostic performance of 15 observers was significantly better with CAD than without CAD (figure of merit [FOM], 0.74 vs 0.71, respectively; P = .02). The average true-positive fraction and false-positive rate per all cases with CAD were 0.56 and 0.26, respectively, whereas those without CAD were 0.47 and 0.20, respectively. Subanalysis showed that the diagnostic performance of interns and residents was significantly better with CAD than without CAD (FOM, 0.70 vs 0.62, respectively; P = .001), whereas for chest radiologists and abdominal radiologists, the FOM with CAD values were greater but not significantly: 0.80 versus 0.78 (P = .38) and 0.74 versus 0.73 (P = .65), respectively. Conclusion CAD significantly improved diagnostic performance in the detection of pulmonary nodules on chest tomosynthesis images for interns and residents, but provided minimal benefit for chest radiologists and abdominal radiologists. ^© RSNA, 2017 Online supplemental material is available for this article.

Comparison of digital tomosynthesis and chest radiography for the detection of pulmonary nodules: systematic review and meta-analysis

OBJECTIVE

To compare the diagnostic accuracy of digital tomosynthesis (DTS) with that of chest radiography for the detection of pulmonary nodules by meta-analysis.

METHODS

A systematic literature search was performed to identify relevant original studies from 1 January 1 1976 to 31 August 31 2016. The quality of included studies was assessed by quality assessment of diagnostic accuracy studies-2. Per-patient data were used to calculate the sensitivity and specificity and per-lesion data were used to calculate the detection rate. Summary receiver-operating characteristic curves were drawn for pulmonary nodule detection.

RESULTS

16 studies met the inclusion criteria. 1017 patients on a per-patient basis and 2159 lesions on a per-lesion basis from 16 eligible studies were evaluated. The pooled patient-based sensitivity of DTS was 0.85 [95% confidence interval (CI) 0.83-0.88] and the specificity was 0.95 (0.93-0.96). The pooled sensitivity and specificity of chest radiography were 0.47 (0.44-0.51) and 0.37 (0.34-0.40), respectively. The per-lesion detection rate was 2.90 (95% CI 2.63-3.19).

CONCLUSION

DTS has higher diagnostic accuracy than chest radiography for detection of pulmonary nodules. Chest radiography has low sensitivity but similar specificity, comparable with that of DTS. Advances in knowledge: DTS has higher diagnostic accuracy than chest radiography for the detection of pulmonary nodules.

Multi-Institutional Evaluation of Digital Tomosynthesis, Dual-Energy Radiography, and Conventional Chest Radiography for the Detection and Management of Pulmonary Nodules

Purpose To conduct a multi-institutional, multireader study to compare the performance of digital tomosynthesis, dual-energy (DE) imaging, and conventional chest radiography for pulmonary nodule detection and management. Materials and Methods In this binational, institutional review board-approved, HIPAA-compliant prospective study, 158 subjects (43 subjects with normal findings) were enrolled at four institutions. Informed consent was obtained prior to enrollment. Subjects underwent chest computed tomography (CT) and imaging with conventional chest radiography (posteroanterior and lateral), DE imaging, and tomosynthesis with a flat-panel imaging device. Three experienced thoracic radiologists identified true locations of nodules (n = 516, 3-20-mm diameters) with CT and recommended case management by using Fleischner Society guidelines. Five other radiologists marked nodules and indicated case management by using images from conventional chest radiography, conventional chest radiography plus DE imaging, tomosynthesis, and tomosynthesis plus DE imaging. Sensitivity, specificity, and overall accuracy were measured by using the free-response receiver operating characteristic method and the receiver operating characteristic method for nodule detection and case management, respectively. Results were further analyzed according to nodule diameter categories (3-4 mm, >4 mm to 6 mm, >6 mm to 8 mm, and >8 mm to 20 mm). Results Maximum lesion localization fraction was higher for tomosynthesis than for conventional chest radiography in all nodule size categories (3.55-fold for all nodules, P < .001; 95% confidence interval [CI]: 2.96, 4.15). Case-level sensitivity was higher with tomosynthesis than with conventional chest radiography for all nodules (1.49-fold, P < .001; 95% CI: 1.25, 1.73). Case management decisions showed better overall accuracy with tomosynthesis than with conventional chest radiography, as given by the area under the receiver operating characteristic curve (1.23-fold, P < .001; 95% CI: 1.15, 1.32). There were no differences in any specificity measures. DE imaging did not significantly affect nodule detection when paired with either conventional chest radiography or tomosynthesis. Conclusion Tomosynthesis outperformed conventional chest radiography for lung nodule detection and determination of case management; DE imaging did not show significant differences over conventional chest radiography or tomosynthesis alone. These findings indicate performance likely achievable with a range of reader expertise. ^© RSNA, 2016 Online supplemental material is available for this article.

Comparison of Digital Tomosynthesis and Chest Radiography for the Detection of Noncalcified Pulmonary and Hilar Lesions

OBJECTIVES

The aim of this study was to compare the sensitivity and specificity of chest digital tomosynthesis (DTS) with chest radiography (CXR) for the detection of noncalcified pulmonary nodules and hilar lesions using computed tomography (CT) as the reference standard.

MATERIALS AND METHODS

A total of 78 patients with suspected noncalcified pulmonary lesions on CXR were included in the study. Two radiologists, blinded to the history and CT, analyzed the CXR and the DTS images (separately), whereas a third radiologist analyzed the CXR and DTS images together. Noncalcified intrapulmonary nodules and hilar lesions were recorded for analysis. The interobserver agreement for CXR and DTS was assessed, and the time taken to report the images was recorded.

RESULTS

A total of 202 lesions were recorded in 78 patients. There were 111 true lesions confirmed on CT in 53 patients; in 25 patients subsequent CT excluded a lesion. The overall sensitivity was 32% for CXR and 49% for DTS. This improved to 54% when the posteroanterior CXR and DTS were reviewed together (CXR-DTS). The overall specificities for CXR, DTS, and CXR-DTS were 49%, 96%, and 98%, respectively. There were 56 suspected hilar lesions with subgroup sensitivities of 76% for CXR, 65% for DTS, and 76% for CXR-DTS. The specificity for hilar lesions was 59%, 92%, and 97% for CXR, DTS, and CXR-DTS, respectively.

CONCLUSIONS

DTS significantly improves the detectability of noncalcified nodules when compared with and when used in combination with CXR. The specificity and interobserver agreement of DTS in the diagnosis of suspected noncalcified pulmonary nodules and hilar lesions are significantly better than those of CXR and approaches those of CT.

AN ANALYSIS OF THE POTENTIAL ROLE OF CHEST TOMOSYNTHESIS IN OPTIMISING IMAGING RESOURCES IN THORACIC RADIOLOGY

The aim of the study was to investigate the potential role of chest tomosynthesis (CTS) at a tertiary referral centre by exploring to what extent CTS could substitute chest radiography (CXR) and computed tomography (CT). The study comprised 1433 CXR, 523 CT and 216 CTS examinations performed 5 years after the introduction of CTS. For each examination, it was decided if CTS would have been appropriate instead of CXR (CXR cases), if CTS could have replaced the performed CT (CT cases) or if CT would have been performed had CTS not been available (CTS cases). It was judged that (a) CTS had been appropriate in 15 % of the CXR examinations, (b) CTS could have replaced additionally 7 % of the CT examinations and (c) CT would have been carried out in 63 % of the performed CTS examinations, had CTS not been available. In conclusion, the potential role for CTS to substitute other modalities during office hours at a tertiary referral centre may be in the order of 20 and 25 % of performed CXR and chest CT, respectively.

EFFECT OF RADIATION DOSE LEVEL ON ACCURACY AND PRECISION OF MANUAL SIZE MEASUREMENTS IN CHEST TOMOSYNTHESIS EVALUATED USING SIMULATED PULMONARY NODULES

The aim of the present study was to investigate the dependency of the accuracy and precision of nodule diameter measurements on the radiation dose level in chest tomosynthesis. Artificial ellipsoid-shaped nodules with known dimensions were inserted in clinical chest tomosynthesis images. Noise was added to the images in order to simulate radiation dose levels corresponding to effective doses for a standard-sized patient of 0.06 and 0.04 mSv. These levels were compared with the original dose level, corresponding to an effective dose of 0.12 mSv for a standard-sized patient. Four thoracic radiologists measured the longest diameter of the nodules. The study was restricted to nodules located in high-dose areas of the tomosynthesis projection radiographs. A significant decrease of the measurement accuracy and intraobserver variability was seen for the lowest dose level for a subset of the observers. No significant effect of dose level on the interobserver variability was found. The number of non-measurable small nodules (≤5 mm) was higher for the two lowest dose levels compared with the original dose level. In conclusion, for pulmonary nodules at positions in the lung corresponding to locations in high-dose areas of the projection radiographs, using a radiation dose level resulting in an effective dose of 0.06 mSv to a standard-sized patient may be possible in chest tomosynthesis without affecting the accuracy and precision of nodule diameter measurements to any large extent. However, an increasing number of non-measurable small nodules (≤5 mm) with decreasing radiation dose may raise some concerns regarding an applied general dose reduction for chest tomosynthesis examinations in the clinical praxis.

VISIBILITY OF STRUCTURES OF RELEVANCE FOR PATIENTS WITH CYSTIC FIBROSIS IN CHEST TOMOSYNTHESIS: INFLUENCE OF ANATOMICAL LOCATION AND OBSERVER EXPERIENCE

The aims of this study were to assess the visibility of pulmonary structures in patients with cystic fibrosis (CF) in digital tomosynthesis (DTS) using computed tomography (CT) as reference and to investigate the dependency on anatomical location and observer experience. Anatomical structures in predefined regions of CT images from 21 patients were identified. Three observers with different levels of experience rated the visibility of the structures in DTS by performing a head-to-head comparison with visibility in CT. Visibility of the structures in DTS was reported as equal to CT in 34 %, inferior in 52 % and superior in 14 % of the ratings. Central and peripheral lateral structures received higher visibility ratings compared with peripheral structures anteriorly, posteriorly and surrounding the diaphragm (p ≤ 0.001). Reported visibility was significantly higher for the most experienced observer (p ≤ 0.01). The results indicate that minor pathology can be difficult to visualise with DTS depending on location and observer experience. Central and peripheral lateral structures are generally well depicted.

Evaluation of a new system for chest tomosynthesis: aspects of image quality of different protocols determined using an anthropomorphic phantom

OBJECTIVE

To compare the image quality obtained with the different protocols in a new chest digital tomosynthesis (DTS) system.

METHODS

A chest phantom was imaged with chest X-ray equipment with DTS. 10 protocols were used, and for each protocol, nine acquisitions were performed. Four observers visually rated the quality of the reconstructed section images according to pre-defined quality criteria in four different classes. The data were analysed with visual grading characteristics (VGC) analysis, using the vendor-recommended protocol [12-s acquisition time, source-to-image distance (SID) 180 cm] as reference, and the area under the VGC curve (AUCVGC) was determined for each protocol and class of criteria.

RESULTS

Protocols with a smaller swing angle resulted in a lower image quality for the classes of criteria "disturbance" and "homogeneity in nodule" but a higher image quality for the class "structure". The class "demarcation" showed little dependency on the swing angle. All protocols but one (6.3 s, SID 130 cm) obtained an AUCVGC significantly <0.5 (indicating lower quality than reference) for at least one class of criteria.

CONCLUSION

The study indicates that the DTS protocol with 6.3 s yields image quality similar to that obtained with the vendor-recommended protocol (12 s) but with the clinically important advantage for patients with respiratory impairment of a shorter acquisition time.

ADVANCES IN KNOWLEDGE

The study demonstrates that the image quality may be strongly affected by the choice of protocol and that the vendor-recommended protocol may not be optimal.

Role of digital tomosynthesis and dual energy subtraction digital radiography in detection of parenchymal lesions in active pulmonary tuberculosis

OBJECTIVE

To assess the role of digital tomosynthesis (DTS) and dual energy subtraction digital radiography (DES-DR) in detection of parenchymal lesions in active pulmonary tuberculosis (TB) and to compare them with digital radiography (DR).

MATERIALS AND METHODS

This prospective study was approved by our institutional review committee. DTS and DES-DR were performed in 62 patients with active pulmonary TB within one week of multidetector computed tomography (MDCT) study. Findings of active pulmonary TB, that is consolidation, cavitation and nodules were noted on digital radiography (DR), DTS and DES-DR in all patients. Sensitivity, specificity, positive and negative predictive values of all 3 modalities was calculated with MDCT as reference standard. In addition presence of centrilobular nodules was also noted on DTS.

RESULTS

Our study comprised of 62 patients (33 males, 29 females with age range 18-82 years). Sensitivity and specificity of DTS for detection of nodules and cavitation was better than DR and DES-DR. Sensitivity and specificity of DTS for detection of consolidation was comparable to DR and DES-DR. DES-DR performed better than DR in detection of nodules and cavitation. DTS was also able to detect centrilobular nodules with sensitivity and specificity of 57.4% and 86.5% respectively.

CONCLUSION

DTS and DES-DR perform better than DR in detection of nodules, consolidation and cavitation in pulmonary TB. DTS gives better results than DES-DR, particularly in detection of cavitation and has moderate sensitivity for detection of centrilobular nodules. Thus DTS can be used for evaluation of patients of suspected pulmonary TB, thereby giving a more confident diagnosis of active disease and also in follow up.

Digital tomosynthesis for evaluating metastatic lung nodules: nodule visibility, learning curves, and reading times

OBJECTIVE

To evaluate nodule visibility, learning curves, and reading times for digital tomosynthesis (DT).

MATERIALS AND METHODS

We included 80 patients who underwent computed tomography (CT) and DT before pulmonary metastasectomy. One experienced chest radiologist annotated all visible nodules on thin-section CT scans using computer-aided detection software. Two radiologists used CT as the reference standard and retrospectively graded the visibility of nodules on DT. Nodule detection performance was evaluated in four sessions of 20 cases each by six readers. After each session, readers were unblinded to the DT images by revealing the true-positive markings and were instructed to self-analyze their own misreads. Receiver-operating-characteristic curves were determined.

RESULTS

Among 414 nodules on CT, 53.3% (221/414) were visible on DT. The main reason for not seeing a nodule on DT was small size (93.3%, ≤ 5 mm). DT revealed a substantial number of malignant nodules (84.1%, 143/170). The proportion of malignant nodules among visible nodules on DT was significantly higher (64.7%, 143/221) than that on CT (41.1%, 170/414) (p < 0.001). Area under the curve (AUC) values at the initial session were > 0.8, and the average detection rate for malignant nodules was 85% (210/246). The inter-session analysis of the AUC showed no significant differences among the readers, and the detection rate for malignant nodules did not differ across sessions. A slight improvement in reading times was observed.

CONCLUSION

Most malignant nodules > 5 mm were visible on DT. As nodule detection performance was high from the initial session, DT may be readily applicable for radiology residents and board-certified radiologists.

The value of digital tomosynthesis of the chest as a problem-solving tool for suspected pulmonary nodules and hilar lesions detected on chest radiography

OBJECTIVES

To assess the capability of digital tomosynthesis (DTS) of the chest compared to a postero-anterior (PA) and lateral chest radiograph (CXR) in the diagnosis of suspected but unconfirmed pulmonary nodules and hilar lesions detected on a CXR. Computed tomography (CT) was used as the reference standard.

MATERIALS AND METHOD

78 patients with suspected non-calcified pulmonary nodules or hilar lesions on their CXR were included in the study. Two radiologists, blinded to the history and CT, prospectively analysed the CXR (PA and lateral) and the DTS images using a picture archiving and communication workstation and were asked to designate one of two outcomes: true intrapulmonary lesion or false intrapulmonary lesion. A CT of the chest performed within 4 weeks of the CXR was used as the reference standard. Inter-observer agreement and time to report the modalities were calculated for CXR and DTS.

RESULTS

There were 34 true lesions confirmed on CT, 12 were hilar lesions and 22 were peripheral nodules. Of the 44 false lesions, 37 lesions were artefactual or due to composite shadow and 7 lesions were real but extrapulmonary simulating non-calcified intrapulmonary lesions. The PA and lateral CXR correctly classified 39/78 (50%) of the lesions, this improved to 75/78 (96%) with DTS. The sensitivity and specificity was 0.65 and 0.39 for CXR and 0.91 and 1 for DTS. Based on the DTS images, readers correctly classified all the false lesions but missed 3/34 true lesions. Two of the missed lesions were hilar in location and one was a peripheral nodule. All three missed lesions were incorrectly classified on DTS as composite shadow.

CONCLUSIONS

DTS improves diagnostic confidence when compared to a repeat PA and lateral CXR in the diagnosis of both suspected hilar lesions and pulmonary nodules detected on CXR. DTS is able to exclude most peripheral pulmonary nodules but caution and further studies are needed to assess its ability to exclude hilar lesions.

Digital tomosynthesis of the chest: current and emerging applications

Digital tomosynthesis (DTS) of the chest is a technique whose basic components are similar to those of digital radiography, but that also provides some of the benefits of computed tomography (CT). The major advantages of DTS over conventional chest radiography are improved visibility of the pulmonary parenchyma and depiction of abnormalities such as pulmonary nodules. Calcifications, vessels, airways, and chest wall abnormalities are also much more readily visualized at DTS than at chest radiography. DTS could potentially be combined with chest radiography to follow up known nodules, confirm or rule out suspected nodules seen at radiography, or evaluate individuals who are at high risk for lung cancer or pulmonary metastases. DTS generates coronal "slices" through the chest whose resolution is superior to that of coronal reconstructed CT images, but it is limited by its suboptimal depth resolution and susceptibility to motion; consequently, potential pitfalls in recognizing lesions adjacent to the pleura, diaphragm, central vessels, and mediastinum can occur. However, the radiation dose and projected cost of chest DTS are lower than those of standard chest CT. Besides pulmonary nodule detection, specific applications of DTS that are under investigation include evaluation of pulmonary tuberculous and nontuberculous mycobacterial disease, cystic fibrosis, interstitial lung disease, and asbestos-related thoracic diseases. A basic understanding of chest DTS and of the emerging applications of this technique can prove useful to the radiologist. Online supplemental material is available for this article.

Stationary chest tomosynthesis using a carbon nanotube x-ray source array: a feasibility study

Chest tomosynthesis is a low-dose, quasi-3D imaging modality that has been demonstrated to improve the detection sensitivity for small lung nodules, compared to 2D chest radiography. The purpose of this study is to investigate the feasibility and system requirements of stationary chest tomosynthesis (s-DCT) using a spatially distributed carbon nanotube (CNT) x-ray source array, where the projection images are collected by electronically activating individual x-ray focal spots in the source array without mechanical motion of the x-ray source, detector, or the patient. A bench-top system was constructed using an existing CNT field emission source array and a flat panel detector. The tube output, beam quality, focal spot size, system in-plane and in-depth resolution were characterized. Tomosynthesis slices of an anthropomorphic chest phantom were reconstructed for image quality assessment. All 75 CNT sources in the source array were shown to operate reliably at 80 kVp and 5 mA tube current. Source-to-source consistency in the tube current and focal spot size was observed. The incident air kerma reading per mAs was measured as 74.47 uGy mAs(-1) at 100 cm. The first half value layer of the beam was 3 mm aluminum. An average focal spot size of 2.5  ×  0.5 mm was measured. The system MTF was measured to be 1.7 cycles mm(-1) along the scanning direction, and 3.4 cycles mm(-1) perpendicular to the scanning direction. As the angular coverage of 11.6°-34°, the full width at half maximum of the artifact spread function improved greatly from 9.5 to 5.2 mm. The reconstructed tomosynthesis slices clearly show airways and pulmonary vascular structures in the anthropomorphic lung phantom. The results show the CNT source array is capable of generating sufficient dose for chest tomosynthesis imaging. The results obtained so far suggest an s-DCT using a distributed CNT x-ray source array is feasible.

A retrospective study of chest tomosynthesis as a tool for optimizing the use of computed tomography resources and reducing patient radiation exposure

RATIONALE AND OBJECTIVES

To investigate potential benefits and drawbacks of the clinical use of chest tomosynthesis (CTS), to what extent CTS obviates the need for chest computed tomography (CT), and what reduction in radiation dose thereby can be achieved.

MATERIALS AND METHODS

The Regional Ethical Review Board approved the follow-up study of patients examined with CTS as part of clinical routine. For each case, two radiologists in consensus determined whether CT would have been performed, had CTS not been an option, and whether CTS was an adequate examination. Thereafter, it was determined whether the use of CTS instead of CT in retrospect was beneficial, neutral, or detrimental for the radiological work-up. The radiation dose to the patient population was determined both for the actual clinical situation and for the alternative scenario that would result, had CTS not been available.

RESULTS

During 1 month 3.5 years before the survey, 149 patients (74 women, age 18-91 years) had undergone CTS for clinical purposes. It was judged that CT would have been performed in 100 cases, had CTS not been available, and that CTS obviated the need for CT in 80 cases. CTS was judged as beneficial, neutral, and detrimental for the radiological work-up in 85, 13, and two cases, respectively. For the entire study population, the use of CTS decreased the average effective dose from 2.7 to 0.7 mSv.

CONCLUSIONS

The present study indicates that CTS may have benefits for the radiological work-up as it has the potential to both optimize the use of CT resources and reduce the effective dose to the patient population. A drawback is that CTS examinations may fail to reveal pathology visible with CT and in clinically doubtful cases further investigations including other imaging procedures should be considered.

Usefulness of Digital Tomosynthesis for the Detection of Airway Obstruction: A Case Report of Bronchial Carcinosarcoma

Bronchial carcinosarcoma is a very rare malignant tumor that is composed of carcinomatous and sarcomatous elements. We describe the first case in which digital tomosynthesis was useful for the evaluation of airway obstruction by bronchial carcinosarcoma that was overlooked on initial chest radiography.

Diagnostic imaging costs before and after digital tomosynthesis implementation in patient management after detection of suspected thoracic lesions on chest radiography

Objectives

To evaluate diagnostic imaging costs before and after DTS implementation in patients with suspected thoracic lesions on CXR.

Methods

Four hundred sixty-five patients (263 male, 202 female; age, 72.47 ± 11.33 years) with suspected thoracic lesion(s) after CXR underwent DTS. Each patient underwent CT when a pulmonary non-calcified lesion was identified by DTS while CT was not performed when a benign pulmonary or extrapulmonary lesion or pseudolesion was identified. The average per-patient imaging cost was calculated by normalising the costs before and after DTS implementation.

Results

In 229/465 patients who underwent DTS after suspicious CXR, DTS showed 193 pulmonary lesions and 36 pleural lesions, while in the remaining 236/465 patients, lesions were ruled out as pseudolesions of CXR. Chest CT examination was performed in 127/465 (27 %) patients while in the remaining 338/465 patients (73 %) CXR doubtful findings were resolved by DTS. The average per-patient costs of CXR, DTS and CT were €15.15, 41.55 and 113.66. DTS allowed an annual cost saving of €8,090.2 considering unenhanced CT and €19,298.12 considering contrast-enhanced CT. Considering a DTS reimbursement rate of € 62.7 the break even point corresponds to 479 DTS examinations.

Conclusion

Per-patient diagnostic imaging costs decreased after DTS implementation in patients with suspected thoracic lesions.

Main Messages

• Digital tomosynthesis improves the diagnostic accuracy and confidence in chest radiography

• Digital tomosynthesis reduces the need for CT for a suspected pulmonary lesion

• Digital tomosynthesis requires a dose level equivalent to that of around two chest radiographies

• Digital tomosynthesis produces a significant per-patient saving in diagnostic imaging costs

The effect of averaging adjacent planes for artifact reduction in matrix inversion tomosynthesis

PURPOSE

Matrix inversion tomosynthesis (MITS) uses linear systems theory and knowledge of the imaging geometry to remove tomographic blur that is present in conventional backprojection tomosynthesis reconstructions, leaving in-plane detail rendered clearly. The use of partial-pixel interpolation during the backprojection process introduces imprecision in the MITS modeling of tomographic blur, and creates low-contrast artifacts in some MITS planes. This paper examines the use of MITS slabs, created by averaging several adjacent MITS planes, as a method for suppressing partial-pixel artifacts.

METHODS

Human chest tomosynthesis projection data, acquired as part of an IRB-approved pilot study, were used to generate MITS planes, three-plane MITS slabs (MITSa3), five-plane MITS slabs (MITSa5), and seven-plane MITS slabs (MITSa7). These were qualitatively examined for partial-pixel artifacts and the visibility of normal and abnormal anatomy. Additionally, small (5 mm) subtle pulmonary nodules were simulated and digitally superimposed upon human chest tomosynthesis projection images, and their visibility was qualitatively assessed in the different reconstruction techniques. Simulated images of a thin wire were used to generate modulation transfer function (MTF) and slice-sensitivity profile curves for the different MITS and MITS slab techniques, and these were examined for indications of partial-pixel artifacts and frequency response uniformity. Finally, mean-subtracted, exposure-normalized noise power spectra (ENNPS) estimates were computed and compared for MITS and MITS slab reconstructions, generated from 10 sets of tomosynthesis projection data of an acrylic slab. The simulated in-plane MTF response of each technique was also combined with the square root of the ENNPS estimate to yield stochastic signal-to-noise ratio (SNR) information about the different reconstruction techniques.

RESULTS

For scan angles of 20° and 5 mm plane separation, seven MITS planes must be averaged to sufficiently remove partial-pixel artifacts. MITSa7 does appear to subtly reduce the contrast of high-frequency "edge" information, but the removal of partial-pixel artifacts makes the appearance of low-contrast, fine-detail anatomy even more conspicuous in MITSa7 slices. MITSa7 also appears to render simulated subtle 5 mm pulmonary nodules with greater visibility than MITS alone, in both the open lung and regions overlying the mediastinum. Finally, the MITSa7 technique reduces stochastic image variance, though the in-plane stochastic SNR (for very thin objects which do not span multiple MITS planes) is only improved at spatial frequencies between 0.05 and 0.20 cycles∕mm.

CONCLUSIONS

The MITSa7 method is an improvement over traditional single-plane MITS for thoracic imaging and the pulmonary nodule detection task, and thus the authors plan to use the MITSa7 approach for all future MITS research at the authors' institution.

The utility of digital linear tomosynthesis imaging of total hip joint arthroplasty with suspicion of loosening: a prospective study in 40 patients

Aim. The clinical utility of digital linear tomosynthesis in musculoskeletal applications has been validated in only a few reports. Technical performance and utility in hip prosthesis imaging have been discussed in technical reports, but no clinical evaluation has been reported. The purpose of the current study was to assess the added clinical utility of digital linear tomosynthesis compared to radiography in loosening of total hip joint arthroplasty. Materials and Methods. In a prospective study, radiography and digital tomosynthesis were performed in 40 consecutive patients with total hip arthroplasty referred for suspect prosthesis loosening. Tomosynthesis images were compared to anterior-posterior (AP) and cross-table lateral radiographs regarding demarcation and extent of demineralization and osteolysis. Further noted were skeletal fractures, cement fractures, fragmentation, and artifacts interfering with the diagnosis. Results. Tomosynthesis was superior to radiography with sharper delineation of demineralization and osteolysis in the AP projection. A limitation was the inability to generate lateral tomosynthesis images, with inferior assessment of the area anterior and posterior to the acetabular cup compared to cross-table radiographs. Artifacts interfering with diagnosis were found in one hip. Conclusion. Tomosynthesis improved evaluation of total hip arthroplasty in the AP projection but was limited by the lack of lateral projections.

Digital tomosynthesis of the thorax: the influence of respiratory motion artifacts on lung nodule detection

BACKGROUND

Digital tomosynthesis considerably reduces problems created by overlapping anatomy compared with chest X-ray (CXR). However, digital tomosynthesis requires a longer scan time compared with CXR, and thus may be vulnerable to motion artifacts.

PURPOSE

To compare the diagnostic performance of digital tomosynthesis in subjects with and without respiratory motion artifacts.

MATERIAL AND METHODS

The institutional review board approved this retrospective study, and the requirement for written informed consent was waived. A total of 46 subjects with imaging containing respiratory motion artifacts were enrolled in this study, 18 of whom were positive and 28 of whom were negative for lung nodules on computed tomography (CT). The control group was comprised of 92 age-matched subjects with imaging devoid of motion artifacts. Of these, 36 were positive and 56 were negative for lung nodules on subsequent CT scan. The size criteria of nodules were 4-10 mm. Three chest radiologists independently evaluated the radiographs and digital tomosynthesis images for the presence of pulmonary nodules. Multireader multicase receiver-operating characteristic (ROC) analyses was used for statistical comparisons.

RESULTS

Within the control group, the areas under curve (AUC) for observer performances in detecting lung nodules on digital tomosynthesis was higher than that on CXR (P = 0.017). Within the study group, there were no significant differences in AUCs for observer performances (P = 0.576).

CONCLUSION

When no motion artifacts are present, the detection performance of nodules (4-10 mm) on digital tomosynthesis is significantly better than that on CXR, whereas there is not a significant difference in cases with motion artifacts.

Digital tomosynthesis of the chest: comparison of patient exposure dose and image quality between standard default setting and low dose setting

Objective

To determine the optimum low dose (LD) digital tomosynthesis (DT) setting, and to compared the image quality of the LD DT with that of the standard default (SD) DT.

Materials and Methods

Nine DT settings, by changing tube voltage, copper filter, and dose ratio, were performed for determining the LD setting. Among combinations of DT setting, a condition providing the lowest radiation dose was determined. Eighty artificial nodules less than 1 cm in diameter (subcentimeter nodules: 40, micronodules less than 4 mm: 40) were attached to a Styrofoam and a diaphragm of the phantom. Among these, 38 nodules were located at the periphery of the lung (thin area) and 42 nodules were located at the paravertebral or sub-diaphragmatic area (thick area). Four observers counted the number of nodules detected in the thick and thin areas. The detection sensitivity in SD and LD settings were calculated separately. Data were analyzed statistically.

Results

The lowest LD setting was a combination of 100 kVp, 0.3 mm additional copper filter, and a 1 : 5 dose ratio. The effective dose for the LD and SD settings were 62 µSv and 140 µSv, separately. A 56.7% dose reduction was achieved in the LD setting compared with the SD setting. Detection sensitivities were not different between the SD and the LD settings except between observers 1 and 2 for the detection of micronodules in the thick area.

Conclusion

LD DT can be effective in nodule detection bigger than 4 mm without a significant decrease in image quality compared with SD DT.

Digital tomosynthesis as a problem-solving imaging technique to confirm or exclude potential thoracic lesions based on chest X-ray radiography

RATIONALE AND OBJECTIVES

To assess the capability of digital tomosynthesis (DTS) as a problem-solving imaging technique to confirm or exclude potential thoracic lesions based on chest x-ray radiography (CXR).

MATERIALS AND METHODS

Four hundred and-sixty five patients (263 male, 202 female; age, 72.47 ± 11.33 years) with suspected thoracic lesion(s) after the initial onsite analysis of CXR underwent DTS. Two independent readers prospectively analyzed in consensus CXR and DTS images on a picture archiving and communications system-integrated workstation and proposed a diagnosis according to a confidence score for each lesion: 1 or 2 = definite or probable pulmonary or pleural benign lesion or pseudolesion deserving no further diagnostic work-up; 3 = indeterminate; 4 or 5 = probable or definite pulmonary lesion deserving further diagnostic work-up by computed tomography (CT). In patients who did not undergo chest CT, the DTS findings had to be confirmed by 6 to 12 months' imaging follow-up.

RESULTS

Finally, 229 pulmonary lesions (193 thoracic and 36 pleural lesions) and 236 pseudolesions were identified. Based on DTS images, readers correctly classified all pseudolesions except for 10/236 (reader 1) or 11/236 (reader 2) pseudolesions and 7 (reader 1) or 6 (reader 2) pulmonary subpleural lesions located in the anterior or posterior lung region close to the thoracic wall. Chest CT was performed in 127/465 (27%) patients, whereas in 338/465 patients (73%) CXR doubtful findings were resolved by DTS.

CONCLUSIONS

DTS allowed to exclude most pseudolesions initially considered as potential thoracic lesions on the preliminary onsite assessment of CXR and allowed to exclude pulmonary lesions deserving CT assessment in about three fourths of the patients.

Comparison of chest digital tomosynthesis and chest radiography for detection of asbestos-related pleuropulmonary disease

AIM

To compare chest digital tomosynthesis (DTS) with digital radiography for the detection of asbestos-related pleuropulmonary disease.

MATERIALS AND METHODS

The institutional review board approved this study and all participants gave informed consent. Forty-five participants with a history of asbestos exposure were examined with DTS and radiography. Low-dose multidetector computed tomography (CT) in the prone position served as the reference. Two observers evaluated all images for the presence of pleural abnormalities and asbestosis. Interobserver agreement was analysed by using the k statistic. Diagnostic performance of the two imaging methods was compared using McNemar's test.

RESULTS

Interobserver agreement regarding DTS findings was moderate to very good (k = 0.544-0.846) and superior to the radiographic findings (k = 0.236-1.000). Overall, the diagnostic accuracy of DTS for the lesion detection was significantly better than with radiography (all p < 0.05, except that for the comparison of diagnostic accuracy of DTS versus radiographic detection of left diaphragmatic plaques and asbestosis). DTS was more sensitive than radiography for the detection of asbestosis (82% versus 27%, p = 0.031).

CONCLUSION

DTS is more accurate than radiography in the detection of pleural plaques and more sensitive than radiography in the detection of asbestosis. Interobserver agreements with respect to the DTS findings were superior to the radiographic findings.

Analysis of the impact of digital tomosynthesis on the radiological investigation of patients with suspected pulmonary lesions on chest radiography

OBJECTIVE

To assess the impact of digital tomosynthesis (DTS) on the radiological investigation of patients with suspected pulmonary lesions on chest radiography (CXR).

METHODS

Three hundred thirty-nine patients (200 male; age, 71.19 ± 11.9 years) with suspected pulmonary lesion(s) on CXR underwent DTS. Two readers prospectively analysed CXR and DTS images, and recorded their diagnostic confidence: 1 or 2 = definite or probable benign lesion or pseudolesion deserving no further diagnostic workup; 3 = indeterminate; 4 or 5 = probable or definite pulmonary lesion deserving further diagnostic workup by computed tomography (CT). Imaging follow-up by CT (n = 76 patients), CXR (n = 256) or histology (n = 7) was the reference standard.

RESULTS

DTS resolved doubtful CXR findings in 256/339 (76 %) patients, while 83/339 (24 %) patients proceeded to CT. The mean interpretation time for DTS (mean ± SD, 220 ± 40 s) was higher (P < 0.05; Wilcoxon test) than for CXR (110 ± 30 s), but lower than CT (600 ± 150 s). Mean effective dose was 0.06 mSv (range 0.03-0.1 mSv) for CXR, 0.107 mSv (range 0.094-0.12 mSv) for DTS, and 3 mSv (range 2-4 mSv) for CT.

CONCLUSIONS

DTS avoided the need for CT in about three-quarters of patients with a slight increase in the interpretation time and effective dose compared to CXR.

Digital tomosynthesis for PNS evaluation: comparisons of patient exposure and image quality with plain radiography

OBJECTIVE

We investigated low dose digital tomosynthesis (DT) for the evaluation of the paranasal sinus (PNS), and compared its diagnostic accuracy with a PNS radiography series (XR).

MATERIALS AND METHODS

We enrolled 43 patients for whom XR, PNS DT, and OMU CT were performed. We measured effective doses (EDs) of XR, DT, and OMU CT using Monte Carlo simulation software. Two radiologists performed independent observation of both XR and DT. For seven PNSs, they scored anatomic conspicuity of sinuses and confidence on the presence of sinusitis using nine point scales. OMU CT was observed by the third radiologist and the findings were regarded as reference standard. We compared scores for conspicuity and sinusitis confidence between XR and DT.

RESULTS

Mean EDs were 29 ± 6 µSv, 48 ± 10 µSv, and 980 ± 250 µSv, respectively, for XR, DT, and CT. Mean scores for conspicuity were 6.3 and 7.4, respectively, for XR and DT. Sensitivity per patient basis for sinusitis detection were 52% and 96%, respectively, for XR and DT in observer 1 (p = 0.001) and 80% and 92% for observer 2 (p = 0.25). Specificities for sinusitis exclusion were 100% for both XR and DT for observer 1 and 89% and 100% for observer 2 (p = 0.50). Accuracies for sinusitis diagnosis were 72% and 98%, respectively, for XR and DT for observer 1 (p = 0.001) and 84% and 95% for observer 2 (p = 0.125).

CONCLUSION

Patient radiation dose from low dose DT is comparable with that of PNS XR. Diagnostic sensitivity of DT for sinusitis was superior to PNS XR.

Digital tomosynthesis for aortic arch calcification evaluation: performance comparison with chest radiography with CT as the reference standard

BACKGROUND

Recently developed digital tomosynthesis has shown improved detection of pulmonary lesions with a radiation dose comparable to conventional CR but with a much lower radiation dose than CT.

PURPOSE

To compare the diagnostic performance of digital tomosynthesis (DT) with that of chest radiography (CR) for the detection of aortic arch calcification (AAC).

MATERIAL AND METHODS

The study included 100 patients who underwent multidetector computed tomography (MDCT), DT, and CR (DT and CR were obtained within one week of CT examination). We evaluated and compared the diagnostic performances of DT and CR for the detection of AAC with MDCT as the reference standard. The extent (four grades 0-3) of AAC on DT and CR was also compared with CT calcium score. Inter-observer agreement was analyzed by using kappa statistics.

RESULTS

On DT, overall accuracy for AAC was superior to that of CR (94% and 71%, respectively, P < 0.01). Inter-observer agreement was good with DT and CR (kappa values = 0.74 and 0.62, respectively) for the presence of AAC, and good with DT and moderate with CR (kappa value = 0.64 and 0.53, respectively) for AAC grading. The overall correlation coefficient on AAC grading between DT and CT (calcium score) was superior to that between CR and CT (0.90 and 0.60, respectively).

CONCLUSION

DT is superior to CR for detection and extent evaluation of AAC.

Fast scanning tomosynthesis for the detection of pulmonary nodules: diagnostic performance compared with chest radiography, using multidetector-row computed tomography as the reference

OBJECTIVES

: To evaluate the diagnostic performance of fast scanning tomosynthesis in comparison with that of chest radiography for the detection of pulmonary nodules, using multidetector-row computed tomography (MDCT) as the reference, and to assess the association of the true-positive fraction (TPF) with the size, CT attenuation value, and location of the nodules.

MATERIALS AND METHODS

: The institutional review board approved this study, and written informed consent was obtained from all patients. Fifty-seven patients with and 59 without pulmonary nodules underwent chest MDCT, fast scanning tomosynthesis, and radiography. The images of tomosynthesis and radiography were randomly read by 3 blinded radiologists; MDCT served as the reference standard. Free-response receiver-operating characteristic (FROC) and receiver-operating characteristic (ROC) analyses, Cochran-Armitage trend or Fisher exact test, a conditional logistic regression model, and McNemar test were used.

RESULTS

: Both FROC and ROC analyses revealed significantly better performance (P < 0.01) of fast scanning tomosynthesis than radiography for the detection of pulmonary nodules. For fast scanning tomosynthesis, the average TPF and false-positive rate as determined by FROC analysis were 0.80 and 0.10, respectively. For both fast scanning tomosynthesis and radiography, the average TPF increased with increasing nodule size and CT attenuation values, and was lower for subpleural nodules (all P < 0.01).

CONCLUSIONS

: The diagnostic performance of fast scanning tomosynthesis for the detection of pulmonary nodules was significantly superior to that of radiography. The TPF was affected by the size, CT attenuation value, and location of the nodule, in both fast scanning tomosynthesis and radiography.