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

Abstract

Cite this article as: Jadidi M, Sundin A, Aspelin P, Båth M, Nyrén S. 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 vendorrecommended protocol [12-s acquisition time, source-toimage distance (SID) 180 cm] as reference, and the area under the VGC curve (AUC VGC ) 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 AUC VGC 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.

Dependency of image quality on acquisition protocol and image processing in chest tomosynthesis—a visual grading study based on clinical data

“…As motion artefacts degrade images in DTS, investigation of different acquisition times is an important part of the optimisation of image quality and this can determine the diagnostic yield in imaging. 10 In a previous visual grading study based on an anthropomorphic chest phantom, a DTS protocol with acquisition time 6.3 s was found to yield images whose quality did not differ significantly for any class of image quality criteria from images obtained by using the protocol recommended by the vendor with acquisition time 12 s. 11 Possible advantages of the protocol with short acquisition time related to the reduced risk of breathing and other motion artefacts could for obvious reasons not affect the outcome of the phantom study. Thus, it is conceivable that this protocol actually could lead to increased image quality in the clinical situation.…”

“…For those patients, a short acquisition time (6.3 s) is essential without compromising the image quality. 11 The second advantageis a reduction of the risk of presence of the respiratory motion artefact. .…”

“…For this study, the criteria instead had to be developed based on the European guidelines for diagnostic radiographic images 21 and chest CT 22 and additionally based on a previous study. 11 A third limitation is that the chest DTS images were evaluated on a laptop, Mac Book Pro, 15" and not on the hospital's picture archiving and communication system workstation used for routine clinical radiology. The reason for this was that two of the observers worked at different hospitals with different geographic location.…”

“…The criteria (Table 5) developed for the study, were based on the European guidelines on quality criteria for diagnostic radiographic images 21,22 and the quality criteria proposed in previous studies. 11,23 The criteria focused on image quality in pre-determined anatomical regions, similar to our previous publication. 11 Image quality was assessed in five defined anatomical regions.…”

“…11,23 The criteria focused on image quality in pre-determined anatomical regions, similar to our previous publication. 11 Image quality was assessed in five defined anatomical regions. In four regions, (1) basal-dorsal, (2) All tomosynthesis projection images were acquired with a filtration of 3.0 mm Al and + 0.2 mm Cu and two different grids, with aluminium interspace, were used; a grid with ratio 10/1 with a focusing distance of 130-140 cm for the protocol with SDD 130 cm and a grid with ratio 12/1 with a focusing distance of 180 cm for the protocol with SDD 180 cm.…”