Sensitivity of Thoracic Digital Tomosynthesis (DTS) for the Identification of Lung Nodules

Abstract

Thoracic computed tomography (CT) is considered the gold standard for detection lung pathology, yet its efficacy as a screening tool in regards to cost and radiation dose continues to evolve. Chest radiography (CXR) remains a useful and ubiquitous tool for detection and characterization of pulmonary pathology, but reduced sensitivity and specificity compared to CT. This prospective, blinded study compares the sensitivity of digital tomosynthesis (DTS), to that of CT and CXR for the identification and characterization of lung nodules. Ninety-five outpatients received a posteroanterior (PA) and lateral CXR, DTS, and chest CT at one care episode. The CXR and DTS studies were independently interpreted by three thoracic radiologists. The CT studies were used as the gold standard and read by a fourth thoracic radiologist. Nodules were characterized by presence, location, size, and composition. The agreement between observers and the effective radiation dose for each modality was objectively calculated. One hundred forty-five nodules of greatest diameter larger than 4 mm and 215 nodules less than 4 mm were identified by CT. DTS identified significantly more >4 mm nodules than CXR (DTS 32 % vs. CXR 17 %). CXR and DTS showed no significant difference in the ability to identify the smaller nodules or central nodules within 3 cm of the hilum. DTS outperformed CXR in identifying pleural nodules and those nodules located greater than 3 cm from the hilum. Average radiation dose for CXR, DTS, and CT were 0.10, 0.21, and 6.8 mSv, respectively. Thoracic digital tomosynthesis requires significantly less radiation dose than CT and nearly doubles the sensitivity of that of CXR for the identification of lung nodules greater than 4 mm. However, sensitivity and specificity for detection and characterization of lung nodules remains substantially less than CT. The apparent benefits over CXR, low cost, rapid acquisition, and minimal radiation dose of thoracic DTS suggest that it may be a useful procedure. Work-up of a newly diagnosed nodule will likely require CT, given its superior cross-sectional characterization. Further investigation of DTS as a diagnostic, screening, and surveillance tool is warranted.

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

“…24,25,27 Also, several studies demonstrated the effective dose of each modality for standard patient in each study protocol, [9][10][11][12]21 and we found that the radiation dose for DTS was approximately twice that for chest radiography and DTS required a much smaller radiation dose in comparison with CT.…”

“…In our meta-analysis, some studies which used CT as the reference standard did not suggest the truenegative number, because they demonstrated only the true-positive number of nodules detected with DTS and chest radiography among nodules detected with CT. 13,22,23 In other studies, sensitivity was estimated on a per-lesion basis, but specificity was exclusively estimated on per-patient basis. 9,11,21,27 Thus, we inevitably analyzed the detection rate from lesion-based data because we considered those information could be significant for evaluating the diagnostic value for the detection of pulmonary nodule despite definite limitations. The meta-analysis for lesion-based studies was performed using two groups.…”

“…9,11,13,[21][22][23] However, we could extract the total numbers of true positives and the total number of pulmonary nodules, which allowed us to calculate and analyze detection rates. Thus, we identified 7 studies (1017 patients) that presented per-patient results 10,12,[17][18][19][20][21] and 10 studies that presented per-lesion results (2159 lesions) 9,11,13,[21][22][23][24][25][26][27] for meta-analysis. Only one study included both per-patient-and per-lesion-based data.…”

Comparison of digital tomosynthesis and computed tomography for lung nodule detection in SOS screening program

“…Most of false-positive findings were due to normal lung structures, such as bronchioles. The position of the nodules in the lobes reflects the non-easy association of nodules to lung lobes more than an actual difference between the two methodologies and the values we found are comparable to those of the literature [28]. Besides, there is a real difficulty in describing nodules that are adjacent to the thoracic wall in DTS with respect to CT, because of the spill-in of higher density region into the lung.…”

“…In the Table 1 SOS study, we showed that 6.5 × 10 −1 % of subjects had lung cancer, to be compared to a nearly 500 times lower risk of REID (0.3 × 10 −3 %) for the same pathology, suggesting that the screening procedure, even if expose the subjects to radiation, is advantageous. All the published studies [14,16,[26][27][28] on DTS report the sensitivity of DTS using CT as a reference, defining sensitivity as the ratio of number of nodules detected by DTS and CT. This is a direct consequence of the design of these studies that were conceived to test DTS on a population of subjects that already performed, for different reasons, a CT scan.…”