The presence of Air Bronchus Sign (ABS) is associated with higher bronchoscopic yield. Usually, only axial cut of CT scan images are viewed. On bedside computer workstations, Multi-Projection Reconstruction (MPR) viewing software allows manual plane tilting that can reveal non-axial ABS pathways towards peripheral lesions. We reviewed whether High Resolution CT (HRCT) can increase ABS and subsequent tissue diagnosis.
We retrospectively reviewed 52 cases with suspected peripheral malignancies. 28 males 24 females; 24 to 84 y/o; RB1/LB1/2: 10(19.23%), RB2: 5(9.62%), RB3/LB3: 16(30.77%), RB4/LB4: 3(5.77%), RB5/LB5: 3(5.77%), RB6/LB6: 7(13.46%), RB8/LB8: 4(7.69%), RB9/LB9: 4(7.69%). Positive ABS defined as a clear airway segment leading to lesions. We noted frequencies of ABS on axial, coronal, sagittal and tilted plane views seen on 3mm slice LRCT and subsequently with 0.5–1.0mm HRCT slices.
Using MPR with plane-tilting for ABS detection to guide bronchoscopic steering, overall tissue diagnostic yield is 84.62%, (55.77% with cancer, 28.85% granulomatous inflammation) and 15.38%(8/52) non diagnostic biopsies. ABS in axial view 15.38%LRCT Vs 38.46%HRCT; coronal: 15.38% LRCT Vs 46.15% HRCT; sagittal 9.62% LRCT Vs 28.85% HRCT, tiled plane: 63.46%LRCT Vs 98.08%HRCT. Presence of axial ABS is relatively low in RB1/LB1/2: 0/10 LRCT/HRCT axial view. Conversely, the presence of ABS in coronal(sagittal) view is relatively high in these segments: 9/10(8/10) HRCT. In RB3/LB3, frequency of axial ABS is comparatively high, especially HRCT: 10/16axial, 4/16coronal, 1/16sagittal.
With existing software tool MPR, routine use of HRCT scan images plus plane-tilting manipulation can successfully obtain positive ABS in the majority of cases(98.08%). HRCT is superior Vs LRCT in most of cases. (p=0.007axial, 0.0006coronal, 0.01sagittal, 0.000003tilted plane, fisher exact) Coronal and sagittal views are superior Vs axial view in RB1/LB1/2 (p=0.00006coronal, 0.0004sagittal). But in RB3/LB3, axial is superior compared with coronal(p=0.03) and sagittal(p=0.001).
Routine pre-bronchoscopy study of CT data acquired by thin cuts and studied by MPR in different views increases ABS detection in procedure planning and potentially increases diagnostic yield.
Di Xu, No Financial Disclosure Information; No Product/Research Disclosure Information