[Multidetector-row CT of the lungs: Multiplanar reconstructions and maximum intensity projections for the detection of pulmonary nodules]

Abstract

Purpose: The present study was performed to evaluate the utility of axial, coronal and sagittal multiplanar reformations (MPR) and maximum intensity projections (MIP) in the detection of pulmonary nodules as compared to axial standard reconstructions (SR).

Materials and methods: 103 patients with suspicion or evidence of pulmonary nodules underwent multidetector-row computed tomography (MDCT; Somatom plus 4 Volume Zoom, Siemens, Germany) of the chest in a single-breath-hold technique. The raw data were acquired with a collimation of 1 mm and a pitch of 6 and underwent reconstruction with 0.6 mm increment. MPR and MIP in three planes [5 mm slice thickness (SL), 4 mm increment] were calculated from the raw data and compared to axial SR (5 mm SL). Three blinded observers evaluated the number, size and the quality of depiction of pulmonary nodules according to a 3-point confidence scale (1 = certain, 2 = probable, 3 = uncertain). Four patient groups were formed using the axial SR. Group 1 presenting no nodules, group 2 presenting probable nodules and group 3 presenting definitively lung nodules. Patients with more than 7 pulmonary nodules (group 4) were not included in the study. The 1 mm slice was used as the gold standard.

Results: Inter-observer correlation was good at r = 0.77. MIP were superior in the depiction of pulmonary nodules at a statistically significant level of p < 0.05 (mean values in group 3 = 2.58 to 1.97 and group 2 = 0.99 to 0.79 with MIP and SR, respectively). In four patients 6 additional lesions were identified with MIP that were missed with axial SR. Overall, with SR 72 nodules, with MPRs 78, and with MIPs 99 nodules were delineated. Pulmonary nodules larger than 5 mm in size were equally well depicted with both modalities, whereas lesions smaller than 5 mm in size were significantly better depicted with MIP (p < 0.05). Diagnostic confidence for all lesions was highest with MIP and least with SR.

Conclusion: MIP reformations on the basis of MDCT data sets are superior in the depiction and diagnosis of pulmonary nodules as compared to axial standard reconstructions and MPR.