Validation of RAH VQ SPECT/CT lobar quantification program using a modified version of GE Q lung.

Abstract

The value of ventilation-perfusion (VQ) single photon emission tomography/computed tomography (SPECT/CT) lobar quantification for pre-operative assessment of lobectomy and lung volume reduction is known. Our in-house developed software, RAH ventilation perfusion SPECT/CT quantification (RAHVQSQ) has been shown to be able to identify the target lobe for collapse in bronchoscopic lung volume reduction (BLVR) for advanced emphysema. We have proven inter and intra observer reproducibility but are yet to validate the accuracy of our program. This study aims to validate the accuracy of our quantitative program through comparison with a modified version of GE Q lung which is a commercial program certified for clinical use. Ventilation-perfusion SPECT/CT data of 19 subjects from our previous study using RAHVQSQ for BLVR assessment were re-analysed using Q lung by 2 technologists independently and in a blinded fashion to determine lobar differential ventilation, perfusion and volume percentages. The data were from GE Hawkeye 4 and external CT, thus a modified version of Q lung was used. To determine interobserver variation in the 3 parameters between the 3 assessors, intraclass correlation coefficient (ICC) and Bland-Altman limits of agreement (LoA) were generated. Paired comparisons between the 3 assessors had high ICC (range for ventilation: 0.69-0.97; perfusion: 0.69-0.97; volume: 0.63-0.97) and means of LoA differences close to zero (range for ventilation: -0.04 - 0.10; perfusion: 0.00-0.02; volume: -0.12 - 0.09) were noted indicative of good concordance for all parameters. Using VQ SPECT/CT data of participants with advanced airway disease, our study has found a close concordance of estimated differential lobar ventilation, perfusion and volume percentages using RAHVQSQ when compared with a duplicated blinded assessment using Q lung. The good concordance supports the validity of our quantitative methodology.