Measurement of Total Lung Capacity: A Comparison of Spiral CT and Spirometry

PURPOSE: To determine the potential of spiral CT as a functional imaging modality of the lung asid from its proven value in morphological depiction. MATERIALS AND METHODS: Spiral CT scan was performed in ten normal female and nine normal male adults (mean age: 39, height: 163cm, weight: 62kg) after single full breath-holding. Three dimensional lung images were reconstructed (minimal threshold value: -1,000HU, maximal threshold values: -150,-250, -350, -450HU) to obtain total lung volume(TLV) on a histogram. Total lung volume measured by spiral CT was compared with TLV obtained by spirometry. RESULTS: Mean TLV measured by spirometry was 5.62 Land TLV measured by CT at maximal threshold values of -150, -250, -350, and -450HU was 6.63, 5.33, 5.15, and 4.98 L, respectively. Mean absolute differences between the modalities of 0.17L(3%), 0.32L(5.6%), 0.48L(8.5%), 0.65L(11.5) were statistically significant(p<0.001). Linear regression coefficients between the modalities were 0.99, 0.97, 0.95,and 0.94 and no statistically significant differences in accuracy of threshold levels in the estimation of lung volume(r=0.99, standard error=0.034L in all) were seen. CONCLUSION: TLV measured by spiral CT closely approximated that measured by spirometry. Spiral CT may be useful as a means of evaluating lung function.

Scintigraphic evaluation of renovascular hypertension

ACE inhibitor challenged renal scintigraphic studies offer noninvasive means of evaluating patients for renovascular hypertension, and provide help in selecting patients who will benefit most from interventional procedures designed for alleviation of renal artery stenosis. These studies provide functional assessment of each kidney which also helps the vascular surgeons to plan which renal artery to repair first, when bilateral renal arteries are stenotic, prior to an abdominal aortic aneurysm repair. Vasotec challenged Tc99mMAG3 renal scintigraphy is one of such tests with several advantages over other similar methods, and appears to have a great potential of being a preferred scintigraphic study for evaluation of renovascular hypertension.