RT Journal Article
SR Electronic
T1 Distribution of Ventilation/Perfusion Ratios in Pulmonary Embolism: An Adjunct to the Interpretation of Ventilation/Perfusion Lung Scans
JF Journal of Nuclear Medicine
JO J Nucl Med
FD Society of Nuclear Medicine
SP 1596
OP 1602
VO 43
IS 12
A1 Emmanuel Itti
A1 Séverine Nguyen
A1 Fabrice Robin
A1 Serge Desarnaud
A1 Jean Rosso
A1 Alain Harf
A1 Michel Meignan
YR 2002
UL http://jnm.snmjournals.org/content/43/12/1596.abstract
AB Diagnosis of pulmonary embolism (PE) by visual interpretation of ventilation/perfusion (V/Q) scans is limited by the high percentages of patients classified in the intermediate- and low-probability categories. This study proposes a quantitative analysis of the distribution of V/Q ratios to better identify patients with PE. Methods: We studied 99 consecutive patients who underwent dual-isotope 81mKr/99mTc-macroaggregate V/Q scanning and arterial blood gas analysis within 48 h. The 8-view V/Q scans were visually analyzed by 2 observers according to the revised criteria of the Prospective Investigation of Pulmonary Embolism Diagnosis (PIOPED) (normal scan or low, intermediate, or high probability of PE). Quantitative analysis of the posterior-view distribution histogram of V/Q ratios was performed using dedicated software. Briefly, regions of interest were drawn around the lungs on the matched V/Q images, smooth filtering was applied, normalized regional V/Q ratios were calculated within each pixel, and a distribution histogram was built. Results: Patients with normal scans (n = 16) had a predominance of V/Q ratios (63.3% ± 13.0%) between 0.8 and 1.2. They had only 9.8% ± 5.8% of ratios > 1.2, and the remaining 26.9% ± 7.5% of ratios were <0.8. By contrast, patients with PE (n = 34) were characterized by a significant increase (15.5 ± 10.0%, P = 0.04) in high V/Q ratios (>1.2) and a significant increase (34.5% ± 8.2%, P = 0.003) in low V/Q ratios (<0.8). Interestingly, a similar pattern was found in patients with a high PIOPED probability of PE, 21.3% ± 11.0% and 37.5% ± 9.2%, respectively. Within the nondiagnostic group (intermediate- + low-probability scans, n = 58), 17 patients were finally diagnosed with PE. Analysis of the distribution histogram in this group allowed the identification of 5 patients with PE (specificity, 78%). Conclusion: A quantitative approach to lung scan interpretation, based on the distribution histogram of V/Q ratios, may be helpful for categorizing patients with suspected PE.