Anatomic Variations in Pulmonary Perfusion and Ventilation Per Quantitative MAA and DTPA SPECT/CT in Patients Receiving Thoracic Radiation Therapy

Abstract

Purpose/Objective(s)Patients who undergo thoracic radiation therapy often have underlying lung co-morbidities that can impact their toxicity from treatment. Evaluation of regional variations in lung function with SPECT/CT ventilation/perfusion imaging may shed light on influential risk factors. We propose to examine the regional variation in lung perfusion and ventilation as it correlates to tumor location using quantitative SPECT/CT parameters in thoracic malignancy patients undergoing radiation therapy.Materials/MethodsRadiation treatment planning CT scans were co-registered with pre-treatment 99mTc-MAA perfusion and 99mTc-DTPA MAA SPECT/CT scans of 9 patients who underwent thoracic radiation with curative intent. Patient characteristics are as follows: 7 had NSCLC, 1 had esophageal squamous cell carcinoma, and 1 had oligometastatic ovarian cancer. Two patients had prior surgical resection and four patients received prior radiation therapy. Gross tumor volume (GTV), total lung minus GTV (TL-GTV), and individual lobes were delineated (LUL, LLL, RUL, RML, RLL). Mean and coefficient of variation in lobe uptake normalized to TL-GTV were calculated. Statistical differences in mean and variance in MAA perfusion and DTPA ventilation uptake were assessed for several groups using non-parametric Mann-Whitney rank-sum independent testing and Wilcoxon sign-rank paired testing: upper vs lower lobes, lobes containing the GTV vs un-involved lobes, and prior treated vs non-treated lobes.ResultsOverall, lower lobes had 17% higher mean perfusion than upper lobes (p = 0.03) and trended towards 7% higher coefficient of variation in perfusion (p = 0.07), while no statistically significant differences in ventilation were observed. Lobes containing the GTV had 6% lower mean perfusion than un-involved lobes (p = 0.05) and trended towards 20% lower mean ventilation (p = 0.09), while neither difference in perfusion or ventilation coefficient of variation reached significance. The study was insufficiently powered to detect differences between prior treated and non-treated lobes.ConclusionsTumor containing lobes of the lung overall had reduced perfusion/ventilation as quantified on MAA and DTPA SPECT/CT when compared to uninvolved lobes. These data suggest that functional avoidance treatment planning that selectively spare uninvolved lobes may reduce radiation induced pulmonary toxicity. Further investigation is warranted to exploit baseline differences in regional pulmonary function and to track spatial variances in functional change in response to radiation. Purpose/Objective(s)Patients who undergo thoracic radiation therapy often have underlying lung co-morbidities that can impact their toxicity from treatment. Evaluation of regional variations in lung function with SPECT/CT ventilation/perfusion imaging may shed light on influential risk factors. We propose to examine the regional variation in lung perfusion and ventilation as it correlates to tumor location using quantitative SPECT/CT parameters in thoracic malignancy patients undergoing radiation therapy. Patients who undergo thoracic radiation therapy often have underlying lung co-morbidities that can impact their toxicity from treatment. Evaluation of regional variations in lung function with SPECT/CT ventilation/perfusion imaging may shed light on influential risk factors. We propose to examine the regional variation in lung perfusion and ventilation as it correlates to tumor location using quantitative SPECT/CT parameters in thoracic malignancy patients undergoing radiation therapy. Materials/MethodsRadiation treatment planning CT scans were co-registered with pre-treatment 99mTc-MAA perfusion and 99mTc-DTPA MAA SPECT/CT scans of 9 patients who underwent thoracic radiation with curative intent. Patient characteristics are as follows: 7 had NSCLC, 1 had esophageal squamous cell carcinoma, and 1 had oligometastatic ovarian cancer. Two patients had prior surgical resection and four patients received prior radiation therapy. Gross tumor volume (GTV), total lung minus GTV (TL-GTV), and individual lobes were delineated (LUL, LLL, RUL, RML, RLL). Mean and coefficient of variation in lobe uptake normalized to TL-GTV were calculated. Statistical differences in mean and variance in MAA perfusion and DTPA ventilation uptake were assessed for several groups using non-parametric Mann-Whitney rank-sum independent testing and Wilcoxon sign-rank paired testing: upper vs lower lobes, lobes containing the GTV vs un-involved lobes, and prior treated vs non-treated lobes. Radiation treatment planning CT scans were co-registered with pre-treatment 99mTc-MAA perfusion and 99mTc-DTPA MAA SPECT/CT scans of 9 patients who underwent thoracic radiation with curative intent. Patient characteristics are as follows: 7 had NSCLC, 1 had esophageal squamous cell carcinoma, and 1 had oligometastatic ovarian cancer. Two patients had prior surgical resection and four patients received prior radiation therapy. Gross tumor volume (GTV), total lung minus GTV (TL-GTV), and individual lobes were delineated (LUL, LLL, RUL, RML, RLL). Mean and coefficient of variation in lobe uptake normalized to TL-GTV were calculated. Statistical differences in mean and variance in MAA perfusion and DTPA ventilation uptake were assessed for several groups using non-parametric Mann-Whitney rank-sum independent testing and Wilcoxon sign-rank paired testing: upper vs lower lobes, lobes containing the GTV vs un-involved lobes, and prior treated vs non-treated lobes. ResultsOverall, lower lobes had 17% higher mean perfusion than upper lobes (p = 0.03) and trended towards 7% higher coefficient of variation in perfusion (p = 0.07), while no statistically significant differences in ventilation were observed. Lobes containing the GTV had 6% lower mean perfusion than un-involved lobes (p = 0.05) and trended towards 20% lower mean ventilation (p = 0.09), while neither difference in perfusion or ventilation coefficient of variation reached significance. The study was insufficiently powered to detect differences between prior treated and non-treated lobes. Overall, lower lobes had 17% higher mean perfusion than upper lobes (p = 0.03) and trended towards 7% higher coefficient of variation in perfusion (p = 0.07), while no statistically significant differences in ventilation were observed. Lobes containing the GTV had 6% lower mean perfusion than un-involved lobes (p = 0.05) and trended towards 20% lower mean ventilation (p = 0.09), while neither difference in perfusion or ventilation coefficient of variation reached significance. The study was insufficiently powered to detect differences between prior treated and non-treated lobes. ConclusionsTumor containing lobes of the lung overall had reduced perfusion/ventilation as quantified on MAA and DTPA SPECT/CT when compared to uninvolved lobes. These data suggest that functional avoidance treatment planning that selectively spare uninvolved lobes may reduce radiation induced pulmonary toxicity. Further investigation is warranted to exploit baseline differences in regional pulmonary function and to track spatial variances in functional change in response to radiation. Tumor containing lobes of the lung overall had reduced perfusion/ventilation as quantified on MAA and DTPA SPECT/CT when compared to uninvolved lobes. These data suggest that functional avoidance treatment planning that selectively spare uninvolved lobes may reduce radiation induced pulmonary toxicity. Further investigation is warranted to exploit baseline differences in regional pulmonary function and to track spatial variances in functional change in response to radiation.