2004 Volume 16 Issue 1 Pages 33-39
Purpose: By means of quantifying the nonuniform distribution of pulmonary perfusion in Lung Perfusion Scintigraphy SPECT (Single Photon Emission Tomography), which is called “SPECT” for short, we evaluated the degree of functional impairment of pulmonary perfusion in non-operated lung cancer patients treated by the radiotherapy.
Materials and Methods: Sixty-eight patients with non-operated lung cancer treated with radiotherapy, and who either received or did not receive chemotherapy, from February, 1996 to August, 2002, were examined using SPECT within 6 weeks prior to, or within 2 weeks following radiotherapy. This group was called “irradiated lung cancer patients”. Twenty-six patients, who were called “follow-up irradiated lung cancer patients”, were reexamined within four weeks after radiotherapy. On the other hand, 323 patients without lung cancer, who were subdivided into four groups; pulmonary, cardiac, cardio-pulmonary, and noncardiopulmonary. The SPECT was examined in the supine position after infusing Tc-99m-MAA, 185 MBq in a bolus, mainly into an antecubital vein with the patient's arm elevated. From reconstructed SPECT images, the volume of lung as a whole calculated at 10 % of thresholds was assumed to be the “Baseline Lung Perfusion Volume” (BPV), and the functional volume rates were calculated in 10 % threshold widths from 10 % to 100 % of the threshold. Assuming the total absolute differences in functional volume rate between each subject and the control to be the distribution index of the lung as a whole (D index), we quantified the degree of nonuniform distribution of the lung as a whole in each subject. In the same way, the distribution index of the left or right lung respectively was calculated as D1 or Dr index assuming the volume of left or right lung were calculated at 10 % of the threshold as left or right BPV and calculating the functional volume rates of each lung in 10% threshold widths from 10 % to 100 % of the threshold.
Results: The D index of irradiated lung cancer patients was 26.4±1.4, which was almost equal to that of the pulmonary group including the chronic obstructive pulmonary diseases, and significantly higher than that of cardiac or non-cardiopulmonary group. The irradiated lung cancer patients with complications of pulmonary or cardiopulmonary diseases showed a significantly increased D index, compared with patients without complications. Distribution index of tumor-bearing lung (Dr/1 index) was significantly higher than that of non-tumor-bearing lung. The Dr/1 index of tumor-bearing lung of small cell carcinoma patients significantly increased, compared with that of adenocarcinoma patients, and significantly increased according to whether or not the primary tumor occupied the hilar region and degree of extension of tumor invasion especially in the hilum as well as the mediastinum. In the follow-up irradiated lung cancer patients, the D index and Dr/1 index of non-tumor-bearing lung post-radiotherapy significantly increased, compared with pre-radiotherapy.
Conclusions: It is considered that the distribution index quantifying nonuniform distibution in the SPECT enables evaluation of the degree of impairment of lung as a whole, tumor-bearing lung, and non-tumorbearing lung in lung cancer patients, and results in presenting a useful indicator for radiotherapeutic planning and following up respiratory function after radiotherapy.
