The role of lung perfusion imaging in predicting the direction of radiation-induced changes in pulmonary function tests.
BACKGROUND
The aim of this study was to determine whether preradiation (pre-RT) single photon emission computed tomography (SPECT) lung perfusion scans can be used to predict RT-induced changes in pulmonary function tests (PFTs).


METHODS
Ninety-four patients irradiated for thoracic tumors had pre-RT SPECT lung perfusion scans. The presence of SPECT hypoperfusion distal to a central mediastinal tumor was qualitatively assessed visually without knowledge of PFT changes. Patients were grouped based on whether the diffusion capacity (DLCO) ever increased post-RT. Comparisons of patient groups were performed using 1-tailed Fisher exact tests. Patient follow-up was 6-56 months (mean, 30 months). To assess SPECT hypoperfusion objectively, the average dose to the computed tomography (CT)-defined lung was compared with the weighted-average dose (based on relative perfusion) to the SPECT-defined lung. The ratio between the CT- and SPECT-defined mean lung dose provided a quantitative assessment of hypoperfusion. The mean ratio for patients with central tumor and adjacent hypoperfusion was compared with that of the others (Wilcoxon rank-sum one-sided test).


RESULTS
In patients with central tumors, 41% (9 of 22) with adjacent hypoperfusion had improvements in DLCO following radiation, versus 18% (3 of 17) of those without hypoperfusion (P = 0.11). In patients with lung carcinoma, the corresponding ratios were 40% (8 of 20) and 10% (1 of 10), respectively (P = 0.10). The mean ratio of CT dose to SPECT dose was 1.35 for patients with central tumors and adjacent hypoperfusion versus 1.16 for others (P = 0.017).


CONCLUSIONS
The presence of SPECT hypoperfusion adjacent to a central mediastinal mass may identify patients likely to have improved PFTs following RT. Thus, SPECT imaging may be useful in models for predicting radiation-induced changes in PFTs.
Marks
L B
LB
Department of Radiation Oncology, Duke University Medical Center, Durham, North Carolina 27710, USA.
Hollis
D
D
Munley
M
M
Bentel
G
G
Garipagaoglu
M
M
Fan
M
M
Poulson
J
J
Clough
R
R
Sibley
G
G
Coleman
R E
RE
Jaszczak
R
R
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002277:Carcinoma / Q000503:physiopathology / Q000532:radiotherapy; D005260:Female; D005500:Follow-Up Studies; D005544:Forecasting; D006801:Humans; D008168:Lung / Q000000981:diagnostic imaging* / Q000503:physiopathology / Q000528:radiation effects; D008175:Lung Neoplasms / Q000503:physiopathology / Q000532:radiotherapy; D008176:Lung Volume Measurements; D008297:Male; D008479:Mediastinal Neoplasms / Q000503:physiopathology / Q000532:radiotherapy; D008875:Middle Aged; D011446:Prospective Studies; D011653:Pulmonary Diffusing Capacity / Q000528:radiation effects; D011829:Radiation Dosage; D019275:Radiopharmaceuticals; D012129:Respiratory Function Tests; D013147:Spirometry; D013223:Statistics as Topic; D013668:Technetium Tc 99m Aggregated Albumin; D013899:Thoracic Neoplasms / Q000503:physiopathology / Q000532:radiotherapy*; D015899:Tomography, Emission-Computed, Single-Photon / Q000379:methods; D014057:Tomography, X-Ray Computed
D019275:Radiopharmaceuticals; D013668:Technetium Tc 99m Aggregated Albumin