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Evaluation of Lung Injury after Three-dimensional Conformal Stereotactic Radiation Therapy for Solitary Lung Tumors: CT Appearance¹

¹ From the Department of Therapeutic Radiology and Oncology, Graduate School of Medicine, Kyoto University, 54 Shogoin Kawahara-cho, Sakyo, Kyoto 606-8507, Japan. Received September 25, 2002; revision requested December 10; final revision received May 17, 2003; accepted June 18. Supported by grants-in-aid no. 09255255, no. 10153231, and no. 13470183 from the Ministry of Education, Culture, Sports, Science, and Technology, and no. 23765293 from the Ministry of Health, Labour, and Welfare in Japan. Address correspondence to Y. Nagata (e-mail: nag@kuhp.kyoto-u.ac.jp).

View larger version (18K): [in a new window]   Figure 1. Graph shows the changes in tumor sizes in all patients. The tumor size was measured as the product of the widest diameter and the perpendicular diameter of the target. Measurements were obtained in the CT image showing the greatest tumor size of each image set.

View larger version (66K): [in a new window]   Figure 2. Transverse CT images obtained in a 69-year-old man with primary lung cancer (T1N0M0, adenocarcinoma) show a representative case of the clinical course after SRT. The irregularly shaped patchy consolidation and homogeneous slight increase in opacity appeared around the tumor 4 months after SRT; after 6 months, a new patchy consolidation appeared. Afterward, the patchy consolidation diminished and changed to solid consolidation with scarring. Although it can not be accurately distinguished between the residual tumor and the solid consolidation in the image 15 months after SRT, no recurrence was observed, even in the 25- and 31-month images, and the tumor was considered as showing partial response.

View larger version (111K): [in a new window]   Figure 3. Transverse CT images show a representative case of patchy consolidation. Left: Image obtained for treatment planning at the isocenter. Right and bottom: Images obtained 5 months after SRT show an irregularly shaped consolidation that does not conform to the dose distribution curve. It is visible with the lung window setting (top right) and can be partially detected with the soft-tissue window setting (bottom).

View larger version (110K): [in a new window]   Figure 4. Transverse CT images show a representative case of homogeneous slight increase in opacity. Left: Image obtained for treatment planning at the isocenter. Right and bottom: Images obtained 6 months after SRT. The opacity around the tumor (arrow) was slightly and homogeneously increased with the lung window setting (top right), and there were no abnormal shadows around the tumor with the soft-tissue window setting (bottom).

View larger version (109K): [in a new window]   Figure 5. Transverse CT images show a representative case of solid consolidation. Left: Image obtained for treatment planning at the isocenter. Right and bottom: Images obtained 13 months after SRT. Consolidation involving the tumor and surrounding lung tissue in the treatment-planning CT image was observed with the lung window setting (top right), and most of this consolidation was detectable with the soft-tissue window setting (bottom).

View larger version (80K): [in a new window]   Figure 6. Transverse CT images show a representative case of discrete consolidation. Left: Image obtained for treatment planning at the isocenter. Right and bottom: Images obtained 10 months after SRT. Consolidation (arrows) involving the high-dose area ( 24 Gy) (not strictly conforming to the 24 Gy isodose line) in the treatment-planning CT image was observed with the lung window setting (top right) and could be partially detected with the soft-tissue window setting (bottom).

View larger version (89K): [in a new window]   Figure 7. Transverse CT images show a representative case of wedge-shaped radiation-induced pulmonary injury. Left: Image obtained for treatment planning at the isocenter. Right and bottom: Images obtained 5 months after SRT. Wedge-shaped discrete consolidation involving the hilar and peripheral side of the tumor was observed. This shadow did not conform to any isodose curves.

View larger version (86K): [in a new window]   Figure 8. Transverse CT images show a representative case of round-shaped radiation-induced pulmonary injury. Left: Image obtained for treatment planning at the isocenter. Right and bottom: Images obtained 4 months after SRT. Round-shaped patchy consolidation was observed around the tumor (arrows).

View larger version (114K): [in a new window]   Figure 9. CT image shows the isodose curve superimposed on radiation-induced pulmonary change 4 months after SRT. In this case, the pulmonary change (contoured with a thick dashed line) appeared on and within the 16-Gy line (thick solid line). The outer thin dashed line indicates the 12-Gy line, and the inner thin solid line indicates the 20-Gy line.

View larger version (12K): [in a new window]   Figure 10. Graph shows correlation between the minimal dose at which radiation-induced pulmonary change occurred and the V20. The dose distribution at CT generated by the three-dimensional treatment-planning system and the radiation-induced pulmonary changes at follow-up CT were compared, and the minimal dose for the appearance of pulmonary change was determined. There was a significant inverse correlation between the minimal dose and V20.