Contrast-enhanced CT images were obtained for one healthy 42-year-old male volunteer in treatment position with inspiration breath-holding in July 2014. CT imaging was performed using a multidetector CT scanner (Aquilion LB; Toshiba Medical Systems, Otawara, Japan) with 16 detector rows. The volunteer received 110 ml of iohexol (Omnipaque, 300 mgI/ml, Daiichi-Sankyo, Tokyo, Japan) intravenously by means of power injector; the injection duration was 50 s. The scan duration was 80 s after the start of the injection. The parameters used in CT imaging were as follows: the field of view was 55 cm, the tube-current was 300 mA, and the tube-voltage was 120 kVp. The beam pitch was 0.8, and auto-exposure control was not used.
The images were imported into a 3D radiotherapy treatment planning system (RTPS) (EclipseTM Treatment Planning System ver. 10.0; Varian Medical Systems, Palo Alto, CA). The lymph node stations were initially contoured on CT images in the RTPS as regions of interest (based on IASLC definitions) by a radiation oncologist who belongs to the Japanese Radiation Oncology Study Group (JROSG). Subsequently, a project group was established by JROSG in October 2014. This group consisted of six additional radiation oncologists, a thoracic radiologist and a thoracic surgeon. All of the contoured CT images were revised, and tentative definitions for the boundaries of lymph node Stations 1–11 in six directions (cranial, caudal, left, right, anterior and posterior) were assigned by the JROSG project group as a draft of the atlas.
Finally, a JLCS–JASTRO joint committee, which consisted of four radiation oncologists, four thoracic surgeons and three thoracic radiologists, was established to revise the draft. The committee held four conferences (in December 2014, and February, April and June 2015) and proposed a consensus-based CT atlas for defining the regional lymph node stations in radiotherapy for lung cancer. This atlas was approved by the Board of Directors of JASTRO in June 2015 and by the Board of Directors of JLCS in July 2015.
The images were imported into a 3D radiotherapy treatment planning system (RTPS) (EclipseTM Treatment Planning System ver. 10.0; Varian Medical Systems, Palo Alto, CA). The lymph node stations were initially contoured on CT images in the RTPS as regions of interest (based on IASLC definitions) by a radiation oncologist who belongs to the Japanese Radiation Oncology Study Group (JROSG). Subsequently, a project group was established by JROSG in October 2014. This group consisted of six additional radiation oncologists, a thoracic radiologist and a thoracic surgeon. All of the contoured CT images were revised, and tentative definitions for the boundaries of lymph node Stations 1–11 in six directions (cranial, caudal, left, right, anterior and posterior) were assigned by the JROSG project group as a draft of the atlas.
Finally, a JLCS–JASTRO joint committee, which consisted of four radiation oncologists, four thoracic surgeons and three thoracic radiologists, was established to revise the draft. The committee held four conferences (in December 2014, and February, April and June 2015) and proposed a consensus-based CT atlas for defining the regional lymph node stations in radiotherapy for lung cancer. This atlas was approved by the Board of Directors of JASTRO in June 2015 and by the Board of Directors of JLCS in July 2015.
