Sequential dual-energy subtraction technique with a dynamic flat-panel detector (FPD): primary study for image-guided radiation therapy (IGRT)

• Published in: Radiological physics and technology Vol. 1; no. 2; pp. 144 - 150
• Main Authors: Tanaka, Rie, Sanada, Shigeru, Matsui, Takeshi, Hayashi, Norio, Matsui, Osamu
• Format: Journal Article
• Language: English
• Published: Tokyo Springer Japan 01.07.2008
• Subjects: Fluoroscopy - methods; Imaging; Lung Neoplasms - radiotherapy; Medical and Radiation Physics; Medicine; Medicine & Public Health; Nuclear Medicine; Radiographic Image Enhancement - instrumentation; Radiographic Image Enhancement - methods; Radiology; Radiotherapy; Radiotherapy, Computer-Assisted - instrumentation; Radiotherapy, Computer-Assisted - methods; Reproducibility of Results; Respiratory Mechanics; Sensitivity and Specificity; Soft Tissue Neoplasms - radiotherapy; Subtraction Technique - instrumentation; Image-guided radiation therapy (IGRT); Target tracking; Respiration; Flat-panel detector; Motion analysis; Dual-energy subtraction
• ISSN: 1865-0333; 1865-0341; 1865-0341
• DOI: 10.1007/s12194-008-0021-6

A sequential dual-energy subtraction technique for image-guided radiation therapy (IGRT) was developed. Here, we report on a computerized method for creating sequential soft-tissue images and the accuracy of tracking targets on the images obtained, in comparison to conventional fluoroscopic images. Two sets of sequential chest images during respiration of a normal subject were obtained with X-rays of different energy separately with a flat-panel detector (FPD). Sequential soft-tissue images were created from the two sets of sequential images consisting of real-time images and reference template images, respectively. The creation of sequential soft-tissue images consisted of three steps: one-to-one image correspondence of the two sequential images, image registration, and image subtraction in each frame. Motion tracking of lung vessels was then performed by the template-matching technique. For evaluation of the accuracy of motion tracking on the sequential soft-tissue images, the results were compared with those on the original sequential images. Sequential soft-tissue images provided more accurate tracking than the original images ( P  < 0.01). There was no significant error throughout all frames in the soft-tissue images, whereas the rib shadow introduced a tracking error in the original images. The maximum errors were 4.1 ± 0.3 mm in the sequential soft-tissue images and 28.1 ± 20.0 mm in the original images. In conclusion, sequential soft-tissue images were helpful for tracking of a target affected by respiratory motion. Dual-energy subtraction has the potential to improve the accuracy of IGRT without implanted markers.