螺旋斷層放射治療系統是一種斷層迴旋式的強度調控放射治療技術(Intensity Modulated Radiation Therapy, IMRT)，具備螺旋式投射的複雜形式，也是一種相當理想的強度調節放射線療法，其同時結合3D電腦反算式優化治療處理計畫系統，影像導引放射治療(Image Guided Radiotherapy-IGRT)，精確的病患位置定位系統與品質確認系統(QA System)整合於單一系統內。在每天治療腫瘤過程當中，可利用斷層掃描影像評估治療腫瘤效果及得知腫瘤縮小的程度，進而評估是否可把照射範圍縮小，減少副作用發生的機率。能兼備電腦掃描影像導引地位技術的放射治療方式，能準確治療癌腫瘤並同時將損傷減至最低，達到高精確、高劑量、高效率、低損傷的治療目標。

Tomotherapy is the delivery of intensity modulated radiation therapy using rotational delivery of a fan beam in the manner of a CT scanner. In helical tomotherapy, the couch and gantry are in continuous motion akin to a helical CT scanner, Helical tomotherapy is inherently capable of acquiring CT images of the patient in treatment position and using this information for image guidance. Tomotherapy is ideal for conformal avoidance of the delivery of dose to sensitive normal tissue. Tomotherapy is used for adjusting the setup position of the patient and as the basis for dose reconstruction and other adaptive radiotherapy processes. Helical tomotherapy is the first integrated planning, delivery and verification system for IMRT.