對腫瘤病患執行放射治療時，強度調控放射治療(Intensity Modulation Rational Therapy)可被視爲一種藝術，放射治療的目的，在於將醫師所要給的處方劑量，經由輻射的方式傳輪到腫瘤，同時，限制健康或危急器官的照射，強度調控放射治療明顯克服某些複雜，且無法以傳統放射治療降低危急器官傷害的困難，例如：頭頸部癌症的唾液腺與脊椎傷害，近年來強度調控放射治療已成爲主要放射治療技術。強度調控放射治療的執行，必須透過電腦治療計劃系統，經由逆向式計劃，針對臨床上醫師對腫瘤與危急器官所要求的極大與極小值做成本函數(Cost Function)的最佳化(Optimization)，產生所要的通量圖(Fluence Map)，通量圖再以葉片序列算式(Leaf Sequence Algorithm)得到一序列的子照野(Subfield)集合。本篇主旨在於描述這些子照野傳輸劑量時，其實已產生劑量的不準確性，即爲系統誤差。

Intensity modulated radiation therapy (IMRT) is a state-of-the-art technique for administering radiation to cancer patients. The goal of a treatment is to deliver a prescribed amount of radiation to the tumor, while limiting the amount absorbed by thesurrounding healthy and critical organs. Planning an IMRT treatment requires determining fluence maps, each consisting of hundreds or more beamlet (or subfield) intensities. Since it is difficult or impossible to deliver a sufficient dose to a tumor without irradiating nearby critical organs, radiation oncologists have developed guidelines to allow tradeoffs by introducing so called dose-volume constraints (DVCs), which specify a given percentage of volume for each critical organ that can be sacrificed if necessary. Such constraints, however, are of combinatorial nature and pose significant challenges to the fluence map optimization problem. The purpose of this paper is to describe how a systematic error happens while we try to introduce the IMRT with multiple segment fields.