任何一種射源都有其獨特的暴露率常數，由於此特性，我們在探討射源所會影響到的區域內，射源的劑量會在某一特定的距離下有特定的等劑量曲線包覆此區域，意即我們選用某種射源使用在近接治療上，不論是單點使用或多點分佈使用，所選取的等劑量曲線和此等劑量曲線所包覆的體積存在一種天然的體積一劑量微量變化之關聯性；除此之外，當我們探討近接治療的電腦治療計劃之優劣的比較準則時，腫瘤區域的劑量均勻度及所選取要做爲治療處方劑量的等劑量曲線對腫瘤的包覆度的幾何圖形之分析都是評定一個近接治療的電腦治療計劃的好壞不可或缺的工具；所以天然的體積一劑量之關聯性，均勻度及包覆度；在此以這三種方式做爲本篇以圖形量化方式在近接治療劑量的最佳曲線選取之研究。由射源強度隨距射源的距離平方成反比的關係可以推導出在近接治療中由射源在某段距離所包覆的體積和劑量率的(下標 -3/2)次方的比值不隨劑量率的改變而有所變化，而採用腫瘤和執行完治療計劃後的幾何相對關係去定義所選取要做爲治療處方劑量的等劑量曲線對腫瘤的包覆度及腫瘤部位劑量的均勻度，以此三種尺標決定一個近接治療的治療計劃之優劣及做爲等劑量曲線最佳化選取之準則。因爲等劑量曲線所包覆的體積和在此處的劑量率的(下標 -3/2)次方的比值不隨劑量率的改變而改變，於是每種射源用在近接治療上都會有一個天然的體積一劑量之最佳分佈，於是對於每種射源的使用，我們必須知道所使用的近接治療射源的特性，以便選取適當的等劑量曲線做爲近接治療劑量最佳化的參考。除了引用自然特性的體積劑量法做爲近接治療等劑量曲線的選取標準外，本篇還探討包覆度(Comformity index)及均勻度(Uniformity index)做爲判斷近接治療劑量最佳化選取之參考。

Any kind of radio-activity sources has its own characteristic for dose delivery to a certain distance and the volume covered by this certain distance, which means there exist some proportionality between volume and the area under the curve. This study is to investigate the optimal dose curve encompass the treat volume in Ir-192 brachytherapy. With mathmatical derivation, these volume and the area under the curve relationship are met by plotting the distribution of volume per unit power of dose rate versus the power of dose rate. Point source and multiple sources are used to study the effects of adding sources to the dose system. Multisource implants are also investigated for volume-dose analysis study to see what is the optimal dose curve selection for different geometric souces setting treatment. In the conceptual approach, dose rate is expressed as the -3/2 power in order to suppress inverse square law effects in volume histograms analysis. The histogram representation of perfect dose uniformity would be a function with narrow spike figure at a particular dose rate. Clinical significant distribution parameters include dose rate uniformity and peak volume extension into normal tissue. This analysis affords a useful method of assessing the quality of implants for individual patients as well as a means for evaluating idealized source configurations in implant planning.