美國國立衛生研究院（NIH）批準資助倫斯勒理工學院的研究員2百萬美元，用于研發一種應用物理原理實時虛擬患者呼吸的模型,即3D模型聯合時間變量所得到的4D模型，它的應用能夠明顯改善肺癌和肝癌放療的精確度和效果。

在德克薩斯州圣安東尼市的癌癥治療和研究中心，George Xu(生物醫學工程和核醫學教授)和Suvranu De(機械工程學副教授)與臨床專業的同事進行多學科合作，研發4D可視圖象人（4-D VIP－Man）。這種虛擬模型是Xu教授正在進行的3-D VIP-Man計劃的延伸項目。此項目是一種先進的電腦模型，能用3-D技術模擬射線如何影響人體的器官和組織。

Xu教授認為，活人不同于靜止的生物，而在腫瘤的放療和成像中，像肺臟或者心臟這樣能夠運動的器官是主要的干擾因素。為了判斷有效放射計量及其精確數值，醫生必須考慮如呼吸運動和空氣容積變化這些問題，它們在放療過程中會受生理因素影響。實時模擬能夠使得醫生在短時間片段內能觀測到肺、肝、腎和心相對與外射線是靜止的。在臨床治療中，做到這點即意味著，醫生在為運動的腫瘤作放療時能更有把握。4-D VIP－Man可以讓醫生和醫學物理學家精確地預測和監測這些解剖改變，從而在任何時候都能提供最有效的治療。但4-D VIP－Man很難研制。

現在，Xu教授和De副教授正集中精力研究呼吸功能。應用先進的計算機技術，模擬肺的運動是可行的；但是，不能做到實時模擬。對于精確放療來說，應用物理技術實時虛擬人體功能能最終解決這個問題。這項計劃的主要難度在于如何研發相應的運算法則，從而依照組織真實的生物力學性質實時模擬肺及臨近組織的運動。Xu教授預測，基于物理學的4-D VIP-Man將最終在生物醫學領域更廣泛地用作解剖模型，幫助治療有呼吸道疾病和心臟病的患者。同時，他將通過計算機學人體影像協會（http://www.virtualphantoms.org）與全世界的研究者合作，繼續研究3-D VIP-Man，創造虛擬患者的“家族譜” 。

Xu教授以前的學生Chengyu Shi（臨床醫學物理學家）和Martin Fuss（放射腫瘤學家）認為，在解決肺的運動問題后，放療效果會更好。在得知他們的興趣后，Xu和田納西州的研究組開始合作。在與De副教授（他曾用3-D VIP-Man技術模擬外科手術中組織的變形）聯系后，將3-D VIP-Man改進為4-D VIP-Man的想法就產生了。

從1997年以來，Xu一直致力于應用先前的可視人體工程計劃（Visible Human Project ）來研究3-D VIP-Man，其數據集來源于美國國家醫學圖書館，經費來源于NIH和國家科學基金會CAREER獎金。新的4年科研基金由美國國家醫學圖書館（NIH的一部分）資助。

“Virtual Patient” To Simulate Real-time Organ Motions For Radiation Therapy

With a $2 million grant from the National Institutes of Health (NIH), researchers from Rensselaer Polytechnic Institute are developing a physics-based virtual model that can simulate a patient's breathing in real time。When used in conjunction with existing 3-D models, adding the fourth dimension of time could significantly improve the accuracy and effectiveness of radiation treatment for lung and liver cancers.

。George Xu, professor of nuclear and biomedical engineering, and Suvranu De, associate professor of mechanical engineering, have formed a multidisciplinary collaboration with clinical colleagues at the Cancer Therapy & Research Center in San Antonio, Texas, to develop the 4-D Visible Photographic Man (VIP-Man)。This virtual model is an extension of Xu's ongoing project involving the 3-D VIP-Man, which is an advanced computer model that simulates in 3-D how radiation affects the organs and tissues in the human body.

"Live patients are not static beings, and a moving organ such as the lung or heart is a main concern in radiation treatment or imaging of tumors that are affected by such organ movement," Xu said。"In order to determine accurate and effective radiation dosages, doctors must consider such issues as the breathing function and air volume change that are affected by several physiological factors over the course of the radiation treatment."

Real-time simulations could allow doctors to spot the small fractions of time when the lungs, liver, kidneys, and eventually the heart, are stationary relative to the external radiation beams。These opportune moments during the actual therapy mean that doctors will have more confidence delivering the radiation to a moving tumor.

"The 4-D VIP-Man will allow doctors and medical physicists to accurately predict and monitor these anatomical changes to provide the most effective treatment possible at any given time," Xu said.

The fourth dimension of the VIP-Man is not easily achieved, according to Xu。Currently Xu and De are focusing their energy on respiratory function。"Using advanced computational tools, it is possible to simulate lung movement; however, not in real time," De said。"For effective radiation therapy, physics-based real-time performance offers the ultimate solution."

The key challenge in this project is to develop the algorithms that will make the virtual lungs and adjacent tissues move in real time according to realistic tissue biomechanical properties, De said.

Xu expects that the physics-based 4-D VIP-Man will eventually be used as an even more general anatomical modeling tool for the biomedical community to help patients with respiratory and cardiac diseases。At the same time, Xu will continue to work on the 3-D VIP-Man to create a "family" of virtual patients, ranging in ages and sizes, in collaboration with researchers worldwide through the Consortium of Computational Human Phantoms (http://www.virtualphantoms.org), co-founded by Xu.

The collaboration with the group in Texas came about when Xu's former student, Chengyu Shi, a clinical medical physicist, and Martin Fuss, a radiation oncologist, expressed their interests to develop better radiation treatment by accounting for lung movement。Xu contacted De, who had been using the 3-D VIP-Man to simulate tissue deformation for surgical procedures, and the idea to take 3-D VIP-Man into the fourth dimension was born.

Xu has been working on the 3-D VIP-Man since 1997 using the original Visible Human Project dataset provided by the National Library of Medicine, also funded by several grants from NIH as well as a National Science Foundation CAREER grant。The new four-year, $2 million grant is funded by the National Library of Medicine, which is part of NIH.