美國國立衛(wèi)生研究院（NIH）批準(zhǔn)資助倫斯勒理工學(xué)院的研究員2百萬美元，用于研發(fā)一種應(yīng)用物理原理實(shí)時(shí)虛擬患者呼吸的模型,即3D模型聯(lián)合時(shí)間變量所得到的4D模型，它的應(yīng)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(yī)學(xué)工程和核醫(yī)學(xué)教授)和Suvranu De(機(jī)械工程學(xué)副教授)與臨床專業(yè)的同事進(jìn)行多學(xué)科合作，研發(fā)4D可視圖象人（4-D VIP－Man）。這種虛擬模型是Xu教授正在進(jìn)行的3-D VIP-Man計(jì)劃的延伸項(xiàng)目。此項(xiàng)目是一種先進(jìn)的電腦模型，能用3-D技術(shù)模擬射線如何影響人體的器官和組織。

Xu教授認(rèn)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(yùn)動(dòng)的器官是主要的干擾因素。為了判斷有效放射計(jì)量及其精確數(shù)值，醫(yī)生必須考慮如呼吸運(yùn)動(dòng)和空氣容積變化這些問題，它們在放療過程中會(huì)受生理因素影響。實(shí)時(shí)模擬能夠使得醫(yī)生在短時(shí)間片段內(nèi)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(diǎn)即意味著，醫(yī)生在為運(yùn)動(dòng)的腫瘤作放療時(shí)能更有把握。4-D VIP－Man可以讓醫(yī)生和醫(yī)學(xué)物理學(xué)家精確地預(yù)測和監(jiān)測這些解剖改變，從而在任何時(shí)候都能提供最有效的治療。但4-D VIP－Man很難研制。

現(xiàn)在，Xu教授和De副教授正集中精力研究呼吸功能。應(yīng)用先進(jìn)的計(jì)算機(jī)技術(shù)，模擬肺的運(yùn)動(dòng)是可行的；但是，不能做到實(shí)時(shí)模擬。對于精確放療來說，應(yīng)用物理技術(shù)實(shí)時(shí)虛擬人體功能能最終解決這個(gè)問題。這項(xiàng)計(jì)劃的主要難度在于如何研發(fā)相應(yīng)的運(yùn)算法則，從而依照組織真實(shí)的生物力學(xué)性質(zhì)實(shí)時(shí)模擬肺及臨近組織的運(yùn)動(dòng)。Xu教授預(yù)測，基于物理學(xué)的4-D VIP-Man將最終在生物醫(yī)學(xué)領(lǐng)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(shí)，他將通過計(jì)算機(jī)學(xué)人體影像協(xié)會(huì)（http://www.virtualphantoms.org）與全世界的研究者合作，繼續(xù)研究3-D VIP-Man，創(chuàng)造虛擬患者的“家族譜” 。

Xu教授以前的學(xué)生Chengyu Shi（臨床醫(yī)學(xué)物理學(xué)家）和Martin Fuss（放射腫瘤學(xué)家）認(rèn)為，在解決肺的運(yùn)動(dòng)問題后，放療效果會(huì)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(shù)模擬外科手術(shù)中組織的變形）聯(lián)系后，將3-D VIP-Man改進(jìn)為4-D VIP-Man的想法就產(chǎn)生了。

從1997年以來，Xu一直致力于應(yīng)用先前的可視人體工程計(jì)劃（Visible Human Project ）來研究3-D VIP-Man，其數(shù)據(jù)集來源于美國國家醫(yī)學(xué)圖書館，經(jīng)費(fèi)來源于NIH和國家科學(xué)基金會(huì)CAREER獎(jiǎng)金。新的4年科研基金由美國國家醫(yī)學(xué)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.