Home About us Editorial board Search Ahead of print Current issue Archives Submit article Instructions Subscribe Contacts Login 
  • Users Online: 16
  • Home
  • Print this page
  • Email this page

 Table of Contents  
Year : 2018  |  Volume : 4  |  Issue : 4  |  Page : 184-190

Investigation on the status of radiation therapy for nasopharyngeal cancer in Chongqing city

1 Department of Oncology, Cancer Institute, Second Affiliated Hospital, Army Medical University, Chongqing, China
2 Department of Oncology, Third Affiliated Hospital, Army Medical University, Chongqing, China
3 Department of Oncology, First Affiliated Hospital, Army Medical University, Chongqing, China
4 Department of Oncology, Chongqing Cancer Hospital, Chongqing, China
5 Department of Oncology, First Affiliated Hospital, Chongqing Medical University, Chongqing, China
6 Department of Oncology, Chongqing Three Gorges Central Hospital, Chongqing, China

Date of Web Publication28-Dec-2018

Correspondence Address:
Jianguo Sun
Department of Oncology, Cancer Institute, Second Affiliated Hospital, Army Medical University, Chongqing 400000
Login to access the Email id

Source of Support: None, Conflict of Interest: None

DOI: 10.4103/digm.digm_32_18

Rights and Permissions

Objective: The objective of the study is to investigate the regional capacity and implementation of radiotherapy for nasopharyngeal carcinoma (NPC) in Chongqing city. Materials and Methods: The questionnaires, self-designed electronic forms in a uniform format, were distributed to 37 radiotherapy institutions, which covered all the medical units equipped with radiotherapy equipment in this city. Results: Of the 37 radiotherapy units in Chongqing, 27 could deliver radiotherapy for NPC, but the remaining 10 institutions could not due to equipment limitations. From January to December 2017, a total of 2904 patients with NPC were treated with radiotherapy. Patients from the five teaching hospitals in the main districts of the city accounted for 86% of the participants. There were four representative types of radiotherapy plan based on radiation technology among these units. Of the 37 units, 18 used intensity-modulated radiotherapy, 6 adopted three-dimensional conformal radiotherapy, 2 chose volumetric modulated arc therapy, and 1 delivered two-dimensional traditional radiotherapy; only 10 units applied magnetic resonance imaging (MRI)-computed tomography registration and fusion for gross tumor volume delineation in NPC treatment, and only 3 units routinely acquired nasopharyngeal and neck MRI scans to evaluate tumor shrinkage during treatment. Conclusion: Obvious distinctions exist between various units in Chongqing city in radiotherapeutic strategy, radiotherapy plan, frequency of image-guided radiation therapy, and mid-treatment evaluation for NPC radiotherapy. We need to learn and apply NPC guideline and consensus to improve NPC radiotherapy in Chongqing and to construct a rule with regional characteristics.

Keywords: Chongqing area, nasopharyngeal cancer, questionnaires, radiotherapy workflow

How to cite this article:
Zhu Y, Wang G, Li G, Li J, Jin F, Zhang T, Liu X, Sun J. Investigation on the status of radiation therapy for nasopharyngeal cancer in Chongqing city. Digit Med 2018;4:184-90

How to cite this URL:
Zhu Y, Wang G, Li G, Li J, Jin F, Zhang T, Liu X, Sun J. Investigation on the status of radiation therapy for nasopharyngeal cancer in Chongqing city. Digit Med [serial online] 2018 [cited 2023 Mar 29];4:184-90. Available from: http://www.digitmedicine.com/text.asp?2018/4/4/184/248982

  Introduction Top

Nasopharyngeal carcinoma (NPC) is one of the most common malignancies in the region of head and neck in China. Radiotherapy is the first choice and primary treatment for NPC due to the anatomical features, special biological behaviors, and radiosensitiveness of the disease.[1] With the development of radiological technology, the 5-year disease-specific survival for NPC has risen from 78% by two-dimensional radiotherapy and 81% by three-dimensional conformal radiotherapy (3D-CRT) to 85% by intensity-modulated radiotherapy (IMRT), and the rate of late toxic effects has dropped from 7.4% to 3.5% and 1.8%.[2] Thus, rational selection of radiotherapy technology forms the basis for taking full advantage of this therapy. However, many factors in radiation treatment can affect the final outcome, and standardized management of the treatment can ensure a good outcome. To evaluate regional radiotherapy capacity and explore existing problems with radiation treatment in a certain area, we conducted a survey in terms of NPC radiotherapy status in Chongqing city.

  Materials and Methods Top

Research respondents

This research covered 38 districts and counties in Chongqing area, and 37 medical units equipped with radiotherapy machines, including medical linear irradiator and gamma knife. After-loading machine, cobalt-60 machine, and KV grade X-ray treatment machine were excluded. These hospitals under research ranged from middle second class to top first class, including public hospitals, military hospitals, and private hospitals.

Research method

This research adopted a self-designed electronic questionnaire in a uniform format. It includes basic information of medical institutions, radiotherapy equipment, staff status, NPC patients, radiotherapy plan and workflow. NPC patients received radiotherapy in the year of 2017. The questionnaire was infilled by director physician or assistant director physician in charge of the radiotherapy unit or the oncology department, to ensure that the information of radiotherapy center was true, reliable, and accurate.

  Results Top

The situation of number and distribution

By December 2017, there had been a total of 37 radiotherapy institutions in Chongqing. Thirty-one were in operation, among which 5 were newly built and 1 was just suspended from operation due to expired equipment.

According to the survey, 32 of the 37 institutions were public hospitals. Together, there were 20 tertiary hospitals, 13 secondary hospitals, 3 military hospitals (top first class), and 2 private hospitals (not rated yet).

The radiotherapy institutions were distributed in 26 districts or counties of Chongqing, and there were 12 districts or counties without radiotherapy equipment.

Status of radiotherapy staff

By December 2017, there had been 161 and 173 radiotherapy oncologists, 51 and 39 physicists, and 127 and 73 technicians in Chongqing downtown and suburbs, respectively [Table 1]. The ratio of the radiotherapy oncologists to the physicists was 3.15:1 and 4.34:1 in teaching hospitals and suburban hospitals, respectively.
Table 1: Distribution of personnel in radiotherapy

Click here to view

Network construction of radiotherapy units, radiotherapy equipment, and technology development

In total, 11 institutions in Chongqing were equipped with advanced radiotherapy information network platforms. Among them, three institutions, collaborated with other radiotherapy ones, were also equipped with remote radiotherapy platform.

With regard to radiotherapy equipment, the number of import accelerators, domestic accelerators, cobalt-60 machine, and after-loading radiation machines in this city was 27, 20, 4, and 5, respectively. Among them, 6 accelerators were newly installed at the end of 2017. Compared to the 2015 national survey, the number of accelerators in Chongqing increased by 38% in the past 3 years, and the accelerator number per million population increased by 25% [Table 2]. The import accelerators were from Varian in 12 institutions, Elekta in 13 institutions, and Siemens in 2 institutions. Moreover, the domestic accelerators were from Xinhua Medical Company in 14 institutions, Shanghai High Tech in 1 institution, Neusoft in 1 institution, and North Medical Institutes in 2 institutions. There were 27 sets of import planning system and 20 sets of domestic planning system.
Table 2: Radiotherapy-related techniques

Click here to view

As for the technology development, 3D-CRT, IMRT, and image-guided radiation therapy (IGRT) technologies are adopted in 35, 30, and 9 radiotherapy institutions, respectively. Three new technologies have been developed as follows: volumetric modulated arc therapy (VMAT) in 2 institutions, stereotactic body radiation therapy in 6 institutions, and stereotactic radiosurgery in 3 institutions [Table 3].
Table 3: The growth of radiotherapy equipment in Chongqing area from 2015 to 2018

Click here to view

Current status of radiotherapy for nasopharyngeal cancer patients

From January 2017 to December 2017, radiotherapy for NPC was carried out in only 27 radiotherapy institutions; 2904 cases of NPC were treated, of which 86% received radiotherapy in 5 teaching hospitals in urban areas [Figure 1].
Figure 1: Distribution map of patients with nasopharyngeal carcinoma in the city in 2017

Click here to view

The research team collected the dose design of the target area of NPC in each radiotherapy institution in the city, and slight differences were observed in the dose required by each institution in the target area. The dose design is divided into three categories [Table 4].
Table 4: Prescription dose mode of nasopharyngeal carcinoma in Chongqing

Click here to view

The applications of NPC irradiation technology were as follows: 2 VMAT, 18 IMRT, 6 3D-CRT, and 1 general.

Auxiliary technology and equipment development: 10 institutions adopted magnetic resonance imaging-computed tomography (MRI-CT) fusion technology in the target area delineation, but 17 institutions did not. Nine radiotherapy institutions adopted image-guided techniques during radiotherapy, of which 8 used cone-beam CT (CBCT) and 1 used electronic portal imaging device.

Three types of image verification during radiotherapy: (1) only one institution performed image verification once a day during the first 3 days of radiotherapy, twice a week from the 2nd week to the end; (2) five institutions performed image verification once a week from the beginning to the end; and (3) three institutions performed image verification only once at the first radiotherapy session. Only a few radiotherapy institutions performed MRI scan of the nasopharynx and neck during radiotherapy.

  Discussion Top

In the 1980s, the World Health Organization (WHO) proposed 2–3 accelerators per million populations. The current survey showed that the linear accelerator occupancy rate of the city was 1.42 units per million populations. Although there was a rapid improvement compared with the year of 2015, there was still a large gap from the WHO recommendation.[3] This survey showed a real problem of insufficient radiotherapy equipment in Chongqing area. At present, 12 districts and counties in Chongqing are not equipped with accelerators, which can be mainly explained by their geographical location and economic underdevelopment. Meanwhile, district and county radiotherapy facilities equipped with accelerators can provide limited improvement for these areas. Moreover, this survey found that nearly two-thirds of the imported accelerators were concentrated in the downtown, and the district and county units accounted for less than one-third. It showed the regional distribution of radiotherapy equipment. Obviously, it is unreasonable and not good to improve the overall development of radiotherapy in Chongqing area. At the same time, 20% of radiotherapy equipment could not carry out IMRT technology, which was related to the low degree of digitization of the equipment, system reliability and stability, the absence of electric gratings, and the thickness of the grating blades. The series of problems had hindered the use of new technologies for radiotherapy in Chongqing area.

According to the National Basic Guidelines for Quality Control of Radiation Therapy in 2018,[4] Chongqing area needs at least 300 physicists, 600 radiotherapy oncologists, and 900 radiotherapy technicians. According to the current survey, there were only 90 physicists, 334 radiotherapy oncologists, and 200 radiotherapy technicians. The ratio of radiotherapy oncologists to physicists in downtown was 3.15:1; the ratio of radiotherapy oncologists to physicists in the districts and counties was 4.34:1. Most of the radiotherapy departments in the districts and counties were affiliated to the oncology department. According to statistical analysis, the radiotherapy oncologists also include physicians. Thus, the professional radiotherapy oncologists are less than the statistical numbers. Half of the middle and senior professional radiotherapy oncologists and 75% of the middle and senior professional physicists worked in downtown. Judging from the requirements of the National Radiotherapy Quality Control Guide for the staffing of institutions that conducted precise radiotherapy, several district and county radiotherapy units did not have the qualification to carry out precise radiotherapy.

The survey found that there were 11 radiotherapy institutions in Chongqing equipped with digital radiotherapy management systems, of which 3 were also equipped with remote collaboration platforms. Most of the work of radiotherapy departments relied on computer-controlled precision equipment. There were a large number of patient planning, treatment, and verification data. The lack of highly integrated radiotherapy management information system might increase the incidence of errors in all aspects of radiotherapy.[5] The brands of accelerators and treatment planning systems between the radiotherapy units were different. The treatment data between different brands of accelerators could not be collected together. The management, sharing, retrieval, and statistics of various radiotherapy data were increased, which hindered the development of radiotherapy. In the context of the serious shortage of radiotherapy personnel and the rapid development of radiotherapy technology, the remote collaborative radiotherapy platform was the best way to solve the imbalance of radiotherapy resources in Chongqing area. Through the remote collaborative platform of radiotherapy, grassroots hospitals could improve their medical and service capabilities and treat more local patients. Similarly, the overloaded central hospitals diverted some patients to the primary hospitals to spare more time to treat severe and intractable diseases. The digital radiotherapy information network was an important part of the hospital's medical information network and an important step in the establishment on a regional integrated precision radiotherapy network system in the future.[6] The radiotherapy unit equipped with radiotherapy network in Chongqing area was still rare, so the construction of radiotherapy network in Chongqing had a long way to go.

According to the survey, there were 9 radiotherapy units for IGRT in Chongqing area and 22 radiotherapy units had not carried out IGRT. IGRT can monitor and correct the placement error during radiotherapy in real time, thereby increasing the repetition rate of placement during radiotherapy and reducing the treatment errors and the exposure volume of normal tissue.[7] Especially, in the era of popularization of IMRT technology, the target dose value and conformability had been significantly improved. Tumor shrink, patient weight loss, and immobilization errors increased the risk of overdose-exposure to organs. Especially, for head-and-neck cancers such as NPC, there were many important risk organs around the target volume, which could lead to serious complications after the excessive dose exposure of organs, which affected the quality of life of patients.[8] Yang et al.[7] selected ten patients with Stage I–IV NPC and collected patients' CBCT image information before each radiotherapy. The results showed that the gross tumor volume retracted at a rate of 9.85 cm3/day and presented a trend of displacement from front to back. The left parotid gland volume retracted at a rate of 5.70 cm3/day, and the right parotid gland volume retracted at a rate of 8.05 cm3/day. The parotid gland both sides showed a tendency to shift to the midline from both sides. The similar results from Yao et al. showed that the center of the parotid glands was displaced from the central axis of the body. Zhang et al.[9] selected 12 patients with NPC, and the CT images before the 25th (24–26) radiotherapy were compared with the original planned target volume and critical organ volume. In some patients, the D1cc of the spinal cord increased to 29%, the D1cc of the brainstem increased to 34%, the D50% of the left parotid gland increased by 38.16%, and the right side reached 46.86%. The advantage of IMRT was based on the positioning of CT images before radiotherapy. However, there were many impact factors during radiotherapy, which increased the random error, which inevitably affected the treatment effect. Therefore, image verification was very important during radiotherapy workflow, but less than half of the radiotherapy units in Chongqing area had been equipped with IGRT.

MRI was able to provide much more information than positron emission tomography (PET)/CT because of its excellent soft-tissue resolution. And compared with PET/CT, MRI could accurately distinguish the nature of abnormal lymph nodes adjacent to tumor tissue. Moreover, MRI scan could perform multidirectional and multisequence scanning, which described the 3D shape of the tumor more stereoscopically and provided accurate image information for target area delineation.[10] Yao et al.[11] selected 8 patients with NPC and drawn the clinical target volume on the CT and MRI images separately, the average volume of MRI-CT (part of the CT target area not included in MRI) was 2.33 cm3; and MRI-CT (part of the MRI target area not included in the CT) had an average volume of 27.72 cm3. According to the guidelines, MRI-CT fusion should be a routine procedure for target and structure delineation in NPC in all radiotherapy units. However, it was only 37% radiotherapy institutions in Chongqing area that used the fused MRI-CT image fusion. Most of the radiotherapy units in districts and counties were equipped with domestic TPS and could not do MRI-CT image fusion.

Insufficient or excessive dose in the target area would influence the effect of radiotherapy, so we should pay more attention to prescription dose. In accordance with all the collected radiotherapy plans of NPC in each radiotherapy unit, different units conducted distinct prescription doses in the target volumes. It was due to the uneven medical level and insufficient number of radiotherapy staff and uneven distribution of radiotherapy oncologists, which was an important factor to hinder the delineation of NPC target area and the standardization of planning design in Chongqing area. Solving the shortage of radiotherapy professionals and improving the overall level of radiotherapy were top tasks in the development of radiotherapy in Chongqing. However, the training period for oncologists and physicists was very long, which could not be solved in a short term. In recent years, artificial intelligence (AI) has focused on the field of tumor radiology, and it could complete the automatic delineation of solid tumors and risk organs. The precision of AI has been gradually improved in some simple organ delineation. It even could replace the work of a radiotherapy oncologist. Applying AI to the NPC target contour and planning design might save much time and ensure accuracy and shorten the difference of treatment in different regions. In this way, it would effectively reduce the gap between the supply and demand of existing medical resources and solve the problem of uneven distribution of medical resources.

The survey also revealed the fact that in most radiotherapy units, the NPC patients had not received nasopharyngeal and neck MRI scan or nasopharyngoscopy during radiotherapy. These units did not have IGRT equipment. It has been stated previously that there were significant changes in the size, shape, and the anatomical location of the target areas and surrounding risk organs, which might cause dosimetry effects during the treatment. Huang et al.[12] selected 19 patients with Stage I–IV NPC. CBCT scan was performed every five times of radiotherapy from the beginning. The results showed that the volume of primary tumors and positive lymph nodes increased by 17.3 ± 10.4%/week and 22.2 ± 15.0%/week, respectively. The maximum receiving doses of brainstem volume increased from 53.21 ± 3.51 Gy before radiotherapy to the most remarkably changed value 56.54 + 3.72 Gy at the 5th week, and the changes were most remarkably in the 1st and 3rd weeks. The V30 of the left and right parotid glands increased from 47.08 ± 2.06 Gy and 43.72 ± 6.49 Gy before radiotherapy to the most obvious changed value 53.37 ± 4.72 Gy and 51.61 ± 0.05 Gy, respectively, in the 5th week, and the changes were most obvious in the 3rd and 4th weeks. Gai et al.[8] showed consistent results. The 13 NPC patients were performed CBCT weekly. The results showed that 92.3% patients had significantly reduced lesions and their tumor volume decreased by 19.6 cc3 on average when they had their 26th radiotherapy. When patients underwent fractional radiotherapy, the target volume and surrounding normal tissues were constantly changing, so the highly conformal dose distribution of IMRT might increase the risk of serious complications for normal tissue under excessive exposure.[13] Therefore, only online modification of the plan could significantly reduce the symptoms of oral mucositis and dry mouth caused by radiotherapy. The departments without IGRT were recommended that the NPC patients should be reviewed routinely the nasopharyngeal and neck MRI scan or nasopharyngoscopy during radiotherapy to improve the accuracy of the target volume exposure and reduce the exposure error.

Chongqing is one of the provinces with high incidence and mortality rate of NPC in China, and the number of NPC patients treated with radiotherapy is much high. However, all the radiotherapy units in the area conduct inconsistent radiotherapy techniques for NPC, and there are differences in radiotherapy plan design. There are still unreasonable delineations in the target area of district and county radiotherapy units. Therefore, professional training is needed to further improve the overall treatment level of NPC in Chongqing area.

  Conclusion Top

In recent years, radiotherapy in Chongqing has developed greatly. Especially, in the past 3 years, it has made remarkable progress in the aspects of the number of radiotherapy equipment and the application of new radiotherapy technologies. However, for the overall quality and quantity of radiotherapy staff, equipment configuration and distribution, and radiotherapy network construction, compared with the level of domestic and international first-class radiotherapy units, there is still a long distance, which also suggests that more efforts should be made to promote the investment of equipment and resource and to strengthen the quality and technology of radiotherapy practitioners.


This research received strong support from colleagues of radiotherapy institutions at all levels in the city (in no particular order: the 324 hospital in PLA [Fu Xiangjian]; Chongqing Traditional Chinese Medicine Hospital [Wang Huaibi]; Chongqing Municipal People's Hospital Zhongshan Campus [Yu Wenlei]; Chongqing Ninth People's Hospital [Jiang Mingdong]; Chongqing Fifth People's Hospital [Wu Yu]; Chongqing Iron and Steel Group Company Hospital [Quan Rong]; Second People's Hospital of Banan District, Chongqing [Zhong Hui]; Third People's Hospital of Chongqing People's Hospital [Deng Peng]; Military Medical University Daping Hospital [Hu Nan]; Chongqing Bishan District People's Hospital [Sun Lan]; Chongqing City Dazu District People's Hospital [Ouyang Ju]; Kaizhou District People's Hospital of Chongqing [Xiong Lin]; Liangping District People's Hospital Cancer Hematology [Chen Weilong]; Nanchuan District People's Hospital [Xiao Zhiji]; Chongqing Nantong Mining Co., Ltd., General Hospital [Zhang Gangyong]; Minjiang District People's Hospital [Tan Qiaoling]; Chongqing Minjiang National Hospital [Yuan Guangjin]; Minjiang Central Hospital [Liu Enqiang]; Shizhu County People's Hospital [Ran Guanghan]; Tongliang District People's Hospital [Li Xiaoping]; Wushan County People's Hospital [Liang Guohong]; Yunyang County People's Hospital [Yu Hejiang]; Chongqing Yunyang County Hospital [Wang Jian]; City Zhongxian People's Hospital [Chen Maosheng]; Chongqing Huajian Youfang Hospital [Fu Shangzhi]; Chongqing Medical University Affiliated Yongchuan Hospital [Zeng Li]; Ankang Hospital of Kaizhou District of Chongqing; Chongqing Jiangjin District People's Hospital [Xiang Debing]; Chongqing Wanzhou District People's Hospital [Cheng Hongwen]; Chongqing Fuling Central Hospital [Zhou Qi]; Chongqing Dianjiang County People's Hospital [He Renqiang]; and Chongqing Fengjie People's Hospital [Yang Rui]).

Financial support and sponsorship

This study was financially supported by the grant from the National key research and development (2016YFC0106400).

Conflicts of interest

There are no conflicts of interest.

  References Top

Chua ML, Wee JT, Hui EP, Chan AT. Nasopharyngeal carcinoma. Lancet 2016;387:1012-24.  Back to cited text no. 1
Lee AW, Ng WT, Chan LL, Hung WM, Chan CC, Sze HC, et al. Evolution of treatment for nasopharyngeal cancer – Success and setback in the intensity-modulated radiotherapy era. Radiother Oncol 2014;110:377-84.  Back to cited text no. 2
Jinyi L, Pei W, Dake W, Hailuo Z, Bing L, Xiaowu D, Lvhua W. An investigation of the basic situation of radiotherapy in mainland China in 2015. Chin J Radiat Oncol 2016;25:541-5.  Back to cited text no. 3
Jie H, Lvhua W, Yexiong L, Jianrong D, Pan M, Zhihui H, et al. Basic guidelines of quality control for radiotherapy. Chin J Radiat Oncol 2018;27:335-42.  Back to cited text no. 4
Junchao C, Jiazhou W, Zhiyong X. The network and information system in radiation oncology. Chin J Med Phys 2011;28:2913-6.  Back to cited text no. 5
Korreman S, Rasch C, McNair H, Verellen D, Oelfke U, Maingon P, et al. The European Society of Therapeutic Radiology and Oncology-European Institute of Radiotherapy (ESTRO-EIR) report on 3D CT-based in-room image guidance systems: A practical and technical review and guide. Radiother Oncol 2010;94:129-44.  Back to cited text no. 6
Yang BB, Wang J, Zhong RM, Jiang QF, Chen NY, Bai S, et al. Volumetric and geometric changes of parotids occurring during IMRT for nasopharyngeal carcinoma (NPC) using daily CBCT. Sichuan Da Xue Xue Bao Yi Xue Ban 2010;41:1024-8.  Back to cited text no. 7
Gai X, Wei Y, Tao H, Zhu J, Li B. Clinical study of the time of repeated computed tomography and replanning for patients with nasopharyngeal carcinoma. Oncotarget 2017;8:27529-40.  Back to cited text no. 8
Daguang Z, Shengpeng J, Zhihua L, Zhengxin F, Peiguo W. The study of anatomical changes and dose distribution deviation during intensity-modulated radiotherapy for nasopharyngeal carcinoma. Chin J Med Phys 2013;30:4239-42.  Back to cited text no. 9
Tzikas A, Karaiskos P, Papanikolaou N, Sandilos P, Koutsouveli E, Lavdas E, et al. Investigating the clinical aspects of using CT vs. CT-MRI images during organ delineation and treatment planning in prostate cancer radiotherapy. Technol Cancer Res Treat 2011;10:231-42.  Back to cited text no. 10
Yao Y, Guo-Hua WU, Xia SA, Zhou RH, Sun H. Influence of CT/MRI fusion image on target volume and 3-D conformal radiotherapy in nasopharyngeal carcinoma. China Oncolo 2006;6:498-502.  Back to cited text no. 11
Huang H, Lu H, Feng G, Jiang H, Chen J, Cheng J, et al. Determining appropriate timing of adaptive radiation therapy for nasopharyngeal carcinoma during intensity-modulated radiation therapy. Radiat Oncol 2015;10:192.  Back to cited text no. 12
Yang H, Hu W, Wang W, Chen P, Ding W, Luo W, et al. Replanning during intensity modulated radiation therapy improved quality of life in patients with nasopharyngeal carcinoma. Int J Radiat Oncol Biol Phys 2013;85:e47-54.  Back to cited text no. 13


  [Figure 1]

  [Table 1], [Table 2], [Table 3], [Table 4]


Similar in PUBMED
   Search Pubmed for
   Search in Google Scholar for
 Related articles
Access Statistics
Email Alert *
Add to My List *
* Registration required (free)

  In this article
Materials and Me...
Article Figures
Article Tables

 Article Access Statistics
    PDF Downloaded184    
    Comments [Add]    

Recommend this journal