Abstract
In radiotherapy, setup precision has great influence on the therapeutic effect. In addition, body movements during the irradiation and physical alternations during the treatment period might cause deviation from the planned irradiation dosage distribution. Both of these factors could undesirably influence the dose absorbed by the target. In order to solve these problems, we developed the “body surface navigation and monitoring system” (hereafter referred to as “Navi‐system”). The purpose of this study is to review the precision of the Navi‐system as well as its usefulness in clinical radiotherapy. The Navi‐system consists of a LED projector, a CCD camera, and a personal computer (PC). The LED projector projects 19 stripes on the patient's body and the CCD camera captures these stripes. The processed image of these stripes in color can be displayed on the PC monitor along with the patient's body surface image, and the digitalized results can be also displayed on the same monitor. The Navi‐system calculates the height of the body contour and the transverse height centroid for the 19 levels and compares them with the reference data to display the results on the monitor on a real‐time basis. These results are always replaced with new data after they are used for display; so, if the results need to be recorded, such recording commands should be given to the computer. 1) Evaluating the accuracy of the body surface height measurement: from the relationship between actual height changes and calculated height changes with torso surface by the Navi‐system, for the height changes from 0.0 mm to ± 10.0 mm, the changes show the underestimation of 1.0–1.5 mm and for ±11.0 mm to ± 20.0 mm, the underestimation of 1.5–3.0 mm. 2) Evaluating the accuracy of the transverse height centroid measurement: displacement of the inclined flat panel to the right by 5.0 mm, 10.0 mm, 15.0 mm and 20.0 mm showed the transverse height centroid calculated by the Navi‐system for 0.024±0.007 line/pair (mean ± SD), 0.045±0.006 line/pair, 0.066±0.006 line/pair and 0.089±0.007 line/pair, respectively. Also, displacement of the inclined flat panel to the left by 5.0 mm, 10.0 mm, 15.0 mm and 20.0 mm showed the transverse height centroid calculated by the Navi‐system for 0.015±0.007 line/pair (mean ± SD), 0.034±0.007 line/pair, 0.053±0.008 line/pair and 0.071±0.007 line/pair, respectively. 3) Clinical usefulness of the Navi‐system: on using the Navi‐system, the frequency of radiotherapy replanning increased from 5.2% to 21.8%, especially in pelvic or abdominal irradiation. We developed a new navigation system for the purpose of compensating for the weakness of MVCT, CBCT and other systems, as well as for having a screening function. This Navi‐system can monitor the patient continuously and measure change in height of the patient's body surface from the basic plane, in real time. It can also show the results both qualitatively and quantitatively on the PC monitor.PACS number:87.52.‐g
Highlights
The setup error may be reduced by using image-guided radiation therapy (IGRT).(1-5) In IGRT, there are several methods for obtaining the images and matching them to the references: megavoltage computed tomography (MVCT)(6) and cone-beam computed tomography (CBCT),(7-10) in which an image of a target area is obtained directly and positioning is achieved by using the images of the target and the surrounding internal organs; linac-graphs (LG) and electric portal imaging device (EPID), in which positioning is achieved by matching with an X-ray image of the bone structure; Exac-Trac system (ETS), in which the marker position is obtained by using an X-ray and infrared camera; photogrammetry surface imaging system (PSIS),(11-19) in which positioning is achieved by capturing and matching body surface contour images
The purpose of this study is to evaluate the accuracy of this new Navi-system and the clinical usefulness of monitoring body movements and changes in the body contour
We developed the Navi-system to compensate for the weakness in systems like MVCT, CBCT and others, as well as to have a screening function
Summary
The setup error may be reduced by using image-guided radiation therapy (IGRT).(1-5) In IGRT, there are several methods for obtaining the images and matching them to the references: megavoltage computed tomography (MVCT)(6) and cone-beam computed tomography (CBCT),(7-10) in which an image of a target area is obtained directly and positioning is achieved by using the images of the target and the surrounding internal organs; linac-graphs (LG) and electric portal imaging device (EPID), in which positioning is achieved by matching with an X-ray image of the bone structure; Exac-Trac system (ETS), in which the marker position is obtained by using an X-ray and infrared camera; photogrammetry surface imaging system (PSIS),(11-19) in which positioning is achieved by capturing and matching body surface contour images.CBCT and MVCT, which are three dimensional matching systems, are considered to have optimum accuracy in acquiring the position of the target. Except for the PSIS, those systems that are the same as the LG and the EPID cannot monitor patient movements during irradiation. Those systems cannot obtain the changes in the body contour (for example, due to weight loss or gain). We have developed a surface navigation and monitoring system, the Navi-system, which can monitor body movements during irradiation, as well as changes in body contour, throughout the treatment period. The purpose of this study is to evaluate the accuracy of this new Navi-system and the clinical usefulness of monitoring body movements and changes in the body contour
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