A preliminary study on CT simulation of vascular distribution in three dimensional design of pelvic irradiation fieldZhu Suyu, Hu Bingqiang,
A preliminary study on CT simulation of vascular distribution in three dimensional design of pelvic irradiation field
Zhu Suyu, Hu Bingqiang, Jin Hekun, to Fang, Luo Rongxi
Department of radiation oncology, Hunan Cancer Hospital, Changsha 410013, China
Abstract: Objective To review the literature according to the preliminary study of pelvic vascular distribution as individual lymph nodes oriented, CT simulation of three-dimensional design of pelvic field. Methods 5 cases of rectal cancer and 5 cases of cervical cancer were simulated by CT scanning, and contoured in small intestine, three dimensional treatment planning system of abdominal aorta, iliac artery, external iliac artery. The corresponding vascular expansion 20mm defined as PTV, using digital image reconstruction (DRR) technique showed pelvic bone and the target area, according to the position of individual vascular distribution design of pelvic field. Compared with the traditional design according to the bony landmarks of pelvic field boundary, according to the design of the vascular distribution field have obvious individual differences the circle and on the side, side wear wild wild before communities were fluctuated between traditional wild border +7mm to -5mm and +5mm to -6mm. The irradiation field volume of small bowel by 202.4± 65.7cm3 21.2cm3. is reduced to 77.5±, and the conclusion is to simulate the distribution of pelvic blood vessels. The three-dimensional design of pelvic irradiation field is likely to achieve the purpose of individual optimal design, which can reduce the volume of small intestinal irradiation
Key words: pelvic irradiation field design, pelvic vascular, CT simulation, three dimensional treatment planning
Use of CT with contouring as guide for node localization to design lymph the pelvic fields a vessel simulation
Zhu Su-Yu, Hu Bing-Qiang, Jin He-Kun, Xiang Fang, Luo Rong-Xi
The Radiation Oncology Department, the Province Tumor Hospital, ChangSha (410013) (HuNan)
Abstract: Purpose: to evaluate the optimal individual pelvic irradiation field design, with contoured pelvic vessels on simulation computed tomography as a guide for lymph node location. Method and materials: Pelvic arteries were contoured on contrast-enhanced CT simulation images of 5 cases of rectal and of cervical cancer patients. 5 cases The PTV was defined as pelvic arteries expanded with 20mm margins. The lateral border of the A-P and P-A fields and the anterior border of the lateral fields were individually placed at the edge of the PTV respectively, the other borders were the same as the conventional fields based on the bony landmarks. The conventional pelvic fields were also outlined on those digitally reconstructed radiographs (D RR The borders of). Those two kinds of fields design were displayed and compared case by case. Results: the lateral borders of the vessels-based A-P and P-A fields were located around the borders of the Convention fields ranged from +7mm to -5mm, and the anterior border of the lateral fields ranged from +5mm to -6mm, which indicated the field borders were individually located with their respective vessel distribution. The volume of the small bowel within the irradiation fields reduced from 202.4 & plusmn; 65.7 cm3 to 77.5 ± 21.2 cm3, with evident reduction favored for the vessels-based pelvic fields. Conclusion: CT simulation with vessel contouring as a guide for lymph node localization may provide more precise and individualized fiel D delineation and exclude small bowel the irradiation compared with the conventional pelvic fields based on within bony landmarks. fields more may
Key words: field design, pelvic vessels, CT simulation, 3-dimensional treatment planning. pelvic
The traditional rectal cancer and cervical cancer pelvic field is simulated according to the Perspective under the condition of anatomic landmark to design 2D. Through surgical anatomy, bilateral lymphangiography, series of studies on the distribution of pelvic lymph nodes and NMR showed that according to the anatomic landmark design of pelvic irradiation can not fully cover the pelvic lymph node [1,2,3]. need to prevent irradiation with three-dimensional conformal radiotherapy technique is widely carried out, the author attempts to depict the layer according to CT simulation and 3D display of pelvic vessels in the spatial distribution of individual design of rectal cancer and cervical cancer pelvic irradiation, the report is as follows:
Materials and methods
From May 2003 to June 2006, 5 cases of rectal cancer and 5 cases of cervical cancer patients were experimenting with new ways to design and implement the pelvic irradiation field radiation therapy. The average age of patients with rectal cancer at the age of 41, male 4 cases, female 1 cases; 4 cases of Dukes B stage, C stage 1 cases; 3 cases of preoperative radiotherapy, 2 cases of postoperative radiotherapy in patients with cervical cancer. The average age of 53 years; 2 patients with stage B underwent preoperative radiotherapy, 3 cases of stage III underwent radical radiotherapy.
Radiotherapy of the concrete design steps are as follows: the wild fixed position and CT simulation scan: the patient supine hands to hold the head, foam vacuum bag trunk to seven joints from third lumbar vertebra to the proximal femur 1/3 layer CT simulation scan, layer spacing is 5mm, the scan image is transmitted through the DICOM interface to three dimensional treatment planning the system (Cadplan, Ver.6.1, Varian Medical System Inc. Palo Alto, CA, USA). The description of target and critical organs: display in 3D treatment planning system of each CT level by depicting the small intestine, abdominal aorta, iliac artery, internal and external iliac artery, the corresponding vascular delineation. 20mm the edge size and defined as PTV, through digital image reconstruction technology of 3D treatment planning system (DRR) structure and organs and bone to outline the three-dimensional reconstruction and display design. The pelvic field: before and after wear The upper bound of wild L4/L5 set at the junction of lower bounds were set at the lower edge of the obturator (after Dixon or upper rectal cancer, cervical cancer and anal margin (Miles) after surgery or in lower rectal cancer), PTV (the outer circle on both sides of the external iliac artery 20mm, with multiple blade grating automatic conformal occlusion), bilateral field the leading edge of PTV circle along the outer edge, rectal cancer after sacrococcyx central to draw line, MLC automatically after occlusion along the vertical line for cervical cancer in S2/S3 at the junction of the upper and lower bounds with the traditional sketch. After the wild field: according to the three-dimensional treatment planning system show that DRR by bony landmarks the traditional field sketch, and three-dimensional conformal field of comparative analysis, including comparison of irradiated target small volume, the corresponding position and the relationship between before and after the side and side before the wild wild world community. The traditional field specific design such as: upper and lower bounds And the side yehou circle at the same three-dimensional conformal field before and after the wild side is really in the widest margin of pelvic 20mm, double angle from 1/4 to 1/3 on the side boundary of a connection block; side of the anterior border of the pubic symphysis in front of the wild.
1 a three-dimensional pelvic irradiation field was designed according to the figure of 1
Before the design of radiation field figure 1.1 cases T3N0M0 upper rectal adenocarcinoma patients. Through CT simulation scan and contoured abdominal aorta, common iliac internal and external iliac arteries, and small intestine; vascular expansion 20mm edge diameter is defined as the PTV boundary, through the three-dimensional treatment planning system (DRR) reconstruction of digital image display PTV, small intestine and pelvic cavity through the bone, bony landmarks and PTV boundary design (a) before and after the wild: upper bound set L4/L5 junction, the lower bound is set on both sides of the lower edge of the obturator, bound for PTV (outer iliac and external iliac artery 20mm, with multiple blade grating automatic conformal shielding) (b) PTV. The front side edge of the wild after the community, along the central line to draw the outline of sacrococcyx, block MLC automatically along the upper and lower bounds with the field.
2 according to the design of the traditional field of bony landmarks and the corresponding design according to the pelvic vascular distribution of individual three-dimensional conformal irradiation, 6 cases of wild side wear circles within 3-7mm 3D radiation field side circles, 4 cases in 3-5mm; 7 cases of wild side before the circle in 3D conformal wild wild side before in 4-6mm, 3 cases in the former 2mm- 5mm. out of bounds (see Table 1).
Table 1 Comparison of the three dimensional conformal boundary of pelvic cavity and pelvic vessels according to the design of the traditional bony landmarks
Distance to the conformal boundary (mm)
Distance from the front of the conformal field (mm)
“ -” expressed within the boundary of 3D conformal field; “ +” expressed outside the boundary of 3D conformal field.
3 the average volume of the small intestine in the traditional irradiation field was 202.4± 65.7cm3, the average volume of the small intestine in the three-dimensional conformal radiation field designed by the vascular distribution was 77.5± (21.2 cm3.)
For a long time, is the anatomic landmark to determine for rectal cancer, cervical cancer and prostate cancer in the whole pelvic irradiation set. Both the cassette fields is the most commonly used technology, the upper bound usually selected at L4/L5 or L5/S1 junction, according to the different parts of the tumor and the lower stage and different operation usually set in the lower edge of the tumor, the obturator distal 2cm and anal edge; the both sides of the field before and after wear wild usually selected 1.5-2CM in the wide edge of the true pelvis; both sides of the field before the world usually choose the pubic symphysis edge, after circles for cervical cancer and prostate cancer to reduce the rectal irradiation volume at the junction located in S2/S3, and for rectal cancer is selected along the sacrococcyx arc to include anterior sacral and rectum and its surrounding lymph tissue and . series of research on the traditional rationality but set the pelvic field boundary Questioned. By lymphangiography, Zunino  and Bonin  on the wild side wear revealing traditional edge diameter is not enough, if you want to cover all the external iliac lymph nodes, they recommended in the community should be on both sides of the true pelvis outside and 2.5 2.6cm. Pendlebury and ] were found to have 2/3 need to modify the traditional cassette field the boundary to cover the lymphography showed lymph nodes in 50 cases, boundary less foot mainly from the wild side and side wear wild before the boundary size is not enough, that's the most wide margin of 2.5cm pelvic pubic symphysis and the outside edge of 0.5cm to cover 90% cases of pelvic lymph nodes, but also found 20% cases to further narrow the field boundary to reduce the cassette irradiated volume of normal tissues. Some scholars even suggest using MRI and pelvic surgery placing metal marker  to determine the main pelvic lymph node position, and thus determine the individual pelvic photos The edge beam diameter range. They found that the distribution of pelvic lymph node distance relative to the individual difference of anatomical landmarks of traditional radiation field positioning bone is larger, but the 99% lymph nodes are located within the pelvic vascular edge diameter of 15mm. The further study of Chao  suggested that the common iliac artery diameter and 15mm side external iliac artery 20mm the edge diameter can ensure 82.3% normal sized lymph nodes in the pelvic irradiation field, pelvic blood vessels is emphasized on the basis of the feasibility of individual pelvic field. Because there are individual differences in obvious pelvic lymph node position, while the conventional implementation of lymphography or surgery to determine the pelvic lymph node position in today is not very practical through CT simulation, scanning and layer outline of pelvic vascular line and go with the edge size range to roughly determine the location of lymph node can achieve the design of individual pelvic irradiation , and is simple and feasible, so the author has made a preliminary attempt to use this method. Considering the setup errors and internal factors such as pelvic structure movement, the author thinks that the choice of peripheral vascular expansion 20mm edge diameter as the distribution range of pelvic lymph nodes is more reasonable. The preliminary results of this study also showed that compared with the conventional pelvic irradiation according to the radiation field, the boundary position setting vascular distribution has obvious individual differences, if according to the traditional design method of radiation field and radiation, may be part of the pelvic lymph nodes were not included in the radiation field, or excessive pelvic irradiation of normal tissue, especially the pelvic small bowel, it inferred according to pelvic distribution of blood vessels can indirectly to location of pelvic lymph node location, the optimal pelvic field potential based on 3D design of individual pelvic irradiation, and the preliminary study The results also showed that included in the target area of small volume decrease greatly. However, according to the distribution of pelvic blood vessels to determine the range of pelvic irradiation field defects, the most obvious is the only concern the pelvic lymph node full target coverage, while ignoring the need to include these potential normal lymph node size as necessary to target perhaps the research area. On the sentinel lymph node had pelvic lymph node region helps to eliminate unnecessary exposure to further narrow the scope of the target area.
In conclusion, this study attempts to discuss and suggest that traditional pelvic field cannot provide the best coverage of pelvic lymph nodes, and through the CT simulation of pelvic vascular distribution to determine the scope of individual irradiation may be more accurate, the design method is simple and reasonable, potentially improve the therapeutic gain, worthy of further observation of pelvic radiotherapy reaction and control rate and recurrence rate to confirm the effectiveness of this method. The design method of pelvic three-dimensional conformal and intensity-modulated radiotherapy target area also provide a reference.
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