ABSTRACT
Object To study the effects of the number of arcs in the treatment of cervical cancer with volumetric modulated arc therapy (VMAT) on the treatment plan, and to provide reference for the selection of the number of arcs in the clinical application.Methods CT images of 10 patients with cervical cancer were selected, it's the radiation therapist that delineated the target area and organs, the prescribed dose was 5040 cGy per 28 times to the target area, and single arc (Arc1), double arc (Arc2) and three (Arc3) plan were designed by RayStation planning system to compare the differences with the dosimetry characteristics of target and organs. The time required for planning optimization was recorded, and the difference between the monitor unit and the delivery time in the three plans was analyzed. A dose validation tool for PTW was used to verify the dose to analyze the influence of the number of arc on the passing rate of gamma verification.Results Single arc plan (Arc1), double arc plan (Arc2) and three arc plan (Arc3) for 10 cases of cervical cancer all proved to meet the clinical requirements. With the increase of arc number, the target area distribution got improved, V40, V45 and Dmean in the organs at risk of rectum, bladder, and femoral head gradually decreased in case of doses of 40 and 45 Gy, and V35, V40 and V45 in the normal tissue were lowered in case of the doses of 35, 40 and 45 Gy. With the increase of the arc number, the optimization time and the delivery time of the plan increased, while the difference between the monitor unit of the three plans was smaller. The passing rate of the three plans was more than 99.5％, and the difference was small.Conclusion Cervical cancer VMAT plan has the target dose distribution and the protection of organs at risk enhanced with the increase of the number of arcs, while the treatment time and cost increased. Therefore, it is necessary to take comprehensive considerations on the number of VMAT plan arcs.
ABSTRACT
Objective To explore features and clinic values of LNR anatomy with multiple planar reconstruction techniques with 16-slice spiral CT at the same slice.Methods The lumbar vertebrae with normal adults of 55 cases and 23 cases with abnormal ENR caused by 8 cases with protrusion of lumbar disc, 5 cases with spinal stenosis,4 cases with malignant tumor,5 cases with trauma and 1 case with lumbar TB confirmed by operation were scanned with 16-slice spiral CT made in American GE company in routine posture of the lumbar vertebrae,reconstructed LNR with UNIX system in workstation (ADW 4.1),and analyzed their normal and abnormal anatomic manifestations at the same slice.Results All of LNR can symmetrically showed on oblique and coronal planes according to different segments:one segment from L1 to L5(55,100% ),two segments: from L1 to L2,L2 to L3 and L3 to L4(55,100% ),three segments: from L1 to L3 (49,88%),from L2to L4(46,84% )and from L3 to L5(20,36% ),four segments: from L1 to L4 (15,27% )and five segments:(8,15% ),respectively.Each LNR,including their whole shapes of passage from starting to end,direction,size,shape,tension and peripheral relationship and so on can showed clearly on oblique and coronal planes and on other planes. However,the later planes can increase LNR but decreasing numbers of LNR and especially increase very long one LNR reconstruction.Primary manifestation of all diseases can be showed on oppressing along its walking line,meanwhile,20 cases with adhesion, 14 cases with displacement,13 cases atrophy and 9 cases with increasing diameter.Conclusions Image anatomy features of full LNR with 16-slice spiral CT with the multiple plane reconstruction techniques is very ideal ways at the same slice.It is a very valuable way to make diagnosis and treatment of LNR diseases.The concept of"road sing"and showing"at the same slice"of LNR are tried to rise from in order to make foundation for studying their image.