Development of a three-dimensional CT simulator and its clinical application

1996年，我们的CT模拟器系统增加了一台新的螺旋CT扫描仪。该CT扫描仪不仅可以实现常规平行扫描的快速扫描，而且可以实现螺旋扫描和连续扫描。然而，重建的螺旋CT图像用于放射治疗计划(RTP)的准确性尚未确定。重建的螺旋CT图像的用处和局限性通过一个丙烯体模进行了演示。一个直径为100 mm的锥形体模是用丙烯体模特制的。为了识别重建CT图像的边缘失真，以5 mm和10 mm的准直，以5 mm或10 mm/s的转台速度扫描锥形体模，扫描参数分别为120kVP和50 mA，扫描时间为1s/转。图像重建采用180度补偿算法(SHI算法)和360度补偿算法(SFI算法)。CT窗和水平分别固定为200HU和120HU，分别为…更奇怪的是。柱状体模还用于测量不同材料边缘表面CT数的梯度。在锥形体模的研究中，变形(D)被测量为在100 mm的半径水平上扫描的较大半径(R)和较小半径(R)之间的差值。在柱状体模的研究中，每隔1 mm测量一层螺旋CT片的CT值，因此，用常规的CT方法扫描圆锥体模时，重建的边缘形状是完全圆形的。然而，当螺旋CT扫描重建时，它出现了变形。当以5 mm或10 mm的准直厚度和10 mm/s的转台速度扫描体模并用SHI算法重建时，100 mm处的最大变形为2 mm。然而，当模型以5 mm或10 mm的准直厚度和5 mm/s的转台速度扫描并用SFI算法重建时，失真低于检测极限。丙烯与空气交界处的CT数变化梯度大于丙烯与水的交界处。在5 mm厚大于10 mm厚、床速为5 mm/s、床速为10 mm/s时，斜率也较大。因此，在进行放射治疗计划时，螺旋CT参数的设置应非常谨慎，因为这些参数容易受到图像失真和CT数的变化。三维治疗计划具有临床应用的可能性。将评估螺旋CT模拟器的临床意义。较少

In 1996, a new helical CT scanner was added to our CT simulator system. This CT scanner facilitates not only rapid CT scanning by the conventional parallel scanning method but also helical and continuous scanning. However, the accuracy of the reconstructed helical CT image for radiotherapy treatment planning (RTP) is not established. The usefulness and limitations of reconstructed helical CT images were demonstrated using an acryl phantom.A conical phantom measuring 100-mm in diameter was specially constructed using acryl. For identification of marginal distortion in the reconstructed CT image, the conical phantom was scanned using 5 mm and 10 mm collimation with 5 or 10mm/sec table speed for 1 sec/rotation with scanning parameters of 120 kVp and 50 mA.Image reconstruction was performed with both the 180-degree compensation algorithm (SHI algorithm) and the 360-degree compensation algorithm (SFI algorithm). The CT window and level was fixed at 200 Hounsfield units (HU), and 120 HU,resp … More ectively. A column phantom was also used for measuring the gradient in the CT number at the marginal surface of different materials. In the study of a conical phantom, the distorsion (D) was measured as a difference netween a larger radius (R) and a smaller radius (r) scanned at the level of 100 mm in radius. In the study of a column phantom, the CT number of each CT slice was measured at every 1 mm intervals.As a result, the reconstructed shape of the margin was competely round when the conical phantom was scanned by the routine conventional CT method. However, distortion appeared when it was reconstructed from helical CT scans. The maximal distortion at a eadius of 100 mm was 2 mm when the phantom was scanned at 5 mm or 10 mm collimation thickness and 10 mm/sec table speed and reconstructed with the SHI algorithm. However, the distortion was below the limits of detection when the phantom was scanned at 5 mm or 10 mm collimation thickness and 5 mm/sec table speed and reconstructed with the SFI algorithm. The gradient of the change in the CT number was larger at the boundary between the acryl and air than at the boundary between the acryl and water. The gradient was also larger at the 5 mm thickness than 10 mm thickness, and at 5 mm/sec table speed than at 10 mm/sec table speed.In conclusion, helical CT parameters should be set up very cautiously for radiotherapy treatment planning because they are subject to image distortion and CT number changes.On the other hand, a network was developed netween the CT simulator and a treatment planning machine. The three-dimensional treatment planning can be possible for clinical application. The clinical significance of the helical CT simulator will be evaluated. Less