Practical design for compact image scanner with large depth of field by compound eye system.

We designed a new image scanner using the reflective optics of a compound eye system that can easily assemble plural imaging optical units (called imaging cells) and is compact with a large depth of field (DOF). Our image scanner is constructed from 32 reflective imaging cells, each of which takes an image of approximately a 10-mm field of view (FOV) that slightly overlap the adjacent imaging cells. The total image is rebuilt by combining the 32 images in post processing. We studied how to fold the optical path in the imaging cells and simplified the structure, resulting in the following three advances of our previous work: 1) greater compactness (50 × 31 mm2 in the cross section), 2) less variable optical characteristics among the imaging cells, and 3) easy assembly thanks to small number of optical components constructing the imaging cell.

Compact image scanner with large depth of field by compound eye system.

A compact image scanner is designed by using a compound eye system with plural optical units in which a ray path is folded by reflective optics. The optical units are aligned in two lines and take each image of a separated field of view (FOV), slightly overlapped. Since the optical units are telecentric in the object space and the magnification ratio is constant regardless of the object distance, the separated pieces of a total image are easily combined with each other even in the defocused position. Since the optical axes between adjacent optical units are crossed obliquely, object distance is derived from the parallax at each boundary position and an adequate deblurring process is achieved for the defocused image.

Calculation of rotational setup error using the real-time tracking radiation therapy (RTRT) system and its application to the treatment of spinal schwannoma.

PURPOSE: The efficacy of a prototypic fluoroscopic real-time tracking radiation therapy (RTRT) system using three gold markers (2 mm in diameter) for estimating translational error, rotational setup error, and the dose to normal structures was tested in 5 patients with spinal schwannoma and a phantom. METHODS AND MATERIALS: Translational error was calculated by comparing the actual position of the marker closest to the tumor to its planned position, and the rotational setup error was calculated using the three markers around the target. Theoretically, the actual coordinates can be adjusted to the planning coordinates by sequential rotation of gamma degrees around the z axis, beta degrees around the y axis, and alpha degrees around the x axis, in this order. We measured the accuracy of the rotational calculation using a phantom. Five patients with spinal schwannoma located at a minimum of 1-5 mm from the spinal cord were treated with RTRT. Three markers were inserted percutaneously into the paravertebral deep muscle in 3 patients and surgically into two consecutive vertebral bones in two other patients. RESULTS: In the phantom study, the discrepancies between the actual and calculated rotational error were -0.1 +/- 0.5 degrees. The random error of rotation was 5.9, 4.6, and 3.1 degrees for alpha, beta, and gamma, respectively. The systematic error was 7.1, 6.6, and 3.0 degrees for alpha, beta, and gamma, respectively. The mean rotational setup error (0.2 +/- 2.2, -1.3 +/- 2.9, and -1.3 +/- 1.7 degrees for alpha, beta, and gamma, respectively) in 2 patients for whom surgical marker implantation was used was significantly smaller than that in 3 patients for whom percutaneous insertion was used (6.0 +/- 8.2, 2.7 +/- 5.9, and -2.1 +/- 4.6 degrees for alpha, beta, and gamma). Random translational setup error was significantly reduced by the RTRT setup (p < 0.0001). Systematic setup error was significantly reduced by the RTRT setup only in patients who received surgical implantation of the marker (p < 0.0001). The maximum dose to the spinal cord was estimated to be 40.6-50.3 Gy after consideration of the rotational setup error, vs. a planned maximum dose of 22.4-51.6 Gy. CONCLUSION: The RTRT system employing three internal fiducial markers is useful to reduce translational setup error and to estimate the dose to the normal structures in consideration of the rotational setup error. Surgical implantation of the marker to the vertebral bone was shown to be sufficiently rigid for the calculation of the rotational setup error. Fractionated radiotherapy for spinal schwannoma using the RTRT system may well be an alternative or supplement to surgical treatment.

A technique for noninvasive respiratory gated radiation treatment system based on a real time 3D ultrasound image correlation: a phantom study.

This paper proposes a new respiratory gated radiation treatment system that allows real-time tumor localization while avoiding invasive operation to a patient. The proposed system employs a three-dimensional (3D) ultrasound device, a 3D digital localizer, and a real-time image processing system. At the planning time, CT and 3D ultrasound reference data are simultaneously acquired under a breath-hold condition. At the treatment time, ultrasound data on three orthogonal planes are acquired and transferred to the image processing system on a real-time basis. Subsequently, normalized image correlation indices using the reference and the real-time ultrasound data are calculated for the three orthogonal planes after performing real-time coordinate transform using the 3D digital localizer attached to an ultrasound probe. Prior to the system execution, the coordinate transform matrices are partially calculated using an ultrasound calibration phantom and the 3D digital localizer. A trigger pulse to a linac can be generated when the normalized image correlation index exceeds a predetermined threshold level. Experiments have been carried out using a moving-target phantom that simulates a patient respiratory motion. We have observed that the variation of the calculated real-time correlation index synchronizes with the periodical motion of the moving-target, suggesting that real-time localization for a moving tumor is feasible with the proposed system.