Assessment of 3D-printed tissue compensators for superficial tumor X-ray radiation compensation / 中华放射医学与防护杂志

Objective:To investigate the advantage of three dimensional(3D)-printed tissue compensators in radiotherapy for superficial tumors at irregular sites.Methods:A subcutaneous xenograft model of prostate cancer in nude mice was established. Mice were randomly divided into no tissue compensator group( n=6), common tissue compensator group( n=6), and 3D-printed tissue compensator group( n=6). Computed tomography (CT) images of nude mice in the 3D-printed tissue compensator group were acquired. Compensator models were made using polylactic acid, and material properties were evaluated by measuring electron density. CT positioning images of the three groups after covering the corresponding tissue compensators were acquired to delineate the gross tumor volume (GTV). Nude mice in the three groups were irradiated with 6 MV X-rays at the prescribed dose. The prescribed dose for the three groups was 1 500 cGy. The dose distribution in the GTV of the three groups was calculated and compared using the analytical anisotropic algorithm in the Eclipse 13.5 treatment planning system. The metal-oxide-semiconductor field-effect transistor was used to verify the actual dose received on the skin surface of nude mice. Results:The air gap in the 3D-printed tissue compensator group and the common tissue compensator group was 0.20±0.07 and 0.37±0.07 cm 3, respectively ( t=4.02, P<0.01). For the no tissue compensator group, common tissue compensator group, and 3D-printed tissue compensator group, the D95% in the target volume was (1 188.58±92.21), (1 369.90±146.23), and (1 440.29±45.78) cGy, respectively ( F=9.49, P<0.01). D98% was (1 080.13±88.30), (1 302.76±158.43), and (1 360.23±48.71) cGy, respectively ( F=11.17, P<0.01). Dmean was (1 549.08±44.22), (1 593.05±65.40), and (1 638.87±40.83) cGy, respectively ( F=4.59, P<0.05). The measured superficial dose was (626.03±26.75), (1 259.83±71.94), and (1 435.30±67.22) cGy, respectively ( F=263.20, P<0.001). The percentage variation in tumor volume growth after radiation was not significantly different between the common tissue compensator group and the 3D-printed tissue compensator group ( P>0.05). Conclusions:3D-printed tissue compensators fit well to the body surface, which reduces air gaps, effectively increases the dose on the body surface near the target volume, and provides ideas for radiotherapy for superficial tumors at some irregular sites.

Fabrication and pre-clinical application of patient-specific 3D silicone rubber bolus for chest wall / 中华放射肿瘤学杂志

Objective To apply 3D printing technology to fabricate patient-specific silicone tissue compensators for the chest wall and compare the advantages and clinical characteristics between conventional bolus and 3D-printed PLA materials. Methods The chest wall data of two breast cancer patients undergoing mastectomy were obtained based upon the CT images. A patient-specific 3D printing silicone rubber bolus (3D-SRB) was designed and fabricated. The conformability of 3D-SRB,3D-PLA and conventional bolus to the chest wall were validated. Ecipse8. 6 planning system was adopted to statistically compare the dosimetric parameters of virtual plan with those after using three tissue compensators. Results The 3D-SRB was successfully designed and fabricated with a similar hardness to conventional bolus. During the process of validating conformability and radiotherapy planning,3D-SRB and 3D-PLA were superior to conventional bolus in terms of conformability to chest wall and planning dosimetric distribution.3D-SRB was advantageous in repeatability, conformability and comfortable experience compared with 3D-PLA. Regarding dosimetric parameters,3D-SRB yielded the highest repeatability with the virtual plan, followed by 3D-PLA and conventional bolus. Conclusion It is applicable to utilize 3D-SRB as the patient-specific compensators for the chest wall,which is of significance in clinical practice.

Preliminary clinical study of copper compensator in IMRT / 中华放射肿瘤学杂志

Objective To study the dosimetry for copper compensator in IMRT.Methods 10 patients (3 nasopharyngeal carcinoma,4 esophageal cancer,3 colorectal cancer) from IMRT plans made in Oncentra Planning System enrolled in this study.The fluence matrices of each plan were converted into compensator thickness matrices based on attenuation coefficient of copper under 6 MV radiation ray which was measured with ion chamber.While irradiating the homogenous phantom with the intensity modulated plans performed by copper compensator,film was used to measure the planar dose.In the end,γanalysis was carried out between the measured and calculated planar doses with the criteria of 3％ DD/3 mm DTA.Paired t test to MU differences of MLC plans and copper compensator plans.Results The γanalysis results showed the planar dose pass rates of 10 plans lie between 90.2％ and 98.2％,which means the IMRf technique based on copper compensator can meet the clinical needs.The MU for copper compensator IMRT plans is less than the MLC IMRT plans (873.9 vs.975.1,P =0.005).Conclusions Compared to conventional IMRT based on MLC,copper compensator has the advantage of lower requirement of hardware and lower scattering dose in patient.Copper compensator can meet the needs of clinical practice.

Voltage Control and Dynamic Performance of Power Transmission Using Static VAR.

The power demand, in the recent years, has increased substantially while the expansion of power generation and transmission has been severely limited due to environmental restrictions and limited resources. As aneffect, some transmission lines are heavily loaded and the system stability and voltage becomes a limiting factor for power transfer. Flexible AC transmission systems (FACTS) controllers have been mainly used for solving various power system steady state control problems. However, studies reveal that FACTS controllers could be employed to enhance voltage profile in the network in addition to their function of power flow control in the network. This paper presents how static var compensator (SVC) can be utilized to control transmission system dynamic performance for system disturbance and effectively regulate system voltage. Static var compensator (SVC) is basically a shunt connected static var generator whose output is adjusted to exchange capacitive or inductive current so as to maintain or control specific power variables, typically, the control variable is the system bus voltage. Voltage control and the increase in system load abilityarethe main applications of SVC in this paper. Firstly, to design a controller for SVC devices on a transmission line, a single machine infinite bus (SMIB) is modeled. A state space model is developed in the MATLAB/SIMULINK to show the improvement in the dynamic performance of the system.

Clinical applied study for cerrobase compensator intensity-modulated radiotherapy technique / 中华放射肿瘤学杂志

ObjectiveTo study the using of cerrobase as the compensation material in the intensitymodulated radiation therapy (IMRT) implementation and impact factors.MethodsWith therapy planning system (TPS) exported the radiation field intensity file (Dicom RT),through measuring the attenuation coefficient of cerrobase,to calculate the processing depth of AUTIMO 3D CNC corresponding for Dicom RT files at each pixel,then using the processed foam casting of Cerrobase,produced the required IMRT compensator.Through the MATRIXX testing the IMRT compensator in clinical implementation.At the same time we compared the MU of using multi-leaf collimator (MLC) and Cerrobase IMRT compensator for 10patients.ResultsWith cerrobase compensation IMRT can get similar dose or dose distribution to dose produced by TPS for point or plane dose,error is within 5％.To comparison with MLC,using cerrobase compensator has fewer treatment times ( (4.44±0.39) min:(5.71±0.57) min (t =10.82,P =0.000) )and fewer MU (462.5 ± 65.8) MU:(524.5±99.6) MU(t=3.14,P=0.012) ).Conclusions Comparison with MLC IMRT,the cerrobase compensation technique has an important application value with its unique advantages.This research provides an implemented method of IMRT radiotherapy for the primaryhospital.

Design of a global sliding mode controller for intra-aorta pump / 医用生物力学

Objective To design a global sliding mode control algorithm for the purpose of eliminating the chattering effect in conventional sliding mode control algorithm on both the controller and controlled plant from the conventional sliding mode control algorithm and regulating the intra aorta pump in response to the demand of blood circulation system in human. Methods A dynamic disturbance compensator was used to estimate the uncertainty of the intra aorta pump control system. Computer simulations and in vitro experiments were also conducted to verify the dynamic characteristics and robustness of the controller. Results As the dynamic disturbance compensator was used to estimate the uncertainty of system, the chattering effect in sliding mode control algorithm was eliminated. When the reference flow rate was set at 5 L/min, the response time was 80 ms without any overshot and static error. When the load torque of the controller was increased to 0.4 N·m, the response time was 25 ms. When the pulsatile signal was input as the reference flow rate, the dynamic response time was 80 ms with the maximum error of flow rate being 0.03 L/min. In the in vitro experiments, as the feedback frequency of flow rate signal and pump speed signal were lower than that in the ideal condition, the controller performance was deteriorative compared with computer simulation. The experimental results demonstrated that when the reference flow rate was set at 5 L/min, the response time was 0.26 s with the error of flow rate being 0.1 L/min. Conclusions The controller provided in this paper can accurately regulate the intra aorta pump according to the reference flow rate. Furthermore, it has a strong robustness for the uncertainty and disturbance of the control system. Due to the use of dynamic disturbance compensator, the chattering effect of the algorithm has been eliminated.

Image Based Quality Assurance of Range Compensator for Proton Beam Therapy / 의학물리

The main benefit of proton therapy over photon beam radiotherapy is the absence of exit dose, which offers the opportunity for highly conformal dose distributions to target volume while simultaneously irradiating less normal tissue. For proton beam therapy two patient specific beam modifying devices are used. The aperture is used to shape the transverse extension of the proton beam to the shape of the tumor target and a patient-specific compensator attached to the block aperture when required and used to modify the beam range as required by the treatment plan for the patient. A block of range shifting material, shaped on one face in such a way that the distal end of the proton field in the patient takes the shape of the distal end of the target volume. The mechanical quality assurance of range compensator is an essential procedure to confirm the 3 dimensional patient-specific dose distributions. We proposed a new quality assurance method for range compensator based on image processing using X-ray tube of proton therapy treatment room. The depth information, boundaries of each depth of plan compensatorfile and x-ray image of compensator were analyzed and presented over 80% matching results with proposed QA program.

The Analysis of a Cerrobend Compensator and a Electronic Compensator Designed by a Radiation Treatment Planning System / 의학물리

In this study, the physical compensator made with the high density material, Cerrobend, and the electronic compensator realized by the movement of a dynamic multileaf collimator were analyzed in order to verify the properness of a design function in the commercial RTP (radiation treatment planning) system, Eclipse. The CT images of a phantom composed of the regions of five different thickness were acquired and the proper compensator which can make homogeneous dose distribution at the reference depth was designed in the RTP. The frame for the casting of Cerrobend compensator was made with a computerized automatic styrofoam cutting device and the Millennium MLC-120 was used for the electronic compensator. All the dose values and isodose distributions were measured with a radiographic EDR2 film. The deviation of a dose distribution was +/-0.99 cGy and +/-1.82 cGy in each case of a Cerrobend compensator and a electronic compensator compared with a +/-13.93 cGy deviation in an open beam condition. Which showed the proper function of the designed compensators in the view point of a homogeneous dose distribution. When the absolute dose value was analyzed, the Cerrobend compensator showed a +3.83% error and the electronic compensator showed a -4.37% error in comparison with a dose value which was calculated in the RTP. These errors can be admtted as an reasonable results that approve the accuracy of the compensator design in the RTP considering the error in the process of the manufacturing of the Cerrobend compensator and the limitation of a film in the absolute dosimetry.

Development of Total Body Irradiation Program / 의학물리

In total body irradiation (TBI) for leukemia, we have a two methode. One is a AP (anterior-posterior) method and the other is a Lateral methode. Our hospital used lateral methode. TBI must consider about body contour, because of homogeneous dose distribution. For compensation about irregular body contour, we use compensator. For TBI treatment, we must be considered, accurate manufacture of compensator and accurate calculation of dose. We developed the automatic program for TBI. This program accomplished for compensator design and dose calculation for irregular body. This program was developed for uses to use in a windows environment using the IDL language. In this program, it use energy data for each energy: TMR, output factor, inverse square law, spoiler, field size factor. This program reduces the error to happen due to the manual. As a development of program, we could decrease the time of treatment plan and care the patient accurately.

Research and experiment of compensator made by split method for static intensity-modulated radiation therapy / 医疗卫生装备

Objective To help the hospitals at all levels in China to realize IMRT by adding the accurate location equipments and TPS based on the existing general radiation therapy from research of the new method for static Intensity-modulated radiation therapy. Method Based on the controlled technique of CRT, a new split method for fabricating the three-dimensional physics compensator to achieve the IMRT was developed. Results The Experiment manifested that the compensator fabricated by the way could make the high dosage shape of target in accordance with the form of tumor and could adjust the distribution of the dosage according to remedy requirement. Conclusion The method is simple and feasible, and has brilliant clinical prospective and popularized significance.

Improved Breast Irradiation Techniques Using Multistatic Fields or Three Dimensional Universal Compensators / 대한방사선종양학회지

PURPOSE: In order to improve dose homogeneity and to reduce acute toxicity in tangential whole breast radiotherapy, we evaluated two treatment techniques using multiple static fields or universal compensators. MATERIALS AND METHODS: 1) Multistatic field technique : Using a three dimensional radiation treatment planning system, Adac Pinnacle 4.0, we accomplished a conventional wedged tangential plan. Examining the isodose distributions, a third field which blocked overdose regions was designed and an opposing field was created by using an automatic function of RTPS. Weighting of the beams was tuned until an ideal dose distribution was obtained. Another pair of beams were added when the dose homogeneity was not satisfactory. 2) Universal compensator technique : The breast shapes and sizes were obtained from the CT images of 20 patients who received whole breast radiation therapy at our institution. The data obtained were averaged and a pair of universal physical compensators were designed for the averaged data. DII (Dose Inhomogeneity Index : percentage volume of PTV outside 95-105% of the prescribed dose), Dmax (the maximum point dose in the PTV) and isodose distributions for each technique were compared. RESULTS: The multistatic field technique was found to be superior to the conventional technique, reducing the mean value of DII by 14.6% ( p value<0.000) and the Dmax by 4.7% ( p value<0.000). The universal compensator was not significantly superior to the conventional technique since it decreased Dmax by 0.3% ( p value=0.867) and reduced DII by 3.7% ( p value=0.260). However, it decreased the value of DII by maximum 18% when patients' breast shapes fitted in with the compensator geometry. CONCLUSION: The multistatic field technique is effective for improving dose homogeneity for whole breast radiation therapy and is applicable to all patients, whereas the use of universal compensators is effective only in patients whose breast shapes fit inwith the universal compensator geometry, and thus has limited applicability.

The thermal expansion compatibility of a new infiltrated ceramic-low-temperat ure compensatory die stone / 实用口腔医学杂志

Objective: To study the thermal expansion compatibili ty of a newly developed low temperature compensatory die stone (CDS) with Al 2O 3 base coping and to determine its setting time and setting expansion rate. Methods: Using HDS (Hieraus Die Stone ) as control. The ther mal expansion compatibility of CDS with Al 2O 3 was determined with TMA method on Du point 2100 thermometer;the setting time and setting expansion rate of CDS were measured with routine technique. Results: CDS showed much smaller thermal expansion with Al 2O 3 base coping than HDS.When the wa ter/powder ratio increased from 0.20 to 0.30,the setting time (h) of CDS increas ed from 12.75?0.7546 to 19.85?0.7472,that of HDS from 12.25?0.7169 to 24.00? 0.8165. The setting expansion of CDS was similar to that of HDS at various water /powder ratio. Conclusion: CDS has suitable thermal expans ion compatibility with Al 2O 3, it also has proper setting time and setting ex pansion rate to meet the clinical needs.

Utilization of Tissue Compensator for Uniform Dose Distribution in Total Body Irradiation / 대한치료방사선과학회지

PURPOSE: This study was performed to verify dose distribution with the tissue compensator which is used for uniform dose distribution in total body irradiation (TBI). MATERIALS AND METHODS: The compensators were made of lead (0.8mm thickness) and aluminum(1mm or 5mm thickness) plates. The humanoid phantom of adult size was made of paraffin as a real treatment position for bilateral total body technique. The humanoid phantom was set at 360cm of source-axis distance(SAD) and irradiated with geographical field size(FS) 144cm' 144cm2(40 40 cm2 at SAD 100cm) which covered the entire phantom. Irradiation was done with 10MV X-ray(CLINAC 1800, Varian Co., USA) of linear accelerator set at Department of Therapeutic Radiology, Chonnam University Hospital. The midline absorbed dose was checked at the various regions such as head, mouth, mid-neck, sternal notch, mid-mediastinum, xiphoid, umbilicus, pelvis, knee and ankle with or without compensator, respectively. We used exposure/exposure rate meter (model 192, Capintec Inc., USA) with ionization chamber(PR 05) for dosimetry. For the dosimetry of thorax region TLD rods of lxlx6mm3 in volume(LiF, Harshaw Co., Nethrland) was used at the commercially available humanoid phantom. RESULTS: The absorbed dose of each point without tissue compensator revealed significant difference(from -11.8% to 21.1%) compared with the umbilicus dose which is a dose prescription point in TBI. The absorbed dose without compensator at sternal notch including shoulder was 11.8% less than the dose of umbilicus. With lead compensator the absorbed doses ranged form +1.3% to -5.3% except midneck which revealed over-compensation (-7.9%). In case of aluminum compensator the absorbed doses were measured with less difference (from -2.6% to 5.3%) compared with umbilicus dose. CONCLUSION: Both of lead and aluminum compensators applied to the skull or lower leg revealed a good compensation effect. It was recognized that boost irradiation or choosing reference point of dose prescription at sternal notch according to the lateral thickness of patient in TBI should be considered.

Total Body Irradiation Technique: Basic Data Measurements and In Vivo Dosimetry / 대한치료방사선과학회지

This paper describes the basic date measurements for total body irradiation with 6 Mv photon beam including compensators designs. The technique uses bilateral opposing field with tissue compensators for the head, neck, lungs, and legs from the hip to toes. In vivo dosimetry was carried out for determining absorbed dose at various regions in 7 patients using diode detectors (MULTIDOSE, Model 9310, MULTIDATA Co., USA). As a results, the dose uniformity of+/-3.5%(generally, within+/-10%) can be achieved with our total body irradiation technique.

Dose Effect of Tissue Compensator for 6 MV X-Ray / 대한치료방사선과학회지

It is ideal thing to compensate tissue deficit without skin contamination in curvatured irradiation field of high energy Photon beam. The 3-dimensional compensating technique utilizing tissue equivalent materials to ensure an adequate dose distribution and skin sparing effect was described. This compensator was made of paraffin(70%) and stearin wax (30%) compound. The parameters for evaluation of the effect on skin dose in application of compensator were considered in the size of the field, the thickness of the compensator and the source-to-axis distance. The results are as follows; the skin doses were not changed even though application of the compensator, but depended on the field size and the source-to-axis distance, and the skin doses were only slightly changed within 1% relative errors as increasing the thickness of the compensator in these experiments.

A Study of Three-dimension Tissue Equivalent Compensator for 6MV X-Rays / 대한치료방사선과학회지

Three-dimension paraffin compensator was designed to construct the tissue equivalent compensator for irregular body contours and obiliques beam incidence. The ratio of compensator thickness to tissue deficit was depended on field size, depth and air gap because the scattered dose loss. The ratio of compensator-tissue was optimized 0.79, 0.73, 0.61 and 0.50 in 6MV x-rays as function of field size 4x4, 10x10, 20x20 and 30x30 cm2 respectively in our study. Using this tissue equivalent compensator, it can be got 2% difference of dose at same mid-plane in phantom study.

A Study on Design and Application of Tissue Compensator for 6MV X-rays / 대한치료방사선과학회지

A radiation beam incident on an irregular or sloping surface produces the non-uniformity of absorbed dose. The use of a tissue compensator can partially correct this dose inhomogeneity. The tissue compensator is designed based on the patient's three dimensional contour. After required compensator thickness was determined according to tissue deficit at 25 cmx 25 cm field size, 10 cm depth for 6MV x-rays, tissue deficit was mapped by isoheight technique using laser beam system. Compensator was constructed along the designed model using 0.5 mm lead sheet or 5 mm acryl plate. Dosimetric verification were performed by film dosimetry using humanoid phantom. Dosimetric measurements were normalized to central axis full phantom readings for both compensated and non-compensated field. Without compensation, the percent differences in absorbed dose ranged as high as 12.1% along transverse axis, 16.8% along vertical axis. With the tissue compensators in place, the difference was reduced to 0~4.3% Therefore, it can be concluded that the compensator system constructed by isoheihnt technique can produce good dose distribution with acceptable inhomogeneity, and such compensator system can be electively applied to clinical radiotherapy.