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Objective:To evaluate the accuracy and stability of stereotactic radiosurgery (SRS) algorithm in optical surface imaging (OSI) system in non-coplanar radiotherapy.Methods:Three OSI imaging systems were used to measure the phantom repeatedly at different couch rotation angles to analyze the accuracy and stability of OSI system. Seven patients with multiple brain metastases who underwent single-center non-coplanar radiotherapy were randomly selected, and the accuracy and stability of OSI for patient imaging were analyzed. Stability is defined as the difference between the two OSI measurements when the couch is turned from 0° to a non 0° angle, and then back to 0°, using the 0° cone beam CT (CBCT) as the "gold standard". Accuracy is defined as the difference between OSI and CBCT (at 0° couch angle) measurement data. The measurement data with normal distribution were described as Mean ± SD. The data with non-normal distribution were expressed as M (Q). The difference of the former data was compared by one-way ANOVA, and the difference of the latter data was assessed by Kruskal-Wallis H nonparametric test. Results:For non-coplanarity, the translation accuracy of the phantom and the patient was ≤ 1.30 mm and ≤ 1.00 mm, and the rotation accuracy was ≤ 0.50° and ≤ 0.60°, respectively. The translation errors mainly occurred in the left-right and head-foot directions. In terms of stability, the maximum standard deviation of phantom coplanar translation and rotation was 0.06 mm and 0.06°. The maximum standard deviation of patient translation and rotation was 0.17 mm and 0.19°.Conclusions:Although the new SRS algorithm improves the non-coplanar accuracy, it still cannot meet the precise requirements of non-coplanar single isocenter radiotherapy for multiple brain metastases, especially in the left-right and head-foot directions. When the couch rotation angle is large, OSI is not recommended for image-guided radiotherapy. However, its high stability can be used to monitor the intrafractional motion of patients.
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Objective:To quantify the registration deviation between CT and cone-beam computed tomography (CBCT) images with different breathing rates and motion amplitudes under free breathing state.Methods:Using the QUASAR respiratory motion phantom, breathing rate and motion amplitude in the superior-inferior (SI) direction were changed to simulate free breathing motion under different states. The CT and CBCT images were acquired under different breathing rates and motion amplitudes, and static states, then the registration errors between CT and CBCT images and CT target volume were obtained and subject to quantitative analysis.Results:Using the static CT image as a reference, the changes in breathing rate exerted no significant effect on the registration error when the motion amplitude was constant. When the motion amplitude was 0.5, 1.0, 2.0, and 3.0 cm, the average registration errors were (0.213±0.020), (0.351±0.009), (0.654±0.010), and (0.972±0.022) cm, respectively. When the motion amplitude was 0.5 and 1.0 cm, the CT target volume varied from -16.92% to 18.78%. When the motion amplitude was 2.0 and 3.0 cm, the CT target volume changed from -16.44% to 81.78%.Conclusions:The changes in breathing rate under free-breathing state has no significant effect on the registration error between CBCT and CT images. When the motion amplitude is 0.5 and 1.0 cm, the CT target volume changes and the registration errors are small. When themotion amplitude is 2.0 and 3.0 cm, the registration errors exceed 0.5 cm and the CT target volume changes may exceed 20%.
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Objective:To evaluate the effects of orthogonal magnetic fields on the dose distribution of 6 MeV X-ray in a uniform water and heterogeneous phantoms.Methods:The Monte Carlo simulation software Gate v8.2 was used to investigate the dose distribution of X-ray beams of different field sizes in a uniform water phantom, water-air/bone-water layer phantom and" custom lung model" in the magnetic field strength of 0.0, 0.5, 1.0, 1.5, 3.0 T, respectively. The relationship between the intensity of magnetic field and the dose distribution of X-rays in the phantoms was analyzed.Results:The existence of a magnetic field would cause the X-ray to shorten the built-up area in the water phantom; when the field was 10 cm×10 cm, the maximum dose on the central axis could change by up to 56.22%(3.0 T). The transverse dose distribution of the radiation field in the direction of the vertical magnetic field shifted to one side by up to 43.64%(-44.55%). The average dose of the air layer in the water-air-water phantom could be reduced by 57.4%(3.0 T). In the water-bone-water phantom, the dose at the proximal end of the bone layer was decreased by 16.5%, whereas the dose at the distal end was increased by 22.6%(1.5 T). The dose change in each layer in the customed lung model was positively correlated with the magnetic field strength.Conclusion:The existence of the orthogonal magnetic field will cause the change of X-ray dose distribution on the built-up area and both sides of the radiation field in the phantoms, which is more obvious adjacent to the interface of heterogeneous phantom.
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Objective:To introduce the stereotactic cardiac radioablation (SCRA) based on the stereotactic body radiotherapy (SBRT), and comprehensively evaluate the new approach by short-term effectiveness and safety.Methods:Patients with ventricular arrhythmia (VA) were evaluated and included in this clinical trial, who were immobilized by vacuum bag and performed simulation with 4-dimensional computed tomography (4DCT). In this study, the planning target volume (PTV) was set as the target to design a SBRT plan using volumetric modulated arc therapy (VMAT), which was evaluated by dose parameters such as R 50%, homogeneity index and conformity index, etc. The results of Holter and echocardiography were monitored during the follow-up and compared with the data before treatment. Results:Three subjects with ventricular tachycardia (VT) and one with premature ventricular contraction (PVC) received the same prescription of 25 Gy in a single fraction. The average volume of PTV was 71.4 cm 3(60.3-89.4 cm 3). The average time of beam delivery was 12.0 min (4.5-21.0 min). And the short-term follow-up lasted for an average of 18 weeks (14-25 weeks), which showed significant decrease in both VT and PVC load without complications. Conclusion:This study reports the implementation method of SCRA and proves its short-term effectiveness and safety, but the effects and standards of the key radiotherapy techniques still need to be explored.
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Objective:To retrospectively analyze the setup errors of thermoplastic head and shoulder molds alone or combined with vacuum pad in hypofractionated stereotactic radiotherapy (HFSRT) for non-small cell lung cancer (NSCLC) with brain metastases.Methods:Fifty-four NSCLC patients with brain metastases who received HFSRT from 2017 to 2019 were enrolled in this study. Twenty-four patients were fixed with thermoplastic head and shoulder molds (group A), and 30 patients were fixed with thermoplastic head and shoulder molds plus vacuum pad (group B). The interfraction and intrafraction setup errors were acquired from cone-beam CT online image registration before and after the HFSRT. Optical surface system was applied in monitoring the intrafraction setup errors. The setup errors in each direction between two groups were analyzed by independent samples t-test. Results:For the interfraction setup errors of the whole group, the proportion of the horizontal setup errors of ≥3mm was 7.0% to 15.4% and 7.0% to 12.6% for the rotation setup errors of ≥2°. In group A, the anteroposterior setup error was (1.035±1.180)mm, significantly less than (1.512±0.955)mm in group B ( P=0.009). In group A, the sagittal rotation setup error was 0.665°±0.582°, significantly less than 0.921°±0.682° in group B ( P=0.021). For the intrafraction setup errors of the whole group, the proportion of horizontal setup errors of ≥1mm was 0% to 0.7%, whereas no rotation setup error of ≥1° were observed. In group B, bilateral, anteroposterior and sagittal rotation setup errors were (0.047±0.212)mm, (0.023±0.152)mm and 0.091°±0.090°, significantly less compared with (0.246±0.474)mm, (0.140±0.350)mm and 0.181°±0.210° in group A ( P=0.004, P=0.020, P=0.001), respectively. Optical surface monitoring data were consistent with the obtained results. Conclusions:Thermoplastic head and shoulder molds (with or without vacuum pad) combined with online image registration and six-dimensional robotic couch correction can be applied in HFSRT for brain metastases from NSCLC. The intrafraction setup errors in group B are smaller than those in group A. Optical surface system has certain value in monitoring the intrafractional movement.
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The training program of radiation therapists in the United States has been established early, and the mode of training, qualification and continuing education are relatively complete. Literature review was conducted at home and abroad and United States Department of Labor, American Registry of Radiologic Technologists, American Society of Radiologic Technologists as well as Joint Review Committee on Education in Radiologic Technology websites were reviewed. The training mode, qualification, work content, continuing education and employment situation of American radiotherapists were analyzed, aiming to provide some reference and enlightenment for the establishment of a new model for the training of professional radiologists suitable for the national conditions of China Mainland.
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Stereotactic radiotherapy (SRT), also known as stereotactic ablative radiotherapy (SABR), includes stereotactic radiosurgery and stereotactic body radiotherapy (SBRT). This technique has the characteristics of large single fractional dose, few fractions, high equivalent biological doses, and rapid fall off-target doses. It can be implemented by relatively special equipment such as Gamma knife, Cyberknife, Tomotherapy and Vero 4D RT system, etc. In many cases, SBRT technique is employed based on linear accelerators. SRT differs from conventional radiotherapy in terms of the plan design and plan evaluation. Consequently, it is necessary to discuss the differences and provide guidance for clinical application and research.
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Radiotherapy is a vital treatment method for pancreatic cancer. However, the therapeutic effect of radiotherapy is significantly limited by the influence of pancreatic motion. More efficient radiotherapy for pancreatic cancer depends upon the improvement of motion management and high-quality image guidance. The emerging MR-guided radiotherapy (MRgRT) can perform functional imaging with high soft tissue resolution and no additional radiation. Multiple researches have demonstrated that MRgRT has significant advantages in terms of precise delineation of target area and organ at risk, motion management and adaptive radiotherapy, which assists radiotherapy to play a better role in the treatment of pancreatic cancer. In this paper, the application of MRgRT in pancreatic cancer was reviewed and prospected.
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Virtual monochromatic images (VMI) that reconstructed on dual-energy computed tomography (DECT) have further application prospects in radiotherapy, and there is still a lack of clinical dose verification. In this study, GE Revolution CT scanner was used to perform conventional imaging and gemstone spectral imaging on the simulated head and body phantom. The CT images were imported to radiotherapy treatment planning system (TPS), and the same treatment plans were transplanted to compare the CT value and the dose distribution. The results show that the VMI can be imported into TPS for CT value-relative electron density conversion and dose calculation. Compared to conventional images, the VMI varies from 70 to 140 keV, has little difference in dose distribution of 6 MV photon treatment plan.
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Electrons , Phantoms, Imaging , Tomography Scanners, X-Ray Computed , Tomography, X-Ray ComputedABSTRACT
In order to adapt to different target shapes and protect the surrounding normal tissues, the design of two-dimensional electron beam radiotherapy planning requires additional lead blocks. But the Pinnacle treatment planning system can not directly shape the lead block conformity to the size of the beam field given by the doctor. Every time, physicists need to manually drag the lead block to form the required beam field. When meeting a two-dimensional electron beam treatment planning with the same field parameters as before, physicists need to rearrange the field for dose calculation, which greatly reduces the design efficiency of the two-dimensional electron beam treatment planning. In this study, we independently developed a two-dimensional electron beam radiotherapy planning system based on Qt Creator. The system can quickly design a two-dimensional electron beam radiotherapy plan, which reduces the repeated work of physicists.
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Electrons , Radiotherapy Dosage , Radiotherapy Planning, Computer-AssistedABSTRACT
In radiotherapy for thoracic and abdominal tumors, the negative effect of respiratory movement on radiotherapy persist throughout the whole process of radiotherapy. Deep inspiration breath-hold technique (DIBH) is a method of respiratory movement management in radiotherapy, which can reduce the negative effect of respiratory movement upon radiotherapy in the whole process of radiotherapy. Meantime, DIBH technique has its own characteristics and operation requirements compared with other respiratory movement management measures (such as 4D CT, gated technology and tracking, etc.). The aim of this review was to introduce the advantages, disadvantages and the application status of DIBH technique.
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Objective To analyze the precision and stability of optical surface imaging system for patients who received radiotherapy with active breath control. Methods Eighteen radiotherapy patients with lung metastasis were managed by active breath control (ABC).The difference error detected by optical surface imaging system and CBCT were defined as the precision of optical surface imaging system. The variation among the error of optical surface imaging positioning the value of correction of treatment position and the error detected by optical surface imaging again were defined as the stability of optical surface imaging system. Intrafractional errors were analyzed by optical surface imaging system through whole treatment process (including breath hold and free breath). Results The optical surface imaging system had precision (systematic (Σ) and random errors (σ)) of 1.78/3.42 mm 2.54/6.57 mm and 2.79/3.22 mm respectively and stability of2.12/2.54 mm 3. 09/4.02 mm and 1.37/3.55 mm respectively in lateral-medial superior-inferior and anterior-posterior directions. The intrafractional errors (Σ and σ) were 0.42/0.85 mm 0.41/1.47 mm and 0.41/1.47 mm respectively for breath hold duration and 4.76/4.16 mm 6.54/7.78 mm and 3.13/5.92 mm for free breath duration in lateral-medial superior-inferior and anterior-posterior directions. Conclusions As an effective method for validate breath hold;Optical surface imaging system can improve the precision and safety of active breath control. However,the factors that affect the accuracy and stability of the optical surface imaging system in patients undergoing radiotherapy with ABC are not clear;it cannot replace the CBCT for positioning verification.
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Objective To investigate the precision and stability of optical surface imaging (OSI)system Catalyst in guiding radiotherapy positioning.Methods A total of 52 patients with five different tumor sites who underwent cone-beam computed tomography (CBCT)-guided radiotherapy were recruited in this investigation.For the first treatment fraction,the setup error was recorded as C after online CBCT correction,and the surface images of patients taken by Catalyst were set as the reference images Cref.For the following treatment fraction,patients were pre-corrected according to the Catalyst Cref image with the acceptable errors within 2 mm/ 2,and the pre-corrected errors were recorded as C1.Then,after online CBCT correction,the setup errors were recorded as C.The errors between post-corrected Catalyst surface image and Cref image were recorded as C2.For each treatment fraction,the difference between Catalyst correction errors C1 and CBCT corrected errors C was recorded as d1,and the difference between the post-corrected Catalyst errors C2 and Cref image was recorded as d2.d3=d1-d2.The values of d1 and d3 in the 6 dimensions were analyzed using single sample t-test.The correlation between C-C1 and d1-d2 was statistically analyzed by Pearson correlation analysis.Results The mean value of d1 and d3 for 52 patients were within 2 mm/2 °.CBCT-C1 and d1-d2 were both significantly correlated (R =3,7,P=0.00,0.01).Conclusions OSI system yield high accuracy and stability in radiotherapy positioning,which is of certain significance in radiotherapy positioning for cancer patients.
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Currently,image-guided radiation therapy (IGRT) is the most advanced technique in the field of radiation oncology.However,the most commonly used image-guided techniques,such as cone beam computed tomograhpy (CBCT) and electronic portal imaging device (EPID) are limited due to extra radiation,poor image quality and failure of real-time monitoring.Optical surface imaging technique generates no additional radiation and can conduct real-time monitoring.Multiple researches have demonstrated that it has significant advantages in terms of guiding positioning,real-time monitoring of the fractionated and divided motion,reducing the frequency of CBCT scanning,breathing door control,etc.In this paper,this novel technique and its application prospect in radiotherapy are reviewed.
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Objective To analyze setup errors in cone beam computed tomography(CBCT)-guided radiotherapy for nasopharyngeal cancer(NPC)and evaluate the use frequency of CBCT. Methods Twenty-six patients newly diagnosed with NPC who received CBCT scan no less than 3 times per week during the whole course(7 weeks)of intensity-modulated radiotherapy(IMRT)were enrolled as subjects. Two setup errors were recorded each week:the setup error in the first CBCT analysis(Ef)and the setup error in the subsequent CBCT analysis(Ec). Comparisons of Efbetween two different weeks, Ecbetween two different weeks,and between Efand Ecin the same week were made by analysis of variance. Results During the 7 weeks,there were no significant differences in Efin the medial-lateral(ML), superior-inferior(SI), or anterior-posterior(AP)direction between any two weeks(all P>0.05);there were also no significant differences in Ecin the ML or SI direction between any two weeks(all P>0.05);there was a significant difference in Ecin the AP direction between two different weeks(P<0.05);there were no significant differences between Efand Ecin the ML or SI direction in any week(P>0.05);there were also no significant differences between Efand Ecin the AP direction in any week(P>0.05)except for the first week (P<0.05). Conclusions In IMRT for NPC,the setup errors in the ML and SI directions are stable in the whole course of radiotherapy,while the setup errors in the AP direction are different between the first week and subsequent weeks. Daily CBCT scan in the first week and weekly CBCT scan in the subsequent weeks are highly recommended for most patients to reduce the use frequency of CBCT.
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Objective To analyze the displacement of titanium clips for tumor bed localization after breast-conserving surgery for breast cancer and its influential factors.Methods A retrospective analysis was performed on the cone-beam computed tomography (CT) images of 14 patients with breast cancer who received radiotherapy after breast-conserving surgery from April to October,2016.The relative position of the chest wall and the errors of the titanium clips in radiotherapy were measured.A Pearson correlation analysis was used to analyze the correlation of the displacement of titanium clips with the relative position of titanium clips,the breast volume,the vertical distance between the titanium clips and the tangential line of the chest wall,and the maximum thickness of the breast.Results The system errors of the chest wall in left-right,superior-inferior,and anterior-posterior directions were 4.42,3.44,and 5.13 mm,respectively,and the random errors were 3.55,3.07,and 4.54 mm,respectively.The titanium clips had a large displacement relative to the chest wall,mainly in the left-right direction.The maximum system error was 4.39 mm and the random error was 2.42 mm.The displacement of titanium clips was not significantly correlated with the breast volume and the maximum thickness of the breast (P>0.05).However,the relative position of titanium clips in superior-inferior direction was significantly correlated with the displacement of the lowest,the most lateral,the most anterior,and the most posterior titanium clips (P<0.05).As to the uppermost clips,there was a significant difference in displacement between the clips close to the chest wall and the clips far from the chest wall (P=0.02).Conclusions Due to large setup error and displacement of titanium clips during radiotherapy,simultaneous integrated boost is not suitable for patients with breast cancer who are immobilized by vacuum cushion and received radiotherapy.The unstable immobilization may be the major influential factor for the displacement of titanium clips.
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Objective To evaluate the image quality and registration accuracy of a three?dimensional ( 3D ) dynamic phantom in four?dimensional computed tomography ( 4DCT ) and four?dimensional cone?beam computed tomography ( 4DCBCT) . Methods The Computerized Imaging Reference Systems Dynamic Thorax Phantom Model 008A was scanned to get 4DCT and 4DCBCT images. Two balls with different diameters ( ?= 1 cm and ?= 2 cm) were used to simulate tumors with different sizes. The motion mode of the balls was 3D sinusoidal motion at 0?25 Hz ( the amplitudes along the x, y, and z axes were ±1?0 cm, ±0?4 cm, and ±0?2 cm, respectively). Gross target volumes (GTVs) from 10?phase bins, internal gross target volumes (IGTV), and target volumes on maximum intensity projection (MIP) and mean intensity projection (MeanIP) images were contoured and calculated. Target volumes on 4DCT or 4DCBCT images were compared with the static and dynamic volumes of the balls ( VS and VD ) . The matching index ( MI) of target volumes between the 4DCT and 4DCBCT images was analyzed after rigid image registration. Results The GTV in each phase of the image was larger than VS . The difference between the average GTV derived from 10 phases of 4DCT or 4DCBCT images and Vs of the small ball was larger than that of the large ball ( 35?03% vs. 22?66%;32?62% vs. 17?00%) . All the IGTVs and target volumes on MIP images were slightly larger than VD , but target volumes on MeanIP images were smaller than VD . The average MI of 10?phase bins of the small ball was smaller than that of the large ball ( 66?76% vs. 82?21%) . Moreover, MIs of IGTV,MIP, and MeanIP of the small ball were also smaller than those of the large ball ( 77?39% vs. 90?29%;75?90% vs. 89?28%;74?47% vs. 82?74%) . Conclusions In the case of a relatively small tumor volume and a relatively large motion amplitude, 4DCT and 4DCBCT should be used with caution for comparison of image registration.
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To investigate the impact of respiratory movement to determine the target volume on cone beam CT (CBCT) for lung tumor, we used CIRS dynamic thorax phantom (Model-CIRS008) to simulate the sinusoidal motion of lung tumor. With a constant amplitude, the ratio of the time of near-end-expiratory and near-end-inspiratory (E/I) changed when it was scanned with CBCT. We analyzed the contrast changes of target by extracting the CT value of each pixel on the center line of the target movement direction. The targets were contoured with region growing method and compared with the motion volume generated by the tumor trajectory method. The result showed that the contrast of near-end-expiratory increased and the contrast of near-end-inspiratory decreased with increasing E/I. The contoured volume generated by region growing method decreased with increasing E/I. When E/I = 4, the amplitude A = 1 cm, diameter of 1 cm and 3 cm target volumes were reduced by 48.2% and 22.7%. The study showed that CBCT was not suitable to be used to accurately determine the range of lung tumor movement. The internal target volume (ITV) may be underestimated in CBCT images.
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Humans , Cone-Beam Computed Tomography , Lung Neoplasms , Diagnostic Imaging , Movement , Phantoms, Imaging , RespirationABSTRACT
Objective To compare the results of three different registration methods in the kilovolt CBCT guided IMRT for nasopharyngeal cancer (NPC).Methods Total 560 CBCT images of 24 NPC patients who received kilovolt CBCT guided IMRT were analyzed off line.Three registration methods were used for alignment between CBCT and planning CT,including translational and rotational errors for bone and grey (BoneT + R,GreyT+ R),only translational errors for grey (GreyT).The registration results were analyzed by mean paired t-test respectively.Results With method BoneT+R,the translational errors on x,y and z axes were (-0.11 ± 1.35) mm,(0.40 ± 2.09) mm and (0.95 ± 1.56) mm and the rotational errors were 1.06° ±0.67°,0.01° ± 1.28° and 0.92° ± 1.00° respectively.With GreyT+R,the translational errors on x,y and z axes were (-0.02 ± 1.06) mm,(0.68 ± 1.92) mm and (0.81 ± 1.46) mm and the rotational errors were 0.85° ±0.61°,-0.05° ± 1.32° and 0.91° ±0.72° respectively.With GreyT,the translational errors on x,y and z axes were (0.58 ± 1.02),(0.52 ± 1.89) and (0.44 ± 1.43) mm.The results of compared mean t-test for different registration methods groups have significant difference (P =0.00-0.01) except for the rotational errors on y and z axes between BoneT+R and GreyT+R (P =0.05,0.62).Conclusions There have different alignment errors when different registration methods used for NPC kilovolt CBCT guided radiotherapy.If there have correct methods for rotation errors,GreyT+R registration method may be a better choice.In opposite,GreyT+R registration method would be used firstly to verify whether the rotational error ＞ 2°or 3°.If the rotational error ＞ 2°or 3°,the patient should be re-setup.If not,according to these alignment results,the GreyT method,manual method would be used to compensate the translational errors.
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Some patients who have neck tumor but cannot tolerate the thermoplastic immobilization may be supported by simple cushions, and are marked on the neck skin during CT simulation. We therefore set 5 mm as the spinal cord-planning risk volume margin in the intensity-modulated radiotherapy plans in our Centre. Cone beam CT (CBCT) scans were acquired for three times, and matched with the simulation CT images in each radiotherapy. The mean and the standard deviation of the individual, the root mean-square and the standard deviation of the individual were calculated. The matched results of the third CBCT were used to calculate the spinal cord- planning risk volume margin. The results showed that the interfraction error was significantly reduced and the intrafraction error was stable by CBCT guiding. CBCT and 5 mm spinal cord-planning organ is feasible and safe without threatening volume margin to high dose radiotherapy for the patients with neck tumor and not able to tolerate thermoplastic immobilization.