Application of Linear Accelerator on Boarding Kilovolt Fan Beam CT and Megavolt Cone Beam CT System on Set-up Errors During Radiation Treatment / 肿瘤防治研究

Objective To quantify the setup errors for the different anatomical sites of patients who received intensity-modulated radiotherapy (IMRT) with linear accelerator on-board kilovolt fan beam CT(kV-FBCT) as non-isocenter IGRT and megavolt cone beam CT (MV-CBCT) as isocenter IGRT. Methods A retrospective analysis was performedon 70 patients who underwent radiotherapy, kV-FBCT, and/or MV-CBCT scans after each routine setup prior to IMRT. The average displacement (M), systematic error (Σ), and random error (б) at different treatment sites in the left-right, anterior-posterior, and cranial-caudal directions were calculated according to the individual displacements. The formula 2.5Σ+0.7б was used to estimate the PTV margin in respective direction. For each single patient, the root mean square in three directions was used as 3D displacement. Results A total of 1130 displacements were recorded in the 70 patients. The PTV margin was estimated to be 1.9-3.1 mm in head and neck cancer, 2.8-5.1 mm in thoracic cancer, 4.6-5.1 mm in breast cancer, 3.0-5.5 mm in upper abdominal cancer, and 3.5-6.8 mm in pelvic tumor. For the 3D mean displacements, the head and neck, thoracic, breast, upper abdominal, and pelvic cancer were 2.4±1.0, 4.0±1.6, 4.1±2.0, 4.6±2.1, and 4.6±2.1 mm, respectively. The average 3D displacement obtained by kV-FBCT and MV-CBCT were 4.1 and 3.4 mm, respectively (P=0.212). Conclusion The quantitative setup-error data can be obtained using linear accelerator on-board FBCT, and the non-isocenter IGRT induced set-up error cannot be negligible.

Advances in magnetic resonance imaging guided radiation therapy / 生物医学工程学杂志

Image-guided radiation therapy using magnetic resonance imaging (MRI) is a new technology that has been widely studied and developed in recent years. The technology combines the advantages of MRI imaging, and can offer online real-time tracking of tumor and adjacent organs at risk, as well as real-time optimization of radiotherapy plan. In order to provide a comprehensive understanding of this technology, and to grasp the international development and trends in this field, this paper reviews and summarizes related researches, so as to make the researchers and clinical personnel in this field to understand recent status of this technology, and carry out corresponding researches. This paper summarizes the advantages of MRI and the research progress of MRI linear accelerator (MR-Linac), online guidance, adaptive optimization, and dosimetry-related research. Possible development direction of these technologies in the future is also discussed. It is expected that this review can provide a certain reference value for clinician and related researchers to understand the research progress in the field.

Kilovoltage cone-beam computed tomography imaging dose estimation and optimization: Need of daily cone-beam computed tomography

Aim: The aim of the present study was to access the need of daily cone-beam computed tomography (CBCT) and the requirement of in-house protocols of image acquisition frequency to reduce unnecessary exposure to the patients undergoing radiotherapy treatment. Materials and Methods: The dose delivered during CBCT procedure (On-Board Imager, Trilogy, Varian medical system, Inc., Palo Alto, California) was assessed for pelvic and head and neck region. For dose estimation, cylindrical polymethyl methacrylate phantoms of 15 cm length, 16 cm, and 32 cm diameter were used to simulate the patient's head and neck and pelvic region thickness, respectively. More than 10 cm scatterer was added on either end of this phantom. Calibrated Ionization chamber DCT10 LEMO SN 1685 iba, dosimetry, Germany (10 cm active length) was used to measure the dose Index. The doses known as cone-beam dose index (CBDI100) were estimated for all the scanning protocols (kV and mAs setting) available on the machine. In this study, image acquisition frequency to correct the setup error was optimized. In-house protocol for image acquisition frequency during treatment has been suggested to reduce the dose. It was based on the principle of as low as reasonable achievable. Results: Optimized dose protocol observed was the “standard dose head” for which the CBDI100 was 2.43 mGy. Whereas for pelvic imaging, single protocol of 125 kV, 80 mA was available by which a dose of 7.61 mGy is likely to be received by the patient during scan. Maximum shift of 6 mm in lateral direction was observed to the patient of Pelvis region and 5 mm was observed in the longitudinal direction for the H and N patients. Angular shift measured in patient position was 3.8° and 3.1° for H and N and pelvic region, respectively. Conclusion: Three consecutive-day CBCT-imaging at the beginning of the treatment followed by once weekly CBCT and two-dimensional (2D) imaging in remaining days of treatment can be an optimized way of imaging for the patient having malignancy in the region of pelvic and abdomen. For H and N, once in a week, CBCT with standard dose head protocol, followed by 2D-imaging in remaining days can be an optimized way of imaging.

Application of CT image registration in the radiotherapy of uterine cervical neoplasms based on 3D Slicer software / 肿瘤研究与临床

Objective To investigate the application of CT image and cone beam computed tomography (CBCT) image registration based on 3D Slicer software in image-guided radiotherapy for uterine cervical neoplasms. Methods Based on 3D Slicer software and Slicer RT toolkit, 10 positioning CT images and 50 CBCT images of 10 patients with uterine cervical neoplasms in Henan Provincial People's Hospital between January 2018 and October 2018 had rigid registration and b-spline deformation registration respectively. The dice similarity coefficient (DSC) and Hausdorff distance (HD) of the bladder, rectum, femoral head, spinal cord, and body of CT-CBCT images were compared by using paired t-test before and after the registration. Results Pre-registration, rigid registration and after b-spline deformation registration of CT images and CBCT images, the DSC in the bladder (0.459±0.177, 0.528±0.184, 0.542±0.187, respectively), the rectum (0.564±0.141, 0.632±0.091, 0.684±0.097, respectively), the femoral head (0.695±0.088, 0.833± 0.030, 0.865±0.027, respectively), the spinal cord (0.587±0.119, 0.746±0.085, 0.834±0.032, respectively) and the body surface (0.922±0.013, 0.948±0.011, 0.959±0.009, respectively) showed an increased trend; HD in the bladder (12.8±7.2, 12.2±7.1, 11.7±7.3, respectively), the rectum (5.0±1.8, 4.4±1.2, 3.4±1.2, respectively), the femoral head (3.6±1.2, 1.8±0.5, 1.5 ±0.5, respectively), the spinal cord (4.0 ±1.0, 2.7 ±1.3, 1.8 ±0.5, respectively) and the body surface (6.3±2.1, 5.2±2.0, 4.3±2.0, respectively) showed a decreased trend. The differences of pairwise comparison in the same parts were statistically significant (all P < 0.05). Conclusions Both rigid registration and b-spline deformation registration of CT-CBCT images based on 3D Slicer softwarecan improve the radiotherapy accuracy of uterine cervical neoplasms, and b-spline deformation registration has more significant advantages.

Efficacy and dosimetry analysis of image-guided radioactive ¹²⁵I seed implantation as salvage treatment for pelvic recurrent cervical cancer after external beam radiotherapy / 부인종양

OBJECTIVE: To investigate the efficacy of image-guided radioactive 125I seed (IGRIS) implantation for pelvic recurrent cervical cancer (PRCC) after external beam radiotherapy (EBRT), and analyze the influence of clinical and dosimetric factors on efficacy. METHODS: From July 2005 to October 2015, 36 patients with PRCC received IGRIS. We evaluated local progression-free survival (LPFS) and overall survival (OS). RESULTS: The median follow up was 11.5 months. The 1- and 2-year LPFS rate was 34.9% and 20%, respectively. The multivariate analysis indicated recurrence site (central or pelvic wall) (hazard ratio [HR]=0.294; 95% confidence interval [CI]=0.121–0.718), lesion volume (HR=2.898; 95% CI=1.139–7.372), D 90 (HR=0.332; 95% CI=0.130–0.850) were the independent factors affecting LPFS. The 1- and 2-year OS rate was 52.0% and 19.6%, respectively. The multivariate analysis suggested pathological type (HR=9.713; 95% CI=2.136–44.176) and recurrence site (HR=0.358; 95% CI=0.136–0.940) were the independent factors affecting OS. The dosimetric parameters of 33 patients mainly included D 90 (128.5±47.4 Gy), D 100 (50.4±23.7 Gy) and V 100 (86.7%±12.9%). When D 90 ≥105 Gy or D 100 ≥55 Gy or V 100 ≥91%, LPFS was extended significantly, but no significant difference for OS. The 79.2% of 24 patients with local pain were suffering from pain downgraded after radioactive 125I seed implantation. CONCLUSION: IGRIS implantation could be a safe and effective salvage treatment for PRCC after EBRT, which could markedly release the pain. Recurrence site, tumor volume and dose were the main factors affected efficacy. Compared with central recurrence, it was more suitable for patients with pelvic wall recurrent cervical cancer after EBRT.

Analysis of influencing factors of intrafractional positioning errors in the hypofractionated radiotherapy for pulmonary tumors / 中华放射肿瘤学杂志

Objective Image-guided radiation therapy(IGRT)was performed to investigate the intrafractional body motion and identify the relevant influencing factors during hypofractionated radiotherapy for malignant pulmonary tumors. Methods A total of ninety-six patients with malignant pulmonary tumors receiving hypofractionated radiotherapy in Jiangsu Cancer Hospital were enrolled in this clinical trial. The kilo-voltage cone beam CT(kV-CBCT)was acquired prior to each fraction and matched to the planning CT images to correct the set-up errors. CBCT was performed immediately after the end of treatment to evaluate the intrafractional variation in the mediolateral,anteroposterior and craniocaudal dimensions.The relationship between relevant influencing factors and intrafractional variation was analyzed using multivariate linear regression. Results In the anteroposterior and craniocaudal directions,the intrafractional positioning errors were reduced along with the increase of ordinal number of fraction(P= 0.000). In the mediolateral direction, the intrafractional positioning errors were increased along with the longer duration of hypofractionated radiotherapy(P=0.010).The intrafractional positioning errors were decreased over larger body weight(P=0.003).The intrafractional positioning errors were significantly increased when vacuum bag and thermoplastic film were utilized for fixation(P= 0.009). Conclusions Certain intrafractional positioning errors occur during hypofractionated radiotherapy. Relevant influencing factors differ in different directions. Relevant influencing factors should be modified to reduce intrafractional positioning variation and improve the treatment accuracy.

Strategic application of radiotherapy for hepatocellular carcinoma

With increasing clinical use, radiotherapy (RT) has been considered reliable and effective method for hepatocellular carcinoma (HCC) treatment, depending on extent of disease and patient characteristics. RT for HCC can improve therapeutic outcomes through excellent local control, downstaging, conversion from unresectable to resectable status, and treatments of unresectable HCCs with vessel invasion or multiple intrahepatic metastases. In addition, further development of modern RT technologies, including image-guided radiotherapy (IGRT), intensity-modulated radiotherapy (IMRT), and stereotactic body radiotherapy, has expanded the indication of RT. An essential feature of IGRT is that it allows image guidance therapy through in-room images obtained during radiation delivery. Compared with 3D-conformal RT, distinctions of IMRT are inverse treatment planning process and use of a large number of treatment fields or subfields, which provide high precision and exquisitely conformal dose distribution. These modern RT techniques allow more precise treatment by reducing inter- and intra-fractional errors resulting from daily changes and irradiated dose at surrounding normal tissues. More recently, particle therapy has been actively investigated to improve effectiveness of RT. This review discusses modern RT strategies for HCC, as well as optimal selection of RT in multimodal approach for HCC.

A study on the set-up accuracy by using body plate with vacuum cushion and thermoplastic mask technique in comparison with the conventional arm support technique in thoracic tumor radiotherapy / 中国癌症杂志

Background and purpose: Radiation therapy has entered the era of precise radiotherapy. Set-up error becomes important factor affecting the effects of radiotherapy. The aim of this study was to analyze the set-up accuracy of the in-house developed technique of body plate with vacuum cushion and thermoplastic mask (Group A) and the conventional technique of arm support (Group B) in thoracic tumor radiotherapy. Methods: A total of 19 patients with thoracic tumor were enrolled in this study and randomly separated into Group A and Group B. The patients of Group A underwent the secondary set-up: align the marker on vacuum cushion and patient's body to the room laser, cover the patient's body with thermoplastic mask and align the marker on the mask to the room laser. The patients of Group B were directly setup by aligning the marker on the patient's body to the room laser. The kilo-voltage cone beam computed tomography (KV-CBCT) was performed on each patient to collect the pre- and post-treatment CBCT images. The CBCT images were registered to the planning CT to analyze the translational error of Group A and Group B. Results: The pre-treatment set-up errors of Group A vs Group B were (1.06±0.58) vs (1.82±0.82) mm in left and right (LR) direction, (1.31±0.40) vs (2.18±1.20) mm in superior and inferior (SI) direction, and (1.28±0.66) vs (2.94±1.81) mm in anterior and posterior (AP) direction. The post-treatment set-up errors of Group A vs Group B were (0.86±0.54) vs (1.29±0.58) mm in LR direction, (1.07±0.58) vs (1.08±0.45) mm in SI direction, and (0.98±0.53) vs (1.56±0.63) mm in AP direction.Conclusion: The in-house developed immobilization technique of body plate with vacuum cushion and thermoplastic mask was more accurate and reproducible than the conventional immobilization technique of arm support in thoracic tumor radiotherapy.

The feasibility of breath control management guided stereotactic ablation body radiotherapy of liver tumors by volumetric modulated arc therapy / 中华放射医学与防护杂志

Objective To investigate the feasibility and plan quality of the image-guided volumetric modulated arc therapy (VMAT) based voluntary deep exhale breath-holding technique in the stereotactic ablative body radiotherapy (SABR) for liver tumors.Methods Fifteen patients with liver tumors were involved in this study.All patients were immobilized with voluntary deep exhale breath hold (vDEBH) combined with real-time position management (RPM) respiratory gating system.Treatment was planned using VMAT with 2 modified partial arc and re-planned using intensity modulated radiation therapy (IMRT) technique for comparison.Dosimetric parameters were calculated for plan quality assessment.Quality assurance studies included absolute dose and multiple planar dose verifications,total monitor units and delivery time analysis.Daily cone beam computed tomography imaging was used to verify the motions.Results There were no significant dosimetric differences between VMAT and conventional IMRT plans (P ＞0.05).Both techniques were able to minimize doses to organs at risk including normal liver,kidneys,spinal cord,and stomach.However,the average monitor units with VMAT were significantly lower 28.1％ than those with IMRT(t =3.064,P ＜0.05).The average beam-on time in VMAT plans was 31.6％ shorter than that in IMRT plans(t =2.278,P ＜ 0.05).Conclusions The utilization of VMAT in the treatment planning of SABR for liver tumors under breath control mode has better dosimetrics.In comparison to conventional IMRT plans,VMAT plans have higher efficiency and feasibility.

Half-Fan-Based Intensity-Weighted Region-of-Interest Imaging for Low-Dose Cone-Beam CT in Image-Guided Radiation Therapy / 대한의료정보학회지

OBJECTIVES: With the increased use of computed tomography (CT) in clinics, dose reduction is the most important feature people seek when considering new CT techniques or applications. We developed an intensity-weighted region-of-interest (IWROI) imaging method in an exact half-fan geometry to reduce the imaging radiation dose to patients in cone-beam CT (CBCT) for image-guided radiation therapy (IGRT). While dose reduction is highly desirable, preserving the high-quality images of the ROI is also important for target localization in IGRT. METHODS: An intensity-weighting (IW) filter made of copper was mounted in place of a bowtie filter on the X-ray tube unit of an on-board imager (OBI) system such that the filter can substantially reduce radiation exposure to the outer ROI. In addition to mounting the IW filter, the lead-blade collimation of the OBI was adjusted to produce an exact half-fan scanning geometry for a further reduction of the radiation dose. The chord-based rebinned backprojection-filtration (BPF) algorithm in circular CBCT was implemented for image reconstruction, and a humanoid pelvis phantom was used for the IWROI imaging experiment. RESULTS: The IWROI image of the phantom was successfully reconstructed after beam-quality correction, and it was registered to the reference image within an acceptable level of tolerance. Dosimetric measurements revealed that the dose is reduced by approximately 61% in the inner ROI and by 73% in the outer ROI compared to the conventional bowtie filter-based half-fan scan. CONCLUSIONS: The IWROI method substantially reduces the imaging radiation dose and provides reconstructed images with an acceptable level of quality for patient setup and target localization. The proposed half-fan-based IWROI imaging technique can add a valuable option to CBCT in IGRT applications.

Margins of planning target volume in cervix cancer with tomotherapy / 中华放射医学与防护杂志

Objective To determine the margins of planning target volume (MPTV) in primary cervical cancer patients with tomotherapy and evaluate the importance of automatic registration(AR) plus manual registration.Methods The setup errors of 29 primary cervical cancer patients receiving external radiation from June 2012 to Dec 2014 were measured by megavoltage computed tomography (MVCT),which were performed at least two times weekly before treatment and were registered with the planning CT.The setup errors between automatic registration and total shift (TS) including both AR and manual registration were compared MPTV was calculated.Results Setup errors were collecte from 443 sets of MVCT in 29 patients.AR and total shift (TS) values in the x,y,z directions and rotation angle were (-0.9±2.3),(0.0±3.1),(1.0±2.6) mm,0.2° ±0.8° and (-0.8±1.8),(-0.4±3.4),(l.4 ± 2.5) mm,0.1° ± 0.5°,respectively.There were statistically significant differences between the two groups in all directions except for the x axis (t =5.1,-5.2,3.2,P ＜ 0.05).MPTV were 4.6,5.7,3.3 mm in the x,y,z directions,respectively.Conclusions Manual registration is necessary after automatic registration in cervical cancer patients with tomotherapy.For patients with cervical cancer treated by tomotherapy,planning target volume MPTV parameters are suggested to be 5,6,4 mm in the x,y,z directions.

Establishment of quality control evaluation system for 3D-ultrasound-based image-guided radiotherapy / 中华放射肿瘤学杂志

Objective To analyze the stability and accuracy of the equipment for three-dimensional ultrasound-based image-guided radiation therapy (3DUS-IGRT) in daily practice, and to provide a basis for clinical application of radiotherapy for soft tissue tumors.Methods A specific calibration phantom was used for continuous calibration and quality control of the 3DUS-IGRT equipment in a year.The method for daily quality control of ultrasound-guided equipment was explored, and its stability and accuracy were monitored.Results The phantom position errors in both Sim and Guide stations of the 3DUS-IGRT equipment were within 1 mm.Conclusions The 3DUS-IGRT equipment has a stable performance with the support of a complete set of stringent and accurate calibration and quality control, which provides a new image-guided method for precise radiotherapy for soft tissue tumors.

Re-irradiation of unresectable recurrent head and neck cancer: using Helical Tomotherapy as image-guided intensity-modulated radiotherapy

PURPOSE: Re-irradiation (re-RT) is considered a treatment option for inoperable locoregionally recurrent head and neck cancer (HNC) after prior radiotherapy. We evaluated the efficacy and safety of re-RT using Helical Tomotherapy as image-guided intensity-modulated radiotherapy in recurrent HNC. MATERIALS AND METHODS: Patients diagnosed with recurrent HNC and received re-RT were retrospectively reviewed. Primary endpoint was overall survival (OS) and secondary endpoints were locoregional control and toxicities. RESULTS: The median follow-up period of total 9 patients was 18.7 months (range, 4.1 to 76 months) and that of 3 alive patients was 49 months (range, 47 to 76 months). Median dose of first radiotherapy and re-RT was 64.8 and 47.5 Gy10. Median cumulative dose of the two courses of radiotherapy was 116.3 Gy10 (range, 91.8 to 128.9 Gy10) while the median interval between the two courses of radiation was 25 months (range, 4 to 137 months). The response rate after re-RT of the evaluated 8 patients was 75% (complete response, 4; partial response, 2). Median locoregional relapse-free survival after re-RT was 11.9 months (range, 3.4 to 75.1 months) and 5 patients eventually presented with treatment failure (in-field failure, 2; in- and out-field failure, 2; out-field failure, 1). Median OS of the 8 patients was 20.3 months (range, 4.1 to 75.1 months). One- and two-year OS rates were 62.5% and 50%, respectively. Grade 3 leucopenia developed in one patient as acute toxicity, and grade 2 osteonecrosis and trismus as chronic toxicity in another patient. CONCLUSION: Re-RT using Helical Tomotherapy for previously irradiated patients with unresectable locoregionally recurrent HNC may be a feasible treatment option with long-term survival and acceptable toxicities.

Optimizing Imaging Conditions in Digital Tomosynthesis for Image-Guided Radiation Therapy / 의학물리

Cone-beam digital tomosynthesis (CBDT) has greatly been paid attention in the image-guided radiation therapy because of its attractive advantages such as low patient dose and less motion artifact. Image quality of tomograms is, however, dependent on the imaging conditions such as the scan angle (beta(scan)) and the number of projection views. In this paper, we describe the principle of CBDT based on filtered-backprojection technique and investigate the optimization of imaging conditions. As a system performance, we have defined the figure-of-merit with a combination of signal difference-to-noise ratio, artifact spread function and floating-point operations which determine the computational load of image reconstruction procedures. From the measurements of disc phantom, which mimics an impulse signal and thus their analyses, it is concluded that the image quality of tomograms obtained from CBDT is improved as the scan angle is wider than 60 degrees with a larger step scan angle (Delta beta). As a rule of thumb, the system performance is dependent on . If the exact weighting factors could be assigned to each image-quality metric, we would find the better quantitative imaging conditions.

The treatment of primary and metastatic renal cell carcinoma (RCC) with image-guided stereotactic body radiation therapy (SBRT)

Purpose: Brain metastases from renal cell carcinoma (RCC) have been successfully treated with stereotactic radiosurgery (SRS). Metastases to extra-cranial sites may be treated with similar success using stereotactic body radiation therapy (SBRT), where image-guidance allows for the delivery of precise high-dose radiation in a few fractions. This paper reports the authors’ initial experience with image-guided SBRT in treating primary and metastatic RCC. Materials and methods: The image-guided Brainlab Novalis stereotactic system was used. Fourteen patients with 23 extra-cranial metastatic RCC lesions (orbits, head and neck, lung, mediastinum, sternum, clavicle, scapula, humerus, rib, spine and abdominal wall) and two patients with biopsy-proven primary RCC (not surgical candidates) were treated with SBRT (24-40 Gy in 3-6 fractions over 1-2 weeks). All patients were immobilised in body cast or head and neck mask. Image-guidance was used for all fractions. PET/CT images were fused with simulation CT images to assist in target delineation and dose determination. SMART (simultaneous modulated accelerated radiation therapy) boost approach was adopted. 4D-CT was utilised to assess tumour/organ motion and assist in determining planning target volume margins. Results: Median follow-up was nine months. Thirteen patients (93%) who received SBRT to extra-cranial metastases achieved symptomatic relief. Two patients had local progression, yielding a local control rate of 87%. In the two patients with primary RCC, tumour size remained unchanged but their pain improved, and their renal function was unchanged post SBRT. There were no significant treatment-related side effects. Conclusion: Image-guided SBRT provides excellent symptom palliation and local control without any significant toxicity. SBRT may represent a novel, non-invasive, nephron-sparing option for the treatment of primary RCC as well as extra-cranial metastatic RCC.

On-line Setup for Lung Cancer Patient in Stereotactic Radiation Surgery using CBCT

PURPOSE: On-line setup procedure was performed before treatment for lung cancer patient for stereotactic radiation surgery (SRS) using recently introduced Cone Beam CT. MATERIALS AND METHODS: Cone Beam CT was performed for 10 patients who did SRS during 18 July and 1 September, 2006 using On Board Imager (OPB) system made by Varian, USA. The treatment position of patient was corrected comparing Images obtaining from CBCT and used in treatment planning. RESULTS: Comparing the CBCT images and CT images used in treatment planning, the movement of the couch is 2.3+/-2.3 mm, 1.8+/-2.8 mm, 0.3+/-3.5 mm for vertical, lateral, and longitudinal direction. It took about 1 hr for conventional treatment procedure in image acquisition of CT before treatment and image registration. But it took about 4~7 minute in on-line setup using CBCT (1~2 min for image acquisition using CBCT, 2~3 min for CT reconstruction of 2.5 mm slice thickness, 1~2 min for on-line setup using image registration). CONCLUTION: The accurate treatment could be performed after tumor localization for SRS using CBCT images. And the consumed time for tumor localization was reduced significantly.