Three-dimensional Treatment Planning System Research Articles

Study on esophageal cancer radiotherapy dosimetry and position verification for volumetric modulated arc therapy

BackgroundThis study analyzed the respective advantages and disadvantages by comparing volumetric modulated arc therapy (VMAT) and intensity modulated radiotherapy (IMRT) on the dose distribution and position verification distribution characteristics in esophageal cancer radiotherapy, in order to provide the reference for the clinical radiotherapy technology optimization of esophageal cancer. MethodsA total of 56 cases of patients with esophageal cancer were selected and applied to the Pinnacle three-dimensional radiation treatment planning system (TPS), in order to design a VMAT plan and IMRT plan under the guidance of image-guided radiotherapy (IGRT). The dosimetry and position verification difference were compared between the two groups. ResultsRevealed that the target dose distribution of the VMAT plan and IMRT plan meets the requirements in clinical dosimetry for all 56 patients in this study. Under the premise of similar target coverage, the conformal index (CI) of the VMAT plan, homogeneity index (HI), target volume, BODY-PTV radiated volume and spinal cord Dmax, bilateral lung V5, V20 and mean lung dose (MLD), monitor unit (MU) and treatment time (TT), as well as position verification and others, were obviously superior to those in the IMRT plan; and the difference was statistically significant. ConclusionCBCT guided VMAT is a potential effective treatment for esophageal cancer and may be more effective and safer than IMRT.

An Inverse Dose Optimization Algorithm for Three-Dimensional Brachytherapy.

PurposeTo investigate an implementation method and the results of an inverse dose optimization algorithm, Gradient Based Planning Optimization (GBPO), for three-dimensional brachytherapy.MethodsThe GBPO used a quadratic objective function, and a dwell time modulation item was added to the objective function to restrict the dwell time variance. We retrospectively studied 4 cervical cancer patients using different applicators and 15 cervical cancer patients using the Fletcher applicator. We assessed the plan quality of GBPO by isodose lines for the patients using different applicators. For the 15 patients using the Fletcher applicator, we utilized dose-volume histogram (DVH) parameters of HR-CTV (D100%, V150%) and organs at risk (OARs) (D0.1cc, D1cc, D2cc) to evaluate the difference between the GBPO plans and the IPSA (Inverse Planning Simulated Annealing) plans, as well as the GBPO plans and the Graphic plans.ResultsFor the 4 patients using different applicators, the dose distributions are conformable. For the 15 patients using the Fletcher applicator, when the dwell time modulation factor (DTMF) is less than 20, the dwell time deviation reduces quickly; however, after the DTMF increased to 100, the dwell time deviation has no remarkable change. The difference in dosimetric parameters between the GBPO plans and the IPSA plans is not statistically significant (P>0.05). The GBPO plans have a higher D100% (3.57 ± 0.36, 3.38 ± 0.34; P<0.01) and a lower V150% (55.73 ± 4.06, 57.75 ± 3.79; P<0.01) than those of the Graphic plans. The differences in other DVH parameters are negligible between the GBPO plans and the Graphic plans.ConclusionsThe GBPO plans have a comparable quality as the IPSA plans and the Graphic plans for the studied cervical cancer cases. The GBPO algorithm could be integrated into a three-dimensional brachytherapy treatment planning system after studying more sites.

Comparison of Gamma Index Passing Rate in Several Treatment Planning System Algorithms

The verification of dose calculation algorithm in a new Treatment Planning System (TPS) can be evaluated by comparing the passing rate of the gamma index analysis of the evaluated algorithm and the clinically implemented algorithms. In the present investigation, the gamma index passing rates was investigated as the reference data in the verification of the new three-dimensional TPS. The algorithms which are used in this study are Pencil Beam Convolution (PBC) version 11.0.31 and Anisotropic Analytical Algorithm (AAA) version 11.0.31 in Eclipse v.11 TPS, and Fast Convolution (FC), Adaptive Convolution (AC), and Collapsed-Cone Convolution (CCC) in Pinnacle 3 v.7.6c TPS. The 6 MV X-ray beam configurations were varied in the depth of measurement points, field sizes, source-to-surface distances, and wedge angles. The dose measurement was done using MatriXX Evolution and PTW 2D-array seven29. Then, OmniPro ImRT and Verisoft 3.1 software were chosen to analyze the gamma index from varied gamma criteria (3 %/3mm, 2 %/3mm, 3 %/2mm, and 2 %/2mm). Overall, the passing rate of AAA is the highest rate obtained of all algorithms. For gamma criterion of 2 %/2mm, the passing rate of AAA was 93.18 % ± 7.21 %, the passing rate of PBC was 89.76 % ± 7.21 %, and the passing rate of convolution algorithms was 76.84 % ± 11.10 %. 800x600 Normal 0 false false false EN-US X-NONE X-NONE MicrosoftInternetExplorer4 /* Style Definitions */ table.MsoNormalTable {mso-style-name:Table Normal; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-parent:; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin:0cm; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:10.0pt; font-family:Times New Roman,serif;}

Ultrasound-guided percutaneous microwave ablation assisted by a three-dimensional visualization preoperative treatment planning system for larger adrenal metastasis (D ≥ 4 cm): Preliminary results.

The objective of this study is to assess the clinical effect and safety of ultrasound-guided percutaneous microwave ablation (US-PMWA) assisted by three-dimensional (3D) visualization operative treatment planning system in larger adrenal metastasis (LAM) (D ≥ 4 cm). From Dec 2011 to Dec 2017, 12 consecutive LAM patients with pathologically proven with a mean diameter of 5.2±1.3cm (range 4.1-7.6) were treated. Artificial ascites and thermal monitoring system as ancillary technique were used. The patients were followed up with imagings and complications were recorded. The median follow-up period was 31 months (ranged 6-52 m). All LAM achieved completely ablation according to the 3D planning preoperation. Complete ablation was achieved in 10 (10/12, 83.3%) patients by one session and 2 patients (2/12, 16.7%) by two sessions. Recurrence was detected at the treated site in 3 patients (3/12, 25.0%) at 5, 9, and 13 months after ablation and received another ablation. Progression of metastasis disease at extra-adrenal sites occurred in 9 patients (9/12, 75%). Seven (7/12, 58.3%) patients died during the follow-up period. Therefore, the 1-, 2-, and 3-year local tumor control rates were 83.3%, 75.0%, and 75.0%, and 1-, 2-, 3- and 4-year overall survival rates were 91.7%, 75.0%, 50.0%, and 41.7%, respectively. No severe complications related to ablation occurred, except 3 (3/12, 25%) patients developed hypertension during ablation. US-PMWA assisted by 3D visualization preoperative treatment planning system maybe a safe and efficient therapy for LAM, which could promote ablation precision, improve the clinical outcomes.

Evaluation of Three-dimensional Treatment Planning System (TPS) performance in dose calculation of virtual wedged fields using film dosimetry

Introduction: Nowadays radiotherapy plays an important role in cancer treatment. Different radiotherapy techniques improvement emphasizes on using of the precise ، appropriate and useful algorithms. one of these techniques are wedged which is used in radiotherapy to compensate missing tissues and create a uniform dose distribution in tissues. The Siemens Artiste linear accelerator supports a virtual wedge ، that this wedge creates a dose distribution similar to a physical wedge without the use of any extra accessory and wedged profiles are produced moving collimator jaw during irradiation with a constant speed but varying the dose rate. In this study ، TPS performance is evaluated in virtual wedged fields by comparing the calculated and measured results. Materials and Methods: The calculations were performed by the collapsed cone superposition algorithm based TPS for two tangent fields in anthropomorphic slab phantom using 15، 30، 45، 60 virtual wedges for field size of 20 × 20 cm2 for 6 and 15 MV photon beams. Measurements were produced by Gafchromic EBT films and reading exposed films with scanner. Results: Good agreement between the measured dose with film dosimetry and calculated dose with collapsed cone superposition algorithm based TPS with using virtual wedge in heterogeneous environment and different energies were found ، with the maximum difference not exceed 3 -5%. The increase in wedge angle due to increase in the difference between calculated and measured data. Conclusion: : The results from this study showed that the accuracy of collapsed cone superposition algorithm based TPS used with the virtual wedges for two tangent fields is enough for the clinical usage under the studied experimental conditions.

Ultrasound-guided percutaneous microwave ablation assisted by three-dimensional visualization operative treatment planning system and percutaneous transhepatic cholangial drainage with intraductal chilled saline perfusion for larger hepatic hilum hepatocellular (D ≥ 3 cm): preliminary results.

To assess the clinical efficiency of ultrasound-guided percutaneous microwave ablation (US-PMWA) assisted by three-dimensional (3D) visualization operative treatment planning system and percutaneous transhepatic cholangial drainage with intraductal chilled saline perfusion (PTCD-ICSP) for larger hepatic hilum hepatocellular carcinoma (HH-HCC) (D ≥ 3 cm). The combination therapy was performed in 14 patients from Sep 2011 to May 2017. The major outcomes for assessment were biliary duct complications, local tumor recurrence, distant recurrence and overall survival rates. Median follow-up period was 26 months. The series of 3D visualization operative treatment planning, PTCD-ICSP and US-PMWA were successfully performed and complete ablation was achieved in all cases. The mean session for one tumor was 1.0 ± 0.4. The mean ablation time for per tumor was 1805 ± 567s. The saline volume used for the PTCD-ICSP was 250–450 ml per session. The 1-, 2-, and 3-year local tumor recurrence rates were 7.1%, 14.3%, and 35.7%, the 1-, 2-, and 3-year distant recurrence rates were 0%, 14.3%, and 28.6%, and 1-, 2-, and 3-year overall survival rates were 100%, 92.9%, and 71.4%, respectively. No severe complications related to ablation occurred.ConclusionsUS-PMWA assisted by 3D visualization operative treatment planning system and PTCD-ICSP appears to be a safe, effective and innovative technique for management for larger HH-HCCs, which improved the prognosis.

A three-dimensional visualization preoperative treatment planning system for microwave ablation in liver cancer: a simulated experimental study.

To evaluate the application value of three-dimensional (3D) visualization preoperative treatment planning system (VPTPS) for microwave ablation (MWA) in liver cancer. The study was a simulated experimental study using the CT imaging data of patients in DICOM format in a model. Three students (who learn to interventional ultrasound for less than 1year) and three experts (who have more than 5years of experience in ablation techniques) in MWA performed the preoperative planning for 39 lesions (mean diameter 3.75±1.73cm) of 32 patients using two-dimensional (2D) image planning method and 3D VPTPS, respectively. The number of planning insertions, planning ablation rate, and damage rate to surrounding structures were compared between2D image planning group and 3D VPTPS group. There were fewer planning insertions, lower ablation rate and higher damage rate to surrounding structures in 2D image planning group than 3D VPTPS group for both students and experts. When using the 2D ultrasound planning method, students could carry out fewer planning insertions and had a lower ablation rate than the experts (p<0.001). However, there was no significant difference in planning insertions, the ablation rate, and the incidence of damage to the surrounding structures between students and experts using 3D VPTPS. 3DVPTPS enables inexperienced physicians to have similar preoperative planning results to experts, and enhances students' preoperative planning capacity, which may improve the therapeutic efficacy and reduce the complication of MWA.

A preliminary study of test and clinical application of a physical model based on the three-dimensional dose verification system using electronic portal imaging device

Objective To establish a physical model and optimize its physical parameters using the electronic portable imaging device (EPID) three-dimensional dose verification system, and to prepare it for clinical application. Methods EPID was used to acquire images of 3, 5, 10, 15, 20, and 25 cm square fields for construction of a physical model. The parameters of the physical model were optimized based on the percentage depth dose, total scatter factor, and off-axis ratio at a depth of 10 cm in a homogeneous water phantom. A thimble ionization chamber and radiochromic films were used to measure the point and planar doses for single fields, combined fields, and IMRT plans in a homogenous phantom and a human phantom. The results were compared with those in the three-dimensional reconstruction. In the human phantom and 10 intensity-modulated radiotherapy (IMRT) plans for tumors in different sites, the passing rates under the criteria of 5%/3 mm and 3%/3 mm were compared between three-dimensional reconstruction and treatment planning system (TPS) calculation. The dose and volume analyses were performed on target volume and organs at risk (OARs) in patients. Results For the single fields, combined fields, and IMRT plans, the mean deviations of point dose were less than 0.5% between three-dimensional reconstruction and ionization chamber measurement, and less than 2.0% between three-dimensional reconstruction and TPS calculation. In the homogenous phantom, the human phantom, and patients, the mean passing rates of both two-and three-dimensional doses were higher than 95% under the criteria of 5%/3 mm and 3%/3 mm. In patients, however, OARs with small volume had relatively large dose deviations. Conclusions A series of pre-clinical tests show that the three-dimensional dose verification system is an effective approach for clinical dose verification and holds promise for clinical application. Key words: Electronic portal imaging device; Three-dimensional dose verification; Physical model; Intensity modulated radiation therapy

Combination therapy of three-dimensional (3D) visualisation operative treatment planning system and US-guided percutaneous microwave ablation in larger renal cell carcinomas (D ≥ 4 cm): preliminary results

Purpose: To analyse the clinical outcomes of combination therapy of three-dimensional (3D) visualisation operative treatment planning system and US-guided percutaneous microwave ablation (PMWA) in larger renal cell carcinomas (RCCs) (D ≥ 4 cm).Materials and methods: The results from 20 patients with 20 larger RCCs treated with a 3D visualisation operative treatment planning system and US-guided PMWA were reviewed retrospectively. The patients were followed up by contrast-enhanced images at 1, 3, and 6 months and every 6 months thereafter. The outcomes of overall survival and local tumour progression rate were statistically analysed.Results: The median follow-up period was 26 months. The mean time of ablation for one tumour was 1.1 ± 0.3 sessions. The average number of ablation points of one tumour was 4.5 ± 0.9. The mean output power of ablation was 50.50 ± 2.2 W. The mean time of ablation for one tumour was 1374.4 ± 391.1 s. Artificial ascites was used in 12 (60%) tumours adjacent to the intestinal tract, and thermal monitoring system was used in all tumours (100%). Technical effectiveness and metastasis-free status were achieved in all tumours. The 1- and 2-year local tumour progression rates were both 5%. The cancer-specific survival rate and 2-year overall survival rates were both 100%. No severe major complications occurred. There was no significant difference in creatinine or urea nitrogen before or 3 days after ablation.Conclusions: Combination therapy of 3D visualisation operative treatment planning system and US-guided PMWA appeared to be a safe and effective technique for the management of larger RCCs, which could improve clinical efficacy.

National key research and development program of China: Three-dimensional visible treatment planning system beyond reality and dream

National key research and development program of China: Three-dimensional visible treatment planning system beyond reality and dream

CT-Guided 125I Seed Interstitial Brachytherapy as a Salvage Treatment for Recurrent Spinal Metastases after External Beam Radiotherapy.

The aim of this study is to evaluate the feasibility, safety, and clinical efficacy of CT-guided 125I seed interstitial brachytherapy in patients with recurrent spinal metastases after external beam radiotherapy (EBRT). Between August 2003 and September 2015, 26 spinal metastatic lesions (24 patients) were reirradiated by this salvage therapy modality. Treatment for all patients was preplanned using a three-dimensional treatment planning system 3–5 days before 125I seed interstitial brachytherapy; dosimetry verification was performed immediately after seed implantation. Median actual D 90 was 99 Gy (range, 90–176), and spinal cord median D max was 39 Gy (range, 6–110). Median local control (LC) was 12 months (95% CI: 7.0–17.0). The 6- and 12-month LC rates were 52% and 40%, respectively. Median overall survival (OS) was 11 months (95% CI: 7.7–14.3); 6-month and 1-, 2-, and 3-year OS rates were 65%, 37%, 14%, and 9%, respectively. Pain-free survival ranged from 2 to 42 months (median, 6; 95% CI: 4.6–7.4). Treatment was well-tolerated, with no radiation-induced vertebral compression fractures or myelopathy reported. Reirradiation with CT-guided 125I seed interstitial brachytherapy appears to be feasible, safe, and effective as pain relief or salvage treatment for patients with recurrent spinal metastases after EBRT.

Use of maximum heart distance to evaluate heart dosimetry for tangential field radiotherapy in left-sided breast cancer after modified radical mastectomy

Objective To assess the value of maximum heart distance (MHD) in predicting the dose of tangential field heart irradiation in left-sided breast cancer. Methods A total of 40 left-sided breast cancer patients who were given adjuvant tangential field irradiation on the left chest wall after modified radical mastectomy in our hospital from January 2010 to December 2011 were selected in this study. For each patient, the following parameters were derived using three-dimensional treatment planning system: MHD, mean dose (Dmean) to organs at risk including the whole heart, left anterior descending (LAD) coronary artery, left ventricle (LV) , and anterior myocardial territory (AMT) , thickness of the contralateral breast tissue, and thickness from the sternum to the body surface (measuring body fat). The relationship between MHD and each Dmean was analyzed by curve fitting equation. The reliability of R2> 0.8 represented a good correlation. Results The MHD of 40 patients was between 1.14 and 5.34 cm ((2.66±0.16) cm)). The R2 values of first-, second-, and third-order curve fitting equations were 0.869, 0.875, and 0.883, respectively, between MHD and whole heart Dmean (all P=0.000) ; 0.777, 0.799, and 0.813, respectively, between MDH and AMT Dmean (all P=0.000) ; 0.598, 0.601, and 0.633, respectively, between MHD and LV Dmean (all P=0.000) ;and 0.418, 0.470, and 0.472, respectively, between MHD and Dmean of the LAD coronary artery (all P=0.000). The Dmean of all the heart compartments was not affected by the body fat thickness. Conclusions MHD is a reliable predictor of the mean dose to organs at risk (whole heart and AMT) in tangential field radiotherapy for left-sided breast cancer. Key words: Maximum heart distance; Mean heart dose; Breast neoplasm/radiotherapy

A three-dimensional visualisation preoperative treatment planning system in microwave ablation for liver cancer: A preliminary clinical application

Objectives: The aim of this study was to evaluate the clinical application value of a 3D visualisation preoperative treatment planning system in microwave ablation for liver cancer.Methods: From December 2011 to November 2012, 94 enrolment patients of liver cancer were divided into two groups. The 3D preoperative planning group included 36 patients with 44 lesions, who underwent microwave ablation with the aid of the self-developed 3D visualisation preoperative treatment planning system. The 2D preoperative planning group included 58 patients with 64 lesions, who underwent microwave ablation according to conventional 2D image preoperative planning methods. After microwave ablation, therapeutic efficacy was assessed by contrast-enhanced imaging during follow-up.Results: The 3D preoperative planning group had a higher success rate of first ablation than the 2D preoperative planning group (p = 0.01). There were more sessions in the 2D preoperative planning group than in the 3D preoperative planning group (p = 0.002). There were no significant differences in technique effectiveness rate between the 2D preoperative planning group (96.55%) and the 3D preoperative planning group (100%) according to the contrast-enhanced imaging follow-up after microwave ablation (p = 0.64). There were no significant differences in the rate of LTP between the 2D preoperative planning group and the 3D preoperative planning group (p = 0.64) during 3–12 months follow up (median 6 months).Conclusions: Compared with the 2D preoperative planning group, the 3D preoperative planning group had a higher success rate of first ablation and fewer sessions. Therefore, the 3D visualisation preoperative treatment planning system has a relatively high clinical application value.

Development of a novel treatment planning test for credentialing rotational intensity-modulated radiotherapy techniques in the UK

The increasing use of tomotherapy and volumetric-modulated arc therapy in UK centres will result in more centres choosing to use this technology in a clinical trial setting. The Radiotherapy Trials Quality Assurance (RTTQA) group has developed a new procedure to integrate into the UK intensity-modulated radiotherapy (IMRT) credentialing programme to cover rotational IMRT delivery techniques. A planning test [three-dimensional treatment planning system (3DTPS)] was designed specifically for rotational IMRT techniques. The feasibility of using this test in the credentialing programme for rotational IMRT was validated by 10 experienced UK centres. The study included five centres using Varian RapidArc™ (RA) (Varian Medical Systems, Milpitas, CA), two using Elekta VMAT™ (VMAT) (Elekta Inc., Norcross, GA) and three using helical tomotherapy (HT) plans. Centres were asked to carry out their own in-house quality assurance (QA) for the plans submitted for this study. A survey was sent out to centres aiming to gather information on their experience in undertaking the exercise and their QA results. All centres fulfilled the primary goal by achieving the dose constraints of the primary planning target volume and organ at risk. Seven centres (three RA, one VMAT and three HT plans) were able to fulfil the secondary goal. Among those seven centres, three centres (two RA and one VMAT plans) achieved the tertiary goal. The results of the survey indicated that the 3DTPS test is a clinically relevant and practical planning test to be used. A planning test for rotational therapy techniques was developed for the RTTQA IMRT credentialing programme. This study validated the feasibility of a 3DTPS test to be used as part of a credentialing programme for rotational IMRT techniques in the UK.

Dosimetric comparison of different inhomogeneity correction algorithms for external photon beam dose calculations

Dose calculation algorithm is one of the main sources of uncertainty in the radiotherapy sequences. The aim of this study was to compare the accuracy of different inhomogeneity correction algorithms for external photon beam dose calculations. The methodology was based on International Atomic Energy Agency TEC-DOC 1583. The phantom was scanned in every center, using computed tomography and seven tests were planned on three-dimensional treatment planning systems (TPSs). The doses were measured with ion chambers and the deviation between measured and TPS calculated dose was reported. This methodology was tested in five different hospitals which were using six different algorithms/inhomogeneity correction methods implemented in different TPSs. The algorithms in this study were divided into two groups: Measurement-based algorithms (type (a)) and model-based algorithms (type (b)). In type (a) algorithms, we saw 7.6% and 11.3% deviations out of agreement criteria for low- and high-energy photons, respectively. While in type (b) algorithms, these values were 4.3% and 5.1%, respectively. As a general trend, the numbers of measurements with results outside the agreement criteria increase with the beam energy and decrease with advancement of TPS algorithms. More advanced algorithm would be preferable and therefore should be implanted in clinical practice, especially for calculation in inhomogeneous medias like lung and bone and for high-energy beams calculation at low depth points.

Left Breast Cancer Treated in Isocentric Lateral Decubitus (ILD) Position: An Alternative Technique Sparing Organs at Risk (OAR)

Purpose : This study was designed to evaluate the doses delivered to two main organs at risk (OAR): the heart and left lung. Materials and Methods : Field design is as follows: the upper border is situated above the upper limit of the breast; the medial border is in the midline, adapted to the individual patient’s anatomy. The lateral (posterior) border is placed 1-2 cm beyond any palpable breast tissue. The inferior border is 1-2 cm below the inframammary fold. This field design allows the treatment of the whole breast, defined clinically by palpation plus a 1-2 cm margin. The isocenter is placed at mid-thickness of the flattened breast. For the medial field, the gantry is usually inclined up to 10°. A simulator computed tomography (CT) scan (Toshiba LB Aquilion) is used to perform localization films of both fields and several CT slices. The CT images are transferred to the Eclipse three-dimensional (3D) treatment planning system allowing graphic verification of the beam position. Using virtual simulation, two medial and lateral isocentric tangential beams with matching posterior borders are set up. In all patients, the breast volume, heart and lung were delineated and dose-volume histograms (DVH) were evaluated. Day-to-day reproducibility was easily verified by using the distance from the top of the treated breast to the corner of the epoxy disposer. Weekly portal imaging controls of both fields were performed in all patients. Individual dosimetric planning was performed with Eclipse V10 software (Varian) and a photon_AAA_100282 algorithm (calculated grid size: 0.25 cm). Results : From March 2012 to February 2013, fifty consecutive patients with early left breast cancer were studied: 33 received a total dose of 66 Gy dose /33 fractions (50 Gy to the breast and 16 Gy boost to the tumor bed), 17 pts received a dose of 41.6 Gy/13 fractions/ 5 weeks. In the 33 pts who received a total dose of 66 Gy, the heart received a mean dose of 1.71 Gy [1.28;2.69] . In the 17 pts who received a total dose of 41.6 Gy, the heart received a mean dose of 0.77 Gy [0.33;1.60]. In the 33 pts who received a total dose of 66 Gy, the lung received a mean dose of 0.97 Gy [0.57;1.61]. In the 17 pts who received a total dose of 41.6 Gy, the lung received a mean dose of 0.71 Gy [0.23;1.90]. Conclusions : Irradiation of the heart and lungs is extremely low in the lateral position using the 3D isocentric technique, despite the good coverage of the breast. This technique appears to be associated with a limited risk of heart and lung complications.

Analysis of the rule of lymph node metastasis and evaluation of the consistence of preoperative computed tomographic findings and postoperative pathologic diagnosis for thoracic esophageal carcinoma

Objective To analyze the rule of lymph node metastasis, compare the preoperative computed tomographic findings with pathological diagnosis in thoracic esophageal carcinoma and to evaluate the clinical value. Methods Six hundred and eighteen patients with esophageal carcinoma after radical resection were enrolled. All patients did not receive any preoperative radiotherapy or chemotherapy, having complete information of postoperative pathological reports. CT scanning were applied to all patients in our hospital. The CT image were transmitted to the three-dimensional treatment planning system via the network at digital format and be reconstructed. In which system the sensitivity, specificity and accuracy rates in diagnosis of lymph node metastasis of the preoperative CT image were observed, measured and recorded. x2 test or Fisdher's statistical methods was adopted for comparing the concord rate of preoperative CT scanning with postoperative pathological diagnosis. Results Lymph nodes metastasis were defected in 242 of the 618 treated patients(39.2%), The rate of lymph node metastasis present in lower neck, upper-mediastinum,middle-mediastinum, lower-mediastinum, and superior abdomen regions in upper-thoracic esophageal carcinoma were 3.2% ,20.8% ,6.4% ,2.4% and 8.0%, in middle-thoracic esophageal carcinoma 1.5%,7.8% ,22.0% ,3.5% and 22.8%, and in lower-thoracic esophageal carcinoma 0% ,2.0% ,21.4% ,6.1% and 32.7%, respectively. The sensitivity, specificity, positive predictive value, negative predictive value,younden index and accuracy rates of diagnosis of lymph node metastasis with preoperative CT scan were 58.3%, 70.7%, 56.2%, 72.5%, 29.0% and 65.9%, respectively. The concordance rate of 0, 1, 2 and ≥ 3 lymph node metastasis by preoperative CT scanning with postoperative pathological diagnosis were 72.4%, 32.2% , 58.3% and 73.1%, respectively in whole group(x2 = 82. 61, P = 0.000). The concordance rate of no lymph node metastasis by CT scan comparing with that by postoperative pathological diagnosis was higher than that of the 1 lymph node metastasis in upper-thoracic esophageal carcinoma 3 lymph node metastasis were 71.1%, 30.1%, 55.6% and 77.8%, respectively(x2 =55.14,P =0.000.Conclusions Preoperative CT image can accurately predict the distribution patterns of the lymph node metastasis in esophageal carcinoma. The concordance rate was the highest in diagnosis of 0 and ≥3 lymph node metastasis, the lowest in diagnosis of one lymph node metastasis. These findings are valuable for definition of the target range of radiotherapy after radical resection of esophageal carcinoma. Key words: Esophageal neoplasms, lymph node metastasis; Tomography, X-ray computed; Pathology

Dosimetric evaluation of a three-dimensional treatment planning system

The computerized treatment planning system plays a major role in radiation therapy in delivering correct radiation dose to the patients within ±5% as recommended by the ICRU. To evaluate the dosimetric performance of the Treatment Planning system (TPS) with three-dimensional dose calculation algorithm using the basic beam data measured for 6 MV X-rays. Eleven numbers of test cases were created according to the Technical Report Series-430 (TRS 430) and are used to evaluate the TPS in a homogeneous water phantom. These cases involve simple field arrangements as well as the presence of a low-density material in the beam to resemble an air in-homogeneity. Absolute dose measurements were performed for the each case with the MU calculation given by the TPS, and the measured dose is compared with the corresponding TPS calculated dose values. The result yields a percentage difference maximum of 2.38% for all simple test cases. For complex test cases in the presence of in-homogeneity, beam modifiers or beam modifiers with asymmetric fields a maximum percentage difference of 5.94% was observed. This study ensures that the dosimetric calculations performed by the TPS are within the accuracy of ±5% which is very much warranted in patient dose delivery. The test procedures are simple, not only during the installation of TPS, but also repeated at periodic intervals.

A dosimetric research on radioactive ~(125)I seed plane implantation

Objective To study the dosimetrie effect of different ~(125)I seeds arrangements when implanted at the same number and activity (2.96×10~7 Bq) in a plane. Methods Nine different arrangements of ~(125)I seed plane implantation were established with the three-dimensional treatment planning system (TPS) and the isodose curves of 60, 80, 130, 145 and 200 Gy were figured out. The areas and radius in these isodose curves were calculated with the professional image analysis software. Results The areas and radius in the same isedose curves were dissimilar when the arrangement was different. The arrangements which had the maxima area in the 60, 80, 130, 145 and 200 Gy isodose curves were X1.5Y1.5, X1Y1.5, X1Y1(2)1.5, X1Y1, X1Y1(2) 0.5 with the area of 1641.91, 1166.42,791.09,718.27,474.63 mm~2 respectively. The seeds arrangement with the maximum area in the same isodose curve had a better dose distribution and there were no cold spots in the target. Conclusion The dose and therapeutic effect was influenced significantly by the arrangemeut of the seeds even the number and activity were equal. Key words: ~(125)I seed; Dosiology; Brachytherapy; Isodose distribution

Verification of Varian enhanced dynamic wedge implementation in MasterPlan treatment planning system

This paper investigates the accuracy of the two available calculation algorithms of the Oncentra MasterPlan three‐dimensional treatment planning system (TPS) – the pencil beam method and collapsed‐cone convolution – in modeling the Varian enhanced dynamic wedge (EDW). Measurements were carried out for a dual high energy (6–15 MV) Varian DHX‐S linear accelerator using ionization chambers for beam axis measurements (wedge factors and depth doses), film dosimetry for off‐axis dose profiles measurements, and a diode matrix detector for two dimensional absolute dose distributions. Using both calculation algorithms, different configuration of symmetric and asymmetric fields varying the wedge's angle were tested. Accuracy of the treatment planning system was evaluated in terms of percentage differences between measured and calculated values for wedge factors, depth doses, and profiles. As far as the absolute dose distribution was concerned, the gamma index method (Low et al. (13) ) was used with 3% and 3 mm as acceptance criteria for dose difference and distance‐to‐agreement, respectively. Wedge factors and percentage depth doses were within 1% deviation between calculated and measured values. The comparison of measured and calculated dose profiles shows that the Van Dyk's acceptance criteria (Van Dyk et al. (14) ) are generally met; a disagreement can be noted for large wedge angles and field size limited to the low dose‐low gradient region only. The 2D absolute dose distribution analysis confirms the good accuracy of the two calculation algorithms in modeling the enhanced dynamic wedge.PACS number: 87.53.Bn, 87.55.kn, 87.56.ng