Intensity-modulated photon arc therapy for treatment of pleural mesothelioma

Radiotherapy plays a key role in the definitive or adjuvant management of patients with mesothelioma of the pleural surface. Many patients are referred for radiation with intact lung following biopsy or subtotal pleurectomy. Delivery of efficacious doses of radiation to the pleural lining while avoiding lung parenchyma toxicity has been a difficult technical challenge. Using opposed photon fields produce doses in lung that result in moderate-to-severe pulmonary toxicity in 100% of patients treated. Combined photon-electron beam treatment, at total doses of 4250 cGy to the pleural surface, results in two-thirds of the lung volume receiving over 2100 cGy. We have developed a technique using intensity-modulated photon arc therapy (IMRT) that significantly improves the dose distribution to the pleural surface with concomitant decrease in dose to lung parenchyma compared to traditional techniques. IMRT treatment of the pleural lining consists of segments of photon arcs that can be intensity modulated with varying beam weights and multileaf positions to produce a more uniform distribution to the pleural surface, while at the same time reducing the overall dose to the lung itself. Computed tomography (CT) simulation is critical for precise identification of target volumes as well as critical normal structures (lung and heart). Rotational arc trajectories and individual leaf positions and weightings are then defined for each CT plane within the patient. This paper will describe the proposed rotational IMRT technique and, using simulated isodose distributions, show the improved potential for sparing of dose to the critical structures of the lung, heart, and spinal cord.     

Development of a simultaneous boost IMRT class solution for a hypofractionated prostate cancer protocol

The purpose of this work was to develop a robust technique for planning intensity-modulated radiation therapy (IMRT) for prostate cancer patients who are to be entered into a proposed hypofractionated dose escalation study. In this study the dose escalation will be restricted to the prostate alone, which may be regarded as a concurrent boost volume within the overall planning target volume (PTV). The dose to the prostate itself is to be delivered in 3 Gy fractions, and for this phase of the study the total prostate dose will be 57 Gy in 19 fractions, with 50 Gy prescribed to the rest of the PTV. If acute toxicity results are acceptable, the next phase will escalate doses to 60 Gy in 20 x 3 Gy fractions. There will be 30 patients in each arm. This work describes the class solution which was developed to create IMRT plans for this study, and which enabled the same set of inverse planning parameters to be used during optimization for every patient with minimal planner intervention. The resulting dose distributions were compared with those that would be achieved from a 3D conformal radiotherapy (3DCRT) technique that used a multileaf collimator (MLC) but no intensity modulation to treat the PTV, followed by a sequential boost to raise the prostate to 57 Gy. The two methods were tested on anatomical data sets for a series of 10 patients who would have been eligible for this study, and the techniques were compared in terms of doses to the target volumes and the organs at risk. The IMRT method resulted in much greater sparing of the rectum and bladder than the 3DCRT technique, whilst still delivering acceptable doses to the target volumes. In particular, the volume of rectum receiving the minimum PTV dose of 47.5 Gy was reduced from a mean value of 36.9% (range 23.4% to 61.0%) to 18.6% (10.3% to 29.0%). In conclusion, it was found possible to use a class solution approach to produce IMRT dose escalated plans. This IMRT technique has since been implemented clinically for patients enrolled in the hypofractionated dose escalation study.     

Forward-planned, multiple-segment, tangential fields with concomitant boost in the treatment of breast cancer

We report on the utility of forward-planned, 3-dimensional (3D), multiple-segment tangential fields for radiation treatment of patients with breast cancer. The technique accurately targets breast tissue and the tumor bed and reduces dose inhomogeneity in the target. By decreasing excess dose to the skin and lung, a concomitant boost to the tumor bed can be delivered during the initial treatment, thereby decreasing the overall treatment time by one week. More than 120 breast cancer patients have been treated with this breast conservation technique in our clinic. For each patient, a 3D treatment plan based upon breast and tumor bed volumes delineated on computed tomography (CT) was developed. Segmented tangent fields were iteratively created to reduce “hot spots” produced by traditional tangents. The tumor bed received a concomitant boost with additional conformal photon beams. The final tumor bed boost was delivered either with conformal photon beams or conventional electron beams. All patients received 45 Gy to the breast target, plus an additional 5 Gy to the surgical excision site, bringing the total dose to 50 Gy to the boost target volume in 25 fractions. The final boost to the excision site brought the total target dose to 60 Gy. With minimum follow-up of 4 months and median follow-up of 11 months, all patients have excellent cosmetic results. There has been minimal breast edema and minimal skin changes. There have been no local relapses to date. Forward planning of multi-segment fields is facilitated with 3D planning and multileaf collimation. The treatment technique offers improvement in target dose homogeneity and the ability to confidently concomitantly boost the excision site. The technique also offers the advantage for physics and therapy staff to develop familiarity with multiple segment fields, as a precursor to intensity-modulated radiation therapy (IMRT) techniques.     

Forward-planned, multiple-segment, tangential fields with concomitant boost in the treatment of breast cancer

We report on the utility of forward-planned, 3-dimensional (3D), multiple-segment tangential fields for radiation treatment of patients with breast cancer. The technique accurately targets breast tissue and the tumor bed and reduces dose inhomogeneity in the target. By decreasing excess dose to the skin and lung, a concomitant boost to the tumor bed can be delivered during the initial treatment, thereby decreasing the overall treatment time by one week. More than 120 breast cancer patients have been treated with this breast conservation technique in our clinic. For each patient, a 3D treatment plan based upon breast and tumor bed volumes delineated on computed tomography (CT) was developed. Segmented tangent fields were iteratively created to reduce “hot spots” produced by traditional tangents. The tumor bed received a concomitant boost with additional conformal photon beams. The final tumor bed boost was delivered either with conformal photon beams or conventional electron beams. All patients received 45 Gy to the breast target, plus an additional 5 Gy to the surgical excision site, bringing the total dose to 50 Gy to the boost target volume in 25 fractions. The final boost to the excision site brought the total target dose to 60 Gy. With minimum follow-up of 4 months and median follow-up of 11 months, all patients have excellent cosmetic results. There has been minimal breast edema and minimal skin changes. There have been no local relapses to date. Forward planning of multi-segment fields is facilitated with 3D planning and multileaf collimation. The treatment technique offers improvement in target dose homogeneity and the ability to confidently concomitantly boost the excision site. The technique also offers the advantage for physics and therapy staff to develop familiarity with multiple segment fields, as a precursor to intensity-modulated radiation therapy (IMRT) techniques.     

Investigation of Simple IMRT Delivery Techniques for Non-Small Cell Lung Cancer Patients with Respiratory Motion Using 4DCT

Techniques for generating simplified IMRT treatment plans for treating non-small cell lung cancer (NSCLC) patients with respiratory motion were investigated. To estimate and account for respiratory motion, 4-dimensional computed tomography (4DCT) datasets from 5 patients were used to design 5-field 6-MV ungated step-and-shoot intensity modulated radiotherapy (IMRT) plans delivering a dose of 66 Gy to the planning target volume (PTV). For each patient, 2 plans were generated using the mean intensity and the maximum intensity of 10 CT datasets from different breathing phases. The plans also utilized different margins around the clinical target volume/internal target volume (CTV/ITV) to account for tumor motion. To reduce the treatment time and ensure accurate dose delivery to moving targets, the number of intensity levels was minimized while maintaining dose coverage to PTV and minimizing dose to organs at risk (OARs). Dose-volume histograms (DVHs), dosimetric metrics, and outcome probabilities were evaluated for all plans. Plans using the averaged CT image dataset were inferior, requiring larger margins around the PTV, with a maximum of 1.5 cm, to ensure coverage of the tumor, and therefore increased the dose to OARs located in proximity of the tumor. The plans based on superimposed CT image datasets achieved full coverage of the tumor, while allowing tight margins around the PTV and minimizing the dose to OARs. A small number of intensity-levels (3 to 5), resulting in IMRT plans with a total of 13 to 30 segments, were sufficient for homogeneous PTV coverage, without affecting the sparing of OARs. In conclusion, a technique involving treatment planning with the superimposed CT scans of all respiratory phases, and the application of IMRT with only a small number of segments was feasible despite significant tumor motion; however, greater patient numbers are needed to support the statistical significance of the results presented in this work.     

Invers geplante intensitätsmodulierte Strahlenbehandlung bei einer Patientin mit rechtsseitigem Mammakarzinom und Trichterbrust

BACKGROUND: A 44-year old woman with breast cancer was transferred to our institution for irradiation. Due to a pronounced funnel chest no satisfying dose distribution was obtained by conventional techniques. Thus an intensity-modulated radiotherapy (IMRT) based on inverse optimisation was carried out. IMRT was compared to conventional techniques regarding dose distribution and feasibility. PATIENT AND METHODS: Tumor site was in the right middle lower quadrant. Target volume included the right breast and the parasternal lymph nodes. Target dose was 50.4 Gy. Based on inverse optimisation irradiation was carried out in "step-and-shoot"-technique with twelve intensity modulated beams with six intensity steps. Additionally, treatment plans were calculated using conventional techniques (technique A with two tangential wedged 6-MV photon beams, technique B with additional oblique 15-MeV electron portal). We analysed conformality and homogeneity of target volume and dose distribution within normal tissue. RESULTS: Dose conformality was substantially improved by IMRT. Dose homogeneity was slightly decreased compared to technique A. Lung volume irradiated with a dose higher than 20 Gy was reduced from 56.8% with technique A and 40.1% with technique B, respectively to 22.1% with IMRT. Treatment was tolerated well by the patient without relevant side effects. Mean treatment time was 19.5 min. CONCLUSION: The inversely planned IMRT using multiple beam directions is suitable for breast irradiation following breast conserving surgery. In the present case of a woman with funnel chest lung dose was substantially reduced without reduction of target dose. In which was the complex treatment technique leads to a clinically detectable advantage is examined at present, in the context of a study.     

Helical tomotherapy for radiotherapy in esophageal cancer: a preferred plan with better conformal target coverage and more homogeneous dose distribution.

We compare different radiotherapy techniques-helical tomotherapy (tomotherapy), step-and-shoot IMRT (IMRT), and 3-dimensional conformal radiotherapy (3DCRT)-for patients with mid-distal esophageal carcinoma on the basis of dosimetric analysis. Six patients with locally advanced mid-distal esophageal carcinoma were treated with neoadjuvant chemoradiation followed by surgery. Radiotherapy included 50 Gy to gross planning target volume (PTV) and 45 Gy to elective PTV in 25 fractions. Tomotherapy, IMRT, and 3DCRT plans were generated. Dose-volume histograms (DVHs), homogeneity index (HI), volumes of lung receiving more than 10, 15, or 20 Gy (V(10), V(15), V(20)), and volumes of heart receiving more than 30 or 45 Gy (V(30), V(45)) were determined. Statistical analysis was performed by paired t-tests. By isodose distributions and DVHs, tomotherapy plans showed sharper dose gradients, more conformal coverage, and better HI for both gross and elective PTVs compared with IMRT or 3DCRT plans. Mean V(20) of lung was significantly reduced in tomotherapy plans. However, tomotherapy and IMRT plans resulted in larger V(10) of lung compared to 3DCRT plans. The heart was significantly spared in tomotherapy and IMRT plans compared to 3DCRT plans in terms of V(30) and V(45). We conclude that tomotherapy plans are superior in terms of target conformity, dose homogeneity, and V(20) of lung.     

Dosimetric Comparison Between 2-Dimensional Radiation Therapy and Intensity Modulated Radiation Therapy in Treatment of Advanced T-Stage Nasopharyngeal Carcinoma: To Treat Less or More in the Planning Organ-At-Risk Volume of the Brainstem and Spinal Cord

The aim of this study is to evaluate the deficiencies in target coverage and organ protection of 2-dimensional radiation therapy (2DRT) in the treatment of advanced T-stage (T3-4) nasopharyngeal carcinoma (NPC), and assess the extent of improvement that could be achieved with intensity modulated radiation therapy (IMRT), with special reference to of the dose to the planning organ-at-risk volume (PRV) of the brainstem and spinal cord. A dosimetric study was performed on 10 patients with advanced T-stage (T3-4 and N0-2) NPC. Computer tomography (CT) images of 2.5-mm slice thickness of the head and neck were acquired with the patient immobilized in semi-extended-head position. A 2D plan based on Ho’s technique, and an IMRT plan based on a 7-coplanar portals arrangement, were established for each patient. 2DRT was planned with the field borders and shielding drawn on the simulator radiograph with reference to bony landmarks, digitized, and entered into a planning computer for reconstruction of the 3D dose distribution. The 2DRT and IMRT treatment plans were evaluated and compared with respect to the dose-volume histograms (DVHs) of the targets and the organs-at-risk (OARs), tumor control probability (TCP), and normal tissue complication probabilities (NTCPs). With IMRT, the dose coverage of the target was superior to that of 2DRT. The mean minimum dose of the GTV and PTV were increased from 33.7 Gy (2DRT) to 62.6 Gy (IMRT), and 11.9 Gy (2DRT) to 47.8 Gy (IMRT), respectively. The D₉₅ of the GTV and PTV were also increased from 57.1 Gy (2DRT) to 67 Gy (IMRT), and 45 Gy (2DRT) to 63.6 Gy (IMRT), respectively. The TCP was substantially increased to 78.5% in IMRT. Better protection of the critical normal organs was also achieved with IMRT. The mean maximum dose delivered to the brainstem and spinal cord were reduced significantly from 61.8 Gy (2DRT) to 52.8 Gy (IMRT) and 56 Gy (2DRT) to 43.6 Gy (IMRT), respectively, which were within the conventional dose limits of 54 Gy for brainstem and of 45 Gy for spinal cord. The mean maximum doses deposited on the PRV of the brainstem and spinal cord were 60.7 Gy and 51.6 Gy respectively, which were above the conventional dose limits. For the chiasm, the mean dose maximum and the dose to 5% of its volume were reduced from 64.3 Gy (2DRT) to 53.7 Gy (IMRT) and from 62.8 Gy (2DRT) to 48.7 Gy (IMRT), respectively, and the corresponding NTCP was reduced from 18.4% to 2.1%. For the temporal lobes, the mean dose to 10% of its volume (about 4.6 cc) was reduced from 63.8 Gy (2DRT) to 55.4 Gy (IMRT) and the NTCP was decreased from 11.7% to 3.4%. The therapeutic ratio for T3-4 NPC tumors can be significantly improved with IMRT treatment technique due to improvement both in target coverage and the sparing of the critical normal organ. Although the maximum doses delivered to the brainstem and spinal cord in IMRT can be kept at or below their conventional dose limits, the maximum doses deposited on the PRV often exceed these limits due to the close proximity between the target and OARs. In other words, ideal dosimetric considerations cannot be fulfilled in IMRT planning for T3-4 NPC tumors. A compromise of the maximal dose limit to the PRV of the brainstem and spinal cord would need be accepted if dose coverage to the targets is not to be unacceptably compromised. Dosimetric comparison with 2DRT plans show that these dose limits to PRV were also frequently exceeded in 2DRT plans for locally advanced NPC. A dedicated retrospective study on the incidence of clinical injury to neurological organs in a large series of patients with T3-4 NPC treated by 2DRT may provide useful reference data in exploring how far the PRV dose constraints may be relaxed, to maximize the target coverage without compromising the normal organ function.     

Dosimetric Comparison Between 2-Dimensional Radiation Therapy and Intensity Modulated Radiation Therapy in Treatment of Advanced T-Stage Nasopharyngeal Carcinoma: To Treat Less or More in the Planning Organ-At-Risk Volume of the Brainstem and Spinal Cord

The aim of this study is to evaluate the deficiencies in target coverage and organ protection of 2-dimensional radiation therapy (2DRT) in the treatment of advanced T-stage (T3-4) nasopharyngeal carcinoma (NPC), and assess the extent of improvement that could be achieved with intensity modulated radiation therapy (IMRT), with special reference to of the dose to the planning organ-at-risk volume (PRV) of the brainstem and spinal cord. A dosimetric study was performed on 10 patients with advanced T-stage (T3-4 and N0-2) NPC. Computer tomography (CT) images of 2.5-mm slice thickness of the head and neck were acquired with the patient immobilized in semi-extended-head position. A 2D plan based on Ho’s technique, and an IMRT plan based on a 7-coplanar portals arrangement, were established for each patient. 2DRT was planned with the field borders and shielding drawn on the simulator radiograph with reference to bony landmarks, digitized, and entered into a planning computer for reconstruction of the 3D dose distribution. The 2DRT and IMRT treatment plans were evaluated and compared with respect to the dose-volume histograms (DVHs) of the targets and the organs-at-risk (OARs), tumor control probability (TCP), and normal tissue complication probabilities (NTCPs). With IMRT, the dose coverage of the target was superior to that of 2DRT. The mean minimum dose of the GTV and PTV were increased from 33.7 Gy (2DRT) to 62.6 Gy (IMRT), and 11.9 Gy (2DRT) to 47.8 Gy (IMRT), respectively. The D₉₅ of the GTV and PTV were also increased from 57.1 Gy (2DRT) to 67 Gy (IMRT), and 45 Gy (2DRT) to 63.6 Gy (IMRT), respectively. The TCP was substantially increased to 78.5% in IMRT. Better protection of the critical normal organs was also achieved with IMRT. The mean maximum dose delivered to the brainstem and spinal cord were reduced significantly from 61.8 Gy (2DRT) to 52.8 Gy (IMRT) and 56 Gy (2DRT) to 43.6 Gy (IMRT), respectively, which were within the conventional dose limits of 54 Gy for brainstem and of 45 Gy for spinal cord. The mean maximum doses deposited on the PRV of the brainstem and spinal cord were 60.7 Gy and 51.6 Gy respectively, which were above the conventional dose limits. For the chiasm, the mean dose maximum and the dose to 5% of its volume were reduced from 64.3 Gy (2DRT) to 53.7 Gy (IMRT) and from 62.8 Gy (2DRT) to 48.7 Gy (IMRT), respectively, and the corresponding NTCP was reduced from 18.4% to 2.1%. For the temporal lobes, the mean dose to 10% of its volume (about 4.6 cc) was reduced from 63.8 Gy (2DRT) to 55.4 Gy (IMRT) and the NTCP was decreased from 11.7% to 3.4%. The therapeutic ratio for T3-4 NPC tumors can be significantly improved with IMRT treatment technique due to improvement both in target coverage and the sparing of the critical normal organ. Although the maximum doses delivered to the brainstem and spinal cord in IMRT can be kept at or below their conventional dose limits, the maximum doses deposited on the PRV often exceed these limits due to the close proximity between the target and OARs. In other words, ideal dosimetric considerations cannot be fulfilled in IMRT planning for T3-4 NPC tumors. A compromise of the maximal dose limit to the PRV of the brainstem and spinal cord would need be accepted if dose coverage to the targets is not to be unacceptably compromised. Dosimetric comparison with 2DRT plans show that these dose limits to PRV were also frequently exceeded in 2DRT plans for locally advanced NPC. A dedicated retrospective study on the incidence of clinical injury to neurological organs in a large series of patients with T3-4 NPC treated by 2DRT may provide useful reference data in exploring how far the PRV dose constraints may be relaxed, to maximize the target coverage without compromising the normal organ function.     

Superiority of conventional intensity-modulated radiotherapy over helical tomotherapy in locally advanced non-small cell lung cancer

PURPOSE: To compare helical tomotherapy (HT) and conventional intensity-modulated radiotherapy (IMRT) using a variety of dosimetric and radiobiologic indexes in patients with locally advanced non-small cell lung cancer (LA-NSCLC). PATIENTS AND METHODS: A total of 20?patients with LA-NSCLC were enrolled. IMRT plans with 4-6 coplanar beams and HT plans were generated for each patient. Dose distributions and dosimetric indexes for the tumors and critical structures were computed for both plans and compared. RESULTS: Both modalities created highly conformal plans. They did not differ in the volumes of lung exposed to >?20?Gy of radiation. The average mean lung dose, volume receiving ≥?30?Gy, and volume receiving ≥?10?Gy in HT planning were 18.3?Gy, 18.5%, and 57.1%, respectively, compared to 19.4?Gy, 25.4%, and 48.9%, respectively, with IMRT (p?=?0.004, p?相似文献   

Postmastectomy radiotherapy for left-sided breast cancer patients: Comparison of advanced techniques

Postmastectomy radiotherapy (PMRT) has been shown to improve the overall survival for invasive breast cancer patients, and many advanced radiotherapy technologies were adopted for PMRT. The purpose of our study is to compare various advanced PMRT techniques including fixed-beam intensity-modulated radiotherapy (IMRT), non-coplanar volumetric modulated arc therapy (NC-VMAT), multiple arc VMAT (MA-VMAT), and tomotherapy (TOMO). Results of standard VMAT and mixed beam therapy that were published by our group previously were also included in the plan comparisons. Treatment plans were produced for nine PMRT patients previously treated in our clinic. The plans were evaluated based on planning target volume (PTV) coverage, dose homogeneity index (DHI), conformity index (CI), dose to organs at risk (OARs), normal tissue complication probability (NTCP) of pneumonitis, lifetime attributable risk (LAR) of second cancers, and risk of coronary events (RCE). All techniques produced clinically acceptable PMRT plans. Overall, fixed-beam IMRT delivered the lowest mean dose to contralateral breast (1.56 ± 0.4 Gy) and exhibited lowest LAR (0.6 ± 0.2%) of secondary contralateral breast cancer; NC-VMAT delivered the lowest mean dose to lungs (7.5 ± 0.8 Gy), exhibited lowest LAR (5.4 ± 2.8%) of secondary lung cancer and lowest NTCP (2.1 ± 0.4%) of pneumonitis; mixed beam therapy delivered the lowest mean dose to heart (7.1 ± 1.3 Gy) and exhibited lowest RCE (8.6 ± 7.1%); TOMO plans provided the most optimal target coverage while delivering higher dose to OARs than other techniques. Both NC-VMAT and MA-VMAT exhibited lower values of all OARs evaluation metrics compare to standard VMAT. Fixed-beam IMRT, NC-VMAT, and mixed beam therapy could be the optimal radiation technique for certain breast cancer patients after mastectomy.     

The clinical implementation of respiratory-gated intensity-modulated radiotherapy.

The clinical use of respiratory-gated radiotherapy and the application of intensity-modulated radiotherapy (IMRT) are 2 relatively new innovations to the treatment of lung cancer. Respiratory gating can reduce the deleterious effects of intrafraction motion, and IMRT can concurrently increase tumor dose homogeneity and reduce dose to critical structures including the lungs, spinal cord, esophagus, and heart. The aim of this work is to describe the clinical implementation of respiratory-gated IMRT for the treatment of non-small cell lung cancer. Documented clinical procedures were developed to include a tumor motion study, gated CT imaging, IMRT treatment planning, and gated IMRT delivery. Treatment planning procedures for respiratory-gated IMRT including beam arrangements and dose-volume constraints were developed. Quality assurance procedures were designed to quantify both the dosimetric and positional accuracy of respiratory-gated IMRT, including film dosimetry dose measurements and Monte Carlo dose calculations for verification and validation of individual patient treatments. Respiratory-gated IMRT is accepted by both treatment staff and patients. The dosimetric and positional quality assurance test results indicate that respiratory-gated IMRT can be delivered accurately. If carefully implemented, respiratory-gated IMRT is a practical alternative to conventional thoracic radiotherapy. For mobile tumors, respiratory-gated radiotherapy is used as the standard of care at our institution. Due to the increased workload, the choice of IMRT is taken on a case-by-case basis, with approximately half of the non-small cell lung cancer patients receiving respiratory-gated IMRT. We are currently evaluating whether superior tumor coverage and limited normal tissue dosing will lead to improvements in local control and survival in non-small cell lung cancer.     

呼吸门控PET/CT对于肺癌放疗靶区勾画的指导

目的 目的通过对肺部肿瘤进行呼吸门控PET/CT研究,给予肺部肿瘤放疗靶区勾画指导,最终使患者接受合理的照射靶区。 方法 对20个恶性结节进行呼吸门控PET/CT与常规PET/CT采集,比较肺部不同位置结节的平均四维PET体积与三维PET体积的差别,以及平均四维CT体积与三维CT体积的差别。以平均四维体积与三维体积的相对差值作为体积间的差异, 分别从结节位置、运动幅度研究其对四维体积与三维体积的影响。 结果 用两种方法测得的平均四维PET体积比三维PET体积大17.2%。体积相对差值与结节呼吸运动幅度及结节位置有关。下肺和肺门病灶平均四维PET体积与三维PET体积的平均差值为26.5%,远远大于上肺和胸膜病灶的平均差值（2.7%）。当结节呼吸运动幅度大于3 mm时,四维与三维PET体积差值的平均值为24.3%;小于3 mm时,平均值为1.8%。平均四维CT体积比三维CT体积大3.9%,体积差值范围为0.2~5.9 cm3,体积比值为1.10依0.32。只有在下肺,平均四维CT体积明显大于三维CT体积,平均差值为11.3%。 结论 对于靠近肝脾的下肺结节,用平均四维PET勾画肿瘤靶区更精确些;对于肺门周围的结节,考虑平均四维PET体积作为肿瘤靶区;对于上肺和胸膜的结节,建议采用低剂量呼吸门控扫描且已经考虑了呼吸运动的平均四维CT体积勾画靶区。     

Conformal breast irradiation with the arm of the affected side parallel to the body

Purpose

To propose a simple, forward-planned three-dimensional conformal radiotherapy (3D-CRT) technique for breast cancer patients with frozen shoulder.

Materials and methods

A technique is described that avoids lateral beams transmitting through the arm of the affected side. One medial, tangentially applied beam deposits most of the dose. Further beams with little weight are used to attain dose homogeneity. In order to quantify dose distribution and homogeneity in the planning target volume (PTV), as well as the scattered dose in organs at risk (OAR), the parameters D95, D5, D1, mean and median dose were determined for the individual volumes. Intensity-modulated radiotherapy (IMRT) and volumetric modulated arc therapy (VMAT) plans were created in order to compare these with the proposed technique.

Results

The described technique achieved homogenous dose deposition within the PTV. A regimen comprising 25 fractions of 2 Gy prescribed to the PTV resulted in the following dose parameters: PTV(D95): 44.3 Gy, PTV(D5): 52.7 Gy, PTV(D1): 54.8 Gy, PTV(mean): 49.3 Gy and PTV(median): 49.9 Gy. Mean lung dose was 7.0 Gy. The ipsilateral lung received a mean dose of 9.9 Gy. This plan was accepted for treatment. The IMRT and VMAT plans achieved a similar dose distribution in the PTV. These techniques also reduced dose deposition in the OAR.

Conclusion

The proposed 3D-CRT technique allows treatment of breast cancer patients who are not able to raise their arms above their head. Homogenous dose distribution in the PTV was achieved while avoiding lateral beams that transmit through the arm of the affected side. Mean lung dose was comparable to that of the conventional technique using opposed tangential beams. IMRT and VMAT also provide good target dose homogeneity with good sparing of OAR. However, these techniques are more demanding in terms of planning and quality assurance.     

Comparison of conventional and advanced radiotherapy techniques for left-sided breast cancer after breast conserving surgery

Whole breast radiotherapy (WBRT) after breast conserving surgery is the standard treatment to prevent recurrence and metastasis of early stage breast cancer. This study aims to compare seven WBRT techniques including conventional tangential, field-in-field (FIF), hybrid intensity-modulated radiotherapy (IMRT), IMRT, standard volumetric modulated arc therapy (STD-VMAT), noncoplanar VMAT (NC-VMAT), and multiple arc VMAT (MA-VMAT). Fifteen patients who were previously diagnosed with left-sided early stage breast cancer and treated in our clinic were selected for this study. WBRT plans were created for these patients and were evaluated based on target coverage and normal tissue toxicities. All techniques produced clinically acceptable WBRT plans. STD-VMAT delivered the lowest mean dose (1.1 ± 0.3 Gy) and the lowest maximum dose (7.3 ± 4.9 Gy) to contralateral breast, and the second lowest lifetime attributable risk (LAR) (4.1 ± 1.4%) of secondary contralateral breast cancer. MA-VMAT delivered the lowest mean dose to lungs (4.9 ± 0.9 Gy) and heart (5.5 ± 1.2 Gy), exhibited the lowest LAR (1.7 ± 0.3%) of secondary lung cancer, normal tissue complication probability (NTCP) (1.2 ± 0.2%) of pneumonitis, risk of coronary events (RCE) (10.3 ± 2.7%), and LAR (3.9 ± 1.3%) of secondary contralateral breast cancer. NC-VMAT plans provided the most conformal target coverage, the lowest maximum lung dose (46.2 ± 4.1 Gy) and heart dose (41.1 ± 5.4 Gy), and the second lowest LAR (1.8 ± 0.4%) of secondary lung cancer and RCE (10.5 ± 2.8%). MA-VMAT and NC-VMAT could be the preferred techniques for early stage breast cancer patients after breast conserving surgery.     

Dosimetric comparison of helical tomotherapy,volumetric-modulated arc therapy,intensity-modulated radiotherapy,and field-in-field technique for synchronous bilateral breast cancer

Purpose: To compare the dosimetric characteristics of helical tomotherapy (HT), volumetric-modulated arc therapy (VMAT), intensity-modulated radiotherapy (IMRT), and tangential field-in-field technique (FIF) for the treatment of synchronous bilateral breast cancer (SBBC). Methods and Materials: Ten patients with early-stage unilateral breast cancer were selected for simulating the patients with SBBC in this retrospective analysis. Treatment plans with HT, VMAT, IMRT, and FIF were generated for each patient with a total dose of 50.4 Gy in 28 fractions to the target. Plan quality, namely conformity index (CI), homogeneity index (HI), dose-volume statistics of organs at risk (OARs), and beam-on time (BOT), were evaluated. Results: HT plans showed a lower mean heart dose (3.53 ± 0.31Gy) compared with the other plans (VMAT = 5.6 ± 1.36 Gy, IMRT = 3.80 ± 0.76 Gy, and FIF = 4.84 ± 2.13 Gy). Moreover, HT plans showed a significantly lower mean lung dose (p < 0.01) compared with the other plans: mean right lung doses were 6.81 ± 0.67, 10.32 ± 1.04, 9.07 ± 1.21, and 10.03 ± 1.22 Gy and mean left lung doses were 6.33 ± 0.87, 8.82 ± 0.91, 7.84 ± 1.07, and 8.64 ± 0.99 Gy for HT, VMAT, IMRT, and FIF plans, respectively. The mean dose to the left anterior descending artery was significantly lower in HT plans (p < 0.01) than in the other plans: HT = 19.41 ± 0.51 Gy, VMAT = 25.77 ± 7.23 Gy, IMRT = 27.87 ± 6.48 Gy, and FIF = 30.95 ± 10.17 Gy. FIF plans showed a worse CI and HI compared with the other plans. VMAT plans showed shorter BOT (average, 3.9 ± 0.2 minutes) than did HT (average, 11.0 ± 3.0 minutes), IMRT (average, 6.1 ± 0.5 minutes), and FIF (average, 4.6 ± 0.7 minutes) plans. Conclusions: In a dosimetric comparison for SBBC, HT provided the most favorable dose sparing of OARs. However, HT with longer BOT may increase patient discomfort and treatment uncertainty. VMAT enabled shorter BOT with acceptable doses to OARs and had a better CI than did FIF and IMRT.     

Larynx-sparing techniques using intensity-modulated radiation therapy for oropharyngeal cancer

The purpose of the current study was to explore whether the laryngeal dose can be reduced by using 2 intensity-modulated radiation therapy (IMRT) techniques: whole-neck field IMRT technique (WF-IMRT) vs. junctioned IMRT (J-IMRT). The effect on planning target volumes (PTVs) coverage and laryngeal sparing was evaluated. WF-IMRT technique consisted of a single IMRT plan, including the primary tumor and the superior and inferior neck to the level of the clavicular heads. The larynx was defined as an organ at risk extending superiorly to cover the arytenoid cartilages and inferiorly to include the cricoid cartilage. The J-IMRT technique consisted of an IMRT plan for the primary tumor and the superior neck, matched to conventional antero-posterior opposing lower neck fields at the level of the thyroid notch. A central block was used for the anterior lower neck field at the level of the larynx to restrict the dose to the larynx. Ten oropharyngeal cancer cases were analyzed. Both the primary site and bilateral regional lymphatics were included in the radiotherapy targets. The averaged V95 for the PTV57.6 was 99.2% for the WF-IMRT technique compared with 97.4% (p = 0.02) for J-IMRT. The averaged V95 for the PTV64 was 99.9% for the WF-IMRT technique compared with 98.9% (p = 0.02) for J-IMRT and the averaged V95 for the PT70 was 100.0% for WF-IMRT technique compared with 99.5% (p = 0.04) for J-IMRT. The averaged mean laryngeal dose was 18 Gy with both techniques. The averaged mean doses within the matchline volumes were 69.3 Gy for WF-MRT and 66.2 Gy for J-IMRT (p = 0.03). The WF-IMRT technique appears to offer an optimal coverage of the target volumes and a mean dose to the larynx similar with J-IMRT and should be further evaluated in clinical trials.     

Integration of computerized tomography imaging with single photon emission in a commercial system for developing radiotherapy fields: application to conformational irradiation for lung carcinoma]

PURPOSE: Single photon emission computed tomography (SPECT) of lung perfusion permits to map functioning lung parenchyma with higher sensitivity than CT. Delivering higher radiation doses is used to increase local control in lung carcinoma; this strategy is based on radiobiological and clinical studies. Lung parenchyma is a dose-limiting tissue in patients irradiated for lung cancer. Functional mapping based on SPECT and CT findings permits to design radiation beams such as to minimize irradiation of functioning lung. MATERIAL AND METHODS: CT and SPECT were used to examine a patient with non small cell lung carcinoma (stage IIIB, T4N0, left lung) candidate to conformal irradiation. Images were spatially correlated based on lung contours and using CT findings as reference. SPECT images were normalized to mean right lung value and expressed as perfusion (functional) contours. CT images and perfusion contours were transferred to the treatment planning system (Cadplan V 2.79, Varian-Dosetek Oy): in this way both functional (SPECT) and anatomical (CT) data were available for planning. A comparison was made between two irradiation techniques defined at TPS with (technique B) or without (technique A) SPECT contour information. The prescribed dose was 70.2 Gy. Rival plans were compared using dose volume histograms of target and risk organs. Both functional and anatomical regions were considered in the lung, together with single lung(s) and lung parenchyma. A second perfusion SPECT was obtained 5 months after irradiation and correlated with pretreatment CT images. RESULTS: SPECT lung scans showed marked heterogeneity in the left lung, which was found neither at CT nor at classic lung function tests. The lung volume with perfusion exceeding 80% of average corresponds to about 70% of the anatomical volume. Mean doses to anatomical and to functional lung parenchyma were 24 Gy and 19 Gy, respectively, with technique A and 23 Gy and 18 Gy, respectively, with technique B. Thirty-five percent and 20%, respectively of anatomical and functional lung parenchyma received > or = 25 Gy (V25) with technique B. The figure for functional lung parenchyma was reduced by 5% with technique B. Optimal design of irradiation field geometry decreased the area of functional parenchyma given high doses, which sparing was greater with smaller irradiation volumes. CONCLUSIONS: We have integrated the functional data provided by SPECT lung perfusion into a commercial irradiation planning system. Lung function mapping permits to design irradiation portals sparing larger areas of functional lung parenchyma.