Search

Intensity-modulated radiotherapy (IMRT) provides better sparing of normal tissue. We evaluated the optimum beam configuration for IMRT based on inverse treatment planning in adjuvant radiotherapy for breast cancer in a case of left-sided tumor. In addition to radiotherapy planning with the conventional technique of tangential wedged 6-MV photon beams and an oblique 15-MeV electron beam, we performed inversely planned IMRT with the step-and-shoot-technique. Dose calculation was carried out using the treatment planning system Virtuos with the inverse optimization module KonRad adapted to it. IMRT plans were generated for 2 to 16 beams. The results were compared with conventional techniques. For a maximum treatment time of 20 minutes, it is shown that IMRT with 12 modulated photon beams and 7 intensity steps is best suited for treatment in the presented case. Compared with a conventional technique with photons combined with electrons, dose conformality and homogeneity of the planning target volume was increased. The mean heart dose was reduced from 9.1 Gy to 6.1 Gy. The volume of heart irradiated with a dose higher than 30 Gy was reduced from 7.6% to 1.9%, and the volume of the left lung from 13.6% to 11.5% as well. Inverse optimization for IMRT with multiple beams is feasible in the adjuvant treatment of breast cancer. Because of the reduction of the high-dose area of a substantial cardiac volume, it is superior to conventional techniques in cases where the parasternal lymph nodes should be integrated into the target volume. Here, a clinical advantage might be detectable.

Spinal chordomas cannot be treated with an effective dose using conventional radiation therapy (RT) without exceeding the tolerance dose of the spinal cord while ensuring sufficient target coverage at the same time. In this study we investigate the potential physical advantages of combined photon intensity-modulated radiation therapy (IMRT) and raster-scanned carbon ion RT over photon IMRT alone. For a representative patient we generated a carbon ion RT plan and a photon IMRT plan. Additionally, combined plans consisting of both carbon ions and photon IMRT were calculated using ratios of 20:40 GyE, 30:30 GyE and 40:20 GyE. The best target coverage was obtained using carbon ions alone. Using a combination of photon IMRT and carbon ions, the target coverage was better than with photon IMRT alone. Due to the applied dose constraints, the sparing of the spinal cord was comparable for all plans. Using carbon ions alone, the non-target tissue volume irradiated to at least 30 GyE/50.4 GyE was reduced by 72%/84% compared to photon IMRT alone. These advantages were evident even with combined techniques. The actually delivered dose distribution is expected to be more dependent on patient misalignment with carbon ions compared with photon IMRT. A combination of carbon ions and photon IMRT might be preferable in order to profit by the physical advantages of carbon ions while ensuring a safe treatment.

Background: In three-dimensional (3-D) precision high-dose radiation therapy of lung tumors, the exact definition of the planning target volume (PTV) is indispensable. Therefore, the feasibility of a 3-D determination of respiratory lung tumor movements by the use of a multislice CT scanner was investigated., Patients and Methods: The respiratory motion of 21 lung tumors in 20 consecutively treated patients was examined. An abdominal pressure device for the reduction of respiratory movement was used in 14 patients. Two regions of the tumor were each scanned repeatedly at the same table position, showing four simultaneously acquired slices for each cycle. Stereotactic coordinates were determined for one anatomic reference point in each tumor region (Figure 1). The 3-D differences of these coordinates between the sequentially obtained cycles were assessed (Figure 2), and a correlation with the tumor localization was performed., Results: In the craniocaudal (Z-) direction the mean tumor movement was 5.1 mm (standard deviation [SD] 2.4 mm, maximum 10 mm), in the ventrodorsal (Y-) direction 3.1 mm (SD 1.5 mm, maximum 6.7 mm), and in the lateral (X-) direction 2.6 mm (SD 1.4 mm, maximum 5.8 mm; Figures 3 to 5). Inter- and intraindividual differences were present in each direction. With an abdominal pressure device no clinically significant difference between tumors in different location was seen., Conclusion: The 3-D assessment of lung tumor movements due to breathing is possible by the use of multislice CT. The determination, indispensable to the PTV definition, should be performed individually for several regions, because of the inter- and intraindividual deviations detected.

Background and Purpose: Complex-shaped malignant pleural mesotheliomas (MPMs) with challenging volumes are extremely difficult to treat by conventional radiotherapy due to tolerance doses of the surrounding normal tissue. In a feasibility study, we evaluated if inversely planned stereotactic intensity-modulated radiation therapy (IMRT) could be applied in the treatment of MPM., Patients and Methods: Eight patients with unresectable lesions were treated after failure of chemotherapy. All patients were positioned using noninvasive patient fixation techniques which can be attached to the applied extracranial stereotactic system. Due to craniocaudal extension of the tumor, it was necessary to develop a special software attached to the inverse planning program KonRad, which can connect two inverse treatment plans and consider the applied dose of the first treatment plan in the area of the matchline of the second treatment plan., Results: Except for one patient, in whom radiotherapy was canceled due to abdominal metastasis, treatment could be completed in all patients and was well tolerated. Median survival after diagnosis was 20 months and after IMRT 6.5 months. Therefore, both the 1-year actuarial overall survival from the start of radiotherapy and the 2-year actuarial overall survival since diagnosis were 28%. IMRT did not result in clinically significant acute side effects. By using the described inverse planning software, over or underdosage in the region of the field matchline could be prevented. Pure treatment time ranged between 10 and 21 min., Conclusion: This study showed that IMRT is feasible in advanced unresectable MPM. The presented possibilities of stereotactic IMRT in the treatment of MPM will justify the evaluation of IMRT in early-stage pleural mesothelioma combined with chemotherapy in a study protocol, in order to improve the outcome of these patients. Furthermore, dose escalation should be possible by using IMRT.

The implementation of computer-assisted three-dimensional radiotherapy treatment planning methods based on computed tomography together with sophisticated beam modeling with individual blocks and multi-leaf-collimators in the 90's enabled the creation of steep dose gradients between the target volume and surrounding radiosensitive normal tissue. For prostate cancer, a clear dose dependence between the treated radiation dose and the treatment success is proven, especially for patients with intermediate and unfavorable prognostic criteria. However, with conventional radiotherapy, rectum and urinary bladder are limiting the applicable dose. New technical methods allow a safe dose escalation without increasing of treatment-related toxicity. An improvement in terms of PSA remission and local control was yielded. This article presents the different established external beam and interstitial treatment techniques and their clinical results.

Purpose: To integrate MRI into CT-based 3D-brachytherapy treatment planning using a software system for image registration and fusion., Methods and Materials: Sixteen patients with recurrent head-and-neck cancer, vulvar cancer, liposarcoma, and cervical cancer were treated with interstitial (n=12) and endocavitary (n=4) brachytherapy. CT and MRI scans were performed after implantation and prior to treatment planning. Image registration to integrate the CT and MR information into a single geometric framework was performed using a software algorithm based on mutual information. Conventional 3D-brachytherapy planning based on CT-information alone was compared to brachytherapy planning based on fused CT and MRI data. The accuracy of the image fusion was measured using predefined corresponding landmarks in the CT and MRI data., Results: The presented automated algorithm proved to be robust and reliable (mean registration error 1.8 mm, range 0.8-4.1 mm, SD 0.9 mm). Tumor visualization was difficult using CT alone in all cases. Brachytherapy treatment planning based on fused CT and MRI data enabled better definition of target volume and risk structures as compared to treatment planning based on CT alone., Conclusions: Image registration and fusion is feasible for afterloading brachytherapy treatment planning. Treatment planning based on fused CT and MRI data resulted in improved target volume and risk structure definition.

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.

Purpose: Inverse treatment planning and intensity-modulated radiation therapy (IMRT) promise advantages in the treatment of tumors of the head and neck region. Currently published studies use IMRT only in the treatment of the primary tumor. In these studies, the lymph nodes of the neck were treated using conventional techniques. The feasibility of an IMRT technique which allows treatment of the complete target volume, including the primary tumor and lymph nodes, without a beam split is described., Patient and Method: For inverse treatment planning, the KonRad planning system was used. The primary as well as the secondary PTV (bilateral lymph node levels) were treated with one intensity-modulated primary plan. To increase the dose in the primary PTV and suspicious lymph nodes, an intensity-modulated boost plan was performed. The "step and shoot" IMRT technique was used. A plan comparison between the described IMRT approach and an IMRT approach using a split-beam technique was performed focusing on the treatment time. A patient with a carcinoma of the nasopharynx was treated with curative intent by a combined radiochemotherapy., Results: The median total dose to the primary PTV was 70 Gy, to suspicious lymph nodes > or = 66.0 Gy, and to the secondary PTV 52 Gy. The defined maximum doses to the organs at risk were not exceeded, and the median dose to the protected parotid gland amounted to 21 Gy. Comparison of the treatment time between both IMRT approaches revealed only a slightly shorter treatment time (1-3 min) for the split-beam IMRT technique without considering the remaining conventional treatment parts of the split-beam IMRT technique. The patient achieved a complete response, and 18 months after treatment no signs of recurrent disease are visible., Conclusions: IMRT allows the treatment of the target volumes with high doses combined with an excellent sparing of the organs at risk. The IMRT approach presented here makes the treatment of the whole target volume with a single-beam arrangement feasible and does not increase the treatment time compared to a split-beam IMRT technique. Treatment time was comparable to a conventional three-field technique combined with electrons. This IMRT technique can prevent over- or underdosage at field matchlines in the head and neck region and, moreover, is able to spare parotid glands and therefore better avoid xerostomia compared to conventional techniques.

Purpose: To evaluate the possibilities of an open low-field magnetic resonance imaging (MRI) scanner in external beam radiotherapy treatment (RT) planning., Methods and Materials: A custom-made flat tabletop was constructed for the open MR, which was compatible with standard therapy positioning devices. To assess and correct image distortion in low-field MRI, a custom-made phantom was constructed and a software algorithm was developed. A total of 243 patients (43 patients with non-small-cell lung cancer, 155 patients with prostate cancer, and 45 patients with brain tumors) received low-field MR imaging in addition to computed tomographic (CT) planning imaging between January 1998 and September 2001 before the start of the irradiation., Results: Open low-field MRI provided adequate images for RT planning in nearly 95% of the examined patients. The mean and the maximal distortions 15 cm around the isocenter were reduced from 2.5 mm to 0.9 mm and from 6.1 mm to 2.1 mm respectively. The MRI-assisted planning led to better discrimination of tumor extent in two-thirds of the patients and to an optimization in lung cancer RT planning in one-third of the patients. In prostate cancer planning, low-field MRI resulted in significant reduction (40%) of organ volume and clinical target volume (CTV) compared with CT and to a reduction of the mean percentage of rectal dose of 15%. In brain tumors, low-field MR image quality was superior compared with CT in 39/45 patients for planning purposes., Conclusions: The data presented here show that low-field MRI is feasible in RT treatment planning when image correction regarding system-induced distortions is performed and by selecting MR imaging protocol parameters with the emphasis on adequate images for RT planning.

Current methods for intensity-modulated radiotherapy (IMRT) in breast cancer use forward planning based on equivalent radiological path length to design intensity modulated tangential beams. Compared to conventional tangential techniques, dose reduction of organs at risk is limited using these techniques. We developed a method for intensity modulation of multiple beams for adjuvant radiotherapy of breast cancer by application of a virtual bolus defined on CT for inverse optimization. This method enables multibeam IMRT, which provides improved sparing of lung and heart tissue. In this paper, we present the general aspects of this approach and an evaluation of the optimum beam configuration for IMRT based on inverse treatment planning. We compared this method to conventional techniques. Different clinical examples illustrate the possible indications and feasibility of this new approach. This method is superior to conventional techniques because of the reduction of high-dose area of a substantial cardiac volume in those cases where the parasternal lymph nodes are part of the target volume.

The purpose of this study was to compare dose distribution of inverse planned intensity modulated radiation therapy (IMRT) with that of conformal radiation therapy (SCRT) in the treatment of esthesioneuroblastoma, and to report initial clinical results. 13 patients with esthesioneuroblastoma were planned both with IMRT and SCRT using complete three-dimensional data sets. A target dose of 60 Gy was prescribed. We performed a detailed dose volume histogram analysis. Dose coverage was equal in both plans while dose distribution was more conformal to the target volume with IMRT. Mean and maximum dose of the brain stem, chiasm, optic nerves and orbits were lower using IMRT than SCRT. The reduction was significant regarding orbit and optic nerve (p<0.05). IMRT was superior in sparing of organs at risk compared with SCRT. The additional sparing by IMRT was positively correlated to the size of the target volume, which was evident with target volumes above 200 cm3. Treatment time was approximately 20 minutes per fraction using IMRT compared with 15 minutes per fraction using SCRT. We conclude that IMRT is both feasible and a valuable tool for more conformal dose distribution in the treatment of esthesioneuroblastoma and to spare organs at risk that are in critical relationship to the tumour. This advantage could be seen especially well in complex shaped target volumes above 200 cm3. Thus, using IMRT, risk of complications may be minimized and local tumour control may be increased.

Background: Intensity modulated radiotherapy (IMRT) provides better sparing of normal tissue. We investigated the feasibility of inverse treatment planning for IMRT in adjuvant radiotherapy for breast cancer., Material and Methods: In addition to radiotherapy planning in conventional technique with tangential wedged 6-MV-photon beams we performed inversely planned IMRT (KonRad). In the CT scans for treatment planning we defined a 10-mm bolus of -60 HE density. The influence of this bolus on planning optimization was determined by optimization without and dose calculation with and without bolus. Dose calculation after dose optimization with bolus was performed using different bolus thickness to determine the influence of the bolus on dose calculation. The results were compared with dose distribution in conventional technique., Results: Inverse optimization with a dose algorithm which considers tissue inhomogeneity results in unintended dose increase at the patient surface. With a virtual 10-mm bolus used for inverse optimization the dose increase was reduced. Thus, skin sparing was identical to conventional planning. The relative dose distribution was negligibly affected by the use of a 10-mm bolus. Difference in absolute dose was 3.4% compared to calculation without bolus. Therefore, the bolus must be removed before final dose calculation., Conclusion: The realization of inverse optimization for IMRT of the breast requires the use of a virtual bolus. Thereby, IMRT in accordance to the consensus recommendations of the EORTC, BCCG and EUSOMA is possible. Especially, the same target definition as in conventional technique may be used. IMRT techniques with a conventional beam arrangement of two tangential fields or multiple beam techniques can be realized.

Advances in conformal radiation therapy to control disease via dose escalation are challenged by set-up uncertainties. Recently, techniques have been developed to use surface features to evaluate the patient's position and correct it where necessary. The aim of this study was to use the patient's surface as a tool for daily set-up control and monitoring. We use a surface scanner based on the projection of coded light to receive--in a daily routine--a large amount of surface points which enables us to register the CT-based planning data with the patients current position. By superimposing current and planned volumes, a volume of congruency was obtained. An error below 1 mm was considered acceptable. In cases where set-up was not satisfactory a map of the surface comparison was evaluated showing the areas of missing alignment. According to this information a manual repositioning was performed. This procedure was repeated until the error was acceptable. No more then 3 repetitions where necessary to obtain an acceptable result. The whole procedure including registration, calculation and visualization took about 20 sec for one repetition. The use of structured light projection in the daily set-up control and monitoring proved to be a noninvasive, easy, quick, inexpensive and reliable solution.

In the treatment of malignant disease external beam radiation therapy (EBRT) is often combined with surgery. Intraoperative radiotherapy (IORT) improves the local control by dose escalation. For reasons of recording, improvement and security of the intervention, it would be necessary to merge the IORT-dose distribution with the postoperative CT-based EBRT-planing. The aim of this work was to develop a method to reconstruct the IORT field and register it with the postoperative planing CT. This enables the reconstruction of the IORT dose distribution and merge it with the CT-based EBRT planing data. We use a surface scanner to receive a large amount of surface points which enables us reconstruct the IORT-field and to register it with the CT-based EBRT planning data. Scanning and calculation time is not over 2 seconds, depending mainly on the CPU power. The error of a single point is below 1 mm. The density of the point cloud is approx. 4 per mm2. In this paper we give an overview of our experimental setup and the accuracy of the method.

Background and Aim: Artifacts due to metal implants are an important problem in diagnostic radiology and radiotherapy planning in tumors such as chordoma of the spine. A strict differentiation between target and radiosensitive structures e.g. spinal cord is absolutely essential for high-dose radiotherapy. Up to now CT and MRI techniques have provided only limited image quality in such situations. We introduce an approach to facilitate segmentation by using the technique of CT-myelography for radiation treatment., Patient and Method: A 48-year-old woman with multiple inoperable relapses of a chordoma in the lumbar spine and extensive metal instrumentation in this area was given to radiotherapy using IMRT-technique (intensity modulated). MRI- and CT-planning images did not allow differentiation between myelon, cauda equina, dural sac and tumor. In this situation we performed a CT-myelography with the patient in treatment position., Result: CT-myelographic images enabled precise differentiation between myelon, cauda equina and intraspinal tumor. A substantial improvement of the segmentation of the spinal cord was obtained. There was no compression of the dural sac along the spine. This information provided the basis for a precise radiotherapy planning in IMRT-technique., Conclusion: In situations where CT- and MRI-techniques are not able to generate precise images which allow differentiation between tumor, myelon and cauda equina because of metal artifacts, CT-myelography is a promising technique which may help the diagnostic radiologist and radiation oncologist in planning radiotherapy.

Purpose: To investigate the feasibility and the clinical response of a stereotactic single-dose radiation treatment for liver tumors., Patients and Methods: Between April 1997 and September 1999, a stereotactic single-dose radiation treatment of 60 liver tumors (four primary tumors, 56 metastases) in 37 patients was performed. Patients were positioned in an individually shaped vacuum pillow. The applied dose was escalated from 14 to 26 Gy (reference point), with the 80% isodose surrounding the planning target volume. Median tumor size was 10 cm(3) (range, 1 to 132 cm(3)). The morbidity, clinical outcome, laboratory findings, and response as seen on computed tomography (CT) scan were evaluated., Results: Follow-up data could be obtained from 55 treated tumors (35 patients). The median follow-up period was 5.7 months (range, 1.0 to 26.1 months; mean, 9.5 months). The treatment was well tolerated by all patients. There were no major side effects. Fifty-four (98%) of 55 tumors were locally controlled after 6 weeks at the initial follow-up based on the CT findings (22 cases of stable disease, 28 partial responses, and four complete responses). After a dose-escalating and learning phase, the actuarial local tumor control rate was 81% at 18 months after therapy. A total of 12 local failures were observed during follow-up. So far, the longest local tumor control is 26.1 months., Conclusion: Stereotactic single-dose radiation therapy is a feasible method for the treatment of singular inoperable liver metastases with the potential of a high local tumor control rate and low morbidity.

Purpose: A number of minimal-invasive methods have been developed for the treatment of non-resectable liver metastases. A focused high dose can be delivered to a liver tumor with sparing of surrounding normal liver tissue using non-invasive stereotactic techniques., Methods: Sixty-six metastases were treated stereotactically in 43 patients during a phase 2 trial., Results: There were no major side effects observed. The actuarial local control was 82% after 18 months. The median actuarial survival was 24 months. However, there was a significantly improved survival in patients without additional extrahepatic tumor manifestation at the time of treatment compared to those, who were treated in palliative intention (87% vs. 24% after 18 months, p = 0.001 (log-rank)., Conclusion: Stereotactic single dose irradiation is a non-invasive and safe treatment option for patients with inoperable liver metastases. Phase III studies will further evaluate this new approach.

Purpose: Target volumes that wrap around the spinal cord are difficult to treat. We present and evaluate a refined multiple arc segment (MAS) technique that is applicable with standard three-dimensional (3D) radiotherapy equipment and may be a solution for facilities that do not yet have full access to intensity-modulated radiotherapy (IMRT)., Methods and Materials: The presented technique consisted of 13 isocentric coplanar beam's eye view shaped fields, delivered as 20 degrees or 10 degrees arc segments with an integrated multileaf collimator (MLC) using automatic sequential field delivery. Dose-volume histograms (DVH) for this technique were compared to a modified bar-arc technique (MBA) modeled as 30 static fields and to an inverse planned IMRT technique using 7 coplanar, equispaced beams delivered with the same MLC., Results: Compared to the MBA technique, maximum dose and target coverage were similar when using 80% of the maximum dose as the reference dose. However, the MAS technique reduced the maximum doses (to > or = 1% of the organs at risk [OAR]) by 9% for the spinal cord, 17% for the esophagus, and 25% for the trachea, as well as the mean doses. Although inverse planned IMRT could further reduce exposure of OAR except for the spinal cord and improve target coverage, our forward planned MAS technique seems to achieve clinically comparable results., Conclusion: Substituting a series of small split-field arc segments for large static fields and using additional narrow paraspinal segments significantly improves the sparing of organs at risk for paraspinal targets. Although these results are not quite as good as those achieved with IMRT, for facilities not yet equipped with inverse treatment planning capability, the presented technique enables dose escalation for primary paraspinal tumors and retreatment of recurrent lesions.

Background: Tumors in the nasal cavity and paranasal sinus are difficult to treat with radiotherapy. Usually, in addition to a two- or three-field photon technique, an interorbital electron field is required. This may result, however, in severe over- or underdosage, the latter being especially detrimental when occurring in the main tumor bulk., Methods and Results: We present a conformal three-dimensional treatment technique that provides sufficient interorbital dose with photons only while sparing the eyes, optic nerves and chiasm, and may be considered for selected tumors in this region.

Background: FLAIR MR imaging has shown to be a valuable imaging modality in pathologic lesions of the brain including intra-axial brain tumors. The aim of the study was to assess the value of a FLAIR technique in the planning process of stereotactic radiotherapy in patients with cerebral gliomas and metastases., Patients and Methods: Thirty-five patients with cerebral gliomas and 12 patients with a total of 39 cerebral metastases were examined by T2/PD-weighted fast spin-echo, fast FLAIR prior and after contrast and contrast enhanced T1-weighted spin-echo using identical slice parameters. The images were evaluated by using quantitative and qualitative criteria. Quantitative criteria were tumor-to-background and tumor-to-cerebrospinal fluid contrast and contrast-to-noise. The qualitative evaluation was performed as a multireader analysis concerning lesion detection, lesion delineation and image artifacts., Results: In the qualitative evaluation (Table 3 and 6), all readers found the fast FLAIR images to be superior to fast spin-echo in the exact delineation of cerebral tumors (p < 0.001) and the delineation of enhancing and non enhancing tumor parts. Fast FLAIR was superior in the delineation of cortically located and small lesions but was limited in lesions adjacent to the ventricles. Fast FLAIR provided a significantly better tumor-to-CSF contrast and tumor-to-CSF contrast-to-noise (p < 0.001) (Tables 1, 2a, 2b, 4, 5). The tumor-to-background contrast and tumor-to-background contrast-to-noise of the fast FLAIR images were lower than that of T2-weighted spin-echo images but were significantly increased after the application of contrast media. FLAIR images had more image artifacts, but the image interpretation was not influenced., Conclusions: FLAIR MR imaging was found to be a valuable sequence in the planning protocol of stereotactic radiotherapy. The concurrent presentation of enhancing and non enhancing tumor tissue on contrast enhanced fast FLAIR imaging enables to use a single imaging sequence in the treatment protocol. This enables to load a reduced image amount into the radiotherapy planning software, is therefore time saving and reduces potential errors.

Background: The effect of 3D radiotherapy planning (3D RTP) in comparison to 2D radiotherapy planning (2D RTP) was evaluated in a usually practiced treatment schedule (starting by v./d. opposing portals, continued with computer-planned portals) for non-small-cell lung cancer., Patients and Methods: In 20 patients with locally advanced non-small-cell lung cancer the computer-planned part of the treatment schedule was calculated 2- and 3-dimensionally. Target volume were the primary tumor, the involved and the electively irradiated mediastinal lymph nodes. The results of the 2D RTP were recalculated 3-dimensionally and the mean doses to target volume and organs at risk were defined. Further the normal tissue complications were calculated., Results: Under the prerequisite of 44 Gy maximally allowed to the spinal cord and a dose to the reference point of 50 Gy a small, but significant advantage with 2.1 Gy to the target (p = 0.004) and a reduction of 3.6 Gy to the heart (p = 0.05) was achievable for 3D RTP. The dose to the lungs did not differ significantly (19.7 Gy for 2D RTP, 20.3 Gy for 3D RTP). The dose to the heart was not estimated critical by NTCP (normal tissue complication probability). The NTCP for the ipsilateral lung was 16.1 and 18.7% for 2D RTP and 3D RTP, respectively. Regarding the simulator-planned ap/pa fields at the start of the radiotherapy the advantage of 3D RTP was further reduced but remained significant. Favorable with respect to the mean lung dose and the NTCP (18.7% NTCP ipsilateral lung for early onset of 3D planned radiotherapy vs 31.7% for late onset of 3D planned radiotherapy) but not significantly measurable is the early start of the treatment by computerized RTP., Conclusion: The main advantage of 3D RTP in treatment of advanced lung cancer is the better coverage of the target volume. A reduction of the mean lung dose cannot be expected. A dose escalation by 3D RTP to target volumes as described here seems not to be possible because of unchanged high lung exposure.

Purpose: A system for digital integration of an open MR scanner (0.23 T, Figure 1) in therapy simulation and 3D radiation treatment planning is described., Method: MR images were acquired using the body coil and various positioning and immobilization aids. A gradient echo sequence (TR/TE 320 ms/24 ms) was used to create axial and coronal data sets. Image distortions were measured and corrected using phantom measurements (Figure 2) and specially developed software., Results: Maximal and mean distortions of the MR images could be reduced from 19 mm to 8.2 mm and from 2.7 mm to 0.7 mm, respectively (Figure 3 to 5, Table 1). Coronal MR images were recalculated in fan beam projection for use at the therapy simulator. Tumor and organ contours were transferred from the MR image to the digitally acquired and corrected simulator image using a landmark matching algorithm (Figure 6 and 7). For 3D treatment planning, image fusion of axial MR images with standard CT planning images was performed using a landmark matching algorithm, as well (Figure 8). Representative cases are shown to demonstrate potential applications of the system., Conclusion: The described system enables the integration of the imaging information from an open MR system in therapy simulation and 3D treatment planning. The low-field MR scanner is an attractive adjunct for the radio-oncologist because of the open design and the low costs.

Background and Purpose: Simulation of 3D-treatment plans for head and neck malignancy is difficult due to complex anatomy. Therefore, CT-simulation and stereotactic techniques are becoming more common in the treatment preparation, overcoming the need for simulation. However, if simulation is still performed, it is an important step in the treatment preparation/execution chain, since simulation errors, if not detected immediately, can compromise the success of treatment. A recently developed PC-based system for on-line image matching and comparison of digitally reconstructed radiographs (DRR) and distortion corrected simulator monitor images that enables instant correction of field placement errors during the simulation process was evaluated. The range of field placement errors with non-computer aided simulation is reported., Materials and Methods: For 14 patients either a primary 3D-treatment plan or a 3D-boost plan after initial treatment with opposing laterals for head and neck malignancy with a coplanar or non-coplanar two- or three-field technique was simulated. After determining the robustness of the matching process and the accuracy of field placement error detection with phantom measurements, DRRs were generated from the treatment planning CT-dataset of each patient and were interactively matched with on-line simulator images that had undergone correction for geometrical distortion, using a landmark algorithm. Translational field placement errors in all three planes as well as in-plane rotational errors were studied and were corrected immediately., Results: The interactive matching process is very robust with a tolerance of <2 mm when suitable anatomical landmarks are chosen. The accuracy for detection of translational errors in phantom measurements was <1 mm and for in-plane rotational errors the accuracy had a maximum of only 1.5 degrees. For patient simulation, the mean absolute distance of the planned versus simulated isocenter was 6.4 +/- 3.9 mm. The in-plane rotational error in both planes was <3 degrees with one exception. Three large field placement errors (two patients with 11.5 and 16.0 mm distances of the planned versus simulated isocenter, respectively and one patient with a 7 degree rotational error) were detected and, as with the smaller errors, were immediately corrected., Conclusion: On-line image matching of treatment planning CT-derived DRRs and distortion corrected treatment simulator images is a precise and reliable method to reduce field placement errors in the simulation of complex 3D-treatment plans for head and neck malignancy and thus enhances accuracy in the first step of the treatment preparation/execution chain. However, out-of-plane rotational errors could not be assessed and assumedly they are comparatively small since due to rigid fixation, detected in-plane errors were small.

Modern imaging techniques are a substantial part of treatment planning for minimally invasive radiotherapeutic procedures. The aim is three-dimensional assessment of the target volume and adjacent critical structures. In this paper, we report on our clinical experience with a precise system for stereotactic image correlation. Hereby, the advantages of each imaging modality can be combined. Precise immobilization of the patient is a prerequisite. The immobilization method has an accuracy of less than 1 mm. This method was evaluated in a clinical study in which a tumor control rate of 93% was achieved in patients with brain metastases after stereotactic single high dose radiotherapy. This indicated the excellent reliability of this treatment planning method. The integration of functional image information, such as blood flow or activation of cerebral cortical areas, will be evaluated in the future.

Purpose: To measure the patient positioning and prostate motion variability and to estimate its influence on the calculated 3D dose distribution in 3D conformal radiotherapy of patients with localized prostate carcinoma., Methods and Materials: Patient positioning variability was determined retrospectively by comparing 54 orthogonal simulator films with 125 corresponding portal films from 27 patients. Prostate motion variability was determined by 107 computed tomography (CT) examinations with a CT simulator in 28 patients during radiotherapy., Results: In each observed direction, the patient positioning variability and prostate motion showed a normal distribution. This observation enabled the calculation of a combined error of both components. The standard deviation (1 SD) of the patient positioning error in three directions ranged from 3.1 to 5.4 mm; the prostate motion variability was significantly greater in the anterior-posterior direction (1 SD = 2.8 mm) than in the mediolateral direction (1 SD = 1.4 mm). The 1 SD of the estimated combined error was in the anterior-posterior direction 6.1 mm and in mediolateral direction 3.6 mm., Conclusion: The range of patient positioning variability and prostate motion were statistically predictable under the patient setup conditions used. Dose-volume histograms demonstrating the influence of the combined error of both components on the calculated dose distribution are presented.

Three-dimensional radiotherapy planning (3-D RTP) is becoming more available in clinical practice, although so far there is little data showing its clinical advantage. The goal of this study was to compare 3-D RTP and dose delivery with conventional treatment planning in pneumonected lung cancer patients, receiving postoperative irradiation. Adjuvant radiotherapy in 20 pneumonected patients was planned with a 3-D system and patients were irradiated according to this plan. The resulting dose distribution was compared with the combination of a simulator and 2-D planned treatment to the same target volume. Dose volume histograms of the target, the lung and the heart of both treatment plans were analysed. A biophysical model was added to estimate the differences in the biological effect. 3-D RTP significantly reduced the mean dose to the lung in 14/20 patients and to the heart in 20/20 patients. The mean dose delivered to the target was equal in both planning methods. The early clinical results do not differ from published results in postoperatively treated lung cancer patients.

The influence of patient immobilization error on 3D planned conformal radiation therapy in tumors of the thorax and pelvis was studied. The mean positioning error in 43 patients with carcinomas of the thorax and pelvis undergoing 3D conformal radiotherapy (laser supported alignment, no immobilization device) was measured. A total of 194 portal films were superposed with the corresponding simulator radiographs according to anatomic landmarks and using a subtrascope. x-, y- and z-axis deviation was determined within a coordinate system. Using specialized software including Fourier transformation the mean positioning error was employed to recalculate the dose distributions of all cases under the influence of random (Gaussian) immobilization uncertainty. The mean two-dimensional positioning error using the data from all patients was 5.5 (+/- 3.7) mm. The distribution was Gaussian. Dose volume histograms (DVHs) of each patient with and without consideration of positioning uncertainty were compared on the base of tumor control probability estimations (TCP) using published DVH reduction and TCP algorithms. Inclusion of the positioning error resulted in a mean decrease in TCP (given as the difference between the TCP assuming no positioning error and the TCP modified by the positioning error) of 2% in a series of esophagus carcinomas and of 5% in the prostate carcinomas when looking at gross tumor volume (GTV), only. Planning target volume (PTV) exhibited a relative decrease in TCP of 5% and 11%, respectively.

Seven patients with large, pendulous breasts received external beam irradiation to the whole breast (50 Gy in 25 fractions plus boost) after lumpectomy. A special breast holding mask was shaped for each patient. Three-dimensional treatment plans and dose-volume histograms of the same patient with and without a mask were compared. Day-to-day variance was checked. This technique provides improvements in dose homogeneity, reproducibility, and sparing of normal tissues. Cosmetic outcome at present is good.

Purpose: A prerequisite for the exact planning of a radiotherapy is the precise accordance of the patient positioning during the planning CT and the therapy simulation. How far possible differences between patient set-up during the planning CT at a therapy simulator with CT option or a conventional CT influence the planned dose distribution is investigated by the example of the tangential breast irradiation., Patients and Methods: In 18 patients transverse sections for treatment planning of tangential breast irradiation were made both using a diagnostic CT scanner and a therapy simulator with CT option. For patient positioning the patient outlines were compared. Furthermore, the treatment plans which were based independently on both transverse sections were compared., Results: In the mean deviations of 1 resp. 0 mm (SD = 7 resp. 8 mm) between the ventral and lateral outlines of the breast were found. The mean breast diameter between the Z-points was 5 mm wider in the simulator CT based plans (SD = 14 mm). The field width was 6 mm wider (SD = 8 mm), the beam angle 1 degree steeper (SD = 4 degrees). The calculated monitor units differed 1% (SD = 6%). None of the differences between measured parameters reached statistical significance. A significant correlation was only seen for the interrelated contours (anteroposterior and lateral diameters)., Conclusion: The results of this investigation show no difference between treatment set-up and treatment planning using information of a CT scanner or a simulator with CT option for tangential breast irradiation.

Influence of MR-imaging on definition of treatment volume was studied prospectively in 43 patients undergoing radiotherapy for mediastinal malignancy (twelve Morbus Hodgkin, four non-Hodgkin-lymphoma, 26 lung cancer, one nephroblastoma). Conventional treatment planning using a simulator and all available information from axial CT-scanning and posterior-anterior and lateral radiographs was compared to a MRI-assisted procedure. Contours from coronary MR-sections acquired in treatment position were superposed onto the simulator radiograph using a subtrascope (MRI-simulation). MR-imaging using T1-weighted sequences resulted in excellent delineation of tumor masses from mediastinal fat, airways and vascular structures. The high soft tissue contrast allowed an exact and reproducible transfer of tumor contours onto the simulator radiograph. This led to changes in field configuration in 11/43 patients concerning mainly tumor extension infracarinally and in the caudal parts of the lung hili. Superiority of MRI-assisted simulation was noted as usefulness of axial CT-scanning to delineate margins was compromised in these areas by partial volume effects of tangentially represented structures and suboptimal contrasted vascular spaces.

The routine use of three-dimensional treatment planning was evaluated in a clinical project funded by the German Krebshilfe at the Radiological Department of the University of Heidelberg. 166 patients entered the prospective study within 14 months, 155 of them were treated according to the 3D-plans. More than 50% of the patients had thoracic tumors, followed by pelvic tumors. One medicine physicist and one specially trained technician performed the treatment planning. The target volumes were contoured in the CT slices at the planning computer by the responsible radiotherapists. A mean of 6.5 hours per patient was necessary for all planning procedures, however, this time consumption shows a trend toward less time of only four hours including about ten optimization steps. Meanwhile approximately 20 to 30% of all computer assisted planning are performed in 3D, corresponding to about one plan per day. The achieved time consumption is a clinically accepted quantity, that allows the introduction of 3D-planning into clinical routine.

Three-dimensional (3-D) radiotherapy planning is applied for the conformation therapy of a bronchial carcinoma. The treatment technique, using dynamically controlled shielding blocks, and the treatment planning procedure are described. The method has now been in clinical routine since 4 years; problems with the patient's positioning are discussed.

For irradiation of the parasternal lymph nodes by high-energy electrons the target volume depth, i.e. the depth of the parasternal nodes below the skin surface, was determined by CT in 25 consecutive female patients with a sternal irradiation field. On measurement at the cranial end of the sternum, at a middle level, and at the caudal part of the sternal field, intraindividual differences were low, whereas interindividual findings differed markedly--depending on thickness of subcutaneous fatty tissue. For individual treatment planning, we recommend measuring target volume depth by CT.

At the Radiotherapy Department of the University Hospital of Freiburg i.Br., an additional diaphragm controlled by an electronic system in dependence on the angles was developed for the optimization of irradiation planning, i.e. administration of the therapeutically necessary dose to the target volume and, at the same time, sparing of risk organs.