Three-dimensional Planning System Research Articles

Long-term results of chemoradiotherapy with elective nodal irradiation for resectable locally advanced esophageal cancer in three-dimensional planning system.

We evaluated the long-term results of definitive chemoradiotherapy (CRT) with elective nodal irradiation (ENI) using a three-dimensional (3D) planning system for resectable, locally advanced esophageal squamous cell carcinoma (LA-ESCC). This retrospective study included 65 patients with LA-ESCC who started CRT between 2006 and 2017. Patients with Stage I-IV LA-ESCC according to the Union for International Cancer Control TNM classification (eighth edition) were included. In stage IV, only supraclavicular lymph node (LN) metastasis was included. All patients received radiotherapy with ENI and concurrent chemotherapy with platinum and 5-fluorouracil. The median age of the patients was 70years (range 52-83years). Stage I, II, III, and IV diseases were observed in 3 (5%), 28 (43%), 22 (34%), and 12 patients (18%), respectively. The median prescription dose was 66Gy (range 50.4-66Gy). The median follow-up period for the survivors was 71months (range 8-175months). The 5-year overall survival (OS) and progression-free survival rates were 54 and 43%, respectively. The 5-year OS rates for stages I-II and III-IV were 67 and 42%, respectively. Recurrence occurred in 29 patients (45%), and recurrence of regional LNs only occurred in 2 patients (3%). Grade 3 or higher late adverse events were observed in 8 patients (12%). Grade 5 heart failure occurred in two patients (3%); both had cardiovascular disease before treatment. The long-term results of definitive CRT with ENI for resectable LA-ESCC were favorable. ENI with a 3D planning system may reduce regional LN recurrence and late adverse events.

Presurgical selection of the ideal aneurysm clip by the use of a three-dimensional planning system

Aneurysm occlusion rate after clipping is higher than after endovascular treatment. However, a certain percentage of incompletely clipped aneurysms remains. Presurgical selection of the proper aneurysm clips could potentially reduce the rate of incomplete clippings caused by inadequate clip geometry. The aim of the present study was to assess whether preoperative 3D image-based simulation allows for preoperative selection of a proper aneurysm clip for complete occlusion in individual cases. Patients harboring ruptured or unruptured cerebral aneurysms prior to surgical clipping were analyzed. CT angiography images were transferred to a 3D surgical-planning station (Dextroscope®) with imported models of 58 aneurysm clips. Intracranial vessels and aneurysms were segmented and the virtual aneurysm clips were placed at the aneurysm neck. Operating surgeons had information about the selected aneurysm clip, and patients underwent clipping. Intraoperative clip selection was documented and aneurysm occlusion rate was assessed by postoperative digital subtraction angiography. Nineteen patients were available for final analysis. In all patients, the most proximal clip at the aneurysm neck was the preselected clip. All aneurysms except one were fully occluded, as assessed by catheter angiography. One aneurysm had a small neck remnant that did not require secondary surgery and was occluded 15 months after surgery. 3D image-based preselection of a proper aneurysm clip can be translated to the operating room and avoids intraoperative clip selection. The associated occlusion rate of aneurysms is high.

Anterior prominence of the femoral condyle varies among prosthesis designs and surgical techniques in total knee arthroplasty

BackgroundPatellofemoral overstuffing after total knee arthroplasty (TKA) can cause limited range of motion and anterior knee pain. This study compared anterior prominence of femoral components among different prothesis designs in surgical simulation models utilizing the anterior reference (AR) and posterior reference (PR) techniques.MethodsSurgical simulations were performed using on a three-dimensional planning system preoperative computed tomography data of consecutive 30 patients with knee osteoarthritis scheduled to undergo TKA. Four implant models were used: Attune, Persona, Journey II, and Legion. Rotational alignment was set parallel to the transepicondylar axis and size was selected based on the absence of notch formation in the femoral anterior cortex and the best fit with the shape of the medial posterior femoral condyle. For each combination of surgical technique (AR or PR method) and implant model, measurements were taken of the maximum medial, central, and lateral prominence of the implant from the anterior femoral cortex.ResultsUsing either the AR or PR method, the medial and central prominences were significantly lower with Journey II than with the other models. The lateral prominence was the lowest with Attune in the AR method. The AR method was associated with significantly less prominence compared with the PR method, regardless of implant model.ConclusionsThe degree of anterior prominence of the femoral implant is affected by the implant design when the AR method is used. The PR method is associated with greater anterior prominence compared with the AR method, and the pitch size is an additional factor in the PR method. Surgeons should be familiar with implant designs, including the thickness of the anterior flange and the available size selections.

Comparison of 3D and 4D Plans in the Radiation Therapy for Lung Cancer Using Real Time Tumor Tracking System

Real time tumor tracking system is usually used for the planning of radiation therapy for lung cancer. Deformations of the target and organs at risk (OARs) during breathing are not considered in this three-dimensional (3-D) planning system, because doses are calculated at the end-exhale computed tomography (CT) images. On the other hand, the four-dimensional (4-D) plans using CT images from all respiratory phases seem to be similar to the actual doses. To know the difference between the calculated doses and actual doses delivered to the target and OARs, doses were calculated using 4-D plans and compared with those of the 3-D plans.

Robotic Stereotactic Radiation Therapy Compared to 3D MR Image Guided HDR Brachytherapy in the Treatment of Cervical Cancer

target and organs at risk (OARs) during breathing are not considered in this three-dimensional (3-D) planning system, because doses are calculated at the end-exhale computed tomography (CT) images. On the other hand, the four-dimensional (4-D) plans using CT images from all respiratory phases seem to be similar to the actual doses. To know the difference between the calculated doses and actual doses delivered to the target and OARs, doses were calculated using 4-D plans and compared with those of the 3-D plans. Materials/Methods: Fourteen patients with lung cancer were treated at our institution from December 2012 to June 2013. 4-D CT scans were performed using multi slice CT and respiratory gating system. 4-D CT images were categorized into 10 respiratory phases. CT images were imported to the treatment planning system and structures were delineated on the endexhale phase CT images. Monte-Carlo algorithm was used for the dose calculation. 48 Gy in four fractions were prescribed at D95 of the PTV. Doses were calculated by both 3-D and 4-D plans in each patient. Maximum doses of the GTV (D-Max), GTV-D99, PTV-D95, Lung-V20, Conformity Index (CI) and Homogeneity index (HI) were compared in each patient. Furthermore, maximum doses of the liver, stomach, esophagus, trachea and spinal cord were also evaluated. Results: The actual doses of 4708.09 cGy 91.62 in PTV-D95 calculated by 4-D plans were significantly decreased in comparison with the prescribed doses of 4800 cGy by 3-D plans (p Z 0.02). The maximum differences of the calculated doses between 3-D and 4-D plans in GTV-D99 and PTV-D95 were 400.0 cGy and 266.7 cGy, respectively. In 3-D plans, doses were overestimated at the average of 2% (max 7.5%). The differences of maximum doses between 3-D and 4-D plans were not statistically significant in each OAR. However, the differences of calculated doses between 3-D and 4-D plans were relatively high in liver (-110.82 cGy 454.28 cGy), esophagus (-86.31 cGy 344.27 cGy) and trachea (-972.89 cGy 536.14 cGy), respectively. Conclusions: Although Monte-Carlo calculation has 2% uncertainty, and deformations of both target and OARs during respiration are inevitable, it was conceivable that the difference of the calculated doses between 3-D plan and 4-D plan to the target tumor were negligible. In contrast, the maximum doses of the OARs varied widely in each case. The accurate margins of OARs were affected by respiratory motions especially in organs such as liver, esophagus, and trachea. 4-D planning should be employed in the treatment planning of the cases with tumor located near the liver, esophagus and trachea to avoid the unexpected overdose-radiation to OARs. Author Disclosure: K. Okawa: None. M. Inoue: None. M. Taro: None. T. Koshi: None. S. Ota: None.

A Comparison of Thyroid Dose Distribution in 3-D Conformal Radiotherapy and Tomotherapy in Patients with Breast Cancer

Background and purpose: During the radiotherapy of breast cancer, especially when the supraclavicular lymph nodes are planned to be treated, a portion of thyroid gland may also be included in the treatment field. In this study we compared thyroid gland dose volume histograms (DVHs) of breast cancer patients receiving radiotherapy, planned in both CT-based three-dimensional planning system and MVCT-based image guidance aspect of helical tomotherapy system. Material and method: 20 breast carcinoma patients who were treated with 3-D conformal radiotherapy technique were evaluated concerning their thyroid gland dose distribution. The estimated minimum, mean and maximum thyroid gland doses were calculated for both 3-D conformal radiothreapy and tomothreapy planning systems. Additionally the volume of thyroid gland that received less than 30 Gy and more than 30 Gy were determined. Results: The maximum, mean and minimum doses of thyroid glands supposed to receive were found to be better with tomotherapy comparing to 3-D conformal therapy plans. The thyroid gland volume that receives more than 30 Gy was smaller in tomothreapy planning system comparing to 3-D conformal therapy planning system. Conclusion: Lower doses of radiation exposure to thyroid gland is possible with Tomotherapy.

Application of a three-dimensional operation planning system for precise hepatectomy in patients with giant hepatocellular carcinoma

Objective To evaluate the feasibility of a three-dimensional (3 D) operation planning system for precise hepatectomy in patients with giant hcpatocellular carcinoma (HCC).Methods The clinical data of 34 patients with giant HCC who received precise hepatectomy at the First Affiliated Hospital of Sun Yat-sen University from May 2009 to May 2011 were retrospectively analyzed.Preoperative evaluation was done based on the computed tomography data,and the resection margin and the volume of resectcd liver were calculated using simulation.The predicted resected liver volume and resection margins were compared with the results of the actual operations.All data were analyzed using the t test,and the correlation between predicted and the actual values was analyzed by calculating Pearson correlation coefficients.Results Hepatic and tumor tissues and the hepatic vessels were reconstructed three-dimensionally using the 3D preoperative simulation software.The volume of simulated resected liver and the length of resection margin were ( 2112 ± 1550 ) ml and ( 12 ± 6) mm,respectively,while the volume of actual resected liver and the length of resection margin were (2031 ± 1411 )ml and ( 12 ± 6)mm,respectively.The predicted and the actual values were statistically correlated ( r =0.961,0.923,P ＜ 0.05 ).There was no significant difference between the predicted and the actual values ( t =1.549,1.143,P ＞ 0.05 ).All patients received precise hepatectomy,and no hepatic failure or death was observed. Conclusion The 3D operation planning system can accurately evaluate the condition of the liver and simulate hepatectomy,and could contribute to safer and more curative precise hepatectomy in patients with giant HCC. Key words: Liver ncoplasms; Three-dimensional reconstruction; Surgical planning; Precise hepatectomy

In Vivo Dosimetry with Semiconducting Diodes for Dose Verification in Total-Body Irradiation

Background and Purpose: For total-body irradiation (TBI) using the translation method, dose distribution cannot be computed with computer-assisted three-dimensional planning systems. Therefore, dose distribution has to be primarily estimated based on CT scans (beam-zone method) which is followed by in vivo measurements to ascertain a homogeneous dose delivery. The aim of this study was to clinically establish semiconductor probes as a simple and fast method to obtain an online verification of the dose at relevant points. Patients and Methods: In 110 consecutively irradiated TBI patients (12.6 Gy, 2 × 1.8 Gy/day), six semiconductor probes were attached to the body surface at dose-relevant points (eye/head, neck, lung, navel). The mid-body point of the abdomen was defined as dose reference point. The speed of translation was optimized to definitively reach the prescribed dose in this point. Based on the entrance and exit doses, the mid-body doses at the other points were computed. The dose homogeneity in the entire target volume was determined comparing all measured data with the dose at the reference point. Results: After calibration of the semiconductor probes under treatment conditions the dose in selected points and the dose homogeneity in the target volume could be quantitatively specified. In the TBI patients, conformity of calculated and measured doses in the given points was achieved with small deviations of adequate accuracy. The data of 80% of the patients are within an uncertainty of ± 5%. Conclusion: During TBI using the translation method, dose distribution and dose homogeneity can be easily controlled in selected points by means of semiconductor probes. Semiconductor probes are recommended for further use in the physical evaluation of TBI.

Evaluating Commercially Available Three-Dimensional Radiotherapy Treatment Planning Systems.

Over the past year we have developed two similar questionnaires on three-dimensional radiotherapy treatment planning (3DRTP) systems and used them to conduct a study of the function and features of commercially available 3DRTP systems. The issues which we reviewed to develop these questionnaires are important to all current and potential users of 3DRTP systems. The items identified in this article should aid readers in developing their own review questionnaire based on the items we discuss as well as their own clinical practice. Because it is not possible to develop a universal questionnaire that will satisfy every clinic because of site-specific treatment techniques and capabilities, this information should aid an institution contemplating the purchase of such a system to develop their own specific set of questions to aid them in their system selection. We believe that a high-level checklist of this nature will prove quite helpful to those institutions preparing to purchase such a system.

Volume definition in radiotherapy planning for lung cancer: how the radiologist can help

Effective treatment for carcinoma of the lung remains one of the biggest challenges in oncology. Radical radiotherapy may be a curative option for patients who are unsuitable for radical surgery either because of disease stage or because of co-morbidity. Long-term disease control with radical radiotherapy is disappointing with only about 6% of patients treated being alive at 5 years . Technological advances involved in the planning and delivery of radiotherapy may improve this. The advent of conformal radiotherapy, utilizing computed tomography and three-dimensional planning systems, allows much more accurate shaping of the radiation fields. This greater accuracy of target volume definition facilitates a reduction in the radiation dose to normal tissues, allowing for dose escalation to the tumour. Delineation of the target volume can be problematic. Conventional CT has limitations in term of distinguishing between benign and malignant tissues, e.g. the size criteria for involved lymph nodes. The oncologist uses a combination of radiological and clinical information when defining the target volume but their radiological interpretation of imaging is inferior to that of a radiologist. The Royal College of Radiologists (RCR) issued guidance in 2004 on the optimal imaging strategies for common cancers. These guidelines address issues regarding the localisation and staging of cancers and treatment planning, and also reporting and training. They recommend the development of closer links between radiologists and oncologists to optimise the interpretation of imaging and target volume definition. This article aims to briefly explain the planning process involved in irradiating lung cancers, highlight problematic areas and suggest ways in which co-operation with radiologists may improve the delivery of radiotherapy and therefore the treatment outcomes for this group of patients.

Evaluation of complex craniomaxillofacial fractures by a new three-dimensional planning system

266-4356/$ – see front matter © 2005 The British Association of Oral and Maxillofac doi:10.1016/j.bjoms.2005.05.021 imPlant Pro, which can read the data from any computed omographic scanner that has the ability to write a DICOM D. After elimination of the cervical spine, the mandible, axilla, and facial bones were isolated by the construction f individual masks. In a similar manner, individual elements f the fractures were isolated and labelled with a different

Radiotherapy of Prostate Cancer with Multileaf Collimators (MLCs)

A technical modification for radiotherapy of prostate cancer is presented to smooth the scalloped dose pattern that occurs at treatment field edge, when a multileaf collimator (MLC) has been used. Ten patients with prostate cancer receiving postoperative, adjuvant irradiation were studied prospectively. By a three-dimensional planning system (TMS, Helax 6.1B) the irradiation was planned for an 18-MV linear accelerator (Primus 1, Siemens). The volumes of interest (VOI) were the planning target volume (PTV; the region of the prostate including the seminal vesicles), the volume of rectum (Vrectum) and urinary bladder (Vbladder). Two four-field techniques (0°, 90°, 180°, 270°) were planned using “beam’s eye view” for setting the leaf position of the MLC. For technique A the MLC was adapted to the PTV using a 0° collimator angle for the lateral fields. For technique B the collimator angle of the lateral fields was optimized to compensate the cascade field shape. Dose-volume histograms of PTV, Vrectum and Vbladder were analyzed. The dose was prescribed for the reference point according to ICRU 50. Film dosimetry was used to show the dose pattern at the field edge produced by the two techniques. Dose to PTV did not differ between technique A and B. Median dose to Vrectum was 82.6% for technique A and 77.3% for technique B (p 0.05). The presented technical modification is an effective method to blur the staggered dose distribution that results, when the MLC is conventionally stepped to adapt to the dorsal, irregular PTV border in irradiation of prostate. Especially for irradiation to escalated dose levels, this modification may reduce the dose to the rectum and thus the rectal side effects in comparison to the conventional MLC fields.

Treatment volume and dose optimization of MammoSite breast brachytherapy applicator

Purpose Limited information has been reported on the dosimetry achieved with the MammoSite breast brachytherapy applicator. We present our results regarding the volume of treatment and a comparison of a single prescription point, single dwell position optimization technique with a six prescription point, multiple dwell position method. Methods and materials Between October 14, 2002 and February 28, 2003, 21 patients with early-stage breast cancer were treated using the MammoSite device. The treatment was delivered in 10 fractions of 3.4 Gy/fraction, b.i.d., with a minimum of 6 hours between the daily fractions. CT of the lumpectomy cavity was obtained both with and without the inflated balloon. A planning target volume was constructed using a three-dimensional planning system. A three-dimensional expansion of the balloon surface was performed using the chest wall and skin as limiting structures. The volume of the inflated balloon was removed from this volume, and the volume of tissue treated in each patient was determined. A sequential expansion in 1-mm increments around the empty lumpectomy cavity was performed until the closest equivalent volume to the planning target volume was obtained. The treatment for the patients in this study was planned using both a single prescription point, single dwell position optimization technique and a six-prescription point, multiple dwell position technique. The single prescription point method has been described in a previous publication. The six-prescription point method used six points placed 1 cm from the balloon surface. Four points are in a plane transverse to the balloon axis perpendicular to the axis of the catheter, and two points are placed along the axis of the catheter. The prescription points along the catheter axis are used to compensate for the decreased dose coverage owing to anisotropy dose distribution of the source. The Nucletron HDR Plato Brachytherapy planning system was used to optimize the source positions and dwell times. Results The volume of breast tissue treated by the MammoSite device was equal to the volume encompassed by a mean 1.6-cm (SD, 0.1) margin around the empty lumpectomy cavity. Compared with the single prescription point optimization method, the six prescription point method provided better dose coverage, with a mean percentage of volume receiving 90% of the prescription dose of 97.2% (SD = 2.1) vs. 89.5% (SD = 4.6) for the single-point method. The mean percentage of volume receiving 100% of the prescription dose was 88.9% (SD = 3.3) for the six-point method vs. 77.6% (SD = 6.1) for the single-point method. However, compared with the single-point method, the six-point optimization method resulted in treatment that was less uniform, with a mean dose homogeneity index of 0.62 (SD = .07) vs. 0.66 (SD = .08) for the single-point method. Conclusion The volume of normal breast tissue treated by the MammoSite device is comparable to other methods of interstitial brachytherapy that treat a 1–2-cm margin of tissue around the excision cavity. The six-prescription point, multiple dwell position method improved dose coverage with a slight decrease in dose homogeneity. The six-point method offers greater reliability of dose coverage compared with the single-point method by providing an increased number of reference points.

Planejamento tridimensional para radioterapia de tumores de esôfago: comparação de técnicas de tratamento e análise de probabilidade de complicações

Para comparar diversas técnicas de irradiação para o câncer de esôfago, foi utilizado sistema de planejamento tridimensional. Em um paciente com carcinoma espinocelular de esôfago médio, foram estudadas as seguintes técnicas de tratamento: dois campos ântero-posteriores e dois campos látero-laterais paralelos e opostos, três campos em "Y" e em "T" e quatro campos em "X". Foram obtidos os histogramas dose-volume, considerando como órgãos de risco medula espinhal e pulmões. Os resultados foram analisados de acordo com as recomendações da Normal Tissue Complication Probability (NTCP) e Tumor Control Probability (TCP). Quanto às doses de irradiação em pulmão, a melhor opção foi a técnica em dois campos ântero-posteriores paralelos e opostos. A medula foi mais poupada quando se utilizaram campos látero-laterais. Sugerimos a combinação de pelo menos duas técnicas de tratamento: ântero-posterior e as técnicas com campos em "Y", "T" ou látero-laterais, para o balanceamento das doses em pulmões e medula espinhal. Ou, ainda, a utilização de técnicas de três campos durante todo o tratamento.

Breast radiotherapy with inclusion of internal mammary nodes: a comparison of techniques with three-dimensional planning

Purpose: To compare the partially wide tangent (PWT) technique of breast and internal mammary chain irradiation with photon/electron (P/E) and standard tangent (ST) techniques in terms of dose homogeneity within breast and the dose to critical structures such as the heart and lung. Methods and Materials: Sixteen left breast cancer patients underwent CT simulation. The breasts, lungs, heart, and internal mammary chain were contoured and treatment plans generated on a three-dimensional planning system (Helax-TMS). Results: The mean dose to the left breast volume with the ST, P/E, and PWT techniques was 94.7%, 98.4%, and 96.5%, respectively ( p = 0.029). The left lung received the lowest mean dose with the ST technique (13.9%) compared with PWT (22.8%) and P/E (24.3%). The internal mammary chain volume was most consistently treated with the PWT (mean dose 99%) vs. P/E (86%) and ST (38.4%) techniques. The heart received the least dose with ST (mean dose 6.7%) vs. PWT (10.3%) and P/E (19%). The PWT treated the greatest amount of contralateral breast (mean dose 5.8%) vs. ST (3.2%) vs. P/E (2.8%). Conclusion: The PWT technique treats the internal mammary chain with acceptable toxicity to major organs, especially the heart, and with reasonable dose homogeneity in patients with mastectomy or intact breasts.

Dosimetric characteristics of the MammoSite RTS, a new breast brachytherapy applicator

Purpose: A new device has been developed with the goal of making breast-conserving therapy more widely available, by making breast brachytherapy as monotherapy simpler and more accurate. This is the first published report on the dosimetric characteristics of this device.Methods and Materials: The experience of a single institution participating in a multi-institutional trial is reported. Twelve patients were enrolled, of whom 8 were treated. Computed tomography scans of all 12 patients were obtained before initiation of treatment. A commercial three-dimensional planning system was used for retrospective detailed analysis of dosimetry, including dose-volume histograms and, in selected patients, skin dose distributions. These data were compared to those of a similar group of patients, analyzed previously, that was treated with interstitial high-dose-rate brachytherapy.Results: Compared with interstitial brachytherapy, the MammoSite device resulted in a treatment dose that was less uniform, with a mean dose homogeneity index of 0.77 vs. 0.93. Coverage and reproducibility were improved, with a mean D90 (minimum dose to 90% of target volume) of 90.0% of prescribed dose (SD 0.5, range: 89.2–90.8%) vs. 69.8% (SD 7.3, range: 61.1–83.5%) for interstitial brachytherapy.Conclusions: Reproducible placement was easily achieved in this very early experience, indicating a much smaller “learning curve” than for interstitial brachytherapy. Because skin doses can be increased with the use of this device, caution is indicated, although simple maneuvers can significantly reduce skin dose.

Intensity-modulated radiation therapy (IMRT) reduces small bowel, rectum, and bladder doses in patients with cervical cancer receiving pelvic and para-aortic irradiation

Purpose: The emergent use of combined modality approach (chemotherapy and radiation therapy) for the treatment of patients with cervical cancer is associated with significant gastrointestinal and genitourinary toxicity. Intensity-modulated radiation therapy (IMRT) has the potential to deliver adequate dose to the target structures while sparing the normal organs and could also allow for dose escalation to grossly enlarged metastatic lymph node in pelvic or para-aortic area without increasing gastrointestinal/genitourinary complications. We conducted a dosimetric analysis to determine if IMRT can meet these objectives in the treatment of cervical cancer. Methods and Materials: Computed tomography scan studies of 10 patients with cervical cancer were retrieved and used as anatomic references for planning. Upon the completion of target and critical structure delineation, the imaging and contour data were transferred to both an IMRT planning system (Corvus, Nomos) and a three-dimensional planning system (Focus, CMS) on which IMRT as well as conventional planning with two- and four-field techniques were derived. Treatment planning was done on these two systems with uniform prescription, 45 Gy in 25 fractions to the uterus, the cervix, and the pelvic and para-aortic lymph nodes. Normalization was done to all IMRT plans to obtain a full coverage of the cervix with the 95% isodose curve. Dose-volume histograms were obtained for all the plans. A Student’s t test was performed to compute the statistical significance. Results: The volume of small bowel receiving the prescribed dose (45 Gy) with IMRT technique was as follows: four fields, 11.01 ± 5.67%; seven fields, 15.05 ± 6.76%; and nine fields, 13.56 ± 5.30%. These were all significantly better than with two-field (35.58 ± 13.84%) and four-field (34.24 ± 17.82%) conventional techniques ( p < 0.05). The fraction of rectal volume receiving a dose greater than the prescribed dose was as follows: four fields, 8.55 ± 4.64%; seven fields, 6.37 ± 5.19%; nine fields, 3.34 ± 3.0%; in contrast to 84.01 ± 18.37% with two-field and 46.37 ± 24.97% with four-field conventional technique ( p < 0.001). The fractional volume of bladder receiving the prescribed dose and higher was as follows: four fields, 30.29 ± 4.64%; seven fields, 31.66 ± 8.26%; and nine fields, 26.91 ± 5.57%. It was significantly worse with the two-field (92.89 ± 35.26%) and with the four-field (60.48 ± 31.80%) techniques ( p < 0.05). Conclusion: In this dosimetric study, we demonstrated that with similar target coverage, normal tissue sparing is superior with IMRT in the treatment of cervical cancer.

A methodology designed to increase accuracy and safety in stereotactic brain surgery.

A series of technical tips and devices designed to increase accuracy and safety in stereotactic surgery are presented. We use stereotactic magnetic resonance imaging with three-dimensional magnetization-prepared rapid gradient-echo (MP-RAGE) imaging to minimize image distortion, and a three-dimensional stereotactic planning system for accurately registering three-dimensional space. We also developed several technical devices useful for stereotactic intracranial procedures; an applicator system attached to the frame which simulates the fiducial markers in order to keep the target at a suitable position in stereotactic space; a torque wrench to set the torque on the fixing pins to the frame reproducibly at 5 inch pounds in order to keep distortion of the frame to a minimum while maintaining secure fixation; an entry point marker to maintain the calculated trajectory angle; a straightening cannula to prevent the thermo-coagulation needle from bending; a microvascular Doppler and its holder to detect significant vessels and to know their precise depth in order to avoid vascular injury from thermocoagulation; a burr hole button device to secure depth electrode cables at the patient's skull.

Predictability of a three-dimensional planning system for oral implant surgery

Predictability of a three-dimensional planning system for oral implant surgery

Planning of beam intensity modulation using an advanced 3D dose calculation algorithm and a simulated annealing method

Purpose: The aim of this work was to develop a fast inverse planning algorithm that will calculate optimum beam intensity distributions and beam shapes, and to incorporate the algorithm into a three-dimensional CT planning system. Method: The algorithm is based on the technique of simulated annealing and produces beam intensity distributions that could in principle be implemented clinically, either by the use of compensators or dynamic multileaf collimation. Dose distributions are calculated using a voxel beam model based on a spherical co-ordinate system, and transformations are given allowing the dose to be determined at any point within the patient. The dose calculation algorithm calculates primary and scattered dose separately from a knowledge of tissue/air ratios and differential scatter/air ratios, and both are corrected for the presence of heterogeneities in three dimensions. Specific attention is given to the execution time of the algorithm, and the methods developed allow satisfactory results to be achieved in calculation times which are sufficiently fast to be used interactively in the planning system. Several objective functions have been developed and can be selected in a simple manner by the user. In general, these attempt to achieve a uniform dose within the target while limiting the dose to organs at risk, either by upper dose limits or by specifying constraints on their dose volume histograms. Results: The beam intensity distributions produced from the optimization have been used automatically by the forward planning system to produce three-dimensional dose distributions, and the results obtained in a number of clinical situations are presented. Conclusions: The inverse planning algorithm developed has been successfully incorporated into a three-dimensional planning system and is capable of producing beam intensity modulated distributions for clinical implementation. The execution time of the algorithm is sufficiently fast to be used as an optimization tool in an interactive forward planning system.