首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 328 毫秒
1.
This study compared the calculated normal tissue complication probability of brain in dogs with a nasal tumor, which had both photon and proton treatment planning. Nine dogs diagnosed with a variety of histologies, but all with large, caudally located nasal tumors were studied. Three-dimensional (3-D) photon dose distribution, and a proton dose distribution was calculated for each dog. To calculate the normal tissue complication probability (NTCP) for brain, the partial brain volume irradiated with the prescribed dose was determined, then a mathematic model relating complications to partial volume and radiation dose was used. The NTCP was always smaller for proton plans as compared to photon plans, indicating conformation of the dose to the target allows a higher dose to be given. If a 5% NTCP were accepted, the mean applicable dose for this group of dogs was 50.2 Gy for photons, but 58.3 Gy for protons. Not all dogs would benefit the same from proton irradiation. If a large partial brain volume has to be irradiated, the advantage becomes minimal. There is also a minimal advantage if the planning target volume (PTV) includes a small, superficial brain volume. However, for a complex PTV shape the degree of conformation is clearly superior for protons and results in smaller calculated NTCPs.  相似文献   

2.
Irradiated brain tumors commonly progress at the primary site, generating interest in focal dose escalation. The aim of this retrospective observational study was to use biological optimization objectives for a modeling exercise with simultaneously‐integrated boost IMRT (SIB‐IMRT) to generate a dose‐escalated protocol with acceptable late radiation toxicity risk estimate and improve tumor control for brainstem tumors in dogs safely. We re‐planned 20 dog brainstem tumor datasets with SIB‐IMRT, prescribing 20 × 2.81 Gy to the gross tumor volume (GTV) and 20 × 2.5 Gy to the planning target volume. During the optimization process, we used biologically equivalent generalized equivalent uniform doses (gEUD) as planning aids. These were derived from human data, calculated to adhere to normal tissue complication probability (NTCP) ≤5%, and converted to the herein used fractionation schedule. We extracted the absolute organ at risk dose‐volume histograms to calculate NTCP of each individual plan. For planning optimization, gEUD(a = 4) = 39.8 Gy for brain and gEUD(a = 6.3) = 43.8 Gy for brainstem were applied. Mean brain NTCP was low with 0.43% (SD ±0.49%, range 0.01‐2.04%); mean brainstem NTCP was higher with 7.18% (SD ±4.29%, range 2.87‐20.72%). Nevertheless, NTCP of < 10% in brainstem was achievable in 80% (16/20) of dogs. Spearman's correlation between relative GTV and NTCP was high (ρ = 0.798, P < .001), emphasizing increased risk with relative size even with subvolume‐boost. Including biologically based gEUD values into optimization allowed estimating NTCP during the planning process. In conclusion, gEUD‐based SIB‐IMRT planning resulted in dose‐escalated treatment plans with acceptable risk estimate of NTCP < 10% in the majority of dogs with brainstem tumors. Risk was correlated with relative tumor size.  相似文献   

3.
Feasibility of delivering a simultaneously integrated boost to canine nasal tumors using helical tomotherapy to improve tumor control probability (TCP) via an increase in total biological equivalent uniform dose (EUD) was evaluated. Eight dogs with varying size nasal tumors (5.8-110.9 cc) were replanned to 42 Gy to the nasal cavity and integrated dose boosts to gross disease of 45.2, 48.3, and 51.3 Gy in 10 fractions. EUD values were calculated for tumors and mean normalized total doses (NTD(mean)) for organs at risk (OAR). Normal Tissue Complication Probability (NTCP) values were obtained for OARs, and estimated TCP values were computed using a logistic dose-response model and based on deliverable EUD boost doses. Significant increases in estimated TCP to 54%, 74%, and 86% can be achieved with 10%, 23%, and 37% mean relative EUD boosts to the gross disease, respectively. NTCP values for blindness of either eye and for brain necrosis were < 0.01% for all boosts. Values for cataract development were 31%, 42%, and 46% for studied boost schemas, respectively. Average NTD(mean) to eyes and brain for mean EUD boosts were 10.2, 11.3, and 12.1 Gy3, and 7.5, 7.2, and 7.9 Gy2, respectively. Using helical tomotherapy, simultaneously integrated dose boosts can be delivered to increase the estimated TCP at 1-year without significantly increasing the NTD(mean) to eyes and brain. Delivery of these treatments in a prospective trial may allow quantification of a dose-response relationship in canine nasal tumors.  相似文献   

4.
Magnetic resonance (MR) images may be useful for radiation planning due to greater contrast resolution. One disadvantage of MR images for radiation planning is the inability to incorporate electron density information into the dose calculation algorithm. To assess the magnitude of this problem, we evaluated radiation dose distribution in canine brain by comparing computed tomography (CT)-based radiotherapy plans with and without electron density correction. Computerized radiotherapy plans were generated for 13 dogs with brain tumors using 6 MV photons. A tissue-contouring program was used to outline the gross tumor volume (GTV) and the planning target volume (PTV) for each patient. Two treatment plans were generated for each dog. First, the plan was optimized without heterogeneity correction. Then the heterogeneity correction was implemented without changing any other plan parameters. Isodose distributions and dose volume histograms (DVHs) were used to compare the two plans. The D95 (dose delivered to 95% of the volume) within the PTV was calculated for each treatment plan and differences in the D95s were compared. The mean D95s without and with heterogeneity correction were 49.1 +/- 0.7 and 48.9 +/- 1.0Gy, respectively. The absolute mean percent dose difference without and with heterogeneity correction was 1.0 - 0.9% (-1.3-3.2%) and was not considered to be clinically significant. We found no clinically significant difference between CT-based radiotherapy plans without and with heterogeneity correction for brain tumors in small animals, which supports the use of MR-based treatment planning for radiotherapy of small animal brain tumors.  相似文献   

5.
Intensity‐modulated radiation therapy (IMRT) allows optimization of radiation dose delivery to complex tumor volumes with rapid dose drop‐off to surrounding normal tissues. A prospective study was performed to evaluate the concept of conformal avoidance using IMRT in canine sinonasal cancer. The potential of IMRT to improve clinical outcome with respect to acute and late ocular toxicity was evaluated. Thirty‐one dogs with sinonasal cancer were treated definitively with IMRT using helical tomotherapy and/or dynamic multileaf collimator (DMLC) delivery. Ocular toxicity was evaluated prospectively and compared with a comparable group of historical controls treated with conventional two‐dimensional radiotherapy (2D‐RT) techniques. Treatment plans were devised for each dog using helical tomotherapy and DMLC that achieved the target dose to the planning treatment volume and limited critical normal tissues to the prescribed dose–volume constraints. Overall acute and late toxicities were limited and minor, detectable by an experienced observer. This was in contrast to the profound ocular morbidity observed in the historical control group treated with 2D‐RT. Overall median survival for IMRT‐treated and 2D‐treated dogs was 420 and 411 days, respectively. Compared with conventional techniques, IMRT reduced dose delivered to eyes and resulted in bilateral ocular sparing in the dogs reported herein. These data provide proof‐of‐principle that conformal avoidance radiotherapy can be delivered through high conformity IMRT, resulting in decreased normal tissue toxicity as compared with historical controls treated with 2D‐RT.  相似文献   

6.
Intensity-modulated radiation therapy (IMRT) can be employed to yield precise dose distributions that tightly conform to targets and reduce high doses to normal structures by generating steep dose gradients. Because of these sharp gradients, daily setup variations may have an adverse effect on clinical outcome such that an adjacent normal structure may be overdosed and/or the target may be underdosed. This study provides a detailed analysis of the impact of daily setup variations on optimized IMRT canine nasal tumor treatment plans when variations are not accounted for due to the lack of image guidance. Setup histories of ten patients with nasal tumors previously treated using helical tomotherapy were replanned retrospectively to study the impact of daily setup variations on IMRT dose distributions. Daily setup shifts were applied to IMRT plans on a fraction-by-fraction basis. Using mattress immobilization and laser alignment, mean setup error magnitude in any single dimension was at least 2.5 mm (0–10.0 mm). With inclusions of all three translational coordinates, mean composite offset vector was 5.9±3.3 mm. Due to variations, a loss of equivalent uniform dose for target volumes of up to 5.6% was noted which corresponded to a potential loss in tumor control probability of 39.5%. Overdosing of eyes and brain was noted by increases in mean normalized total dose and highest normalized dose given to 2% of the volume. Findings suggest that successful implementation of canine nasal IMRT requires daily image guidance to ensure accurate delivery of precise IMRT distributions when non-rigid immobilization techniques are utilized. Unrecognized geographical misses may result in tumor recurrence and/or radiation toxicities to the eyes and brain.  相似文献   

7.
Eighteen dogs with malignant nasal cavity tumors were treated with radiation therapy, including a boost technique. Three 3:0 Gy boost doses were added to a treatment protocol consisting of sixteen 3.0 Gy daily fractions, bringing the total dose to 57 Gy. This boost technique was implemented without an associated increase in overall treatment time by giving the boost doses on a twice-a-day basis. Boost doses were given during the first half of the radiation therapy period. The treatment was completed as planned in 16 of the 18 dogs; two dogs received lower doses (51 and 54 Gy). Median survival was 177 days, poorer than in some other reported studies of nasal tumor irradiation. Acute effects were unacceptable, with 11 of the 18 dogs developing severe mucositis, desquamation, edema, swelling, and pruritus. The extensive nature of the acute reactions compromised assessment of the effect of the increased radiation dose on the tumor. Although there is justification for assessing more aggressive radiation protocols in canine nasal tumor patients, total doses approximating 60 Gy can not be given as described because of the inability of acutely responding normal tissues to compensate.  相似文献   

8.
Radiotherapy with or without surgery is a common choice for brain tumors in dogs. Although numerous studies have evaluated use of three‐dimensional conformal radiotherapy, reports of definitive‐intent, IMRT for canine intracranial tumors are lacking. Intensity‐modulated radiation therapy has the benefit of decreasing dose to nearby organs at risk and may aid in reducing toxicity. However, increasing dose conformity with IMRT calls for accurate target delineation and daily patient positioning, in order to decrease the risk of a geographic miss. To determine survival outcome and toxicity, we performed a multi‐institutional retrospective observational study evaluating dogs with brain tumors treated with IMRT. Fifty‐two dogs treated with fractionated, definitive‐intent IMRT at four academic radiotherapy facilities were included. All dogs presented with neurologic signs and were diagnosed via MRI. Presumed radiological diagnoses included 37 meningiomas, 12 gliomas, and one peripheral nerve sheath tumor. One dog had two presumed meningiomas and one dog had either a glioma or meningioma. All dogs were treated in the macroscopic disease setting and were prescribed a total dose of 45‐50 Gy (2.25‐2.5 Gy per fraction in 18‐20 daily fractions). Median survival time for all patients, including seven cases treated with a second course of therapy was 18.1 months (95% confidence of interval 12.3‐26.6 months). As previously described for brain tumors, increasing severity of neurologic signs at diagnosis was associated with a worse outcome. Intensity‐modulated radiation therapy was well tolerated with few reported acute, acute delayed, or late side effects.  相似文献   

9.
Hege  Kippenes  DVM  PHD  Patrick R.  Gavin  DVM  PHD  Homayon  Parsaei  PHD  Mark H.  Phillips  PHD  Paul S.  Cho  PHD  Charles W.  Leathers  DVM  PHD  Ronald D.  Sande  DVM  MS  PHD 《Veterinary radiology & ultrasound》2003,44(3):360-366
Intensity modulated radiation therapy (IMRT) theoretically allows detailed tailoring of the dose distribution in tissue. The goal of this study was to determine if a method of dynamic IMRT could be used to deliver a high dose of radiation to a concave shaped target around the cervical spinal cord. Fifteen young adult dogs from our laboratory population were randomly divided into two groups. A radiation dose of 84 Gy in 4 Gy fractions was delivered with a conventional 4 field technique for Group A dogs, and with dynamic IMRT for Group B dogs to a "C-shaped" target close to the cervical spinal cord. Neurologic status, magnetic resonance imaging results and histopathologic changes were compared among dogs in the two groups. Group A dogs developed myelomalacia with a latency period of 65 +/- 9 days. Group B dogs did not have any histologic changes to the cervical spinal cord when euthanasia was performed 12 months after irradiation. The results demonstrate that this IMRT technique can be safely and precisely delivered to a patient in a clinical situation.  相似文献   

10.
Although anisotropic analytical algorithm (AAA) and Acuros XB (AXB) are both radiation dose calculation algorithms that take into account the heterogeneity within the radiation field, Acuros XB is inherently more accurate. The purpose of this retrospective method comparison study was to compare them and evaluate the dose discrepancy within the planning target volume (PTV). Radiation therapy (RT) plans of 11 dogs with intranasal tumors treated by radiation therapy at the University of Georgia were evaluated. All dogs were planned for intensity‐modulated radiation therapy using nine coplanar X‐ray beams that were equally spaced, then dose calculated with anisotropic analytical algorithm. The same plan with the same monitor units was then recalculated using Acuros XB for comparisons. Each dog's planning target volume was separated into air, bone, and tissue and evaluated. The mean dose to the planning target volume estimated by Acuros XB was 1.3% lower. It was 1.4% higher for air, 3.7% lower for bone, and 0.9% lower for tissue. The volume of planning target volume covered by the prescribed dose decreased by 21% when Acuros XB was used due to increased dose heterogeneity within the planning target volume. Anisotropic analytical algorithm relatively underestimates the dose heterogeneity and relatively overestimates the dose to the bone and tissue within the planning target volume for the radiation therapy planning of canine intranasal tumors. This can be clinically significant especially if the tumor cells are present within the bone, because it may result in relative underdosing of the tumor.  相似文献   

11.
Thirteen dogs with malignant tumors of the nasal cavity were treated with a combination of slow release cisplatin and megavoltage radiation. Radiation was delivered on a Monday through Friday schedule using a 6 MV linear accelerator. The median total dose was 49.5 Gy (range 49.5-56 Gy). Cisplatin was given using an open-cell polylactic acid polymer, impregnated with the drug and implanted intramus-cularly at a distant site, as a slow release delivery system (OPLAn-Pt [THM Biomedical, Inc]). The median dose used was 60 mg/m2 (range 60–100 mg/m2). When combined with radiation, this delivery system caused no systemic drug toxicity, and a local tissue reaction was seen in only two dogs. Acute side effects to normal tissue from radiation were not enhanced, as measured by subjective assessment. When compared to a group of historical controls that received radiation without OPLA-Pt, the dogs that received combined radiation and cisplatin had longer overall survival times, with a median of 580 days. The control group had a median survival of 325 days. Previously reported median survival times for comparable megavoltage radiation treatment range from 6 to 13 months. Some dogs in both groups also received adjubant chemotherapy but this did not influence survival time. By multivariate analysis, only the use of OPLA-Pt was found to significantly influence survival, with a p value of p = 0.023. Mega-voltage radiation and slow release cisplatin appears to be a well tolerated combination that may favorably affect survival of dogs with nasal tumors.  相似文献   

12.
Gemcitabine (2',2'-difluorodeoxycytidine) was given intravenously twice weekly to 10 cats with oral squamous cell carcinoma and 15 dogs with nasal carcinoma undergoing radiotherapy as a radiosensitizing agent. The average total radiation dose was 50 Gy for dogs and 54 Gy for cats given Monday-Friday (planned dose of 54 and 57 Gy, respectively). Dogs received an average of five doses of gemcitabine beginning at 50 mg/m2, and cats received an average of five doses of gemcitabine beginning at 25 mg/m2. Twelve of 15 dogs and five of 10 cats required chemotherapy dose reduction or postponement because of hematologic or normal tissue toxicity. The results herein do not support the use of gemcitabine at the studied dose and schedule, as significant hematologic and local tissue toxicity was observed in the studied patients. Pharmacokinetic data are necessary to best define the efficacy and optimal dose and schedule of gemcitabine in combination with traditional radiotherapy.  相似文献   

13.
Intensity-modulated radiation therapy (IMRT) is a valuable tool in human radiation oncology, but information on its use in veterinary medicine is lacking. In this study, 12 dogs with nasal tumors were treated with IMRT at a median radiation dose of 54 Gy. Patient survival times and frequency and severity of side effects on ocular structures, oral mucosa, and skin were recorded. Eight dogs (67%) had resolution of clinical signs during radiation therapy. Median overall survival time was 446 d with a 50% 1-year and a 25% 2-year survival rate. Minimal grade 2 or 3 acute skin toxicity, no grade 2 or 3 late skin toxicity, and no grade 2 or 3 toxicity to oral mucosa or the eye opposite the tumor were identified in the dogs treated with IMRT in this study. The ipsilateral eye could not be routinely spared due to its proximity to the tumor.  相似文献   

14.
Radiation therapy is the treatment of choice for many primary canine brain tumors. The radiation dose tolerated by surrounding healthy brain tissue can be a limiting factor for radiation treatment and total dose as well as fractionation schedules, and volume effects may play a role in the outcome of patients undergoing radiation therapy. The purpose of this retrospective study was to evaluate the efficacy of radiation therapy in dogs with brain tumors that showed signs of neurologic disease. Forty-six dogs with brain tumors were included in the analysis. In 34 dogs, computer-generated treatment plans were available, and dose-volume data could be obtained. The totally prescribed radiation therapy doses ranged from 35 to 52.5 Gy (mean = 40.9 [SD +/- 2.91) applied in 2.5- to 4-Gy fractions (mean = 3.2). The median overall survival time calculated for deaths attributable to worsening of neurologic signs was 1,174 days (95% confidence interval [CI], 693-1,655 days). Assuming that all deaths were due to disease or treatment consequences, the median survival time was 699 days (95% CI, 589-809 days). No prognostic clinical factors such as the location or size of the tumor or neurologic signs at presentation were identified. With computerized treatment planning and accurate positioning, high doses of radiation (> 80% of the total dose) could be limited to mean relative brain volumes of 35.3% (+/- 12.6). These small volumes may decrease the probability of severe late effects such as infarction or necrosis. In this study, very few immediate or early delayed adverse effects and no late effects were noted, and quality of life was good to excellent.  相似文献   

15.
  相似文献   

16.
To compare changes in dose distribution in irregularly shaped volumes treated using fields with noncoincident isocenters compared with fields with coincident isocenters. The hypothesis was that use of fields with noncoincident isocenters would result in improved homogeneity of dose distribution. We chose to test the hypothesis in canine nasal tumors because of the increased dorsoventral thickness of the caudal compared with the rostral nasal cavity. Computed tomography images from eight dogs with nasal tumors were selected. A tissue-contouring program was used to outline contours, including the mandible as a normal tissue structure and the planning target volume (PTV), divided into a rostral and caudal volume. A traditional computerized treatment plan consisting of two parallel-opposed fields was constructed for each dog. A second treatment plan using a third caudally located field having a different isocenter was constructed for comparison. Dose-volume histograms were generated and compared for each contoured structure in both plans. In all dogs the use of noncoincident fields resulted in increased dose to the ethmoid region through the caudal field. Minimum dose in the caudal tumor PTV increased as well. At the same time, dose delivered to the mandible, prone to develop significant side effects, was lower in all dogs with the use of noncoincident fields, as it was possible to reduce the dose delivered from the ventral field. Use of photon fields with noncoincident isocenters can improve the dose distribution in irregularly shaped volumes in comparison with fields with coincident isocenters. Improved tumor dose distribution was achieved with the addition of a smaller field having a different isocenter.  相似文献   

17.
Previous trials showed the importance of administering radiation therapy (RT) with small doses per fraction in canine pelvic tumours to maintain acceptable toxicity levels. With increased accuracy/precision of RT, namely intensity‐modulated RT (IMRT), this approach might be challenged. Theoretical toxicity calculations for a new definitive‐intent moderately hypofractionated RT protocol for canine anal sac adenocarcinomas (ASAC) were performed, focussing on the risk of toxicity in pelvic organs at risk (OAR). Computed tomography datasets of 18 dogs with stage 3b ASAC were included. Re‐planning with margins for daily image‐guidance/IMRT was performed and a new protocol isoeffective to previously described definitive‐intent protocols was computed. Dose‐volume information were derived from individual plans and used for normal tissue complication probability (NTCP) computations. A 12 × 3.8 Gy protocol was computed for risk estimation. Tumour volumes ranged from 27.9 to 820.4 cm3 (mean 221.3 cm3 ± 188.9). For late rectal toxicity/bleeding ≥grade 2, median risk probability was 2.3% inter quartile range (IQR: 5.9; 95% confidence interval (CI): 1.2, 8.4) (rho = 0.436) and 3.4% (IQR: 0.96; 95%CI: 3.1, 4.0) (rho = 0.565), respectively. Median late toxicities in urinary bladder, kidneys and small bowel were <1%, except in one kidney. Myelopathy/myelonecrosis had a median risk probability of 4.1% (IQR: 23.5; 95%CI: 2.1, 25.2) (rho = 0.366) and 5.6% (IQR: 13.5; 95%CI: 3.1, 14.1) (rho = 0.363), respectively. However, graded risk showed a probability estimate for late spinal cord toxicity of ≥5% in 8/18 patients. The daily‐imaging IMRT 12 × 3.8 Gy protocol for canine ASAC seems tolerable for most cases, even in advanced disease. Theoretical dose computations serve as estimate, but are safe measures before implementing new protocols into clinical use.  相似文献   

18.
  相似文献   

19.
Canine nasal tumors are typically treated with radiation therapy but most patients develop local recurrence. Our purpose was to evaluate tumor and normal tissue response to reirradiation in nine dogs. The median dose delivered with the first protocol was 50 Gy (range 44–55 Gy) and the median fraction number was 18 (range 15–20). For the second protocol, the median dose was lower intentionally, median of 36 Gy (range 23–44 Gy), without changing the median fraction number of 18 (range 14–20) to avoid late effects. The median time between protocols was 539 days (range 258–1652 days). Median survival was 927 days (95% confidence interval [CI] 423–1767 days). Median time to progression following the first and second courses was 513 days (95% CI 234–1180 days) and 282 days (95% CI 130–453 days), respectively. These were not significantly different (P=0.086). The qualitative response assessment was better for the first course compared with the second (P=0.018). Severity and timing of skin, mucous membrane, and ocular effects were similar for early side effects between the two courses (P>0.05 for all comparisons). All dogs experienced some late side effects, with two out of nine being classified as severe. These severe effects were blindness in each dog, possibly related to tumor recurrence. Reirradiation of canine nasal tumors resulted in a second clinical remission in eight of nine dogs, although the second response was less complete. Acute and late effects for seven of nine patients were not life threatening, indicating that reirradiation of canine nasal tumors may be a viable treatment option after recurrence.  相似文献   

20.
Thirty dogs with spontaneous tumors were irradiated with proton therapy using a novel spot scanning technique to evaluate the safety and efficacy of the system, and to study the acute and late radiation reactions. Nasal tumors, soft tissue sarcomas, and miscellaneous tumors of the head were treated with a median total dose of 52.5 Gy given in 3.5 Gy fractions. Acute effects, late effects, tumor response, and outcome were analyzed. No unexpected radiation reactions were seen, however two dogs did develop in-field osteosarcoma, and one dog developed in-field bone necrosis. Complete response to therapy was seen in 40% (12/30), partial response in 47% (14/30), and no response in 13% (4/30). Median survival for all dogs was 385 days (range of 14–4583 days). Dogs with nasal cavity tumors had a median survival of 385 days (range of 131–1851 days) and dogs with soft tissue sarcomas had a median survival time of 612 days (range of 65–4588 days). Treatment outcome was similar to historical controls. This new proton spot scanning technique proved to be safe and reliable.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号