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1.
Med Dosim ; 2020 Feb 28.
Artigo em Inglês | MEDLINE | ID: mdl-32122694

RESUMO

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

2.
Radiat Oncol ; 15(1): 67, 2020 Mar 17.
Artigo em Inglês | MEDLINE | ID: mdl-32178694

RESUMO

BACKGROUND: Hypofractionated whole-breast irradiation is a standard adjuvant therapy for early-stage breast cancer. This study evaluates the plan quality and efficacy of an in-house-developed automated radiotherapy treatment planning algorithm for hypofractionated whole-breast radiotherapy. METHODS: A cohort of 99 node-negative left-sided breast cancer patients completed hypofractionated whole-breast irradiation with six-field IMRT for 42.56 Gy in 16 daily fractions from year 2016 to 2018 at a tertiary center were re-planned with an in-house-developed algorithm. The automated plan-generating C#-based program is developed in a Varian ESAPI research mode. The dose-volume histogram (DVH) and other dosimetric parameters of the automated and manual plans were directly compared. RESULTS: The average time for generating an autoplan was 5 to 6 min, while the manual planning time ranged from 1 to 1.5 h. There was only a small difference in both the gantry angles and the collimator angles between the autoplans and the manual plans (ranging from 2.2 to 5.3 degrees). Autoplans and manual plans performed similarly well in hotspot volume and PTV coverage, with the autoplans performing slightly better in the ipsilateral-lung-sparing dose parameters but were inferior in contralateral-breast-sparing. The autoplan dosimetric quality did not vary with different breast sizes, but for manual plans, there was worse ipsilateral-lung-sparing (V4Gy) in larger or medium-sized breasts than in smaller breasts. Autoplans were generally superior than manual plans in CI (1.24 ± 0.06 vs. 1.30 ± 0.09, p < 0.01) and MU (1010 ± 46 vs. 1205 ± 187, p < 0.01). CONCLUSIONS: Our study presents a well-designed standardized fully automated planning algorithm for optimized whole-breast radiotherapy treatment plan generation. A large cohort of 99 patients were re-planned and retrospectively analyzed. The automated plans demonstrated similar or even better dosimetric quality and efficacy in comparison with the manual plans. Our result suggested that the autoplanning algorithm has great clinical applicability potential.

3.
J Appl Clin Med Phys ; 20(7): 109-120, 2019 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-31207034

RESUMO

The major challenge in treating a mobile target is obtaining the temporal and spatial information imaging and treatment details. This phantom study quantitatively evaluates the geometric and dosimetric effects of various treatment techniques under different respiratory patterns. The regular motion model was a sinusoidal waveform with a longitudinal range of ±1.5 cm and a period of 4 sec, while irregular motion models were generated by extracting signals from clinical cases. Helical CT for a static target and 4D CT with retrospective sorting were acquired. Phase bin, maximum, and average intensity projection (MIP and AIP) CT datasets were reconstructed. RapidArc and IMRT plans were generated on static and moving target CT datasets with different motion patterns using the phase-based gating and nongating treatment. Dose measurements were performed using EBT3 films. Dose profile and gamma analysis (±3%/1 mm criteria) were used for dose comparisons. For the irregular motions, internal target volume variations between AIP and MIP datasets (AIP/MIP) had slight differences (-6.2% to -7.7%) for gated plans, and larger differences (-12.3% to -15.2%) for nongated plans. Dosimetric measurements showed a high gamma passing rate (>98.5%) for the static plan in the target region, while the AIP and MIP gated plans had average passing rates of 92.2% ± 5.7% and 85.8% ± 9.5%, respectively. Nongated plans had significantly lower and deviated passing rates, while the AIP and MIP plans had passing rates of 43.6% ± 22.2% and 66.7% ± 28.2%, respectively (p < 0.05). Lung stereotactic body radiotherapy treatment delivered with the gated technique did not compromise the gross tumor volumes coverage, and was insensitive to the breathing irregularities and plan techniques. Adequate margins should be accounted to cover the mis-gating effect when using the phase-based gating under irregular motion.


Assuntos
Tomografia Computadorizada Quadridimensional/métodos , Neoplasias Pulmonares/fisiopatologia , Neoplasias Pulmonares/cirurgia , Imagens de Fantasmas , Radiocirurgia/métodos , Planejamento da Radioterapia Assistida por Computador/métodos , Respiração , Humanos , Processamento de Imagem Assistida por Computador/métodos , Neoplasias Pulmonares/diagnóstico por imagem , Movimento , Órgãos em Risco/efeitos da radiação , Dosagem Radioterapêutica , Radioterapia de Intensidade Modulada/métodos , Estudos Retrospectivos
4.
Radiol Oncol ; 53(2): 256-264, 2019 04 05.
Artigo em Inglês | MEDLINE | ID: mdl-30969940

RESUMO

Background The aim of the study was investigate the impact of body-mass factors (BMF) on setup displacement during pelvic radiotherapy in patients with lower abdominal cancers. Patients and methods The clinical data of a training cohort composed of 60 patients with gynecological, rectal, or prostate cancer were analyzed. The daily alignment data from image-guided radiotherapy (IGRT) were retrieved. Setup errors for were assessed by systematic error (SE) and random error (RE) through the superior-inferior (SI), anterior-posterior (AP), and medial-lateral (ML) directions. Several BMFs and patient-related parameters were analyzed with binary logistic regression and receiver-operating characteristic curves. A scoring system was proposed to identify those with greater setup displacement during daily treatment. The results were validated by another cohort. Results A large hip lateral diameter correlated with a greater SI-SE and AP-SE, whereas a large umbilical AP diameter correlated with a greater ML-SE and ML-RE. A higher SI-RE was associated with a large hip circumference. The positive predictors for setup uncertainty were chosen to dichotomize patients into groups at high risk and low risk for setup displacement. Based on the scoring system, the adequate treatment margins for the SI direction in the high-and low-risk groups were 5.4 mm and 3.8 mm, whereas those for the ML direction were 8.2 mm and 4.2 mm, respectively. The validated cohort showed a similar trend. Conclusions Large BMFs including hip lateral diameter, hip circumference, and umbilical AP diameter are associated with greater setup uncertainty. Based on the scores, IGRT or required treatment margins can be adapted for patients with high risk features.


Assuntos
Neoplasias dos Genitais Femininos/radioterapia , Neoplasias da Próstata/radioterapia , Erros de Configuração em Radioterapia , Radioterapia Guiada por Imagem , Neoplasias Retais/radioterapia , Adulto , Idoso , Idoso de 80 Anos ou mais , Análise de Variância , Feminino , Neoplasias dos Genitais Femininos/diagnóstico por imagem , Quadril/anatomia & histologia , Humanos , Masculino , Pessoa de Meia-Idade , Tamanho do Órgão , Neoplasias da Próstata/diagnóstico por imagem , Curva ROC , Planejamento da Radioterapia Assistida por Computador , Neoplasias Retais/diagnóstico por imagem , Incerteza , Circunferência da Cintura
5.
Radiat Oncol ; 13(1): 222, 2018 Nov 13.
Artigo em Inglês | MEDLINE | ID: mdl-30424789

RESUMO

PURPOSE: The dosimetric leaf gap (DLG) and multileaf collimator (MLC) transmission are two important systematic parameters used to model the rounded MLC leaf ends effect when commissioning an Eclipse treatment planning system (TPS). Determining the optimal DLG is a time consuming process. This study develops a simple and reliable method for determining the DLG using the cross-field dose width. METHODS AND MATERIALS: A Varian TrueBeam linac with 6 MV, 10 MV, 6 MV flattening filter free (FFF) and 10 MV FFF photon beams and equipped with the 120 Millennium MLC and the Eclipse™ TPS was used in this study. Integral sliding fields and static slit MLC field doses with different gap widths were measured with an ionization chamber and GAFCHROMIC EBT3 films, respectively. Measurements were performed for different beam energies and at depths of 5 and 10 cm. DLGs were derived from a linear extrapolation to zero dose and intercepting at the gap width axis. In the ion chamber measurements method, the average MLC leaf transmission to the gap reading for each gap (RgT) were calculated with nominal and cross-field dose widths, respectively. The cross-field dose widths were determined according to the dose profile measured with EBT3 films. Additionally, the optimal DLG values were determined using plan dose measurements, as the value that produced the closest agreement between the planned and measured doses. DLGs derived from the nominal and cross-field dose width, the film measurements, and the optimal process, were obtained and compared. RESULTS: The DLG values are insensitive to the variations in depth (within 0.07 mm). DLGs derived from nominal gap widths showed a significantly lower values (with difference about 0.5 mm) than that from cross-field dose widths and from film measurements and from plan optimal values. The method in deriving DLGs by correcting the nominal gap widths to the cross-field dose widths has shown good agreements to the plan optimal values (with difference within 0.21 mm). CONCLUSIONS: The DLG values derived from the cross-field dose width method were consistent with the values derived from film measurements and from the plan optimal process. A simple and reliable method to determine DLG for rounded leaf-end MLC systems was established. This method provides a referable DLG value required during TPS commissioning.


Assuntos
Neoplasias/radioterapia , Aceleradores de Partículas/instrumentação , Imagens de Fantasmas , Planejamento da Radioterapia Assistida por Computador/métodos , Radioterapia de Intensidade Modulada/instrumentação , Radioterapia de Intensidade Modulada/métodos , Humanos , Dosagem Radioterapêutica
6.
Cancer Immunol Immunother ; 67(4): 551-562, 2018 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-29270668

RESUMO

Rectal cancer, which comprises 30% of all colorectal cancer cases, is one of the most common forms of cancer in the world. Patients with locally advanced rectal cancer (LARC) are often treated with neoadjuvant chemoradiotherapy (neoCRT) followed by surgery. However, after neoCRT treatment, approximately one-third of the patients progress to local recurrence or distant metastasis. In these studies, we found that patients with tumors that exhibited cytosolic HMGB1(Cyto-HMGB1) translocation and/or the presence of PD-1+ tumor-infiltrating lymphocytes (TILs) before treatment had a better clinical outcome. The better outcome is likely due to the release of HMGB1, which triggers the maturation of dendritic cells (DCs) via TLR4 activation, and the subsequent recruitment of PD-1+ tumor-infiltrating lymphocytes to the tumor site, where they participate in immune-scavenging. In conclusion, our results provide evidence that cyto-HMGB1 and/or PD-1+TIL are not only predictive biomarkers before treatment, but they can also potentially designate patients for personalized oncological management including immunotherapy.


Assuntos
Biomarcadores Tumorais/metabolismo , Citosol/metabolismo , Proteína HMGB1/metabolismo , Linfócitos do Interstício Tumoral/imunologia , Terapia Neoadjuvante/mortalidade , Receptor de Morte Celular Programada 1/metabolismo , Neoplasias Retais/patologia , Microambiente Tumoral/imunologia , Idoso , Quimiorradioterapia Adjuvante , Feminino , Humanos , Masculino , Recidiva Local de Neoplasia/imunologia , Recidiva Local de Neoplasia/metabolismo , Recidiva Local de Neoplasia/patologia , Recidiva Local de Neoplasia/terapia , Prognóstico , Neoplasias Retais/imunologia , Neoplasias Retais/metabolismo , Neoplasias Retais/terapia , Taxa de Sobrevida
7.
Stereotact Funct Neurosurg ; 95(3): 142-148, 2017.
Artigo em Inglês | MEDLINE | ID: mdl-28486221

RESUMO

PURPOSE: To analyze and compare the characteristics of dose distributions for Leksell Gamma Knife Perfexion (LGK-PFX) and CyberKnife (CK) in treating arteriovenous malformations (AVMs). SUBJECTS AND METHODS: Twenty-four patients with AVMs who received CK radiosurgery at a prescribed dose (PD) of 16-25 Gy in a single fraction were selected. A LGK-PFX treatment plan with the same PD was designed for each patient. Dosimetric values for both systems were compared with respect to the conformity index (CI); selectivity index (SI); gradient index (GI) of 75, 50, and 25% of the PD; heterogeneity index; volume of the brain tissue covered by doses of 10 and 12 Gy; maximum dose delivered to the brainstem; and beam-on time. RESULTS: The CIs of LGK-PFX and CK were 0.744 ± 0.075 and 0.759 ± 0.071 (p = 0.385), respectively. The SIs of LGK-PFX and CK were 0.764 ± 0.081 and 0.780 ± 0.076 (p = 0.424), respectively. The GI75%, GI50%, and GI25% values of LGK-PFX and CK were 1.028 ± 0.123 and 2.439 ± 0.338 (p < 0.001), 3.169 ± 0.265 and 4.972 ± 0.852 (p < 0.001), and 8.650 ± 0.914 and 14.261 ± 2.476 (p < 0.001), respectively. Volumes of the brain tissue covered by 10 Gy and 12 Gy for LGK-PFX and CK (p < 0.001) exhibited a significant difference. CONCLUSIONS: LGK-PFX and CK exhibited similar dose conformity. LGK-PFX showed superior normal tissue sparing.


Assuntos
Malformações Arteriovenosas/radioterapia , Malformações Arteriovenosas/cirurgia , Encéfalo/efeitos da radiação , Encéfalo/cirurgia , Radiocirurgia/métodos , Dosagem Radioterapêutica , Humanos , Planejamento da Radioterapia Assistida por Computador
8.
Radiat Oncol ; 12(1): 55, 2017 Mar 20.
Artigo em Inglês | MEDLINE | ID: mdl-28320428

RESUMO

BACKGROUND: To improve local control rate in patients with breast cancer receiving adjuvant radiotherapy after breast conservative surgery, additional boost dose to the tumor bed could be delivered simultaneously via the simultaneous integrated boost (SIB) modulated technique. However, the position of tumor bed kept changing during the treatment course as the treatment position was aligned to bony anatomy. This study aimed to analyze the positional uncertainties between bony anatomy and tumor bed, and a topology-based approach was derived to stratify patients with high variation in tumor bed localization. METHODS: Sixty patients with early-stage breast cancer or ductal carcinoma in situ were enrolled. All received adjuvant whole breast radiotherapy with or without local boost via SIB technique. The delineation of tumor bed was defined by incorporating the anatomy of seroma, adjacent surgical clips, and any architectural distortion on computed tomography simulation. A total of 1740 on-board images were retrospectively analyzed. Positional uncertainty of tumor bed was assessed by four components: namely systematic error (SE), and random error (RE), through anterior-posterior (AP), cranial-caudal (CC), left-right (LR) directions and couch rotation (CR). Age, tumor location, and body-mass factors including volume of breast, volume of tumor bed, breast thickness, and body mass index (BMI) were analyzed for their predictive role. The appropriate margin to accommodate the positional uncertainty of the boost volume was assessed, and the new plans with this margin for the tumor bed was designed as the high risk planning target volume (PTV-H) were created retrospectively to evaluate the impact on organs at risk. RESULTS: In univariate analysis, a larger breast thickness, larger breast volume, higher BMI, and different tumor locations correlated with a greater positional uncertainty of tumor bed. However, BMI was the only factor associated with displacements of surgical clips in the multivariate analysis and patients with higher BMI were stratified as high variation group. When image guidance was aligned to bony structures, the SE and RE of clip displacement were consistently larger in the high variation group. The corresponding PTV-H margins for the high- and low-variation groups were 7, 10, 10 mm and 4, 9, 6 mm in AP, CC, LR directions, respectively. The heart dose between the two plans was not significantly different, whereas the dosimetric parameters for the ipsilateral lung were generally higher in the new plans. CONCLUSIONS: In patients with breast cancer receiving adjuvant radiotherapy, a higher BMI is associated with a greater positional uncertainty of the boost tumor volume. More generous margin should be considered and it can be safely applied through proper design of beam arrangement with advanced treatment techniques.


Assuntos
Neoplasias da Mama/radioterapia , Carcinoma Intraductal não Infiltrante/radioterapia , Radiometria , Planejamento da Radioterapia Assistida por Computador/métodos , Radioterapia/métodos , Adulto , Idoso , Índice de Massa Corporal , Feminino , Humanos , Pessoa de Meia-Idade , Estudos Retrospectivos , Instrumentos Cirúrgicos , Incerteza
9.
Sci Rep ; 5: 17863, 2015 Dec 11.
Artigo em Inglês | MEDLINE | ID: mdl-26658746

RESUMO

Applicators containing metal have been widely used in recent years when applying brachytherapy to patients with cervical cancer. However, the high dose rate (HDR) treatment-planning system (TPS) that is currently used in brachytherapy still assumes that the treatment environment constitutes a homogeneous water medium and does not include a dose correction for the metal material of the applicator. The primary purpose of this study was to evaluate the HDR (192)Ir dose distribution in cervical cancer patients when performing brachytherapy using a metal-containing applicator. Thermoluminescent dosimeter (TLD) measurements and Monte Carlo N-Particle eXtended (MCNPX) code were used to explore the doses to the rectum and bladder when using a Henschke applicator containing metal during brachytherapy. When the applicator was assumed to be present, the absolute dose difference between the TLD measurement and MCNPX simulation values was within approximately 5%. A comparison of the MCNPX simulation and TPS calculation values revealed that the TPS overestimated the International Commission of Radiation Units and Measurement (ICRU) rectum and bladder reference doses by 57.78% and 49.59%, respectively. We therefore suggest that the TPS should be modified to account for the shielding effects of the applicator to ensure the accuracy of the delivered doses.


Assuntos
Braquiterapia/métodos , Metais , Dosagem Radioterapêutica , Simulação por Computador , Humanos , Método de Monte Carlo , Radiometria , Planejamento da Radioterapia Assistida por Computador , Reto , Bexiga Urinária
10.
Biomed Res Int ; 2015: 959504, 2015.
Artigo em Inglês | MEDLINE | ID: mdl-25767810

RESUMO

Radiation pneumonitis (RP) is a common complication for radiotherapy of esophageal cancer and is associated with the low dose irradiated lung volume. This study aims to reduce the mean lung dose (MLD) and the relative lung volume at 20 Gy (V 20) and at low dose region using various designs of the fan-shaped complete block (FSCB) in helical tomotherapy. Hypothetical esophageal tumor was delineated on an anthropomorphic phantom. The FSCB was defined as the fan-shaped radiation restricted area located in both lungs. Seven treatment plans were performed with nonblock design and FSCB with different fan angles, that is, from 90° to 140°, with increment of 10°. The homogeneous index, conformation number, MLD, and the relative lung volume receiving more than 5, 10, 15, and 20 Gy (V 5, V 10, V 15, and V 20) were determined for each treatment scheme. There was a substantial reduction in the MLD, V 5, V 10, V 15, and V 20 when using different types of FSCB as compared to the nonblock design. The reduction of V 20, V 15, V 10, and V 5 was 6.3%-8.6%, 16%-23%, 42%-57%, and 42%-66% for FSCB 90°-140°, respectively. The use of FSCB in helical tomotherapy is a promising method to reduce the MLD, V 20, and relative lung volume in low dose region, especially in V 5 and V 10 for esophageal cancer.


Assuntos
Neoplasias Esofágicas/radioterapia , Pulmão/patologia , Pulmão/efeitos da radiação , Pneumonite por Radiação/prevenção & controle , Radioterapia de Intensidade Modulada/efeitos adversos , Radioterapia de Intensidade Modulada/métodos , Relação Dose-Resposta à Radiação , Humanos , Imagens de Fantasmas , Pneumonite por Radiação/patologia , Dosagem Radioterapêutica
11.
PLoS One ; 9(8): e104831, 2014.
Artigo em Inglês | MEDLINE | ID: mdl-25133789

RESUMO

This study explores how the metal materials of the applicator influence the dose distribution when performing brachytherapy for cervical cancer. A pinpoint ionization chamber, Monte Carlo code MCNPX, and treatment planning system are used to evaluate the dose distribution for a single Ir-192 source positioned in the tandem and ovoid. For dose distribution in water with the presence of the tandem, differences among measurement, MCNPX calculation and treatment planning system results are <5%. For dose distribution in water with the presence of the ovoid, the MCNPX result agrees with the measurement. But the doses calculated from treatment planning system are overestimated by up to a factor of 4. This is due to the shielding effect of the metal materials in the applicator not being considered in the treatment planning system. This result suggests that the treatment planning system should take into account corrections for the metal materials of the applicator in order to improve the accuracy of the radiation dose delivered.


Assuntos
Braquiterapia/instrumentação , Humanos , Imagens de Fantasmas , Radiometria , Aço Inoxidável
12.
Biomed Res Int ; 2014: 741326, 2014.
Artigo em Inglês | MEDLINE | ID: mdl-25170514

RESUMO

PURPOSE: Limited-tomotherapy and hybrid-IMRT treatment techniques were compared for reductions in ipsilateral and contralateral lung, heart, and contralateral breast radiation doses. METHODS AND MATERIALS: Thirty consecutively treated left-sided early-stage breast cancer patients were scheduled for lTomo and hIMRT. For the hIMRT plan conventional tangential-field and four-field IMRT plans were combined with different weightings in the prescribed dose. For the lTomo plan a geometrically limited arc was designed for the beamlet entrance. A D p of 50.4 Gy in 28 fractions was used for the PTV. The dose coverage, homogeneity index, conformity index of the target, and the dose volumes of critical structures were compared. RESULTS: Both modalities presented similar target coverage. The homogeneity and conformity were improved for lTomo with P < 0.001 and P = 0.006, respectively. In the lTomo plan a concave dose distribution was generated with significant dose reductions in both high and low dose regions for ipsilateral lung and heart (P < 0.001). Conclusions. lTomo plan can have similar dose coverage and better homogeneity and conformity to the target. By properly designing the directionally and completely blocked structure, lTomo plan was developed successfully in reducing doses to the healthy tissues for early-stage left-sided breast cancer radiotherapy.


Assuntos
Neoplasias da Mama/radioterapia , Mama/efeitos da radiação , Radioterapia de Intensidade Modulada/métodos , Radioterapia/efeitos adversos , Neoplasias da Mama/patologia , Feminino , Coração/efeitos da radiação , Humanos , Pulmão/efeitos da radiação , Dosagem Radioterapêutica
13.
Biomed Res Int ; 2013: 717589, 2013.
Artigo em Inglês | MEDLINE | ID: mdl-24175298

RESUMO

A 36-year-old woman was diagnosed with a therapy-refractory cutaneous CD4+ T-cell lymphoma, T3N0M0B0, and stage IIB. Helical irradiation of the total skin (HITS) and dose painting techniques, with 30 Gy in 40 fractions interrupted at 20 fractions with one week resting, 4 times per week were prescribed. The diving suit was dressed whole body to increase the superficial dose and using central core complete block (CCCB) technique for reducing the internal organ dose. The mean doses of critical organs of head, chest, and abdomen were 2.1 to 29.9 Gy, 2.9 to 8.1 Gy, and 3.6 to 15.7 Gy, respectively. The mean dose of lesions was 84.0 cGy. The dosage of left side pretreated area was decreased 57%. The tumor regressed progressively without further noduloplaques. During the HITS procedure, most toxicity was grade I except leukocytopenia with grade 3. No epitheliolysis, phlyctenules, tumor lysis syndrome, fever, vomiting, dyspnea, edema of the extremities, or diarrhea occurred during the treatment. HITS with dose painting techniques provides precise dosage delivery with impressive results, sparing critical organs, and offering limited transient and chronic sequelae for previously locally irradiated, therapy-refractory cutaneous T-cell lymphoma.


Assuntos
Linfócitos T CD4-Positivos , Linfoma Cutâneo de Células T/radioterapia , Radioterapia Guiada por Imagem , Radioterapia de Intensidade Modulada , Neoplasias Cutâneas/radioterapia , Adulto , Feminino , Humanos , Linfoma Cutâneo de Células T/patologia , Neoplasias Cutâneas/patologia
14.
Biomed Res Int ; 2013: 108794, 2013.
Artigo em Inglês | MEDLINE | ID: mdl-23984313

RESUMO

An anthropomorphic phantom was used to investigate a treatment technique and analyze the dose distributions for helical irradiation of the total skin (HITS) by helical tomotherapy (HT). Hypothetical bolus of thicknesses of 0, 10, and 15 mm was added around the phantom body to account for the dose homogeneity and setup uncertainty. A central core structure was assigned as a "complete block" to force the dose tangential delivery. HITS technique with prescribed dose (D p ) of 36 Gy in 36 fractions was generated. The radiochromic EBT2 films were used for the dose measurements. The target region with 95.0% of the D p received by more than 95% of the PTV was obtained. The calculated mean doses for the organs at risk (OARs) were 4.69, 3.10, 3.20, and 2.94 Gy for the lung, heart, liver, and kidneys, respectively. The measurement doses on a phantom surface for a plan with 10 mm hypothetical bolus and bolus thicknesses of 0, 1, 2, and 3 mm are 89.5%, 111.4%, 116.9%, and 117.7% of D p , respectively. HITS can provide an accurate and uniform treatment dose in the skin with limited doses to OARs and is safe to replace a total skin electron beam regimen.


Assuntos
Elétrons , Imagens de Fantasmas , Fótons , Radioterapia de Intensidade Modulada/instrumentação , Radioterapia de Intensidade Modulada/métodos , Pele Artificial , Pele/efeitos da radiação , Relação Dose-Resposta à Radiação , Humanos , Especificidade de Órgãos/efeitos da radiação , Incerteza
15.
Med Dosim ; 37(4): 417-24, 2012.
Artigo em Inglês | MEDLINE | ID: mdl-22552120

RESUMO

In patients given postmastectomy radiotherapy (PMRT), the chest wall is a very thin layer of soft tissue with a low-density lung tissue behind. Chest wall treated in this situation with a high-energy photon beam presents a high dosimetric uncertainty region for both calculation and measurement. The purpose of this study was to measure and to evaluate the surface and superficial doses for patients requiring PMRT with different treatment techniques. An elliptic cylinder cork and superflab boluses were used to simulate the lung and the chest wall, respectively. Sets of computed tomography (CT) images with different chest wall thicknesses were acquired for the study phantom. Hypothetical clinical target volumes (CTVs) were outlined and modified to fit a margin of 1-3 mm, depending on the chest wall thickness, away from the surface for the sets of CT images. The planning target volume (PTV) was initially created by expanding an isotropic 3-mm margin from the CTV, and then a margin of 3 mm was shrunk from the phantom surface to avoid artifact-driven results in the beam-let intensity. Treatment techniques using a pair of tangential wedged fields (TWFs) and 4-field intensity-modulated radiation therapy (IMRT) were designed with a prescribed fraction dose (D(p)) of 180 cGy. Superficial dose profiles around the phantom circumference at depths of 0, 1, 2, 3, and 5 mm were obtained for each treatment technique using radiochromic external beam therapy (EBT) films. EBT film exhibits good characteristics for dose measurements in the buildup region. Underdoses at the median and lateral regions of the TWF plans were shown. The dose profiles at shallow depths for the TWF plans show a dose buildup about 3 mm at the median and lateral tangential incident regions with a surface dose of about 52% of D(p). The dose was gradually increased toward the most obliquely tangential angle with a maximum dose of about 118% of D(p.) Dose profiles were more uniform in the PTV region for the 4-F IMRT plans. Most of the PTV region had doses >94% of D(p) at depths >1 mm. The mean surface dose was about 65% of D(p) for the 4-F IMRT plans. The maximum dose for the 4-F IMRT plans was <118.4% of D(p). The application of added bolus has to consider the treatment technique, tumor coverage, and possible skin reactions. For PMRT, if the chest surface and wall are treated adequately, at least 3 mm bolus should be added to the chest wall when tangential beams and 6-MV photon energy are arranged. However, when the surface and superficial regions are not high-risk areas, an IMRT plan with tangential beams and 6-MV photon energy can provide uniform dose distributions within the PTV, spare the skin reaction, and deliver sufficient doses to the chest wall at depths >1 mm.


Assuntos
Neoplasias da Mama/diagnóstico por imagem , Neoplasias da Mama/terapia , Mastectomia , Radiometria/métodos , Planejamento da Radioterapia Assistida por Computador/métodos , Tomografia Computadorizada por Raios X/métodos , Feminino , Humanos , Imagens de Fantasmas , Dosagem Radioterapêutica , Radioterapia Adjuvante/métodos , Tomografia Computadorizada por Raios X/instrumentação
16.
Med Phys ; 39(4): 2013-20, 2012 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-22482622

RESUMO

PURPOSE: The need for an accurate estimate of absorbed doses within and around irradiated thorax tissues necessitates the use of carefully selected materials from which phantoms are constructed. A lung substitute is more difficult to establish mostly due to its low physical density. Although many researchers have used cork as a lung substitute, very little research data address cork's characteristics to determine which type of cork is optimal as a substitute for lung tissue. METHODS: Natural cork, composition cork, rubber cork, ATOM, RANDO, and a reference lung material (ICRU-44 lung tissue) were investigated to establish comparisons of physical properties. Following the determination of the respective physical properties, the dose distributions from 6 MV photon beams in water/lung substitute/water phantoms were assessed using the Monte Carlo method. Physical and electron densities affecting the dose distributions through lung tissues in different field size conditions were investigated. RESULTS: The physical properties (physical density, electronic density, and effective atomic number) of the composition cork are the most similar to those of the ICRU-44 lung, and the CT number of the composition cork is very similar to that of humans aged 30-60. PDD of the composition cork and the RANDO phantom are the most comparable to that of ICRU-44 lung in 1 × 1 cm(2) field size due to the combined properties of physical density (PD) and electron density per gram (EDG) of the studied lung materials. PD and EDG affect the lung dose primarily in small field size. The effects of PD are minimal in large fields, having a more rapid lateral electron equilibrium. EDG dominates PDD pattern in lung material when large fields are applied. Combined effects of PD and EDG are nonlinear for all field sizes. CONCLUSIONS: The composition cork is the preferred lung substitute based on physical and dosimetric properties.


Assuntos
Materiais Biomiméticos/química , Pulmão/química , Radiometria , Absorção , Humanos , Teste de Materiais , Doses de Radiação
17.
Med Phys ; 38(3): 1435-43, 2011 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-21520855

RESUMO

PURPOSE: Dosimetric uncertainty in the surface and superficial regions is still a major concern for radiation therapy and becomes more important when using the inverse planning algorithm for IMRT. The purpose of this study was to measure dose distributions and to evaluate the calculation accuracy in the superficial region for different planning target volume (PTV) shrinkage methods for head and neck IMRT plans. METHODS: A spherical polystyrene phantom 160 mm in diameter (ball phantom) was used to simulate the shape of the head. Strips of superflab bolus with thicknesses of 3.5 and 7.0 mm were spread on the surface of the ball phantom. Three sets of CT images were acquired for the ball phantom without and with the bolus. The hypothetical clinical target volume (CTV) and critical structures (spinal cord and parotid glands) were outlined on each set of CT images. The PTVs were initially created by expanding an isotropic 3 mm margin from the CTV and then margins of 0, 3, and 5 mm were shrunk from the phantom surface for dosimetric analysis. Seven-field IMRT plans with a prescribed dose of 180 cGy and same dose constraints were designed using an Eclipse treatment planning system. Superficial doses at depths of 0, 3.5, and 7.0 mm and at seven beam axis positions (gantry angles of 0 degrees, 30 degrees, 60 degrees, 80 degrees, 330 degrees, 300 degrees, and 280 degrees) were measured for each PTV shrinkage margin using 0.1 mm ultrathin thermoluminescent dosimeters. For each plan, the measured doses were compared to the calculated doses. RESULTS: The PTV without shrinkage had the highest intensity and the steepest dose gradient in the superficial region. The mean measured doses for different positions at depths of 0, 3.5, and 7.0 mm were 106 +/- 18, 185 +/- 16, and 188 +/- 12 cGy, respectively. For a PTV with 3 mm shrinkage, the mean measured doses were 94 +/- 13, 183 +/- 8, and 191 +/- 8 cGy. For a PTV with 5 mm shrinkage, the mean measured doses were 86 +/- 11, 173 +/- 8, and 187 +/- 5 cGy. The comparisons indicated that more than 73.3% of the calculated points are with doses lower than the measured points and the difference of the dose becomes more significant in the shallower region. At 7.0 mm depth, the average difference between calculations and measurements was 2.5% (maximum 5.5%). CONCLUSIONS: Application of the PTV shrinkage method should take into account the calculation inaccuracy, tumor coverage, and possible skin reaction. When the tumor does not invade the superficial region, an adequate shrinkage margin from the surface is helpful for reducing the skin reaction. As the tumor invades the superficial region, adding a bolus is a method better than only contouring PTV with skin inclusion.


Assuntos
Neoplasias de Cabeça e Pescoço/radioterapia , Doses de Radiação , Planejamento da Radioterapia Assistida por Computador/métodos , Radioterapia de Intensidade Modulada/métodos , Derme/efeitos da radiação , Epiderme/efeitos da radiação , Imagens de Fantasmas , Radiometria , Dosagem Radioterapêutica , Radioterapia de Intensidade Modulada/efeitos adversos , Propriedades de Superfície
18.
Laryngoscope ; 116(11): 2012-7, 2006 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-17075415

RESUMO

OBJECTIVES: To investigate the value of pretreatment computed tomography (CT) volumetric analysis for the prediction of treatment outcome in patients with hypopharyngeal cancer (HPC) treated by definitive radiotherapy (RT). METHODS: From January 2000 through February 2004, 63 patients with HPC were enrolled for a retrospective analysis. The pyriform sinus was the principle site of involvement in 62 cases. All patients received with 1.8 Gy daily to a total dose of 68.4 to 73.8 Gy (median, 70.2 Gy). Contrast-enhanced CT images were transferred to a planning system. Tumor volume measurement was derived from summation of the primary and metastatic nodal tumor. RESULTS: With a median follow-up of 38 (range, 24-68) months, the 5 year local relapse-free survival (LRFS) was 83% for patients with T1 to T2 disease, 46% for those with T3 disease, and 40% for those with T4 disease (P = .01). The 5 year LRFS was 75% for those with tumors less than 40 mL and 26% when volumes were 40 mL of larger (P = .0001). For patients with T3 to T4 disease, the 5 year LRFS was 70% for those with tumors less than 40 mL and 24% when volumes were 40 mL or larger (P = .0005). Multivariate analyses of local relapse-free survival revealed two prognostic factors: tumor volume more than 40 mL and the involvement of the larynx. CONCLUSIONS: CT-based tumor volumes are a strong predictor of outcomes for HPC treated using definitive RT. A selected group of patients, mainly those with tumor volumes less than 40 mL, should be considered for laryngeal preservation.


Assuntos
Carcinoma de Células Escamosas/diagnóstico por imagem , Carcinoma de Células Escamosas/radioterapia , Neoplasias Hipofaríngeas/diagnóstico por imagem , Neoplasias Hipofaríngeas/radioterapia , Tomografia Computadorizada por Raios X , Adulto , Idoso , Idoso de 80 Anos ou mais , Carcinoma de Células Escamosas/patologia , Intervalo Livre de Doença , Feminino , Humanos , Neoplasias Hipofaríngeas/patologia , Laringe/patologia , Masculino , Pessoa de Meia-Idade , Análise Multivariada , Invasividade Neoplásica , Recidiva Local de Neoplasia/epidemiologia , Prognóstico , Estudos Retrospectivos , Resultado do Tratamento
19.
Med Dosim ; 30(4): 219-27, 2005.
Artigo em Inglês | MEDLINE | ID: mdl-16275564

RESUMO

This study compared the target volume coverage and normal tissues sparing of simultaneous integrated boost (SIB-IMRT, 1-phase) and sequential-IMRT (2-phase) for nasopharyngeal carcinoma (NPC). Fourteen consecutive patients with newly diagnosed primary NPC were enrolled in this study. The CT images were transferred to a commercial planning system for structural delineation. The gross tumor volume (GTV) included gross nasopharyngeal tumor and involved lymph nodes of more than 1-cm diameter. The clinical target volume (CTV) modeled two regions considered to represent different risks. CTV1 encompassed the GTV with 5-10-mm margin of adjacent tissues. CTV2 encompassed ipsilateral or contralateral elective nodal regions at risk of harboring microscopic tumor. A commercial IMRT treatment planning system (Eclipse Version 7.1) was used to provide treatment planning. Seven fixed-gantry (0 degrees, 50 degrees, 100 degrees, 150 degrees, 210 degrees, 260 degrees, 310 degrees ) angles were designated. The 14 patients were treated with sequential-IMRT, and treatment was then replanned with an SIB strategy to compare the dosimetric difference. For the sequential strategy, the dose delivered to CTV1/CTV2 in the first course was 54 Gy (1.8 Gyx30 Fr); while CTV1 was boosted by an additional 16.2 Gy (1.8 Gyx9 Fr) in the second course. For SIB-IMRT, the dose prescribed to CTV1 was 69.7 Gy (2.05 Gyx34 Fr); 56.1 Gy was given to CTV2 (1.65 Gyx34 Fr). A statistical analysis of the dose-volume-histogram of target volumes and critical organs was performed. Paired Student's t-test was used to compare the dosimetric differences between the two techniques. The mean dose to CTV1 was 101.7+/-2.4% and 102.3+/-3.1% of the prescribed dose for SIB-IMRT and sequential-IMRT, respectively. The mean CTV2 dose was 109.8+/-4.7% of the prescribed dose for SIB-IMRT and 112.6+/-6.0% of the prescribed dose for sequential-IMRT. The maximal dose to the spinal cord was 4489+/-495 cGy and 3547+/-767 cGy for SIB and sequential-IMRT (p=0.0001), respectively. The maximal dose to brain stem was significantly higher using SIB technique (5284+/-551 cGy) than sequential-IMRT (4834+/-388 cGy) (p=0.0001). The mean dose to the parotid gland and ear apparatus was significantly lower using SIB-IMRT. The mean dose to the right/left parotids was 2865+/-320 cGy/2903+/-429 cGy and 3567+/-534 cGy/3476+/-489 cGy for SIB and sequential-IMRT, respectively (p=0.0001). Target coverage was the same for both techniques; the dose distribution in the elective nodal area with SIB was superior to that with sequential-IMRT. SIB-IMRT provides better sparing of parotid gland and inner ear structures. Extra caution should be taken when applying SIB-IMRT since critical organs close to the boost volume may receive higher doses.


Assuntos
Carcinoma/radioterapia , Neoplasias Nasofaríngeas/radioterapia , Planejamento da Radioterapia Assistida por Computador , Radioterapia de Intensidade Modulada/métodos , Algoritmos , Carcinoma/diagnóstico por imagem , Carcinoma/patologia , Fracionamento da Dose de Radiação , Humanos , Neoplasias Nasofaríngeas/diagnóstico por imagem , Neoplasias Nasofaríngeas/patologia , Radiometria , Tomografia Computadorizada por Raios X
20.
Clin Nucl Med ; 30(4): 278-80, 2005 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-15764892

RESUMO

Thallium-201 single-photon emission computed tomography (Tl-201 SPECT) and F-18 fluorodeoxyglucose positron emission tomography (FDG PET) are accurate and excellent methods for detecting malignant tumors and related metabolic abnormalities. However, there are still some limitations in clinical application. The major limitation of SPECT is poor image resolution. PET is less sensitive for detecting lesions of the urinary system adjacent to the bladder because of bladder radioactivity. Both T1-201 and F-18 FDG PET often provide less information than x-ray computed tomography (CT) about the anatomic landmarks needed to precisely locate lesions. Recent development of multimodality image registration and fusion has been shown to be an excellent tool to resolve these drawbacks. The authors present a rare case of residual cervical carcinoma with bladder invasion, which was detected by fusion imaging of Tl-201 SPECT and FDG PET with CT. This noninvasive image technique may become a valuable alternative to identify bladder invasion in cervical cancer.


Assuntos
Adenocarcinoma/diagnóstico por imagem , Fluordesoxiglucose F18 , Compostos Radiofarmacêuticos , Técnica de Subtração , Bexiga Urinária/diagnóstico por imagem , Neoplasias do Colo do Útero/diagnóstico por imagem , Adenocarcinoma/patologia , Feminino , Humanos , Pessoa de Meia-Idade , Invasividade Neoplásica , Tomografia por Emissão de Pósitrons/métodos , Tomografia Computadorizada de Emissão de Fóton Único/métodos , Tomografia Computadorizada por Raios X/métodos , Bexiga Urinária/patologia , Neoplasias do Colo do Útero/patologia
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