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Claudio Sibata

Publications and source records attributed to Claudio Sibata.

8 recordsLinked to original sources
PubMed2005

An ultrasonic device for source to skin surface distance measurement in patient setup.

PURPOSE: To develop an ultrasound-based source to skin surface distance (SSD) measurement technique and device for patient setup and test its feasibility and accuracy. METHODS AND MATERIALS: The ultrasonic SSD measurement device (USD) prototype consists of two main parts: a probe plate with an ultrasonic transducer in the center and a control unit that displays the SSD in millimeters. The probe plate can be slid into the block tray accessory slot of any treatment machine at the time of the SSD measurement. The probe plate contains an ultrasonic transducer as both the source and the detector for measuring the distance between the transducer and the target surfaces on the basis of an echo-detecting technique. The device was calibrated by a mechanical ruler with an accuracy of 0.01 mm and corrected by an offset of 601.7 mm, which is the distance from the radiation source to the ultrasonic transducer surface for the Siemens Primus linear accelerator (Linac). The ultrasound device provided digital readout with an accuracy of +/-0.1 mm for a flat surface after calibration. The SSD measurement experiments were done with the USD, an optical distance indicator (ODI), and an AKTINA 53-104 Mechanical Front Pointer (FP) on a Siemens Primus Linac with a full-sized female phantom. Ten measurements were carried out at each gantry angle of 0 degrees , 52 degrees , 85 degrees , 90 degrees , and 227 degrees for anatomic locations of head, thorax, breast, and pelvis, to obtain the average values and standard deviations. RESULTS: The comparison study with the ODI and FP showed that the USD had an accuracy of less than +/-1.0 mm and that USD measurements had the minimum standard deviations among the three methods; therefore, USD gave more consistent and accurate readouts for SSD measurement. When considering the FP as a reference, the USD yields smaller deviations than the ODI for all measured locations (less than +/-2 mm). The variation of USD digital readout with a room temperature change of +/-2 degrees C is +/-0.1 mm, which is sufficiently accurate for SSD measurement. CONCLUSIONS: The USD method has the following advantages. First, it decreases patient setup time by avoiding problems related to the blocking of the device by the patient or by the immobilization device. Second, it is more accurate than the other two methods currently used, as the test data show. Last, the digital readout eliminates the possibility of human reading error associated with the visual scales.

Calibration↗
PubMed2004

Breast cancer with chest wall progression: treatment with photodynamic therapy.

BACKGROUND: Chest wall progression of breast carcinoma affects up to 5% of breast cancer patients and is a major source of their pain. Treatment options are limited or may not be offered to these patients. Low-dose Photofrin-induced photodynamic therapy (PDT) offers an excellent clinical response with minimal morbidity. We report our continued experience with PDT in this setting. METHODS: Fourteen patients with more than 500 truncal metastases were treated with PDT. All received off-label Photofrin (.8 mg/kg) i.v. and light treatment at 630 nm from a diode laser with a microlens at a fluence of 1800 mW and a total light dose of 150 to 200 J/cm2 at 48 hours. One patient required re-treatment because of extensive disease. RESULTS: Follow-up was at least 6 months, and several extended to >24 months. All patients demonstrated tumor necrosis, with 9 of 14 complete responses, including with lesions >2 cm in thickness. Disease progression occurred outside of the treatment field. Several patients had initial regression of untreated lesions. Wound care, especially with disease in the deep tissues, was an issue. CONCLUSIONS: Low-dose Photofrin-induced PDT offers patients with chest wall progression a treatment option with an excellent clinical response. To date, the response is prolonged and offers good local control. Surgical oncologists have an active role in this treatment option.

Adult↗
PubMed2003

Plug pattern optimization for gamma knife radiosurgery treatment planning.

PURPOSE: To develop a novel dose optimization algorithm for improving the sparing of critical structures during gamma knife radiosurgery by shaping the plug pattern of each individual shot. METHOD AND MATERIALS: We first use a geometric information (medial axis) aided guided evolutionary simulated annealing (GESA) optimization algorithm to determine the number of shots and isocenter location, size, and weight of each shot. Then we create a plug quality score system that checks the dose contribution to the volume of interest by each plug in the treatment plan. A positive score implies that the corresponding source could be open to improve tumor coverage, whereas a negative score means the source could be blocked for the purpose of sparing normal and critical structures. The plug pattern is then optimized via the GESA algorithm that is integrated with this score system. Weight and position of each shot are also tuned in this procedure. RESULTS: An acoustic tumor case is used to evaluate our algorithm. Compared to the treatment plan generated without plug patterns, adding an optimized plug pattern into the treatment planning process boosts tumor coverage index from 95.1% to 97.2%, reduces RTOG conformity index from 1.279 to 1.167, lowers Paddick's index from 1.34 to 1.20, and trims the critical structure receiving more than 30% maximum dose from 16 mm(3) to 6 mm(3). CONCLUSIONS: Automated GESA-based plug pattern optimization of gamma knife radiosurgery frees the treatment planning team from the manual forward planning procedure and provides an optimal treatment plan.

Algorithms↗
PubMed2003

Dosimetric considerations for patients with HIP prostheses undergoing pelvic irradiation. Report of the AAPM Radiation Therapy Committee Task Group 63.

This document is the report of a task group of the Radiation Therapy Committee of the AAPM and has been prepared primarily to advise hospital physicists involved in external beam treatment of patients with pelvic malignancies who have high atomic number (Z) hip prostheses. The purpose of the report is to make the radiation oncology community aware of the problems arising from the presence of these devices in the radiation beam, to quantify the dose perturbations they cause, and, finally, to provide recommendations for treatment planning and delivery. Some of the data and recommendations are also applicable to patients having implanted high-Z prosthetic devices such as pins, humeral head replacements. The scientific understanding and methodology of clinical dosimetry for these situations is still incomplete. This report is intended to reflect the current state of scientific understanding and technical methodology in clinical dosimetry for radiation oncology patients with high-Z hip prostheses.

Advisory Committees↗
PubMed2002

An anthropomorphic phantom for quality assurance and training in gynaecological brachytherapy.

BACKGROUND AND PURPOSE: An anthropomorphic water filled polymethylmethacrylate (PMMA) phantom designed to serve as a Quality Assurance (QA) tool and a training aid in brachytherapy of gynaecological tumours is investigated and presented. Several dosimetric parameters associated with the dose rate calculation can be verified with the aid of this phantom such as the source positioning, its imaging reconstruction from radiographs and the accuracy of the algorithm used for manual or computer dose rate calculation. MATERIAL AND METHODS: The phantom walls and the internal structure are 5mm thick and consist of PMMA, in the form of the abdomen taken from a female Alderson Phantom Marker points representing the organs of interest were determined from computed tomography scans of a patient of similar size. Three PMMA inserts designed to hold a Farmer type ionization chamber of 0.6 cm(3) were positioned at the points to represent the bladder, rectum and point A. The formalism proposed by the IAEA TRS-277 dosimetry protocol was used for the conversion of readings of the ionization chamber to dose rate values with a modification to take into account the dose rate gradient in the detector. Five 137Cs sources were used and the dose rate was evaluated by measurements and Monte Carlo simulations using the PENELOPE code. Four different treatment planning systems with different algorithms and source reconstruction techniques were also used in this investigation and compared with the manual dose rate calculations made using Karen and Breitman's tables. RESULTS: The dose rate calculations performed with Monte Carlo and the four treatment planning systems are in good agreement with the experimental results as well as with the manual calculations when the colpostat shielding and the tandem attenuation are taken into account. The comparison between experiment and calculations by the four treatment planning systems shows a maximum variation of 5.1% between the calculated and measured dose rate at the point A. CONCLUSIONS: This phantom is suitable for use during the acceptance tests of treatment planning systems and applicators, as educational tool, for dosimetric research problems and for the QA of brachytherapy sources.

Brachytherapy↗
PubMed2002

Implementation of the isocenter-shift technique for smoothing MLC field edge on a 3D treatment planning system.

Stepped leaf edges are the major limitation of conforming to the prescribed treatment contour defined by the conventional multileaf collimator (MLC), which produces a scalloped dose pattern. The commercial HD-270 MLC (HDI) technique provides a software solution of the conventional MLC to achieve smoothed edge and optimal penumbra of the MLC shaped field. We implemented the HDI functionality on a 3D treatment planning system and compared the dosimetric effects of the HDI delivery in simulation with those in experiment for a number of the MLC fields. The fields from the contour of varied shapes with different sizes of the leaf stepping were tested for the HDI delivery. There is a good agreement of the dose distribution between the calculation as implemented in the planning system and the measurement performed on the treatment machine. It has been shown that the HDI delivery significantly smooths the stepped field edge with the reduced isodose undulation and effective penumbra. A problem may be present when the HDI is applied for the treatment of the circular contour of smaller diameter, and the conformity of the MLC shaping may not be achievable satisfactorily with the existing system. The optimization of leaf configuration is suggested to improve the conformity of the HDI technique. The HDI planning then can be used to assist in the decision making of applying the HDI treatment delivery.

Humans↗
PubMedDate not supplied

High-dose-rate brachytherapy in combination with stenting offers a rapid and statistically significant improvement in quality of life for patients with endobronchial recurrence.

Symptomatic endobronchial recurrence after treatment failure is common in advanced non-small cell lung cancer. Optimal palliation has yet to be defined. We examined the combination of near-simultaneous, high-dose-rate (HDR) brachytherapy with stenting in this cohort of patients. Informed consent for intervention was obtained for 10 patients experiencing severely symptomatic (hemoptysis and oxygen-dependent shortness of breath), biopsy-proven endobronchial recurrence. All patients (eight men, two women, aged 52-77 years) had failed to respond to chemoradiotherapy for stage IIIB non-small cell lung cancer. Intervention consisted of placement of a self-expanding metallic stent (Nitinol/Ultraflex stent, Boston Scientific Co., Natick, MA) into the obstructing region. During that same bronchoscopy, HDR catheters were introduced. A dose of 6 Gy at 0.5 cm from the catheter was then delivered via an HDR unit. Two additional HDR sessions followed at weekly intervals for a total dose of 18 Gy. Patients under went follow-up bronchoscopes 1 month after the last HDR and when clinically indicated. All patients completed the prescribed therapy. No morbidity was noted from bronchoscopy, HDR, or stenting. All patients had rapid relief of signs and symptoms. At 1 week after stenting/first HDR, a statistically significant improvement in Karnofsky status was noted. Pulmonary palliation was maintained for the duration of their survival. The radio-opaque stent also offered significant advantages for catheter placement and verification during the HDR procedure. Although this series is small, the beneficial outcome obtained deserves further evaluation.

Aged↗