Evaluation of a novel patient-specific quality assurance phantom for robotic single-isocentre, multiple-target stereotactic radiosurgery, and stereotactic radiotherapy

OBJECTIVES

To evaluate patient-specific quality assurance (PSQA) of 3 targets in a single delivery using a novel film-based phantom.

METHODS

The phantom was designed to rotate freely as a sphere and could measure 3 targets with film in a single delivery. After identifying the coordinates of 3 targets in the skull, the rotation angles about the equator and meridian were computed for optimal phantom setup, ensuring the film plane intersected the 3 targets. The plans were delivered on the CyberKnife system using fiducial tracking. The irradiated films were scanned and processed. All films were analysed using 3 gamma criteria.

RESULTS

Fifteen CyberKnife test plans with 3 different modalities were delivered on the phantom. Both automatic and marker-based registration methods were applied when registering the irradiated film and dose plane. Gamma analysis was performed using a 3%/1 mm, 2%/1 mm, and 1%/1 mm criteria with a 10% threshold. For the automatic registration method, the passing rates were 98.2% ± 1.9%, 94.2% ± 3.7%, and 80.9% ± 6.3%, respectively. For the marker-based registration approach, the passing rates were 96.4% ± 2.7%, 91.7% ± 4.3%, and 78.4% ± 6.2%, respectively.

CONCLUSIONS

A novel spherical phantom was evaluated for the CyberKnife system and achieved acceptable PSQA passing rates using TG218 recommendations. The phantom can measure true-composite dose and offers high-resolution results for PSQA, making it a valuable device for robotic radiosurgery.

ADVANCES IN KNOWLEDGE

This is the first study on PSQA of 3 targets concurrently on the CyberKnife system.

The ASACUSA antihydrogen and hydrogen program: results and prospects

The goal of the ASACUSA-CUSP collaboration at the Antiproton Decelerator of CERN is to measure the ground-state hyperfine splitting of antihydrogen using an atomic spectroscopy beamline. A milestone was achieved in 2012 through the detection of 80 antihydrogen atoms 2.7 m away from their production region. This was the first observation of 'cold' antihydrogen in a magnetic field free region. In parallel to the progress on the antihydrogen production, the spectroscopy beamline was tested with a source of hydrogen. This led to a measurement at a relative precision of 2.7×10^-9 which constitutes the most precise measurement of the hydrogen hyperfine splitting in a beam. Further measurements with an upgraded hydrogen apparatus are motivated by CPT and Lorentz violation tests in the framework of the Standard Model Extension. Unlike for hydrogen, the antihydrogen experiment is complicated by the difficulty of synthesizing enough cold antiatoms in the ground state. The first antihydrogen quantum states scan at the entrance of the spectroscopy apparatus was realized in 2016 and is presented here. The prospects for a ppm measurement are also discussed.This article is part of the Theo Murphy meeting issue 'Antiproton physics in the ELENA era'.

Follow-Up of BI-RADS 3 Breast Mammograms, Results of a West France “Departement” Breast Cancer Screening Programme

Background: French breast cancer screening program lies on a decentralized system. Each administrative division of a region (departement) organizes, coordinates and assesses their programme under the aegis of the French National Cancer Institute (INCa).The screening programme includes every two years, for women between 50 and 74 years of age a clinical examination and a breast mammogram. Conclusions are reported using the Breast Imaging and Reporting Data System (BI-RADS) of the American College of Radiology (ACR).French recommendations for low-suspicion lesions of the breast (BI-RADS 3) consist in a new screening 4 or 6 months later, then another one at one year and a third one year later before returning to the breast screening programme.Objectives: To evaluate the medical organisation and patients' observance for the follow-up of low suspicion breast lesions (BI-RADS 3).Material and Methods: Between January 2005 and January 2007 every BI-RADS 3 breast mammogram exams were listed in our departement and each radiologist was asked about their patient's health status.Patients who had not had their control mammogram were contacted.Their general practitioners were asked in case of no response.Results: Between January 2005 and January 2007 126 385 women were invited to take part in the breast cancer screening programme (screening rate 59.55%).2 209 exams were considered BI-RADS 3 (2.90%).383 patients (17.5%) were lost of sight.2111 women underwent an ultrasound scan examination (40.67%).20 women had MRI (0.39%).182 had biopsies (8.23%).BI-RADS 3 predictive value for a breast cancer lesion was 3.35%.Control mammograms were proposed at 4 months for 339 patients (18.7%) and 6 months for 1 125 patients (62.1%).1247 patients had only one control mammogram (60.9%), 388 (18.9%) patients had two and 60 (2.9%) had at least 3 controls.47.2% of BI-RADS 3 was re classified after first control and 60% after second control.Patients' observance was 91.26% for the first control, 62.9% for the second and decreased to 27% at fourth.1226 (55.5%) were re classified BI-RADS 1 or 2.185 (8.4%) were up graded to BI-RADS 4 or 5.154 (7%) are on attempt of re classification, 152 (6.90%) had no definitive conclusion after 24 months and 109 (4.90%) declined the medical follow-up supervision.The median time needed for re classified BI-RADS 3 was 276 days.Discussion: Our BI-RADS 3 rate (2.90%) is similar to those already published (3-7.7%).French recommendations are applied for the first and second control.Our cancer rate for BI-RADS 3 lesions (3.35%) is higher than those published (0.3%-1.7%).Patients' observance decreases rapidly, and patients' loss-of-sight remains high (17.3%).Initial BI-RADS 3 classification must be improved and recommendations for follow-up may be modified into a delayed control at 9 months that could settle for a BI-RADS 2 classification or lead to a histopathological exam.Waiting for new recommendations, we now contact each woman with BI-RADS 3 one month before control and in the absence of control we contact radiologist and general practitioner to improve observance and reduce the number of lost-of-sight patients.

Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 4013.

Quasiunimodal tunable pulsed dye laser at 440 nm: theoretical development for using a quad prism beam expander and one or two gratings in a pulsed dye laser oscillator cavity

In the first section of this paper a theoretical discussion is presented for the performance of a pulsed dye laser oscillator cavity, without an intracavity etalon, using the Gaussian beam approximation. Optimal conditions for achievement of narrow spectral linewidth are discussed (location of the grating or of the beam expander). Various configurations of oscillator cavities are investigated, including a dispersive device composed of one grating and one virtual grating. The use of a beam expander is treated. We find that the same spectral linewidth is obtained theoretically for the optical cavity with two gratings as with one grating and a virtual grating. In the second part we describe the performance (in terms of spectral linewidth 1.3-GHz FWHM quasiunimodal structure, divergence of the beam, etc.) of the dye laser in light of the theoretical arguments. The complete laser contains an oscillator stage, a preamplifier stage, and an amplifier stage, each pumped by an UV beam (355 nm) from a pulsed Nd:YG laser.