Background
The use of optical surface positioning to support or replace X-ray-based image-guided radiotherapy (IGRT) may reduce patient exposure to extra dose. In specifically designed phantom tests, ...we analyzed the potential of a new scanning device preclinically. The system’s clinical performance was evaluated in comparison to cone-beam computed tomography (CBCT) in a prospective study.
Materials and methods
We first evaluated the scanning performance in terms of accuracy and reproducibility using phantom tests. An institutional review board (IRB)-approved clinical evaluation encompassing 224 fractions in 13 patients treated in three different regions (head and neck, thorax, pelvis) was then performed. Patients were first positioned using CBCT and then scanned with the Catalyst
TM
(C-RAD, Uppsala, Sweden) optical system to define the resulting difference vector.
Results
Individual system settings are necessary for different scanning conditions. Reproducibility tests with phantoms showed a mean difference of 0.25 ± 0.21 cm. Accuracy tests showed a mean difference of less than 0.52 ± 0.41 cm. Considering all patients, clinical data showed residual target position differences between Catalyst
TM
(surface-driven) and CBCT (target-driven) systems within 0.07 ± 0.28 cm/− 0.13 ± 0.40 cm/0.15 ± 0.36 cm/0.11 ± 1.57°/− 0.43 ± 1.68/− 0.10 ± 1.67° (lateral/longitudinal/vertical/rotation/roll/pitch).
Conclusion
Scanning quality depends on the color and shape of the scanned surface. Upon prospective clinical evaluation, excellent agreement between target- and contour driven positioning was observed. Catalyst
TM
may reduce CBCT scan frequency in patients where tumor location is fixed relative to the surface.
Full text
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, VSZLJ, ZAGLJ
A design study has been performed for a positron beam with an energy of 500 MeV to be realized at the applied physics area of the Mainz Microtron MAMI. Positrons will be created after pair conversion ...of bremsstrahlung, produced by the 855 MeV electron beam at MAMI in a tungsten converter target. From the two conceivable geometries (1) pair conversion in the bremsstrahlung converter target itself, and (2) bremsstrahlung pair conversion in a separated lead foil, the former was considered in detail. Positrons will be energy selected within an outside open electron beam-line bending magnet, and bent back by an additional sector magnet. Magnetic focusing elements in between are designed to prepare in a well shielded positron target chamber about 6 m away from the target a beam with horizontal and vertical emittances of
ϵ
v
= 0.055
π
mm mrad (1
σ
), and
ϵ
h
=
0.12
π
mm mrad (1
σ
), respectively, for a 10
μ
m thick amorphous tungsten target and negligible momentum spread. At an accepted positron band width of 1 MeV, spots are expected vertically with an angular spread of 0.064 mrad and a size of 5.0 mm (FWHM), and horizontally with an angular spread of 0.64 mrad and a size of 7.7 mm (FWHM). The positron yield amounts to 13.1 per second, 1 MeV positron energy band width, and 1 nA electron beam current.
Graphic abstract
Full text
Available for:
DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, SIK, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Objective
The Gamma Knife Icon (Elekta AB, Stockholm, Sweden) allows frameless stereotactic treatment using a combination of cone beam computer tomography (CBCT), a thermoplastic mask system, and an ...infrared-based high-definition motion management (HDMM) camera system for patient tracking during treatment. We report on the first patient with meningioma at the left petrous bone treated with adaptive fractionated stereotactic radiotherapy (a-gkFSRT).
Methods
The first patient treated with Gamma Knife Icon at our institute received MR imaging for preplanning before treatment. For each treatment fraction, a daily CBCT was performed to verify the actual scull/tumor position. The system automatically adapted the planned shot positions to the daily position and recalculated the dose distribution (online adaptive planning). During treatment, the HDMM system recorded the intrafractional patient motion. Furthermore, the required times were recorded to define a clinical treatment slot.
Results
Total treatment time was around 20 min. Patient positioning needed 0.8 min, CBCT positioning plus acquisition 1.65 min, CT data processing and adaptive planning 2.66 min, and treatment 15.6 min. The differences for the five daily CBCTs compared to the reference are for rotation: −0.59 ± 0.49°/0.18 ± 0.20°/0.05 ± 0.36° and for translation: 0.94 ± 0.52 mm/−0.08 ± 0.08 mm/−1.13 ± 0.89 mm. Over all fractions, an intrafractional movement of 0.13 ± 0.04 mm was observed.
Conclusion
The Gamma Knife Icon allows combining the accuracy of the stereotactic Gamma Knife system with the flexibility of fractionated treatment with the mask system and CBCT. Furthermore, the Icon system introduces a new online patient tracking system to the clinical routine. The interfractional accuracy of patient positioning was controlled with a thermoplastic mask and CBCT.
Full text
Available for:
EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, VSZLJ, ZAGLJ
Background
Laser scanning-based patient surface positioning and surveillance may complement image-guided radiotherapy (IGRT) as a nonradiation-based approach. We investigated the performance of an ...optical system compared to standard kilovoltage cone-beam computed tomography (CBCT) and its potential to reduce the number of daily CBCTs.
Patients and methods
We analyzed the patient positioning of 153 treatment fractions in 21 patients applied to three different treatment regions. Patients were first scanned with CBCT, shifted to the optimal isocenter position, and an optical scan was performed to verify the matching in relation to CBCT.
Results
For the head-and-neck region, the lateral/longitudinal/vertical/rotational/roll and pitch shift was 0.9 ± 1.8 mm/−2.7± 3.8 mm/−0.8± 3.6 mm/0.0± 1.1°/−0.5± 2.1°/0.2± 1.6°. For the thorax, the lateral/longitudinal/vertical/roll and pitch shift was −1.2± 3.6 mm/0.8± 5.1 mm/0.8± 4.3 mm/0.6± 1.4°/0.1± 0.9°/0.3± 1.0°. For the pelvis, the respective values were −2.5± 4.1 mm/4.6± 7.3 mm/−5.1± 7.4 mm/0.3± 1.1°/-0.5± 1.0°/0.3± 2.1°. In total, the recorded disagreement was −1.0± 3.6 mm/1.0± 6.3 mm/−1.8± 5.9 mm/0.3± 1.2°/−0.3± 1.5°/0.2± 1.7°.
Conclusion
This analysis showed good agreement between the optical scanner approach and CBCT. The optical system holds potential to ensure precise patient positioning and reduced CBCT frequency in tumor locations with fixed relation to surface structures.
Full text
Available for:
EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, VSZLJ, ZAGLJ
The Mu3e experiment is searching for the charged lepton flavour violating decay\break μ+→e+e−e+, aiming for an ultimate sensitivity of one in 1016 decays. In an environment of up to 109 muon decays ...per second the detector needs to provide precise vertex, time and momentum information to suppress accidental and physics background. The detector consists of cylindrical layers of 50μm thin High Voltage Monolithic Active Pixel Sensors (HV-MAPS) placed in a 1T magnetic field. The measurement of the trajectories of the decay particles allows for a precise vertex and momentum reconstruction. Additional layers of fast scintillating fibre and tile detectors provide sub-nanosecond time resolution. The MuPix8 chip is the first large scale prototype, proving the scalability of the HV-MAPS technology. It is produced in the AMS aH18 180nm HV-CMOS process. It consists of three sub-matrices, each providing an untriggered datastream of more than 10MHits/s. The latest results from laboratory and testbeam characterisation are presented, showing an excellent performance with efficiencies >99.6% and a time resolution better than 10ns achieved with time walk correction.
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