scholarly journals A dynamic collimation and alignment system for the Helmholtz linear accelerator

2021 ◽  
Vol 92 (11) ◽  
pp. 113306
Author(s):  
S. Lauber ◽  
K. Aulenbacher ◽  
W. Barth ◽  
M. Basten ◽  
C. Burandt ◽  
...  
Keyword(s):  
Linear Accelerator ◽  
Alignment System

Injector for a 100-500 kV Linac Electron Microscopy Source

1967 ◽  
Vol 25 ◽  
pp. 274-275
Author(s):  
John W. Coleman
Keyword(s):  
Electron Microscopy ◽  
Linear Accelerator ◽  
Beam Current ◽  
Ion Trapping ◽  
University Of Virginia ◽  
Electron Injector ◽  
Illumination System ◽  
Radio Corporation Of America ◽  
The University ◽  
Optical Integration

The injector to be described is a component in the Electron Injector-Linear Accelerator—Condenser Module for illumination used on the variable 100-500kV electron microscope being built at the Radio Corporation of America for the University of Virginia.The injector is an independently powered, autonomous unit, operating at a constant 6kV positive with respect to accelerator potential, thereby making beam current independent of accelerator potential. The injector provides for on-axis ion trapping to prolong filament lifetime, and incorporates a derived Einzel lens for optical integration into the overall illumination system for microscopy. Electrostatic beam deflectors for alignment are an integral part of the apparatus. The entire injector unit is cantilevered off a door for side loading, and is topped with a 4-filament turret released electrically but driven by a self-contained Negator spring motor.

On-line alignment and astigmatism correction using a TV and personal computer

1993 ◽  
Vol 51 ◽  
pp. 202-203
Author(s):  
F. Hosokawa ◽  
Y. Kondo ◽  
T. Honda ◽  
Y. Ishida ◽  
M. Kersker
Keyword(s):  
High Resolution ◽  
Personal Computer ◽  
Block Diagram ◽  
Incident Beam ◽  
Ccd Camera ◽  
Alignment Procedure ◽  
Astigmatism Correction ◽  
Transmission Electron ◽  
Alignment System ◽  
On Line

High-resolution transmission electron microscopy must attain utmost accuracy in the alignment of incident beam direction and in astigmatism correction, and that, in the shortest possible time. As a method to eliminate this troublesome work, an automatic alignment system using the Slow-Scan CCD camera has been introduced recently. In this method, diffractograms of amorphous images are calculated and analyzed to detect misalignment and astigmatism automatically. In the present study, we also examined diffractogram analysis using a personal computer and digitized TV images, and found that TV images provided enough quality for the on-line alignment procedure of high-resolution work in TEM. Fig. 1 shows a block diagram of our system. The averaged image is digitized by a TV board and is transported to a computer memory, then a diffractogram is calculated using an FFT board, and the feedback parameters which are determined by diffractogram analysis are sent to the microscope(JEM- 2010) through the RS232C interface. The on-line correction system has the following three modes.

The measurement of photoneutron dose around an 18 MV Varian linear accelerator by TLD600 and TLD700 dosimeters inside the polyethylene sphere of neutron probe LB 6411

2014 ◽  
Vol 6 (1) ◽  
pp. 1049-1057
Author(s):  
Samiei F ◽  
Nedaie H A ◽  
Darestani H ◽  
Banaee N ◽  
Shagholi N ◽  
...  
Keyword(s):  
Linear Accelerator ◽  
Neutron Probe

Bremsstrahlung  X-rays  from  high-energy  linear    accelerators  (Linacs)  produce  neutrons  as  a  result  of  photonuclear  reactions  mainly  with  the  different  materials  constituting  the  accelerator  head.  The  neutrons  produced  during  high  energy  radiotherapy  should  be  considered  in  terms  of  protection  and  ose  escalation.  Due  to  the  very  intense  photon  component  in  the  Linac  field  causing  pulse  pile-up  and  dead-time  effects  in  detectors,  measurement  of  the  corresponding  neutron  dose  by  active  dosimeters  is  extremely  troublesome.  In  this  study,  the  neutron  probe  LB  6411,  which  active  detector  of  3He  proportional  counter  tube  was  replaced  with  the  passive  detectors  of  TLD600  and  TLD700,  has  been  used  to  perform  neutron  measurements  at  four  points  around  the  18  MV  Varian  2100C  Linac  facility.  The  neutron  dose  equivalent  at  the  distance  of  1  and  2  m  from  the  isocentre  on  the  patient  couch  was  obtained  2.2  and  0.75  mSv.Gy-1  respectively.  According  to  the  results,  the  dose  equivalent  from  emitted  photoneutrons  is  not  negligible  and  therefore  treatment  conditions  should  be  optimized.  The  results  of  this  study  emphasized  that  TLD600  and  TLD700  dosimeters  inside  the  polyethylene  sphere  of  neutron  probe  LB  6411  is  an  appropriate  choice  for  studying  photoneutron  production  in  the  vicinity  of  the  accelerator.

Dosimetric comparison of fractionated radiosurgery plans using frameless Gamma Knife ICON and CyberKnife systems with linear accelerator–based radiosurgery plans for multiple large brain metastases

2020 ◽  
Vol 132 (5) ◽  
pp. 1473-1479 ◽  
Author(s):  
Eun Young Han ◽  
He Wang ◽  
Dershan Luo ◽  
Jing Li ◽  
Xin Wang
Keyword(s):  
Brain Metastases ◽  
Gamma Knife ◽  
Linear Accelerator ◽  
Treatment Time ◽  
Target Volume ◽  
Planning System ◽  
Treatment Planning System ◽  
Normal Brain ◽  
Large Brain ◽  
The Mean

OBJECTIVEFor patients with multiple large brain metastases with at least 1 target volume larger than 10 cm3, multifractionated stereotactic radiosurgery (MF-SRS) has commonly been delivered with a linear accelerator (LINAC). Recent advances of Gamma Knife (GK) units with kilovolt cone-beam CT and CyberKnife (CK) units with multileaf collimators also make them attractive choices. The purpose of this study was to compare the dosimetry of MF-SRS plans deliverable on GK, CK, and LINAC and to discuss related clinical issues.METHODSTen patients with 2 or more large brain metastases who had been treated with MF-SRS on LINAC were identified. The median planning target volume was 18.31 cm3 (mean 21.31 cm3, range 3.42–49.97 cm3), and the median prescribed dose was 27.0 Gy (mean 26.7 Gy, range 21–30 Gy), administered in 3 to 5 fractions. Clinical LINAC treatment plans were generated using inverse planning with intensity modulation on a Pinnacle treatment planning system (version 9.10) for the Varian TrueBeam STx system. GK and CK planning were retrospectively performed using Leksell GammaPlan version 10.1 and Accuray Precision version 1.1.0.0 for the CK M6 system. Tumor coverage, Paddick conformity index (CI), gradient index (GI), and normal brain tissue receiving 4, 12, and 20 Gy were used to compare plan quality. Net beam-on time and approximate planning time were also collected for all cases.RESULTSPlans from all 3 modalities satisfied clinical requirements in target coverage and normal tissue sparing. The mean CI was comparable (0.79, 0.78, and 0.76) for the GK, CK, and LINAC plans. The mean GI was 3.1 for both the GK and the CK plans, whereas the mean GI of the LINAC plans was 4.1. The lower GI of the GK and CK plans would have resulted in significantly lower normal brain volumes receiving a medium or high dose. On average, GK and CK plans spared the normal brain volume receiving at least 12 Gy and 20 Gy by approximately 20% in comparison with the LINAC plans. However, the mean beam-on time of GK (∼ 64 minutes assuming a dose rate of 2.5 Gy/minute) plans was significantly longer than that of CK (∼ 31 minutes) or LINAC (∼ 4 minutes) plans.CONCLUSIONSAll 3 modalities are capable of treating multiple large brain lesions with MF-SRS. GK has the most flexible workflow and excellent dosimetry, but could be limited by the treatment time. CK has dosimetry comparable to that of GK with a consistent treatment time of approximately 30 minutes. LINAC has a much shorter treatment time, but residual rotational error could be a concern.

Functional stereotactic radiosurgery involving a dedicated linear accelerator and gamma unit: a comparison study

2004 ◽  
pp. 373-380 ◽  
Author(s):  
Timothy D. Solberg ◽  
Steven J. Goetsch ◽  
Michael T. Selch ◽  
William Melega ◽  
Goran Lacan ◽  
...  
Keyword(s):  
Stereotactic Radiosurgery ◽  
Linear Accelerator ◽  
Treatment Plan ◽  
Single Shot ◽  
Submillimeter Range ◽  
Primate Model ◽  
Content Type ◽  
Stereotactic Frame ◽  
Targeting Ability ◽  
Fine Print

Object. The purpose of this work was to investigate the targeting and dosimetric characteristics of a linear accelerator (LINAC) system dedicated for stereotactic radiosurgery compared with those of a commercial gamma knife (GK) unit. Methods. A phantom was rigidly affixed within a Leksell stereotactic frame and axial computerized tomography scans were obtained using an appropriate stereotactic localization device. Treatment plans were performed, film was inserted into a recessed area, and the phantom was positioned and treated according to each treatment plan. In the case of the LINAC system, four 140° arcs, spanning ± 60° of couch rotation, were used. In the case of the GK unit, all 201 sources were left unplugged. Radiation was delivered using 3- and 8-mm LINAC collimators and 4- and 8-mm collimators of the GK unit. Targeting ability was investigated independently on the dedicated LINAC by using a primate model. Measured 50% spot widths for multisource, single-shot radiation exceeded nominal values in all cases by 38 to 70% for the GK unit and 11 to 33% for the LINAC system. Measured offsets were indicative of submillimeter targeting precision on both devices. In primate studies, the appearance of an magnetic resonance imaging—enhancing lesion coincided with the intended target. Conclusions. Radiosurgery performed using the 3-mm collimator of the dedicated LINAC exhibited characteristics that compared favorably with those of a dedicated GK unit. Overall targeting accuracy in the submillimeter range can be achieved, and dose distributions with sharp falloff can be expected for both devices.

The possibility of using tantalum oxide microparticles in phosphate glass for radiation therapy of malignant neoplasms

2020 ◽  
pp. 85-87
Author(s):  
O. S. Plotnikova ◽  
V. I. Apanasevich ◽  
M. A. Medkov ◽  
A. A. Polezhaev ◽  
V. I. Nevozhai ◽  
...  
Keyword(s):  
Phosphate Glass ◽  
Linear Accelerator ◽  
Malignant Tumors ◽  
Video Recording ◽  
Tantalum Oxide ◽  
Vertical Plane ◽  
Secondary Radiation ◽  
Semiconductor Diode ◽  
Malignant Neoplasms ◽  
Diode Detector

Objective: The creation of the medicine for a local radiomodification of tumors.Methods: The level of the secondary radiation on the surface of the phosphate glass powder with the inclusion of tantalum oxide processed by 6 MeV deceleration emission was studied. Medical linear accelerator TrueBeam (Varian, USA), and Semiconductor diode detector PDI 2.0 (Sun Nuclear Corp., USA) having the system of moving in vertical plane and the system of position video recording were used.Results: The presence of the phosphate glass (containing 20% Та2О5) on the surface gave a 63.7% increase to the secondary radiation. It’s around two thirds of the overall level.Conclusion: An opportunity to create a medicine on the basis of phosphate glass, containing tantalum oxide, for local radiomodification of malignant tumors. 

scholarly journals A high-resolution solar spectrum 2000 Å–2200 Å

1970 ◽  
Vol 36 ◽  
pp. 271-273
Author(s):  
B. B. Jones ◽  
B. C. Boland ◽  
R. Wilson ◽  
S. T. F. Engstrom
Keyword(s):  
High Resolution ◽  
Solar Spectrum ◽  
Solar Image ◽  
Roll Control ◽  
North East ◽  
The North ◽  
Alignment System ◽  
Optical Alignment ◽  
South Axis ◽  
System Operating

A high-resolution solar spectrum in the range 2000–2200 Å was obtained in a recent flight of a sunpointing Skylark rocket. This was launched at 04.21 hr UT on April 22, 1969 from Woomera and reached an apogee of 178 km. An optical alignment system operating on the main vehicle pointing system gave a net stabilisation of ±3 arc sec in the position of the solar image relative to the spectrograph slit. The slit, of length 1.0 mm, was set in the north-east quadrant parallel to and 5 arc min from the north/south axis, its lower edge being 1 arc min from the equator. The roll control of ±2.5° was provided entirely by the standard Elliott Bros. type of vehicle stabilisation.

scholarly journals Initial Clinical Experience Treating Patients with Breast Cancer on a 6-MV Flattening-Filter-Free O-Ring Linear Accelerator

2019 ◽  
Vol 4 (4) ◽  
pp. 571-578 ◽  
Author(s):  
Andrew R. Barsky ◽  
Fionnbarr O'Grady ◽  
Christopher Kennedy ◽  
Neil K. Taunk ◽  
Lei Dong ◽  
...  
Keyword(s):  
Breast Cancer ◽  
Clinical Experience ◽  
Linear Accelerator ◽  
Flattening Filter Free ◽  
Flattening Filter ◽  
Initial Clinical Experience
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