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Development and characterization of sensitive, energy-independent solid-state photon dosemeters with high spatial and temporal resolution. Applications in clinical radiology and radiation protection.

Herrnsdorf, Lars LU (2018) In Lund University, Faculty of Medicine Doctoral Dissertation Series 2018:82(82).
Abstract
Abstract
Modern medicine and health care rely on a variety of diagnostic and therapeutic equipment and methods that involve ionizing radiation. To guarantee quality and the safety of patients and staff, advanced radiation detectors and dosemeters are needed that have low energy and operate with directional independence for X-ray and γ-ray photons. Similar instruments are also of great importance for measurements used in radiation protection and safety outside of hospitals and the health care sector and for nuclear and radiological emergencies.
In this thesis, new sensors, detectors, and dosemeters based on silicon were designed, manufactured, characterized, and tested.
The aim was to develop dosemeters with signals that are... (More)
Abstract
Modern medicine and health care rely on a variety of diagnostic and therapeutic equipment and methods that involve ionizing radiation. To guarantee quality and the safety of patients and staff, advanced radiation detectors and dosemeters are needed that have low energy and operate with directional independence for X-ray and γ-ray photons. Similar instruments are also of great importance for measurements used in radiation protection and safety outside of hospitals and the health care sector and for nuclear and radiological emergencies.
In this thesis, new sensors, detectors, and dosemeters based on silicon were designed, manufactured, characterized, and tested.
The aim was to develop dosemeters with signals that are as independent as possible of the energy and direction of the incoming X-ray and γ-ray photons. Starting with a 350 µm silicon wafer, a sensor was constructed with electrical contacts on one side only. A flex card was adapted with anisotropic conductive adhesive (ACA) and mounted to the sensor. Since all components have low X-ray attenuation, the disturbance of the radiation field by the detector is minimal from all directions.
Another important component is the metal filter encapsulating the silicon detector. Made of stainless steel, this encompassing filter compensates for the energy and directional variation of sensitivity of the silicon detector. The filter was designed using a series of Monte Carlo calculations. The hole pattern was selected so that the signal (proportional to the absorbed dose) was independent of the X-ray source position (in 4π). Due to the small structures, additive manufacturing (AM) in the form of metal 3D printing was needed to fabricate the filter.
The functionality of the 4π dosemeter was verified by simulation to meet the quality criterion that the energy dependence is less than 5% for the IEC beam qualities RQR and RQT in the range 65–145 kV. The best way to microfabricate the sensor, sensor holder, flex card, and energy filter was evaluated and a method to control its mounting accuracy is proposed.
The application of silicon detectors in radiology (CT, CBCT, and planar radiography) was tested, and a specific dosemeter construction also was tested for eye lens dosimetry and for emergency situations.
To broaden the use of silicon detectors in future medical imaging and dosimetry applications, an overview of silicon photomultipliers (SiPM) for this area is included and a learning and training program targeted to graduate students is described.
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author
supervisor
opponent
  • Ass. professor Bornefalk, Hans, KTH, Stockholm
organization
publishing date
type
Thesis
publication status
published
subject
keywords
Si PIN, sensor, detector, dosemeter, CT, CBCT, dose profile, CTDP, R100, SiPM, Medipix, MCNP, AM, 4π detector, ACA, flex card micro assembly
in
Lund University, Faculty of Medicine Doctoral Dissertation Series
volume
2018:82
issue
82
pages
77 pages
publisher
Lund University: Faculty of Medicine
defense location
Lilla aulan, Jan Waldenströms gata 5, Skånes Universitetssjukhus i Malmö
defense date
2018-06-08 09:15:00
ISSN
1652-8220
ISBN
978-91-7619-648-9
language
English
LU publication?
yes
id
024269e2-897e-459f-9bd1-c172eae60b95
date added to LUP
2018-09-28 16:29:32
date last changed
2020-03-13 10:36:02
@phdthesis{024269e2-897e-459f-9bd1-c172eae60b95,
  abstract     = {Abstract<br/>Modern medicine and health care rely on a variety of diagnostic and therapeutic equipment and methods that involve ionizing radiation. To guarantee quality and the safety of patients and staff, advanced radiation detectors and dosemeters are needed that have low energy and operate with directional independence for X-ray and γ-ray photons. Similar instruments are also of great importance for measurements used in radiation protection and safety outside of hospitals and the health care sector and for nuclear and radiological emergencies. <br/>In this thesis, new sensors, detectors, and dosemeters based on silicon were designed, manufactured, characterized, and tested. <br/>The aim was to develop dosemeters with signals that are as independent as possible of the energy and direction of the incoming X-ray and γ-ray photons. Starting with a 350 µm silicon wafer, a sensor was constructed with electrical contacts on one side only. A flex card was adapted with anisotropic conductive adhesive (ACA) and mounted to the sensor. Since all components have low X-ray attenuation, the disturbance of the radiation field by the detector is minimal from all directions. <br/>Another important component is the metal filter encapsulating the silicon detector. Made of stainless steel, this encompassing filter compensates for the energy and directional variation of sensitivity of the silicon detector. The filter was designed using a series of Monte Carlo calculations. The hole pattern was selected so that the signal (proportional to the absorbed dose) was independent of the X-ray source position (in 4π). Due to the small structures, additive manufacturing (AM) in the form of metal 3D printing was needed to fabricate the filter. <br/>The functionality of the 4π dosemeter was verified by simulation to meet the quality criterion that the energy dependence is less than 5% for the IEC beam qualities RQR and RQT in the range 65–145 kV. The best way to microfabricate the sensor, sensor holder, flex card, and energy filter was evaluated and a method to control its mounting accuracy is proposed. <br/>The application of silicon detectors in radiology (CT, CBCT, and planar radiography) was tested, and a specific dosemeter construction also was tested for eye lens dosimetry and for emergency situations. <br/>To broaden the use of silicon detectors in future medical imaging and dosimetry applications, an overview of silicon photomultipliers (SiPM) for this area is included and a learning and training program targeted to graduate students is described. <br/>},
  author       = {Herrnsdorf, Lars},
  isbn         = {978-91-7619-648-9},
  issn         = {1652-8220},
  language     = {eng},
  number       = {82},
  publisher    = {Lund University: Faculty of Medicine},
  school       = {Lund University},
  series       = {Lund University, Faculty of Medicine Doctoral Dissertation Series},
  title        = {Development and characterization of sensitive, energy-independent solid-state photon dosemeters with high spatial and temporal resolution. Applications in clinical radiology and radiation protection.},
  url          = {https://lup.lub.lu.se/search/files/51975493/Lars_Herrnsdorf_kappa.pdf},
  volume       = {2018:82},
  year         = {2018},
}