| 1. |
- Barday, R., et al.
(författare)
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ELECTRON BEAM POLARIMETRY AT LOW ENERGIES AND ITS APPLICATIONS
- 2011
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Ingår i: POLARIZED SOURCES, TARGETS AND POLARIMETRY. - : WORLD SCIENTIFIC PUBL CO PTE LTD. - 9789814324915 - 9789814462747 ; , s. 105-112
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Konferensbidrag (refereegranskat)abstract
- Low energy (E-k similar to 100 keV) Mott scattering polarimetry is a widely established technique to measure the polarization of an electron beam. We analyze the feasibility of Mott scattering at energies up to 20 MeV. For further studies of the electron spin dynamics in the scattering process a correlation between the linear polarization of bremsstrahlung radiation and the electron beam polarization has been measured for the first time using a planar HPGe Compton polarimeter at the 100 keV source of polarized electrons at TU Darmstadt.
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| 2. |
- Schässburger, Kai-Uwe
(författare)
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Minimally-invasive breast interventions : methods for high yield, low risk, precision biopsy and curative thermal ablation
- 2018
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Advances in medical imaging and the introduction of population-based screening programs have increased the detection rate and overall proportion of small breast tumors. In addition, progress in technology and medical science, in combination with efforts to minimize morbidity, have resulted in the emergence of minimally invasive image-guided interventional procedures for both diagnosis and treatment of breast cancer. The aim of this thesis was to develop and validate new technologies for minimally-invasive diagnosis and treatment of breast cancer. Specifically, to develop and validate a new biopsy system incorporating novel mechanisms for needle insertion and tissue acquisition designed for accurate lesion targeting and high yield tissue sampling; to clinically validate a biopsy enhancement technology using radiofrequency (RF) pulses to counteract dissemination of tumor cells; and to improve and validate radiofrequency ablation (RFA) for the treatment of small carcinoma and demonstrate feasibility in non-operable elderly patients. During the course of this work a new biopsy device has been developed which incorporates a pneumatic insertion mechanism combined with a novel needle design. Paper I presented the device, compared sampling performance to a standard core needle biopsy (CNB) device in three representative bench models, measured needle dynamics on a specially designed needle trajectory test and evaluated ex vivo sample quality. Mean weight of samples were 3.5, 4.6, and 4.3 times higher (p <0.01) than standard CNB device in turkey breast, calf thymus and swine pancreas. The method of tissue acquisition had no negative impact on the histopathologic quality of samples obtained from resected specimens. Maximum measured needle velocity was 21.2 ±2.5 m/s on a stroke length of 2.5 mm. Paper II investigated whether a technology incorporating the application of RF pulses to the biopsy needle could counteract dissemination of tumor cells. In this proof-of-principle setting the technology was adapted to fine needle aspiration (FNA) and prospectively used in 31 patients. Eighty-eight patients underwent routine FNA. Blood emerging from the skin orifice was analyzed for the presence of tumor cells. Viable tumor cells were found in 74% (65/88) of cases for routine FNA and in 0% (0/31) of cases (p <0.001) when RF pulses where applied. It was observed that application of RF pulses had a hemostatic effect, did not degrade the cytological sample inside the needle and caused no additional pain compared with standard FNA. In Papers III, IV & V, the technology, method and protocol for RFA in breast cancer were successively developed and evaluated in a total of 55 patients. Specifically, in Paper III the feasibility of a newly developed RF device for ablation of unifocal breast carcinoma <16 mm immediately prior to partial mastectomy was assessed. In 84% (26/31) of cases complete ablation was achieved as assessed by Hematoxylin and Eosin (H&E) staining. Non-complete ablation was associated with incorrect electrode positioning within the lesion and underestimation of lesion extent due to inaccurate preoperative imaging. In Paper IV, tumors ≤20 mm were included and the feasibility under local anesthesia three weeks prior to planned resection using improved technology and protocol was assessed. Magnetic resonance imaging (MRI) was utilized for patient selection. Exclusion criteria included multifocality, diffuse growth patterns, >25% intraductal components and lobular histology. Magnetic resonance imaging, H&E staining and cytokeratine 8 (CK8) immunostaining were used to determine complete ablation. A pneumatic–mechanical insertion mechanism was developed to improve electrode insertion and positioning. Pain was assessed using the Visual Analogue Scale (VAS). In 100% (18/18) of cases MRI showed no residual tumor growth and devitalization of the entire tumor was shown by at least one histologic method. Pain was reported to be a median of 2 and 2.5 for injection of anesthetics and during ablation, respectively, and the difference was not significant (p =0.512). In Paper V the feasibility of RFA as an alternative to surgical resection in elderly breast cancer patients with severe comorbidities that were unfit for or refused surgery was assessed. Six patients aged ≥85 years were included. In all cases, complete ablation was confirmed using MRI and contrast enhanced ultrasound (CEUS) at 1 month as well as staining assays for H&E and CK8 in tissue samples at 6 months. The procedure was well tolerated with mild to moderate pain during the ablation procedure. Follow-up was a median (range) of 54 months (11 to 94 months). Three patients died of non-cancer related causes. Three patients remained alive at 74, 86 and 94 months of which one experienced a loco-regional recurrence at 59 months. In conclusion, this thesis demonstrates that the newly developed biopsy system enables for a novel method of precision needle insertion and achieves high yield tissue sampling. Furthermore, this thesis demonstrates that the presented biopsy enhancement technology can prevent dissemination of tumor cells. Finally, it demonstrates that RF ablation of small breast carcinoma has a high rate of complete ablation, can be performed under local anesthesia with mild to moderate pain, and is feasible as an individualized treatment option in elderly patients with severe co-morbidity who are refusing, or are unfit for surgery.
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| 3. |
- Tashenov, S., et al.
(författare)
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Bremsstrahlung polarization correlations and their application for polarimetry of electron beams
- 2014
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Ingår i: 28th International Conference on Photonic, Electronic and Atomic Collisions, ICPEAC 2013. - : Institute of Physics Publishing.
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Konferensbidrag (refereegranskat)abstract
- The correlation between electron spin and photon linear polarization in atomic-field bremsstrahlung was measured with a polarized electron beam. The angle of photon polarization and the photon emission intensity were found to be correlated with the spin orientation. These effects are interpreted in terms of spin-orbit interaction. They lead to a new technique of electron beam polarimetry.
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| 4. |
- Tashenov, S., et al.
(författare)
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Bremsstrahlung polarization correlations and their application for polarimetry of electron beams
- 2013
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Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622. ; 87:2, s. 022707-
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Tidskriftsartikel (refereegranskat)abstract
- Linear polarization of hard x rays emitted in the process of atomic-field electron bremsstrahlung has been measured with a polarized electron beam. The correlation between the initial orientation of the electron spin and the angle of photon polarization has been systematically studied by means of Compton and Rayleigh polarimetry techniques applied to a segmented germanium detector. The results are in good agreement with those of fully relativistic calculations. The observed correlations are also explained classically and in a unique way manifest that due to the spin-orbit interaction the electron scattering trajectory is not confined to a single scattering plane. The developed photon polarimetry technique with a passive scatterer is very efficient and accurate and thus allows for additional applications. Bremsstrahlung polarization correlations lead to an alternative method of polarimetry of electron beams. Such a method is sensitive to all three components of the electron spin. It can be applied in a broad range of the electron beam energies from approximate to 100 keV up to a few tens of MeV. The results of a measurement at 100 keV are shown. The optimum scheme for electron polarimetry is analyzed and the relevant theoretical predictions are presented.
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| 5. |
- Tashenov, Stanislav, et al.
(författare)
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Hard X-ray polarimetry by means of Rayleigh scattering
- 2009
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Ingår i: Nuclear Instruments and Methods in Physics Research Section A. - : Elsevier BV. - 0168-9002 .- 1872-9576. ; 600:3, s. 599-603
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Tidskriftsartikel (refereegranskat)abstract
- A new linear polarimetry technique based on Rayleigh scattering is introduced. Its properties are compared to the Compton technique. Experimental verification was realized using a 5 x 5 segmented planar HPGe pixel detector. In the proof-of-principle experiment a measurement of Rayleigh scattering off lead atoms was performed for linearly polarized; approximate to 53.3 keV photons at two scattering angles.
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| 6. |
- Tashenov, S., et al.
(författare)
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Observation of the spin-orbit interaction in bremsstrahlung
- 2013
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Ingår i: Physica scripta. T. - 0281-1847. ; T156, s. 014071-
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Tidskriftsartikel (refereegranskat)abstract
- The effects of the spin-orbit interaction are pronounced for an electron scattered in a Coulomb field of the nucleus. They cause the electron scattering plane to turn or precess as the electron moves. This precession is visible through linear polarization of bremsstrahlung. The first experiment to observe it is described in this contribution.
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