| 1. |
- Andreassen, Björn, 1975-, et al.
(författare)
-
Development of an efficient scanning and purging magnet system for IMRT with narrow high energy photon beams
- 2009
-
Ingår i: Nuclear Instruments and Methods in Physics Research Section A. - : Elsevier BV. - 0168-9002 .- 1872-9576. ; 612:1, s. 201-208
-
Tidskriftsartikel (refereegranskat)abstract
- Due to the clinical advantages of Intensity Modulated Radiation Therapy (IMRT) high flexibility and accuracy in intensity modulated dose delivery is desirable to really maximize treatment outcome. Although it is possible to deliver IMRT by using broad beams in combination with dynamic multileaf collimation the process is rather time consuming and inefficient. By using narrow scanned high energy photon beams the treatment outcome can be improved, the treatment time reduced and accurate 3D in vivo dose delivery monitoring is possible by PET-CT based dose delivery imaging of photo nuclear reactions in human tissues. Narrow photon beams can be produced by directing a low emittance high energy electron beam on a thin target, and then cleaning the therapeutic photon beam from transmitted high energy electrons, and photon generated charged leptons, with a dedicated purging magnet placed directly downstream of the target. To have an effective scanning and purging magnet system the purging magnet should be placed immediately after the bremsstrahlung target to deflect the transmitted electrons to an efficient electron stopper. In the static electron stopper the electrons should be safely collected independent of the desired direction of the therapeutic scanned photon beam. The SID (Source to Isocentre Distance) should preferably be short while retaining the ability to scan over a large area on the patient and consequently there are severe requirements both on the strength and the geometry of the scanning and purging magnets. In the present study an efficient magnet configuration with a purging and scanning magnet assembly is developed for electron energies in the 50-75 MeV range and a SID of 75 cm. For a bremsstrahlung target of 3mm Be these electron energies produce a photon beam of 25-17 mm FWHM (Full Width Half Maximum) at a SID of 75 cm. The magnet system was examined both in terms of the efficiency in scanning the narrow bremsstrahlung beam and the deflection of transmitted and photon generated electrons. The simulations show that its is possible to have a scan area on the patient of up to 43 x 40 cm2 for an incident electron energy of 50 MeV and 28 x 40 cm2 at 75 MeV, while at the same time adequately deflecting the transmitted electron beam.
|
|
| 2. |
|
|
| 3. |
- Bergman, Olle, 1978, et al.
(författare)
-
Do polymorphisms in transcription factors LMX1A and LMX1B influence the risk for Parkinson's disease?
- 2009
-
Ingår i: Journal of neural transmission (Vienna, Austria : 1996). - : Springer Science and Business Media LLC. - 1435-1463 .- 0300-9564. ; 116:3, s. 333-8
-
Tidskriftsartikel (refereegranskat)abstract
- The key symptoms of Parkinson's disease (PD) are caused by degeneration of dopamine neurons originating in substantia nigra. Whereas, transcription factor LMX1A is crucial for the differentiation of mesencephalic dopamine neurons, LMX1B appears to be important for both the development and the survival of these cells. The aim of this study was to investigate if genetic variation in LMX1A and LMX1B differs between patients with PD (n = 357) and control subjects (n = 1428) by genotyping 33 single nucleotide polymorphisms (SNPs) in LMX1A and 11 SNPs in LMX1B. Three SNPs in LMX1A and one in LMX1B were associated with PD. After splitting for gender, six SNPs were associated with PD in women and four in men. The significances obtained did not survive correction for multiple testing, and our results should hence be interpreted with caution, but are partly in line with a previous report, and should thus be of sufficient interest to encourage further studies of these genes in PD.
|
|
| 4. |
- Brahme, Anders, et al.
(författare)
-
Application of Geant4 in the development of new radiation therapy treatment methods
- 2006
-
Ingår i: Proceedings of the 9th Conference, Astroparticle, Particle and Space Physics, Detectors and Medical Physics Applications. - 5 Toh Tuck Link, singapore : World Scientific Publishing Co. Pte. Ltd.. - 9812567984 ; , s. 451-461
-
Konferensbidrag (refereegranskat)abstract
- There is a very fast development of new radiation treatment methods today, from advanced use of intensity modulated photon and electron beams to light ion therapy with narrow scanned beam based treatment units. Accurate radiation transport calculations are a key requisite for these developments where Geant4 is a very useful Monte Carlo code for accurate design of new treatment units. Today we cannot only image the tumor by PET-CT imaging before the treatment but also determine the tumor sensitivity to radiation and even measure in vivo the delivered absorbed dose in three dimensions in the patient. With such methods accurate Monte Carlo calculations will make radiation therapy an almost exact science where the curative doses can be calculated based on patient individual response data. In the present study results from the application of Geant4 are discussed and the comparisons between Geant4 and experimental and other Monte Carlo data are presented.
|
|
| 5. |
- Brink-Elfegoun, T., et al.
(författare)
-
Neuromuscular and circulatory adaptation during combined arm and leg exercise with different maximal work loads
- 2007
-
Ingår i: European Journal of Applied Physiology. - : Springer Science and Business Media LLC. - 1439-6319 .- 1439-6327. ; 101:5, s. 603-611
-
Tidskriftsartikel (refereegranskat)abstract
- Cardiopulmonary kinetics and electromyographic activity (EMG) during exhausting exercise were measured in 8 males performing three maximal combined arm + leg exercises (cA+L). These exercises were performed at different rates of work (mean ± SD; 373 ± 48, 429 ± 55 and 521 ± 102 W) leading to different average exercise work times in all tests and subjects. reached a plateau versus work rate in every maximal cA+L exercise (range 6 min 33 s to 3 min 13 s). The three different exercise protocols gave a maximal oxygen consumption of 4.67 ± 0.57, 4.58 ± 0.52 and 4.66 ± 0.53 l min−1 (P = 0.081), and a maximal heart rate (HRmax) of 190 ± 6, 189 ± 4 and 189 ± 6 beats min−1 (P = 0.673), respectively. Root mean square EMG (EMGRMS) of the vastus lateralis and the triceps brachii muscles increased with increasing rate of work and time in all three cA+L protocols. The study demonstrates that despite different maximal rates of work, leading to different times to exhaustion, the circulatory adaptation to maximal exercise was almost identical in all three protocols that led to a plateau. The EMGRMS data showed increased muscle recruitment with increasing work rate, even though the HRmax and was the same in all three cA+L protocols. In conclusion, these findings do not support the theory of the existence of a central governor (CG) that regulates circulation and neuronal output of skeletal muscles during maximal exercise. Thibault Brink-Elfegoun and Hans-Christer Holmberg contributed equally to this article.
|
|
| 6. |
- Buervenich, Silvia, et al.
(författare)
-
A rare truncating mutation in ADH1C (G78Stop) shows significant association with Parkinson disease in a large international sample.
- 2005
-
Ingår i: Archives of neurology. - : American Medical Association (AMA). - 0003-9942. ; 62:1, s. 74-8
-
Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Alcohol dehydrogenases (ADHs) may be involved in the pathogenesis of neurodegenerative disorders because of their multiple roles in detoxification pathways and retinoic acid synthesis. In a previous study, significant association of an ADH class IV allele with Parkinson disease (PD) was found in a Swedish sample. PATIENTS: The previously associated single-nucleotide polymorphism plus 12 further polymorphisms in the ADH cluster on human chromosome 4q23 were screened for association in an extension of the original sample that now included 123 Swedish PD patients and 127 geographically matched control subjects. A rare nonsense single-nucleotide polymorphism in ADH1C (G78stop, rs283413) was identified in 3 of these patients but in no controls. To obtain sufficient power to detect a possible association of this rare variant with disease, we screened a large international sample of 1076 PD patients of European ancestry and 940 matched controls. RESULTS: The previously identified association with an ADH class IV allele remained significant (P<.02) in the extended Swedish study. Furthermore, in the international collaboration, the G78stop mutation in ADH1C was found in 22 (2.0%) of the PD patients but only in 6 controls (0.6%). This association was statistically significant (chi(2)(1) = 7.5; 2-sided P = .007; odds ratio, 3.25 [95% confidence interval, 1.31-8.05]). In addition, the G78stop mutation was identified in 4 (10.0%) of 40 Caucasian index cases with PD with mainly hereditary forms of the disorder. CONCLUSION: Findings presented herein provide further evidence for mutations in genes encoding ADHs as genetic risk factors for PD.
|
|
| 7. |
- Constantinescu, Radu, 1966, et al.
(författare)
-
Levels of brain related proteins in cerebrospinal fluid: An aid in the differential diagnosis of parkinsonian disorders.
- 2009
-
Ingår i: Parkinsonism & related disorders. - : Elsevier BV. - 1353-8020. ; 15:3, s. 205-12
-
Forskningsöversikt (refereegranskat)abstract
- Parkinsonian disorders such as Parkinson's disease (PD), multiple system atrophy (MSA), progressive supranuclear palsy (PSP), and corticobasal degeneration (CBD), are a large group of common neurodegenerative diseases. The initial differential diagnosis can be extremely challenging with major implications for prognosis. The 42 amino acid fragment of amyloid-beta (Abeta42), neurofilament light chain (NFL), neurofilament heavy chain (pNFH), tau protein, glial fibrillary acidic protein (GFAP), neuron specific enolase (NSE), S-100B protein, and myelin basic protein (MBP) are brain related proteins (BRP) present in neurons and glia cells. They are released in the cerebrospinal fluid (CSF) after brain tissue damage caused by a variety of neurological diseases, including the parkinsonian disorders. A review of the literature shows that, carefully interpreted, the CSF levels of BRP can be of value in the differential diagnosis of parkinsonian disorders.
|
|
| 8. |
|
|
| 9. |
- Holmberg, Björn, 1974-
(författare)
-
Estimating Human Limb Motion Using Skin Texture and Particle Filtering
- 2008
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Estimating human motion is the topic of this thesis. We are interested in accurately estimating the motion of a human body using only video images capturing the subject in motion. Video images from up to two cameras are considered.The first main topic of the thesis is to investigate a new type of input data. This data consists of some sort of texture. This texture can be added to the human body segment under study or it can be the actual texture of the skin.In paper I we investigate if added texture together with the use of a two camera system can provide enough information to make it possible to estimate the knee joint center location. Evaluation is made using a marker based system that is run in parallel to the two camera video system. The results from this investigation show promise for the use of texture. The marker and texture based estimates differ in absolute values but the variations are similar indicating that texture is in fact usable for this purpose.In paper II and III we investigate further the usability in images of skin texture as input for motion estimation. Paper II approaches the problem of estimating human limb motion in the image plane. An image histogram based mutual information criterion is used to decide if an extracted image patch from frame k is a good match to some location in frame k+1. Eval- uation is again performed using a marker based system synchronized to the video stream. The results are very promising for the application of skin texture based motion estimation in 2D. In paper III, basically the same approach is taken as in paper II with the substantial difference that here estimation of three dimensional motion is addressed. Two video cameras are used and the image patch matching is performed both between cameras (inter-camera) in frame k and also in each cameras images (intra-camera) for frame k to k+1. The inter-camera matches yield triangulated three dimensional estimates on the approximate surface of the skin. The intra-camera matches provide a way to connect the three dimensional points between frame k and k+1 The resulting one step three dimensional trajectories are then used to estimate rigid body motion using least squares methods. The results show that there is still some work to be done before this texture based method can be an alternative to the marker based methods.In paper IV the second main topic of the thesis is discussed. Here we present an investigation in using model based techniques for the purpose of estimating human motion. A kinematic model of the thigh and shank segments are built with an anatomic model of the knee. Using this model, the popular particle filter and typical simulated data from the triangulation in paper III, an estimate of the motion variables in the thigh and shank segment can be achieved. This also includes one static model parameter used to describe the knee model. The results from this investigation show good promise for the use of triangulated skin texture as input to such a model based approach.
|
|
| 10. |
|
|
