| 1. |
- Alm Carlsson, Gudrun, et al.
(författare)
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Monte Carlo metoden : ett verktyg inom strålningsfysiken
- 1995
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Detta kompendium är tänkt att användas som ett propedeutiskt kursmaterial för kursdeltagare i kursen "Monte Carlo simulering av foton- och elektrontransport vid diagnostiska och radioterapeutiska strålkvaliteter". Först följer en kort repetition av den grundläggande statistik som utnyt1jas i beräkningarna. Därefter följer en beskrivning av slumptal. det fundament som metoden bygger på. Vidare beskrivs val ur olika frekvensfunktioner. Valet kan även göras ur så kallade falska fördelningar för att reducera variansen i den skattade storheten. Metoderna belyses i ett avsnitt om problemlösningsmetodik. först i allmänna termer för att sen gå in på ett specifikt problem (Buffons nålproblem) där en analys och strukturering av problemet görs varefter flödesschema och kodning exemplifieras. Så följer två moment där en beskrivning görs av färderna av fotoner respektive elektroner genom materia. För elektronfärderna gör man en indelning i klass 1- och klass II-färder. Vad detta innebär och hur deltapartiklar tas om hand beskrivs i ett kapitel. Till sist kommer en kort introduktion till de tre laborationerna med laborationshandledningar. Speciell vikt har lagts vid att initiera laboranten att fundera på fysiken i de simulerade experimenten. Detta kompendium har tillkommit som examinationsarbete vid en kurs i "Monte Carlo simulering av foton- och elektrontransport vid diagnostiska och radioterapeutiska strålkvaliteter", med andra ord den kurs du själv nu ämnar studera. Författarna önskar dig lycka till med kursen och hoppas att du kommer att få glädje av den. Speciellt hoppas vi att denna skrift ska underlätta för dig att tillgodogöra dig informationen vid föreläsningarna och under laborationerna.
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| 2. |
- Gunnarsson, Thorsteinn, 1967-, et al.
(författare)
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Mobile computerized tomography scanning in the neurosurgery intensive care unit : increase in patient safety and reduction of staff workload
- 2000
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Ingår i: Journal of Neurosurgery. - : Journal of Neurosurgery Publishing Group (JNSPG). - 0022-3085 .- 1933-0693. ; 93:3, s. 432-436
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Tidskriftsartikel (refereegranskat)abstract
- Object. Transportation of unstable neurosurgical patients involves risks that may lead to further deterioration and secondary brain injury from perturbations in physiological parameters. Mobile computerized tomography (CT) head scanning in the neurosurgery intensive care (NICU) is a new technique that minimizes the need to transport unstable patients. The authors have been using this device since June 1997 and have developed their own method of scanning such patients.Methods. The scanning procedure and radiation safety measures are described. The complications that occurred in 89 patients during transportation and conventional head CT scanning at the Department of Radiology were studied prospectively. These complications were compared with the ones that occurred during mobile CT scanning in 50 patients in the NICU. The duration of the procedures was recorded, and an estimation of the staff workload was made. Two patient groups, defined as high- and medium-risk cases, were studied. Medical and/or technical complications occurred during conventional CT scanning in 25% and 20% of the patients in the high- and medium-risk groups, respectively. During mobile CT scanning complications occurred in 4.3% of the high-risk group and 0% of the medium-risk group. Mobile CT scanning also took significantly less time, and the estimated personnel cost was reduced.Conclusions. Mobile CT scanning in the NICU is safe. It minimizes the risk of physiological deterioration and technical mishaps linked to intrahospital transport, which may aggravate secondary brain injury. The time that patients have to remain outside the controlled environment of the NICU is minimized, and the staff's workload is decreased.
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| 3. |
- Johansson, Bengt, 1958-
(författare)
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Long-term outcome research on PDR brachytherapy with focus on breast, base of tongue and lip cancer
- 2010
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Brachytherapy (BT) with continuous low dose rate (LDR) has been used for 100 years and is considered as the radiotherapy method able to deliver a dose in the shortest time with high efficacy and low risk of side effects. The drawbacks are need for patient isolation and radiation exposure of the staff during the treatment. Brenner and Hall published the radiobiology concept for pulsed dose rate (PDR) in 1991. Short (10-20 minutes), hourly pulses of high dose rate (HDR) given to the same dose, with same overall treatment time will virtually simulate continuous LDR. At the same time new afterloading machine technology became available, where a single millimetre sized radiation 192Iridium source sequentially moves through the applicator in small individually timed steps. The advantages are that the radiation dose can be optimized along the applicator and with no radiation exposure of the staff and no need for patient isolation more than during the pulse. This work deals with four different aspects of PDR BT An experimental comparison of measured absorbed doses outside a left sided breast target on a body equivalent Alderson phantom was made. Five external beam radiotherapy (EBRT) whole breast treatments to 50 Gy versus five accelerated partial breast irradiations (APBI) by PDR BT to 50 Gy were studied. The absorbed doses were measured in 67 different positions inside the body phantom by thermoluminescence dosimeters. The result shows that dose points distant to the left breast will have 1-1.4 % of the prescribed dose with no difference between EBRT and PDR BT. Organs at risk in short distance (<5 cm) to the target (such as parts of the left lung, heart muscle and the right breast) will have significantly less dose by PDR BT. In conclusion PDR BT has dosimetric advantages close to the target compared to EBRT and cannot do more damage to remote organs. PDR APBI as the adjuvant RT treatment to breast conserving surgery after early breast cancer was studied. Between 1994-2004 we treated 50 women and 51 breasts. The median age of the population was 53 (40-72) years. The cases were radically resected, unifocal T1-2N0-1M0 tumours. PDR BT was given to a dose of 50 Gy for 5 days directed to the operated sector of the breast. The median treated volume was 160 cm3, constituting in median 31 % of the breast volume. The treatment is called accelerated because total treatment time is 5 days compared to 5 weeks for EBRT. After a median follow-up of 130 months (>10 years) we noted 5 (10 %) local recurrences in the treated breast. Four of these recurrences were outside the treated volume. Three women (6 %) developed cancers in the other breast. Early side effects were mild and less than with EBRT. As late side effects we found mild to moderate local fibroses in the treated volume. A cosmetic evaluation was done by both the patient and a nurse and was found to be lower than in other published data (56 % = good to excellent). The 10 years local failure rate is similar to the result from a large Swedish randomized study on whole breast radiotherapy to 50 Gy. The study indicates that PDR BT is highly effective. A combination of EBRT (40.8 Gy) and PDR boost (35 Gy) to T1-4N0-3M0, base of tongue (BOT) cancer, treated during 1994-2007 was analyzed. The study is the first with PDR and second largest with BT worldwide. A number of 83 patients with a median age of 60 (38-82) years were included. BT was given to a mean volume of 58 ccm 2 days after the neck dissection. Median follow-up was 54 months. At 5 years we found 89 % local tumour control, 95 % neck control, 80 % disease free survival and an overall survival of 65 %. Late side effects were 13 % minor transient soft tissue necrosis and 12 % long lasting or permanent soft tissue- or osteoradio-necrosis. The results are among the best published worldwide. An extensive quality of life analysis was done on 45 patients at last follow-up and showed limited, persistent xerostomia and dysphagia. The global quality of life was rated good in 75 % of the patients. The last study presented was PDR mono-brachytherapy (55-60 Gy) to cancer of the lip (T1-3N0M0). The study included 43 patients with a median age of 74 (37-92) years. The treatment time was 5.5-6 days and the mean treated volume was 15 ccm. The median follow-up time was 54 (1-158) months. Five year Kaplan-Meier data showed, local control 94 %, disease free survival 86 % and overall survival 59 %. An early side effect was a strong radiation mucositis and dermatitis, which healed in 1 month. Late side effects were uncommon and the cosmetic appearance and the lip function were found to be normal. Our data in total and per T-stage was compared to a European survey from 1993 on 2794 patients treated by LDR BT. The results are similar and are a strong indication of equal efficacy between PDR and LDR.
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| 4. |
- Andersson, Karin M., 1989-, et al.
(författare)
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Metal artefact reduction in CT imaging of hip prostheses-an evaluation of commercial techniques provided by four vendors
- 2015
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Ingår i: British Journal of Radiology. - : British Institute of Radiology. - 0007-1285 .- 1748-880X. ; 88:1052
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Tidskriftsartikel (refereegranskat)abstract
- Objective: The aim of this study was to evaluate commercial metal artefact reduction (MAR) techniques in X-ray CT imaging of hip prostheses.Methods: Monoenergetic reconstructions of dual-energy CT (DECT) data and several different MAR algorithms, combined with single-energy CT or DECT, were evaluated by imaging a bilateral hip prosthesis phantom. The MAR images were compared with uncorrected images based on CT number accuracy and noise in different regions of interest.Results: The three MAR algorithms studied implied a general noise reduction (up to 67%, 74% and 77%) and an improvement in CT number accuracy, both in regions close to the prostheses and between the two prostheses. The application of monoenergetic reconstruction, without any MAR algorithm, did not decrease the noise in the regions close to the prostheses to the same extent as did the MAR algorithms and even increased the noise in the region between the prostheses.Conclusion: The MAR algorithms evaluated generally improved CT number accuracy and substantially reduced the noise in the hip prostheses phantom images, both close to the prostheses and between the two prostheses. The study showed that the monoenergetic reconstructions evaluated did not sufficiently reduce the severe metal artefact caused by large orthopaedic implants.Advances in knowledge: This study evaluates several commercially available MAR techniques in CT imaging of large orthopaedic implants.
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| 5. |
- Andersson, Karin, 1989-
(författare)
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Metal artifacts in computed tomography : impact of reduction methods on image quality and radiotherapy treatment planning
- 2018
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Degradation of image quality by metal artifacts is a common problem in computed tomography (CT) imaging, which can limit the diagnostic value of a CT examination and also introduce inaccuracies in radiotherapy (RT) treatment planning. In recent years, commercial metal artifact reduction (MAR) methods have been launched by several CT vendors. The overall aim of this thesis was to evaluate MAR methods in diagnostic imaging and RT treatment planning.Evaluations of hip prosthesis phantom CT images showed that MAR algorithms in general improved image quality, based on both visual grading analysis and quantitative measures, while the application of virtual monoenergetic reconstructions insufficiently reduced metal artifacts. In some cases additional artifacts were introduced by the MAR algorithms. MAR algorithms were also evaluated in hip prosthesis phantom CT imaging used for proton therapy treatment planning, where improvements in dose calculation accuracy were observed.Studies of Head & Neck (H&N) implant CT images in RT treatment planning were also performed. By visual grading of anatomy visualization with respect to target delineation in dental implant patient images, MAR algorithms were shown to significantly improve image quality. However, only minor effects of H&N implant artifacts on proton dose distributions were seen. The impact might be greater for more severe artifacts than those studied here, and thus further investigations of such cases are needed.In conclusion, MAR algorithms have been shown to enhance image quality for diagnostic applications and to improve anatomy visualization in RT treatment planning. The MAR algorithms led to increased proton dose calculation accuracy in some cases, while in other situations only minor changes were seen.
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| 6. |
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| 7. |
- Dance, David, et al.
(författare)
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Optimisation of the design of antiscatter grids by computer modelling
- 1995
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Ingår i: Radiation Protection Dosimetry. - 0144-8420 .- 1742-3406. ; 57:1, s. 207-210
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Tidskriftsartikel (refereegranskat)abstract
- A Monte Carlo computer program has been developed to model diagnostic radiological examinations, and has been used to study and optimise the design of antiscatter grids. This is important because the use of an inappropriate or poorly designed grid can lead to increased patient dose. Optimal grid parameters may be different for large and small scattering volumes. The program treats the patient as a rectangular block of tissue and takes account of the grid and image receptor. Image quality is measured in terms of contrast and signal-to-noise ratio and patient risk in terms of mean absorbed dose. Test objects of appropriate size and composition are used in the calculation of these image quality parameters. A new performance comparison and optimisation procedure has been developed, and the program has been used to study grid design in screen-film and digital radiology for small, medium and large scattering volumes.
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| 8. |
- Dance, David, et al.
(författare)
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The use of carbon fibre material in radiographic cassettes: estimation of the dose and contrast advantages
- 1997
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Ingår i: British Journal of Radiology. - 0007-1285 .- 1748-880X. ; 70, s. 383-390
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Tidskriftsartikel (refereegranskat)abstract
- A Monte Carlo simulation has been used to estimate the dose and contrast advantages of replacing radiographic cassette fronts fabricated from aluminium with cassette fronts fabricated from low atomic number material (carbon fibre). The simulation used a realistic imaging geometry and calculations were made both with and without an anti-scatter grid. Account was taken of the scatter generated in the cassette front and the effect of beam hardening on primary contrast. Dose and contrast were evaluated for a range of cassette front thicknesses and tube potentials (60-150 kV) as well as for four examinations representative of situations with varying amounts of scatter. The results with an anti-scatter grid show a clear dose and contrast advantage in all cases when an aluminium cassette front is replaced with a low attenuation cassette front. The contrast advantage is dependent upon the examination and is generally greater for imaging bony structures than for imaging soft tissue. If a 1.74 mm aluminium cassette front is compared with a 1.1 mm carbon fibre cassette front, then the dose advantages are 16%, 9%, 8% and 6% and the contrast advantages are 10%, 7%, 4% and 5% for the AP paediatric pelvis examination at 60 kV, the anteroposterior (AP) lumbar spine examination at 80 kV, the lateral lumbar spine examination at 100 kV and the posteroanterior (PA) chest examination at 150 kV, respectively. The results without an anti-scatter grid show an increased dose advantage when a low attenuation cassette front is used, but the contrast advantage is small and in some situations negative.
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| 9. |
- Edoff, Karin, et al.
(författare)
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The developmental skeletal growth in the rat foot is reduced after denervation
- 1997
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Ingår i: Anatomy and Embryology. - : Springer Science and Business Media LLC. - 0340-2061 .- 1432-0568. ; 195:6, s. 531-538
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Tidskriftsartikel (refereegranskat)abstract
- It has long been known that bone is innervated. In recent years it has been suggested that the local nerves may influence the growth and metabolism of bone by way of neuropeptides. The transient local presence of nerve-containing cartilage canals just before formation of secondary ossification centres in rat knee epiphyses seems to support that view. The purpose of the present study was to see if denervation affects the developmental growth of metatarsal bones in the rat hindfoot. We made sciatic and femoral neurectomies in 7- day-old rat pups and examined the hindfeet at various times after surgery. Immunohistochemical analysis showed that denervation was complete. Radiographic examination revealed that the metatarsal bones were significantly shorter in denervated hindfeet 30 days after denervation (average relative shortening 9.9±2.3%). Measurements of total foot length showed that denervated feet were subnormally sized already five days postoperatively, before the onset of secondary ossification. The timing of the latter was not affected by denervation. Control rats subjected to tenotomies exhibited normal metatarsal bone lengths. On the basis of these results we suggest that the local nerves may influence the growth of immature bones but do not affect secondary ossification.
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| 10. |
- Fransson, Sven Göran, 1949-, et al.
(författare)
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Patient radiation exposure during coronary angiography and intervention
- 2000
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Ingår i: Acta Radiologica. - 0284-1851 .- 1600-0455. ; 41:2, s. 142-144
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Tidskriftsartikel (refereegranskat)abstract
- Purpose: To prospectively register fluoroscopic and cine times in a random fashion, and to measure patient radiation exposure from routine coronary angiography and coronary balloon angioplasty. We also evaluated an optional dose reduction system used during interventions. Material and Methods: The incident radiation to the patient was measured as kerma area product (KAP) in Gycm2, obtained from an ionisation chamber mounted on the undercouch tube during 65 coronary angiography procedures and another 53 percutaneous transluminal coronary angioplasties (including 29 stent procedures), mostly directly following complete coronary angiography. Results and Conclusion: The values from coronary angiography were comparable to other reports with a mean fluoroscopic time of 4.4 min and a mean KAP value of 62.6 Gycm2. The corresponding figures from coronary balloon angioplasty without stenting were lower than otherwise reported, with 8.2 min and 47.9 Gycm2, respectively. The use of coronary stents did prolong the mean fluoroscopic time (10.5 min) but did not significantly enhance the patient mean radiation dose (51.4 Gycm2). The dose reduction technique resulted in a significant KAP value reduction of 57%. In conclusion, with regard to radiation exposure, coronary angiography and balloon angioplasty are considered safe procedures.
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