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| 5. |
- Asklund, Thomas, et al.
(författare)
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PET response and tumor stabilization under erlotinib and bevacizumab treatment of an intracranial lesion non-invasively diagnosed as likely chordoma
- 2011
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Ingår i: Clinical Neuropathology. - Deisenhofen : Dustri-Verlag Feistle. - 0722-5091. ; 30:5, s. 242-246
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Tidskriftsartikel (refereegranskat)abstract
- INTRODUCTION: Chordoma is a rare and a slow-growing tumor originating from the notochord and commonly localized in the skull base. Surgery and occasionally radiotherapy have emerged as the treatments of choice. In the relapsed situations available treatment options are strictly limited; however, recently molecularly targeted agents have been proposed to be of potential beneficial value. THE CASE: A 63-year-old male presenting with seizures and an extradural mass in the left brain hemisphere. An attempt to resect the tumor was followed by severe bradycardia when manipulating with the dura and therefore discontinued. It was considered too hazardous even to take a biopsy specimen. The tumor was considered radiologically and macroscopically as a chordoma. As the tumor progressed after radiotherapy, chemotherapy with erlotinib in combination with cetuximab was initiated. This treatment was interrupted due to progressive disease and toxicity. However, combination treatment with erlotinib and bevacizumab normalized the uptake of [11C]methionine PET signal and resulted in a slight tumor shrinkage on MRI. The patient is still (March 2011) free of symptoms, without cranial nerve deficits or seizures. DISCUSSION: This report shows that erlotinib and bevacizumab in combination may completely quench the transport of the essential amino acid methionine to a treatment refractory intracranial tumor bearing radiological and clinical characteristics of a chordoma. Further studies are necessary to establish this strategy as a treatment option for this indication.
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| 6. |
- Asklund, Thomas, et al.
(författare)
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Synergistic Killing of Glioblastoma Stem-like Cells by Bortezomib and HADC Inhibitors.
- 2012
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Ingår i: Anticancer Research. - : International Institute of Anticancer Research. - 0250-7005 .- 1791-7530. ; 32:7, s. 2407-2413
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Tidskriftsartikel (refereegranskat)abstract
- Background: The malignant brain tumour glioblastoma is a devastating disease that remains a therapeutic challenge. Materials and Methods: Effects of combinations of the US Food and Drug Administation (FDA) approved proteasome inhibitor bortezomib and the histone deacetylase (HDAC) inhibitors vorinostat, valproic acid and sodium phenylbutyrate were studied on primary glioblastoma stem cell lines and conventional glioblastoma cell lines. Cell survival, proliferation and death were analyzed by fluorometric microculture cytotoxicity assay (FMCA), propidium iodide labeling and flow cytometry, and cell cloning through limiting dilution and live-cell bright-field microscopy. Results: Bortezomib and the HDAC inhibitors showed synergistic cell killing at clinically relevant drug concentrations, while the conventional cell lines cultured in serum-containing medium were relatively resistant to the same treatments. Conclusion: These findings of synergistic glioblastoma stem cell killing by bortezomib and three different FDA-approved HDAC inhibitors confirm and expand previous observations on co-operative effects between these classes of drugs.
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| 7. |
- Asklund, Thomas, et al.
(författare)
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Överlevnaden vid maligna gliom har ökat senaste tio åren - Analys av kvalitetsregisterdata : [Survival in malignant gliomas has increased the last decade. Analysis of quality data]
- 2012
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Ingår i: Läkartidningen. - : Läkartidningen Förlag. - 0023-7205 .- 1652-7518. ; 109:17-18, s. 875-878
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Tidskriftsartikel (refereegranskat)abstract
- Den årliga incidensen av högmaligna gliom, WHO grad III–IV, i Sverige är ungefär 400.Medianöverlevnaden för höggradiga gliom har ökat från 8,1 månader till 10,0 månader under det senaste decenniet i en oselekterad svensk population.För åldersgruppen 60–69 år har medianöverlevnaden ökat från 5,8 månader till 10,5 månader under denna period, dvs nästan en fördubbling.Utveckling av befintliga behandlingsmetoder, nya behandlingsstrategier och en mer aktiv inställning till terapi har sannolikt bidragit till de beskrivna överlevnadsvinsterna.
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| 8. |
- Asklund, Thomas, et al.
(författare)
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Överlevnanden vid maligna gliom har ökat senaste tio åren. Analys av kvalitetsregisterdata.
- 2012
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Ingår i: Läkartidningen. - : Läkartidningen Förlag AB. - 0023-7205 .- 1652-7518. ; 109:17-18, s. 875-878
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Tidskriftsartikel (refereegranskat)abstract
- The annual incidence rate of high grade malignant glioma (WHO grade III-IV) in Sweden is approximately 400 patients. The objective for the Swedish National CNS-tumor Group is to lay a foundation for research efforts and facilitate implementation and assessment of therapeutic strategies and health care for this patient group. In the analyses the diagnoses of high grade malignant gliomas are compared for the years 1999-2003, 2004-2006 and 2007-2009 for the Northern Region, the Uppsala Region and the South-east Region of Sweden, a population of 1844 patients. Survival was estimated from Kaplan-Meier survival curves, and a log-rank test was performed to assess whether the survival curves differed. The crude hazard ratio between years of diagnosis was estimated from a Cox regression model. Median survival for all patients 2004-2006 was 10.0 months (95 % confidence interval (CI) 8.9-10.9) compared to 8.1 months 1999-2003 (95 % CI 7.3-8.8). For patients 60-69 years of age almost a doubling of the survival rate has occurred during the last decade. Medan survival has increased from 5.8 months (95 % CI 5.1-7.5) 1999-2003 to 8.5 months (95 % CI 7.0-10.3) for 2004-2006 and to 10.5 months (95 % CI 9.0-12.6) for 2007-2009. Concomitant radiochemotherapy, but also the development of neurosurgical and radiotheraputic techniques and a more active therapeutic attitude, including the older patient groups, have probably contributed to the improved survival rate. A national population based registry, with a close to 100% registration compliance for important diagnostic and outcome parameters is probably an efficient instrument for evaluation of quality measures and implementation of new therapeutic strategies.
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| 9. |
- Brynolfsson, Patrik, et al.
(författare)
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ADC texture-An imaging biomarker for high-grade glioma?
- 2014
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Ingår i: Medical physics (Lancaster). - : Wiley. - 0094-2405. ; 41:10, s. 101903-
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Tidskriftsartikel (refereegranskat)abstract
- Purpose:Survival for high-grade gliomas is poor, at least partly explained by intratumoral heterogeneity contributing to treatment resistance. Radiological evaluation of treatment response is in most cases limited to assessment of tumor size months after the initiation of therapy. Diffusion-weighted magnetic resonance imaging (MRI) and its estimate of the apparent diffusion coefficient (ADC) has been widely investigated, as it reflects tumor cellularity and proliferation. The aim of this study was to investigate texture analysis of ADC images in conjunction with multivariate image analysis as a means for identification of pretreatment imaging biomarkers.Methods:Twenty-three consecutive high-grade glioma patients were treated with radiotherapy (2 Gy/60 Gy) with concomitant and adjuvant temozolomide. ADC maps and T1-weighted anatomical images with and without contrast enhancement were collected prior to treatment, and (residual) tumor contrast enhancement was delineated. A gray-level co-occurrence matrix analysis was performed on the ADC maps in a cuboid encapsulating the tumor in coronal, sagittal, and transversal planes, giving a total of 60 textural descriptors for each tumor. In addition, similar examinations and analyses were performed at day 1, week 2, and week 6 into treatment. Principal component analysis (PCA) was applied to reduce dimensionality of the data, and the five largest components (scores) were used in subsequent analyses. MRI assessment three months after completion of radiochemotherapy was used for classifying tumor progression or regression.Results:The score scatter plots revealed that the first, third, and fifth components of the pretreatment examinations exhibited a pattern that strongly correlated to survival. Two groups could be identified: one with a median survival after diagnosis of 1099 days and one with 345 days, p = 0.0001.Conclusions:By combining PCA and texture analysis, ADC texture characteristics were identified, which seems to hold pretreatment prognostic information, independent of known prognostic factors such as age, stage, and surgical procedure. These findings encourage further studies with a larger patient cohort. (C) 2014 Author(s).
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| 10. |
- Eriksson, Magnus, et al.
(författare)
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Theodor Kallifatides, Bodil Malmsten, Hugo Hamilton,Fransk 1800-talsprosa, Marcel Pagnol, Vilhelm Moberg,Språkundervisning
- 2010
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Theodor Kallifatides var gäst vid Mälardalens högskolas författardag 2008 och 2010 stod Bodil Malmsten i fokus under detta årliga evenemang. De fyra första bidragen i detta nummer av Litteratur och språk är föredrag som hölls under dessa båda dagar.Magnus Eriksson visar hur Kallifatides i sitt skrivande utforskat kärlekens vägval, de många variationer och moraliska konflikter kärleks- och vänskapstemat kan bjuda på. Inkännande följer han författarens skildringar av kärlekens väsen och vånda, svek och livslögn, men också den självuppgivande ögonblicklighetens förvillelse som drabbar den förälskade. Enligt Magnus Eriksson har Kallifatides bild av kärleken ”slående likheter med den medeltida mystikerns upplevelse av uppgåendet i Gud.”Birgitta Cremnitzer å sin sida gör en interkulturell resa genom Kallifatides författarskap, en resa ”som främst handlar om sökandet efter identitet och kampen mot främlingsskapets dilemma”. Hon tar sina egna upplevelser av två länder, två språk och två kulturer som utgångspunkt och visar hur Kallifatides förmår göra läsaren till medresenär kring emigrantskapets villkor. Detta innebär enligt Cremnitzer bl.a. att differensperspektivet alltid finns hos den som emigrerat och att livet i exil kan upplevas som ett slags amputation med återkommande fantomsmärtor.Sara Granath tar i sitt bidrag till författardagen upp personliga intryck av Bodil Malmstens dramatik. Hon talar bl.a. om svårigheterna i att levandegöra ett samhälle sceniskt och framhåller betydelsen av den rumsliga gestaltningen i Malmstens pjäser. Här är det inte enbart yttre rum det är fråga om, utan lika mycket människors inre rum. För Granath är det just Malmstens speciella sätt att behandla yttre och inre rum som verkar vara en ”fruktbar tråd att följa i hennes dramatik och teater”.Ingemar Haag återvänder i sin essä till lyrikern Bodil Malmsten, som under senare år överskuggats av ”självbiografen” och dramatikern Malmsten. I hennes lyrik stiftar vi bekantskap med ett tilltal som spänner mellan högt och lågt, tyst och uppfordrande. I dialogen med Samuel Beckett, ett av 1900-talets stora författarskap, anknyter Malmsten till såväl föregångarens existentiella perspektiv som det humoristiska anslaget.I sin studie om intratextuell motivering kommenterar Hans Färnlöf hur olika narrativa element länkas samman i några franska 1800-talsberättelser. Med motivering menas hur författaren kan ”motivera” (i betydelsen ”berättiga”, ”rättfärdiga”), hur karaktärer agerar eller varför vissa händelser bör – eller inte bör – inträffa enligt berättelsens logik. Det handlar således om att etablera orsak och verkan i en fiktiv värld. Färnlöf visar hur man genom att fokusera på den intratextuella motiveringen, dvs. de orsakssamband som byggs upp genom referenser inne i texten i stället för att hänvisa till verkligheten, tydligare kan skönja textens etapper och progression, från inledning till avslutning.Utifrån kortberättelserna Nazi Christmas och The Irish Worker av den irländsktyske författaren Hugo Hamilton lyfter Thorsten Päplow och Birte Schulz fram frågor som hänger samman med formandet av den kulturella identiteten hos barn med bakgrund i två kulturer. Deras bidrag ger en kort introduktion till forskningen kring ”biculturalism” och använder sig av psykologiska och sociologiska insikter från detta område vid den litterära analysen. Fokus ligger här på huruvida kortberättelsernas huvudfigur, som växer upp med en tysk mor och en irländsk far, genomgår en identitetskris på grund av sitt dubbla kulturella arv.I sitt andra bidrag behandlar Hans Färnlöf Marcel Pagnol som genom sitt filmskapande på framför allt 1930-talet tillhör den franska filmens klassiska regissörer. Som författare ses han dock huvudsakligen som ”regional” berättare. Det innebär att tema, struktur, bildspråk, stilistik och andra litterära aspekter i hans verk sällan diskuteras. Med sin studie av de fyra elementen i romandiptyken L’Eau des collines (”Vattnet från kullarna”) visar Färnlöf hur det vid första anblicken transparenta, referentiella landskapet, liksom handlingen och karaktärerna, innehåller både episk bredd och symboliskt djup.Om litterär skildring handlar det även i Thomas Asklunds artikel som tar upp Vilhelm Mobergs berättarteknik i utvandrarserien. Med exempel från olika passager ur ett kapitel i Invandrarna visar Asklund hur Moberg använder växlande berättarperspektiv och upprepande stilfigurer för att skapa verklighetsillusion i den fiktiva berättelsen.I det avslutande bidraget framhåller Helena Darnell-Berggren att skolans kunskapsuppdrag är en självklarhet för varje lärare, men hon frågar sig samtidigt hur det ska kunna vara möjligt att få undervisningstiden att räcka till för att även fostra elever till demokratiska samhällsmedborgare. I sin genomgång av olika styrdokument för skolan och även tillämplig didaktisk forskning ger Darnell-Berggren olika perspektiv på hur språkundervisning kan bli till ett meningsskapande, där båda dessa uppdrag kan kombineras.Red.
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| 11. |
- Garpebring, Anders, et al.
(författare)
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Phase-based arterial input functions in humans applied to dynamic contrast-enhanced MRI: potential usefulness and limitations
- 2011
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Ingår i: Magma. - : Springer Science and Business Media LLC. - 1352-8661 .- 0968-5243. ; 24:4, s. 233-245
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Tidskriftsartikel (refereegranskat)abstract
- Object Phase-based arterial input functions (AIFs) provide a promising alternative to standard magnitude-based AIFs, for example, because inflow effects are avoided. The usefulness of phase-based AIFs in clinical dynamic contrast-enhanced MRI (DCE-MRI) was investigated, and relevant pitfalls and sources of uncertainty were identified. Materials and methods AIFs were registered from eight human subjects on, in total, 21 occasions. AIF quality was evaluated by comparing AIFs from right and left internal carotid arteries and by assessing the reliability of blood plasma volume estimates. Results Phase-based AIFs yielded an average bolus peak of 3.9 mM and a residual concentration of 0.37 mM after 3 min, (0.033 mmol/kg contrast agent injection). The average blood plasma volume was 2.7% when using the AIF peak in the estimation, but was significantly different (p < 0.0001) and less physiologically reasonable when based on the AIF tail concentration. Motion-induced phase shifts and accumulation of contrast agent in background tissue regions were identified as main sources of uncertainty. Conclusion Phase-based AIFs are a feasible alternative to magnitude AIFs, but sources of errors exist, making quantification difficult, especially of the AIF tail. Improvement of the technique is feasible and also required for the phase-based AIF approach to reach its full potential.
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| 12. |
- Garpebring, Anders, et al.
(författare)
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Uncertainty estimation in dynamic contrast-enhanced MRI
- 2013
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Ingår i: Magnetic Resonance in Medicine. - : Wiley-Blackwell. - 0740-3194 .- 1522-2594. ; 69:4, s. 992-1002
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Tidskriftsartikel (refereegranskat)abstract
- Using dynamic contrast-enhanced MRI (DCE-MRI), it is possible to estimate pharmacokinetic (PK) parameters that convey information about physiological properties, e.g., in tumors. In DCE-MRI, errors propagate in a nontrivial way to the PK parameters. We propose a method based on multivariate linear error propagation to calculate uncertainty maps for the PK parameters. Uncertainties in the PK parameters were investigated for the modified Kety model. The method was evaluated with Monte Carlo simulations and exemplified with in vivo brain tumor data. PK parameter uncertainties due to noise in dynamic data were accurately estimated. Noise with standard deviation up to 15% in the baseline signal and the baseline T1 map gave estimated uncertainties in good agreement with the Monte Carlo simulations. Good agreement was also found for up to 15% errors in the arterial input function amplitude. The method was less accurate for errors in the bolus arrival time with disagreements of 23%, 32%, and 29% for Ktrans, ve, and vp, respectively, when the standard deviation of the bolus arrival time error was 5.3 s. In conclusion, the proposed method provides efficient means for calculation of uncertainty maps, and it was applicable to a wide range of sources of uncertainty.
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| 14. |
- Henriksson, Roger, et al.
(författare)
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Impact of therapy on quality of life, neurocognitive function and their correlates in glioblastoma multiforme : a review
- 2011
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Ingår i: Journal of Neuro-Oncology. - Boston : Nijhoff. - 0167-594X .- 1573-7373. ; 104:3, s. 639-646
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Forskningsöversikt (refereegranskat)abstract
- The maintenance of quality of life (QoL) in patients with high-grade glioma is an important endpoint during treatment, particularly in those with glioblastoma multiforme (GBM) given its dismal prognosis despite limited advances in standard therapy. It has proven difficult to identify new therapies that extend survival in patients with recurrent GBM, so one of the primary aims of new therapies is to reduce morbidity, restore or preserve neurologic functions, and the capacity to perform daily activities. Apart from temozolomide, cytotoxic chemotherapeutic agents do not appear to significantly impact response or survival, but produce toxicity that is likely to negatively impact QoL. New biological agents, such as bevacizumab, can induce a clinically meaningful proportion of durable responses among patients with recurrent GBM with an acceptable safety profile. Emerging evidence suggests that bevacizumab produces an improvement or preservation of neurocognitive function in GBM patients, suggestive of QoL improvement, in most poor-prognosis patients who would otherwise be expected to show a sudden and rapid deterioration in QoL.
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| 15. |
- Johansson, Adam, 1984-, et al.
(författare)
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CT substitutes derived from MR images reconstructed with parallel imaging
- 2014
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Ingår i: Medical physics (Lancaster). - : Wiley. - 0094-2405. ; 41:8, s. 474-480
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Tidskriftsartikel (refereegranskat)abstract
- Purpose: Computed tomography (CT) substitute images can be generated from ultrashort echo time (UTE) MRI sequences with radial k-space sampling. These CT substitutes can be used as ordinary CT images for PET attenuation correction and radiotherapy dose calculations. Parallel imaging allows faster acquisition of magnetic resonance (MR) images by exploiting differences in receiver coil element sensitivities. This study investigates whether non-Cartesian parallel imaging reconstruction can be used to improve CT substitutes generated from shorter examination times.Methods: The authors used gridding as well as two non-Cartesian parallel imaging reconstruction methods, SPIRiT and CG-SENSE, to reconstruct radial UTE and gradient echo (GE) data into images of the head for 23 patients. For each patient, images were reconstructed from the full dataset and from a number of subsampled datasets. The subsampled datasets simulated shorter acquisition times by containing fewer radial k-space spokes (1000, 2000, 3000, 5000, and 10 000 spokes) than the full dataset (30 000 spokes). For each combination of patient, reconstruction method, and number of spokes, the reconstructed UTE and GE images were used to generate a CT substitute. Each CT substitute image was compared to a real CT image of the same patient.Results: The mean absolute deviation between the CT number in CT substitute and CT decreased when using SPIRiT as compared to gridding reconstruction. However, the reduction was small and the CT substitute algorithm was insensitive to moderate subsampling (≥5000 spokes) regardless of reconstruction method. For more severe subsampling (≤3000 spokes), corresponding to acquisition times less than aminute long, the CT substitute quality was deteriorated for all reconstructionmethods but SPIRiT gave a reduction in the mean absolute deviation of down to 25 Hounsfield units compared to gridding.Conclusions: SPIRiT marginally improved the CT substitute quality for a given number of radial spokes as compared to gridding. However, the increased reconstruction time of non-Cartesian parallel imaging reconstruction is difficult to motivate from this improvement. Because the CT substitute algorithm was insensitive to moderate subsampling, data for a CT substitute could be collected in as little as minute and reconstructed with gridding without deteriorating the CT substitute quality.
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| 16. |
- Johansson, Adam, et al.
(författare)
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Improved quality of computed tomography substitute derived from magnetic resonance (MR) data by incorporation of spatial information : potential application for MR-only radiotherapy and attenuation correction in positron emission tomography
- 2013
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Ingår i: Acta Oncologica. - 0284-186X .- 1651-226X. ; 52:7, s. 1369-1373
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Tidskriftsartikel (refereegranskat)abstract
- Background: Estimation of computed tomography (CT) equivalent data, i.e. a substitute CT (s-CT), from magnetic resonance (MR) images is a prerequisite both for attenuation correction of positron emission tomography (PET) data acquired with a PET/MR scanner and for dose calculations in an MR-only radiotherapy workflow. It has previously been shown that it is possible to estimate Hounsfield numbers based on MR image intensities, using ultra short echo-time imaging and Gaussian mixture regression (GMR). In the present pilot study we investigate the possibility to also include spatial information in the GMR, with the aim to improve the quality of the s-CT. Material and methods: MR and CT data for nine patients were used in the present study. For each patient, GMR models were created from the other eight patients, including either both UTE image intensities and spatial information on a voxel by voxel level, or only UTE image intensities. The models were used to create s-CT images for each respective patient. Results: The inclusion of spatial information in the GMR model improved the accuracy of the estimated s-CT. The improvement was most pronounced in smaller, complicated anatomical regions as the inner ear and post-nasal cavities. Conclusions: This pilot study shows that inclusion of spatial information in GMR models to convert MR data to CT equivalent images is feasible. The accuracy of the s-CT is improved and the spatial information could make it possible to create a general model for the conversion applicable to the whole body.
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| 17. |
- Johansson, Adam, et al.
(författare)
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Voxel-wise uncertainty in CT substitute derived from MRI
- 2012
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Ingår i: Medical physics (Lancaster). - : American Association of Physicists in Medicine. - 0094-2405. ; 39:6, s. 3283-3290
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Tidskriftsartikel (refereegranskat)abstract
- Purpose: In an earlier work, we demonstrated that substitutes for CT images can be derived from MR images using ultrashort echo time (UTE) sequences, conventional T2 weighted sequences, and Gaussian mixture regression (GMR). In this study, we extend this work by analyzing the uncertainties associated with the GMR model and the information contributions from the individual imaging sequences.Methods: An analytical expression for the voxel-wise conditional expected absolute deviation (EAD) in substitute CT (s-CT) images was derived. The expression depends only on MR images and can thus be calculated along with each s-CT image. The uncertainty measure was evaluated by comparing the EAD to the true mean absolute prediction deviation (MAPD) between the s-CT and CT images for 14 patients. Further, the influence of the different MR images included in the GMR model on the generated s-CTs was investigated by removing one or more images and evaluating the MAPD for a spectrum of predicted radiological densities.Results: The largest EAD was predicted at air-soft tissue and bone-soft tissue interfaces. The EAD agreed with the MAPD in both these regions and in regions with lower EADs, such as the brain. Two of the MR images included in the GMR model were found to be mutually redundant for the purpose of s-CT generation.Conclusions: The presented uncertainty estimation method accurately predicts the voxel-wise MAPD in s-CT images. Also, the non-UTE sequence previously used in the model was found to be redundant.
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| 18. |
- Jonsson, Joakim, 1984-, et al.
(författare)
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Treatment planning of intracranial targets on MRI derived substitute CT data
- 2013
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Ingår i: Radiotherapy and Oncology. - : Elsevier BV. - 0167-8140 .- 1879-0887. ; 108:1, s. 118-122
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: The use of magnetic resonance imaging (MRI) as a complement to computed tomography (CT) in the target definition procedure for radiotherapy is increasing. To eliminate systematic uncertainties due to image registration, a workflow based entirely on MRI may be preferable. In the present pilot study, we investigate dose calculation accuracy for automatically generated substitute CT (s-CT) images of the head based on MRI. We also produce digitally reconstructed radiographs (DRRs) from s-CT data to evaluate the feasibility of patient positioning based on MR images. METHODS AND MATERIALS: Five patients were included in the study. The dose calculation was performed on CT, s-CT, s-CT data without inhomogeneity correction and bulk density assigned MRI images. Evaluation of the results was performed using point dose and dose volume histogram (DVH) comparisons, and gamma index evaluation. RESULTS: The results demonstrate that the s-CT images improves the dose calculation accuracy compared to the method of non-inhomogeneity corrected dose calculations (mean improvement 2.0 percentage points) and that it performs almost identically to the method of bulk density assignment. The s-CT based DRRs appear to be adequate for patient positioning of intra-cranial targets, although further investigation is needed on this subject. CONCLUSIONS: The s-CT method is very fast and yields data that can be used for treatment planning without sacrificing accuracy.
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| 19. |
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| 20. |
- Larsson, Anne, et al.
(författare)
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Evaluation of an attenuation correction method for PET/MR imaging of the head based on substitute CT images
- 2013
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Ingår i: Magnetic Resonance Materials in Physics, Biology and Medicine. - : Springer Science and Business Media LLC. - 0968-5243 .- 1352-8661. ; 26:1, s. 127-136
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this study was to evaluate MR-based attenuation correction of PET emission data of the head, based on a previously described technique that calculates substitute CT (sCT) images from a set of MR images. Images from eight patients, examined with F-18-FLT PET/CT and MRI, were included. sCT images were calculated and co-registered to the corresponding CT images, and transferred to the PET/CT scanner for reconstruction. The new reconstructions were then compared with the originals. The effect of replacing bone with soft tissue in the sCT-images was also evaluated. The average relative difference between the sCT-corrected PET images and the CT-corrected PET images was 1.6 % for the head and 1.9 % for the brain. The average standard deviations of the relative differences within the head were relatively high, at 13.2 %, primarily because of large differences in the nasal septa region. For the brain, the average standard deviation was lower, 4.1 %. The global average difference in the head when replacing bone with soft tissue was 11 %. The method presented here has a high rate of accuracy, but high-precision quantitative imaging of the nasal septa region is not possible at the moment.
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| 21. |
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