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Nyholm, Tufve
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Publikasjoner (10 av 87) Visa alla publikasjoner
Witoszynskyj, S., Andrzejewski, P., Georg, D., Hacker, M., Nyholm, T., Rausch, I. & Knaeusl, B. (2019). Attenuation correction of a flat table top for radiation therapy in hybrid PET/MR using CT- and Ge-68/Ga-68 transmission scan-based mu-maps. Physica medica (Testo stampato), 65, 76-83
Åpne denne publikasjonen i ny fane eller vindu >>Attenuation correction of a flat table top for radiation therapy in hybrid PET/MR using CT- and Ge-68/Ga-68 transmission scan-based mu-maps
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2019 (engelsk)Inngår i: Physica medica (Testo stampato), ISSN 1120-1797, E-ISSN 1724-191X, Vol. 65, s. 76-83Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

Hybrid PET/MR offers new opportunities in radiation oncology for tissue/tumour characterisation and response assessment. Attenuation correction (AC) is an important issue especially in the presence of immobilization devices and flat table tops (FTT). The goal of this study was to compare two methods of AC using CT- and Ge-68/Ga-68 transmission scan-based attenuation maps (mu-maps) for a custom-designed FTT. Measurements were performed in the mMR PET/MR and TrueV PET/CT Biograph Siemens scanners with three different phantoms, namely the Siemens MR-QA, a cubic canister and the NEMA IEC body phantom. The study revealed that the MR image quality is not hampered by the presence of the FTT. For cubic canister applying the scanner's inherent AC alone resulted in inaccuracies in PET images, with up to -4.0% underestimation of the activity. The mean NEMA sphere activity measurements without FTT, agreed within 3.5% with the respective inserted activity. Placing the FTT in the PET/MR scanner resulted in a difference to the injected activity of 4.5% when the table was not corrected for. By introducing the mu-maps the discrepancy between the used activity and the measurements decreased down to 2.6%. To improve the AC of the FTT the creation of a dedicated mu-map was necessary while the CT-based mu-map performed equally good as the source transmission scan-based one.

sted, utgiver, år, opplag, sider
ELSEVIER SCI LTD, 2019
Emneord
Attenuation correction, PET/MR, mu-Map, Radiation oncology
HSV kategori
Identifikatorer
urn:nbn:se:umu:diva-164478 (URN)10.1016/j.ejmp.2019.08.005 (DOI)000488034100012 ()31437602 (PubMedID)
Tilgjengelig fra: 2019-10-22 Laget: 2019-10-22 Sist oppdatert: 2019-10-22bibliografisk kontrollert
Adjeiwaah, M., Bylund, M., Lundman, J. A., Söderström, K., Zackrisson, B., Jonsson, J. H., . . . Nyholm, T. (2019). Dosimetric Impact of MRI Distortions: A Study on Head and Neck Cancers. International Journal of Radiation Oncology, Biology, Physics, 103(4), 994-1003
Åpne denne publikasjonen i ny fane eller vindu >>Dosimetric Impact of MRI Distortions: A Study on Head and Neck Cancers
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2019 (engelsk)Inngår i: International Journal of Radiation Oncology, Biology, Physics, ISSN 0360-3016, E-ISSN 1879-355X, Vol. 103, nr 4, s. 994-1003Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

Purpose: To evaluate the effect of magnetic resonance (MR) imaging (MRI) geometric distortions on head and neck radiation therapy treatment planning (RTP) for an MRI-only RTP. We also assessed the potential benefits of patient-specific shimming to reduce the magnitude of MR distortions for a 3-T scanner.

Methods and Materials: Using an in-house Matlab algorithm, shimming within entire imaging volumes and user-defined regions of interest were simulated. We deformed 21 patient computed tomography (CT) images with MR distortion fields (gradient nonlinearity and patient-induced susceptibility effects) to create distorted CT (dCT) images using bandwidths of 122 and 488 Hz/mm at 3 T. Field parameters from volumetric modulated arc therapy plans initially optimized on dCT data sets were transferred to CT data to compute a new plan. Both plans were compared to determine the impact of distortions on dose distributions.

Results: Shimming across entire patient volumes decreased the percentage of voxels with distortions of more than 2 mm from 15.4% to 2.0%. Using the user-defined region of interest (ROI) shimming strategy, (here the Planning target volume (PTV) was the chosen ROI volume) led to increased geometric for volumes outside the PTV, as such voxels within the spinal cord with geometric shifts above 2 mm increased from 11.5% to 32.3%. The worst phantom-measured residual system distortions after 3-dimensional gradient nonlinearity correction within a radial distance of 200 mm from the isocenter was 2.17 mm. For all patients, voxels with distortion shifts of more than 2 mm resulting from patient-induced susceptibility effects were 15.4% and 0.0% using bandwidths of 122 Hz/mm and 488 Hz/mm at 3 T. Dose differences between dCT and CT treatment plans in D-50 at the planning target volume were 0.4% +/- 0.6% and 0.3% +/- 0.5% at 122 and 488 Hz/mm, respectively.

Conclusions: The overall effect of MRI geometric distortions on data used for RTP was minimal. Shimming over entire imaging volumes decreased distortions, but user-defined subvolume shimming introduced significant errors in nearby organs and should probably be avoided.

sted, utgiver, år, opplag, sider
Elsevier, 2019
HSV kategori
Identifikatorer
urn:nbn:se:umu:diva-157192 (URN)10.1016/j.ijrobp.2018.11.037 (DOI)000459153600031 ()30496879 (PubMedID)
Tilgjengelig fra: 2019-04-15 Laget: 2019-04-15 Sist oppdatert: 2019-10-31bibliografisk kontrollert
Vu, M., Sznitman, R., Nyholm, T. & Löfstedt, T. (2019). Ensemble of Streamlined Bilinear Visual Question Answering Models for the ImageCLEF 2019 Challenge in the Medical Domain. In: Linda Cappellato, Nicola Ferro, David E. Losada, and Henning Müller (Ed.), CLEF 2019: Working Notes of CLEF 2019 - Conference and Labs of the Evaluation Forum. Paper presented at CLEF 2019 - Conference and Labs of the Evaluation Forum, Lugano, Switzerland, Sept 9-12, 2019. , 2380
Åpne denne publikasjonen i ny fane eller vindu >>Ensemble of Streamlined Bilinear Visual Question Answering Models for the ImageCLEF 2019 Challenge in the Medical Domain
2019 (engelsk)Inngår i: CLEF 2019: Working Notes of CLEF 2019 - Conference and Labs of the Evaluation Forum / [ed] Linda Cappellato, Nicola Ferro, David E. Losada, and Henning Müller, 2019, Vol. 2380Konferansepaper, Publicerat paper (Annet vitenskapelig)
Abstract [en]

This paper describes the contribution by participants from Umeå University, Sweden, in collaboration with the University of Bern, Switzerland, for the Medical Domain Visual Question Answering challenge hosted by ImageCLEF 2019. We proposed a novel Visual Question Answering approach that leverages a bilinear model to aggregateand synthesize extracted image and question features. While we did not make use of any additional training data, our model used an attention scheme to focus on the relevant input context and was further boosted by using an ensemble of trained models. We show here that the proposed approach performs at state-of-the-art levels, and provides an improvement over several existing methods. The proposed method was ranked 3rd in the Medical Domain Visual Question Answering challenge of ImageCLEF 2019.

HSV kategori
Identifikatorer
urn:nbn:se:umu:diva-166758 (URN)
Konferanse
CLEF 2019 - Conference and Labs of the Evaluation Forum, Lugano, Switzerland, Sept 9-12, 2019
Tilgjengelig fra: 2019-12-27 Laget: 2019-12-27 Sist oppdatert: 2020-01-02bibliografisk kontrollert
Fetty, L., Kuess, P., Nesvacil, N., Nyholm, T., Georg, D. & Furtado, H. (2019). Evaluating different generator networks of a conditional generative adversarial network. Paper presented at 38th Annual Meeting of the European-Society-for-Radiotherapy-and-Oncology (ESTRO), Milan, ITALY, April 26-30, 2019. Radiotherapy and Oncology, 133, S555-S555
Åpne denne publikasjonen i ny fane eller vindu >>Evaluating different generator networks of a conditional generative adversarial network
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2019 (engelsk)Inngår i: Radiotherapy and Oncology, ISSN 0167-8140, E-ISSN 1879-0887, Vol. 133, s. S555-S555Artikkel i tidsskrift, Meeting abstract (Annet vitenskapelig) Published
sted, utgiver, år, opplag, sider
Elsevier, 2019
HSV kategori
Identifikatorer
urn:nbn:se:umu:diva-160314 (URN)10.1016/S0167-8140(19)31425-2 (DOI)000468315602270 ()
Konferanse
38th Annual Meeting of the European-Society-for-Radiotherapy-and-Oncology (ESTRO), Milan, ITALY, April 26-30, 2019
Tilgjengelig fra: 2019-06-17 Laget: 2019-06-17 Sist oppdatert: 2019-06-17bibliografisk kontrollert
Löfstedt, T., Brynolfsson, P., Nyholm, T. & Garpebring, A. (2019). Gray-level invariant Haralick texture features. PLoS ONE, 14(2), Article ID e0212110.
Åpne denne publikasjonen i ny fane eller vindu >>Gray-level invariant Haralick texture features
2019 (engelsk)Inngår i: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 14, nr 2, artikkel-id e0212110Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

Haralick texture features are common texture descriptors in image analysis. To compute the Haralick features, the image gray-levels are reduced, a process called quantization. The resulting features depend heavily on the quantization step, so Haralick features are not reproducible unless the same quantization is performed. The aim of this work was to develop Haralick features that are invariant to the number of quantization gray-levels. By redefining the gray-level co-occurrence matrix (GLCM) as a discretized probability density function, it becomes asymptotically invariant to the quantization. The invariant and original features were compared using logistic regression classification to separate two classes based on the texture features. Classifiers trained on the invariant features showed higher accuracies, and had similar performance when training and test images had very different quantizations. In conclusion, using the invariant Haralick features, an image pattern will give the same texture feature values independent of image quantization.

sted, utgiver, år, opplag, sider
Public Library of Science, 2019
HSV kategori
Identifikatorer
urn:nbn:se:umu:diva-134995 (URN)10.1371/journal.pone.0212110 (DOI)000459709100037 ()30794577 (PubMedID)2-s2.0-85062005861 (Scopus ID)
Merknad

Originally included in thesis in manuscript form

Tilgjengelig fra: 2017-05-15 Laget: 2017-05-15 Sist oppdatert: 2019-11-19bibliografisk kontrollert
Sandgren, K., Westerlinck, P., Jonsson, J. H., Blomqvist, L., Thellenberg Karlsson, C., Nyholm, T. & Dirix, P. (2019). Imaging for the Detection of Locoregional Recurrences in Biochemical Progression After Radical Prostatectomy: A Systematic Review. European Urology Focus, 5(4), 550-560
Åpne denne publikasjonen i ny fane eller vindu >>Imaging for the Detection of Locoregional Recurrences in Biochemical Progression After Radical Prostatectomy: A Systematic Review
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2019 (engelsk)Inngår i: European Urology Focus, ISSN 2405-4569, Vol. 5, nr 4, s. 550-560Artikkel, forskningsoversikt (Fagfellevurdert) Published
Abstract [en]

Context: Local and regional recurrence after radical prostatectomy (RP) can be treated using salvage radiotherapy (SRT). If the recurrence can be delineated on diagnostic imaging, this could allow for increasingly individualized SRT.

Objective: This systematic review aimed at evaluating the evidence regarding the usefulness of positron emission tomography (PET) and magnetic resonance imaging (MRI) in identifying local and regional recurrences, with the aim to further individualize the SRT treatment.

Evidence acquisition: A systematic PubMed/Medline search was conducted in December 2015. Studies included were imaging studies of post-RP patients focusing on local and/or regional recurrence where sensitivity and specificity of MRI or PET were the primary end points. Only studies using biopsy, other histological analysis, and/or treatment follow-up as reference standard were included. Quality Assessment of Diagnostic Accuracy Studies-2 was used to score the study quality. Twenty-five articles were deemed of sufficient quality and included in the review.

Evidence synthesis: [11C]Acetate had the highest pooled sensitivity (92%), while [11C]choline and [18F]choline had pooled sensitivities of 71% and 84%, respectively. The PET tracer with highest pooled specificity was [11C]choline (86%). Regarding MRI, MR spectroscopy combined with dynamic contrast enhanced (DCE) MRI showed the highest pooled sensitivity (89%). High pooled sensitivities were also seen using multiparametric MRI (84%), diffusion-weighted MRI combined with T2-weigthed (T2w) imaging (82%), and DCE MRI combined with T2w imaging (82%). These also showed high pooled specificities (85%, 89%, and 92%, respectively).

Conclusions: Both MRI and PET have adequate sensitivity and specificity for the detection of prostate cancer recurrences post-RP. Multiparametric MRI, using diffusion-weighted and/or DCE imaging, and the choline-labeled tracers showed high pooled sensitivity and specificity, although their ranges were broad.

Patient summary: After reviewing imaging studies of recurrent prostate cancer after prostatectomy, we concluded that choline positron emission tomography and diffusion-weighted magnetic resonance imaging can be proposed as the current standard, with high sensitivity and specificity.

sted, utgiver, år, opplag, sider
Elsevier, 2019
Emneord
Magnetic resonance imaging, Positron emission tomography, Prostate cancer, Recurrence, Salvage radiotherapy
HSV kategori
Identifikatorer
urn:nbn:se:umu:diva-142318 (URN)10.1016/j.euf.2017.11.001 (DOI)000486156800009 ()29133278 (PubMedID)2-s2.0-85033577338 (Scopus ID)
Tilgjengelig fra: 2017-11-27 Laget: 2017-11-27 Sist oppdatert: 2019-11-05bibliografisk kontrollert
Daniel, M., Kuess, P., Andrzejewski, P., Nyholm, T., Helbich, T., Polanec, S., . . . Baltzer, P. (2019). Impact of androgen deprivation therapy on apparent diffusion coefficient and T2w MRI for histogram and texture analysis with respect to focal radiotherapy of prostate cancer. Strahlentherapie und Onkologie (Print), 195(5), 402-411
Åpne denne publikasjonen i ny fane eller vindu >>Impact of androgen deprivation therapy on apparent diffusion coefficient and T2w MRI for histogram and texture analysis with respect to focal radiotherapy of prostate cancer
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2019 (engelsk)Inngår i: Strahlentherapie und Onkologie (Print), ISSN 0179-7158, E-ISSN 1439-099X, Vol. 195, nr 5, s. 402-411Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

Purpose: Accurate prostate cancer (PCa) detection is essential for planning focal external beam radiotherapy (EBRT). While biparametric MRI (bpMRI) including T2-weighted (T2w) and diffusion-weighted images (DWI) is an accurate tool to localize PCa, its value is less clear in the case of additional androgen deprivation therapy (ADT). The aim of this study was to investigate the value of a textural feature (TF) approach on bpMRI analysis in prostate cancer patients with and without neoadjuvant ADT with respect to future dose-painting applications.

Methods: 28 PCa patients (54–80 years) with (n = 14) and without (n = 14) ADT who underwent bpMRI with T2w and DWI were analyzed retrospectively. Lesions, central gland (CG), and peripheral zone (PZ) were delineated by an experienced urogenital radiologist based on localized pre-therapeutic histopathology. Histogram parameters and 20 Haralick TF were calculated. Regional differences (i. e., tumor vs. PZ, tumor vs. CG) were analyzed for all imaging parameters. Receiver-operating characteristic (ROC) analysis was performed to measure diagnostic performance to distinguish PCa from benign prostate tissue and to identify the features with best discriminative power in both patient groups.

Results: The obtained sensitivities were equivalent or superior when utilizing the TF in the no-ADT group, while specificity was higher for the histogram parameters. However, in the ADT group, TF outperformed the conventional histogram parameters in both specificity and sensitivity. Rule-in and rule-out criteria for ADT patients could exclusively be defined with the aid of TF.

Conclusions: The TF approach has the potential for quantitative image-assisted boost volume delineation in PCa patients even if they are undergoing neoadjuvant ADT.

sted, utgiver, år, opplag, sider
Springer Berlin/Heidelberg, 2019
Emneord
Radiomics, Tissue characterization, Boost volume, Quantitative imaging, ADC
HSV kategori
Identifikatorer
urn:nbn:se:umu:diva-159876 (URN)10.1007/s00066-018-1402-3 (DOI)000466399900005 ()30478670 (PubMedID)
Tilgjengelig fra: 2019-06-10 Laget: 2019-06-10 Sist oppdatert: 2019-06-10bibliografisk kontrollert
Vu, M., Grimbergen, G., Simkó, A., Nyholm, T. & Löfstedt, T. (2019). Localization Network and End-to-End Cascaded U-Nets for Kidney Tumor Segmentation. In: : . Paper presented at MICCAI 2019, Shenzhen, China, Oct 13-17, 2019.
Åpne denne publikasjonen i ny fane eller vindu >>Localization Network and End-to-End Cascaded U-Nets for Kidney Tumor Segmentation
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2019 (engelsk)Konferansepaper, Oral presentation only (Annet vitenskapelig)
Abstract [en]

Kidney tumor segmentation emerges as a new frontier of computer vision in medical imaging. This is partly due to its challenging manual annotation and great medical impact. Within the scope of the Kidney Tumor Segmentation Challenge 2019, that is aiming at combined kidney and tumor segmentation, this work proposes a novel combination of 3D U-Nets---collectively denoted TuNet---utilizing the resulting kidney masks for the consecutive tumor segmentation. The proposed method achieves a Sørensen-Dice coefficient score of 0.902 for the kidney, and 0.408 for the tumor segmentation, computed from a five-fold cross-validation on the 210 patients available in the data.

HSV kategori
Identifikatorer
urn:nbn:se:umu:diva-166757 (URN)
Konferanse
MICCAI 2019, Shenzhen, China, Oct 13-17, 2019
Tilgjengelig fra: 2019-12-27 Laget: 2019-12-27 Sist oppdatert: 2020-01-02bibliografisk kontrollert
Wallstén, E., Axelsson, J., Jonsson, J. H., Thellenberg Karlsson, C., Nyholm, T. & Larsson, A. (2019). PET/MRI attenuation correction in the pelvic region with a statistical decomposition method. Paper presented at 32nd Annual Congress of the European-Association-of-Nuclear-Medicine (EANM), Barcelona, SPAIN, OCT 12-16, 2019. European Journal of Nuclear Medicine and Molecular Imaging, 46(SUPPL 1), S289-S290
Åpne denne publikasjonen i ny fane eller vindu >>PET/MRI attenuation correction in the pelvic region with a statistical decomposition method
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2019 (engelsk)Inngår i: European Journal of Nuclear Medicine and Molecular Imaging, ISSN 1619-7070, E-ISSN 1619-7089, Vol. 46, nr SUPPL 1, s. S289-S290Artikkel i tidsskrift, Meeting abstract (Annet vitenskapelig) Published
Abstract [en]

Aim/Introduction: Quantification in PET/MRI is of importance, and its accuracy is currently limited by the MR based attenuation correction estimate. A common method for attenuation correction of the pelvic region is based on a 2-echo Dixon MRI sequence for segmentation of fat and water and does not account for bone. In this work, we evaluate a new method for attenuation correction using an algorithm based on statistical decomposition of a T2 weighted MRI scan.

Materials and Methods: Substitute CT images (sCTs) were calculated from T2 weighted MRI scans with a statistical decomposition algorithm, originally developed for MRI-based radiotherapy dose-planning [1]. These sCTs benefits from having bone density information included, in addition to fat and water information. Prostate cancer patients from the PARAPLY study [2] were retrospectivelyselected, scanned with PET/MRI 11C-Acatate and CT the same day. The stand-alone CT images were transformed to the same geometry as the PET and MR images, using a non-rigid registration. CT images, generated sCT images, and the Dixonbased attenuation maps (MRAC), all in the same geometry, were together with the PET raw data used to reconstruct attenuation-corrected PET images using the PETrecon toolbox [GE Healthcare]. The two MR-based attenuation corrections were compared to the CT-based attenuation correction with root mean squared error (RMSE). Lesion analysis will also be reported. PET/MRI images were acquired on a Signa PET/MRI (GE Healthcare), and the CT images on a Brilliance Big Bore (Phillips Healthcare). The study will include 12 patients and a subset of 6 patients has been analyzed so far and is presented here.

Results: Soft tissue in-between pelvic bone structures were overestimated with 13% in MRAC-PET, and the error was reduced to 5% with sCT attenuation corrected PET (sCT-PET). For the whole patient volume, an average underestimation of 6% was found in the MRAC-PET, compared to 1% for sCTPET. RMSE within the body was reduced with a factor 2.5 with sCT-PET (RMSE=3.6%), compared to MRAC-PET (RMSE=8.8%).

Conclusion: Applying sCT from statistical decomposition as a base for calculation of attenuation maps reduces quantification errors in PET-images of the pelvic region compared to the common Dixon based method.

sted, utgiver, år, opplag, sider
Springer, 2019
HSV kategori
Identifikatorer
urn:nbn:se:umu:diva-165323 (URN)000492444402146 ()
Konferanse
32nd Annual Congress of the European-Association-of-Nuclear-Medicine (EANM), Barcelona, SPAIN, OCT 12-16, 2019
Tilgjengelig fra: 2019-12-03 Laget: 2019-12-03 Sist oppdatert: 2019-12-03bibliografisk kontrollert
Daniel, M., Kuess, P., Andrzejewski, P., Nyholm, T., Nyholm, T., Heilmann, M., . . . Georg, D. (2019). Pilot study: Textural features of mpMRI for response assessment in prostate cancer patients. Paper presented at 38th Annual Meeting of the European-Society-for-Radiotherapy-and-Oncology (ESTRO), Milan, ITALY, April 26-30, 2019. Radiotherapy and Oncology, 133, S1113-S1113
Åpne denne publikasjonen i ny fane eller vindu >>Pilot study: Textural features of mpMRI for response assessment in prostate cancer patients
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2019 (engelsk)Inngår i: Radiotherapy and Oncology, ISSN 0167-8140, E-ISSN 1879-0887, Vol. 133, s. S1113-S1113Artikkel i tidsskrift, Meeting abstract (Annet vitenskapelig) Published
sted, utgiver, år, opplag, sider
Elsevier, 2019
HSV kategori
Identifikatorer
urn:nbn:se:umu:diva-160313 (URN)10.1016/S0167-8140(19)32448-X (DOI)000468315605227 ()
Konferanse
38th Annual Meeting of the European-Society-for-Radiotherapy-and-Oncology (ESTRO), Milan, ITALY, April 26-30, 2019
Tilgjengelig fra: 2019-06-17 Laget: 2019-06-17 Sist oppdatert: 2019-06-17bibliografisk kontrollert
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