| 1. |
- Waldenberg, Christian, 1987, et al.
(författare)
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Dose integration and dose rate characteristics of a NiPAM polymer gel MRI dosimeter system
- 2017
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Ingår i: Journal of Physics: Conference Series. - : IOP Publishing. - 1742-6588 .- 1742-6596. ; 847:1
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Tidskriftsartikel (refereegranskat)abstract
- The normoxic polymer gel dosimeter based on N-isopropyl acrylamide (NiPAM) is a promising full 3D-dosimeter with high spatial resolution and near tissue equivalency. NiPAM gel samples were irradiated to different doses using a linear accelerator. The absorbed dose was evaluated using MRI and statistical significance of the analysed data was calculated. The analysis was carried out using an in-house developed software. It was found that the gel dosimeter responded linearly to the absorbed dose. The gel exhibited a dose rate dependence, as well as a dependence on the sequential beam irradiation scheme. A higher dose rate, as well as a higher dose per sequential beam, resulted in a lower dose response.
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| 2. |
- Eriksson, Stefanie, et al.
(författare)
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Texture Analysis of Magnetic Resonance Images Enables Phenotyping of Potentially Painful Annular Fissures.
- 2022
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Ingår i: Spine. - 1528-1159. ; 47:5, s. 430-437
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Tidskriftsartikel (refereegranskat)abstract
- Retrospective analysis of prospectively collected data.To investigate whether intervertebral disc (IVD) image features, extracted from magnetic resonance (MR) images, can depict the extension and width of annular fissures and associate them to pain.Annular fissures are suggested to be associated with low back pain (LBP). Magnetic resonance imaging (MRI) is a sensitive method, yet fissures are sometimes unobservable in T2-weighted MR-images, even though fissure information is present in the image. Image features can mathematically be calculated from MR-images and might reveal fissure characteristics.44 LBP patients who underwent MRI, low-pressure discography (<50psi) and computed tomography (CT) sequentially in one day, were reviewed. After semi-automated segmentation of 126 discs, image features were extracted from the T2-weighted images. The number of image features were reduced with principle component analysis (PCA). CT-discograms were graded and dichotomized regarding extension and width of fissures. IVDs were divided into fissures extending to outer annulus vs. short/no fissures. Fissure width was dichotomized into narrow (<10%) vs. broad fissures (>10%), and into moderately broad (10%-50%) vs. very broad fissures (>50%). Logistic regression was performed to investigate if image features could depict fissure extension to outer annulus and fissure width. As a sub-analysis, the association between image features used to depict fissure characteristics and discography-provoked pain-response were investigated.Fissure extension could be depicted with sensitivity/specificity=0.97/0.77 and area under curve (AUC)=0.97. Corresponding results for width depiction were sensitivity/specificity=0.94/0.39 and 0.85/0.62, and AUC=0.86 and 0.81 for narrow vs. broad and moderately broad vs. very broad fissures respectively. Pain prediction with image features used for depicting fissure characteristics showed sensitivity/specificity=0.90/0.36, 0.88/0.4, 0.93/0.33; AUC=0.69, 0.75 and 0.73 respectively.Standard MR-images contains fissure information associated to pain that can be depicted with image features, enabling non-invasive phenotyping of potentially painful annular fissures.Level of Evidence: 2.
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| 3. |
- Torén, Leif, et al.
(författare)
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MRI During Spinal Loading Reveals Intervertebral Disc Behavior Corresponding to Discogram Findings of Annular Fissures and Pain Provocation. : Torén L, Lagerstrand K, Waldenberg C, Brisby H, Hebelka H.
- 2020
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Ingår i: Spine. - 0362-2436 .- 1528-1159. ; 45:22
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Tidskriftsartikel (refereegranskat)abstract
- Study design: Retrospective analysis of prospectively collected data. Objective: The aim of this study was to investigate whether spinal loading, depicted with magnetic resonance imaging (MRI), induces regional intervertebral disc (IVD) differences associated with presence and width of annular fissure and induced pain at discography. Summary of background data: Annular fissures play a role in low back pain (LBP) but cannot be accurately characterized with conventional MRI. Recently, annular fissures were suggested to influence different load-induced IVD behavior during MRI when comparing LBP-patients and controls. Thus, the loading effect could characterize behavior related to annular fissures noninvasively with MRI. Methods: Lumbar spines of 30 LBP-patients were investigated with MRI with and without loading, discography and CT. Five IVD regions were outlined on sagittal MRI images. Difference in normalized signal intensity (SI) with and without loading was calculated for each region. Eighty-three CT-discograms were graded regarding presence and width of fissures. Discograms were classified as pain-positive if a concordant pain response was obtained at a pressure <50 psi. Results: Comparing IVDs with outer fissures with IVDs without fissures, loading induced different behavior in the two ventral regions and in the posterior region. Higher SI increase in the central region was induced in IVDs with narrower fissures compared to IVDs with wider fissures. In the group of pain-negative discograms, a SI decrease was induced in the dorsal region whereas lack of such in the pain-positive group. Conclusion: The spinal loading-effect, depicted with MRI, reveals different regional behaviors between IVDs with outer fissures compared to those without, and between IVDs with narrow and broad fissures, as well as within posterior annulus between pain-positive and pain-negative discograms. Findings are of importance for future attempts to uncover phenotypes of painful IVDs.
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| 4. |
- Waldenberg, Christian, 1987, et al.
(författare)
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Associations between Vertebral Localized Contrast Changes and Adjacent Annular Fissures in Patients with Low Back Pain: A Radiomics Approach
- 2023
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Ingår i: Journal of Clinical Medicine. - 2077-0383. ; 12:15
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Tidskriftsartikel (refereegranskat)abstract
- Low back pain (LBP) is multifactorial and associated with various spinal tissue changes, including intervertebral disc fissures, vertebral pathology, and damaged endplates. However, current radiological markers lack specificity and individualized diagnostic capability, and the interactions between the various markers are not fully clear. Radiomics, a data-driven analysis of radiological images, offers a promising approach to improve evaluation and deepen the understanding of spinal changes related to LBP. This study investigated possible associations between vertebral changes and annular fissures using radiomics. A dataset of 61 LBP patients who underwent conventional magnetic resonance imaging followed by discography was analyzed. Radiomics features were extracted from segmented vertebrae and carefully reduced to identify the most relevant features associated with annular fissures. The results revealed three important texture features that display concentrated high-intensity gray levels, extensive regions with elevated gray levels, and localized areas with reduced gray levels within the vertebrae. These features highlight patterns within vertebrae that conventional classification systems cannot reflect on distinguishing between vertebrae adjacent to an intervertebral disc with or without an annular fissure. As such, the present study reveals associations that contribute to the understanding of pathophysiology and may provide improved diagnostics of LBP.
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| 5. |
- Waldenberg, Christian, 1987, et al.
(författare)
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Detection of Imperceptible Intervertebral Disc Fissures in Conventional MRI-An AI Strategy for Improved Diagnostics.
- 2022
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Ingår i: Journal of clinical medicine. - : MDPI AG. - 2077-0383. ; 12:1
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Tidskriftsartikel (refereegranskat)abstract
- Annular fissures in the intervertebral discs are believed to be closely related to back pain. However, no sensitive non-invasive method exists to detect annular fissures. This study aimed to propose and test a method capable of detecting the presence and position of annular fissures in conventional magnetic resonance (MR) images non-invasively. The method utilizes textural features calculated from conventional MR images combined with attention mapping and artificial intelligence (AI)-based classification models. As ground truth, reference standard computed tomography (CT) discography was used. One hundred twenty-three intervertebral discs in 43 patients were examined with MR imaging followed by discography and CT. The fissure classification model determined the presence of fissures with 100% sensitivity and 97% specificity. Moreover, the true position of the fissures was correctly determined in 90 (87%) of the analyzed discs. Additionally, the proposed method was significantly more accurate at identifying fissures than the conventional radiological high-intensity zone marker. In conclusion, the findings suggest that the proposed method is a promising diagnostic tool to detect annular fissures of importance for back pain and might aid in clinical practice and allow for new non-invasive research related to the presence and position of individual fissures.
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| 6. |
- Waldenberg, Christian, 1987
(författare)
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Development of new MRl-based analysis methods for improved diagnosis of low back pain patients
- 2023
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- BACKGROUND Low back pain (LBP) is the leading cause of disability worldwide, where three of four individuals experience back pain at some point in their lives. The pathophysiological background of LBP is probably multifactorial, where bone marrow damage, tissue changes in the vertebral endplates, and intervertebral disc (IVD) degeneration have been recognized as tissue changes linked to pain. Annular fissures within the IVD are of particular interest, as they may be associated with vascular and nerve ingrowth. However, these tissue changes are also common in asymptomatic individuals, making it difficult to correctly identify the cause of pain in the individual patient. AIM. This thesis aims to develop data-driven MRI-based analysis methods to improve the understanding of spinal tissue changes and their association with LBP with the ultimate purpose of improving diagnostics. PAPER I. MR images of 49 IVDs in 10 LBP patients were analyzed with unsupervised clustering methods to objectively and continuously classify the IVD heterogeneity related to degenerative changes. IVD degeneration could successfully be quantified with the proposed method. PAPER II. The lumbar IVDs of 25 LBP patients and 12 matched controls were examined with T2 mapping to quantify possible differences in IVD signal behaviors between patients and controls. The cohorts differed significantly in nucleus pulposus signal. A sub-analysis revealed that this signal difference was related to IVD fissures, visible as high-intensity zones at the outer part of the annulus fibrosis. PAPER III. Radiomics features were extracted from 123 IVDs (n=43 LBP patients) and examined with conventional MRI followed by discography and computed tomography. The features were further analyzed using artificial neural networks and a radiomics-based attention mapping technique to identify the presence and position of possible annular fissures. The method showed great potential and was found to classify the presence of fissures with 100% sensitivity and 97% specificity. The method also identified the position of fissures in 87% of the analyzed IVDs. Paper IV. Radiomic features from 61 LBP patients examined with conventional MR imaging were extracted and then analyzed using machine-learning techniques to explore possible associations between annular fissures and vertebral lesions. The findings suggest that radiomics can objectively detect vertebral tissue changes associated with adjacent annular fissures. CONCLUSION. With data-driven methods, such as radiomics and attention mapping, tissue changes both within the IVD and the vertebra were well revealed in LBP patients. Further, the methods could be used to find associations between different types of tissue changes and were sensitive to subtle and imperceptible changes associated with disc degeneration and annular fissuring. These analysis methods could contribute to improved MRI diagnostics for LBP patients.
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| 7. |
- Waldenberg, Christian, 1987, et al.
(författare)
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Differences in IVD characteristics between low back pain patients and controls associated with HIZ as revealed with quantitative MRI
- 2019
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Ingår i: Plos One. - : Public Library of Science (PLoS). - 1932-6203. ; 14:8
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Tidskriftsartikel (refereegranskat)abstract
- Background Magnetic resonance imaging (MRI) can provide objective continuous intervertebral disc (IVD) measures in low back pain (LBP) patients. However, there are limited studies comparing quantitative IVD measures of symptomatic and asymptomatic individuals. This study aimed to investigate possible differences in IVD tissue composition in patients with chronic LBP and controls using quantitative MRI and correlate IVD measures with the phenotype High-Intensity Zone (HIZ). The lumbar spine of 25 LBP-patients (25-69y, mean 38y, 11 males) and 12 controls (25-59y, mean 38y, 7 males) was examined with T2-mapping on a 1.5T MRI scanner. The mean T2-map value and standard deviation were determined in three midsagittal IVD slices and five sub-regions dividing each IVD in the sagittal plane. The distribution of T2-map values over the IVD was also determined with histogram analysis (Delta mu = distribution width). When compared to controls, patient IVDs displayed lower values for all metrics, with significant differences for the T2-map value, standard deviation (p = 0.026) and Delta mu (p = 0.048). Significantly different T2-map values were found between cohorts in the region representing nucleus pulposus and the border zone between nucleus pulposus and posterior annulus fibrosus (p = 0.047-0.050). Excluding all IVDs with HIZs resulted in no significant difference between the cohorts for any of the analyzed metrics (p = 0.053-0.995). Additionally, the T2-map values were lower in patients with HIZ in comparison without HIZ. Differences in IVD characteristics, measured with quantitative MRI, between LBP patients and controls were found. The T2-differences may reflect altered IVD function associated with HIZ. Future studies are recommended to explore IVD functionality in relation to HIZ and LBP.
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| 8. |
- Waldenberg, Christian, 1987, et al.
(författare)
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MRI histogram analysis enables objective and continuous classification of intervertebral disc degeneration.
- 2018
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Ingår i: European spine journal : official publication of the European Spine Society, the European Spinal Deformity Society, and the European Section of the Cervical Spine Research Society. - : Springer Science and Business Media LLC. - 1432-0932. ; 27:5, s. 1042-1048
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Tidskriftsartikel (refereegranskat)abstract
- Magnetic resonance imaging (MRI) is the best diagnostic imaging method for low back pain. However, the technique is currently not utilized in its full capacity, often failing to depict painful intervertebral discs (IVDs), potentially due to the rough degeneration classification system used clinically today. MR image histograms, which reflect the IVD heterogeneity, may offer sensitive imaging biomarkers for IVD degeneration classification. This study investigates the feasibility of using histogram analysis as means of objective and continuous grading of IVD degeneration.Forty-nine IVDs in ten low back pain patients (six males, 25-69years) were examined with MRI (T2-weighted images and T2-maps). Each IVD was semi-automatically segmented on three mid-sagittal slices. Histogram features of the IVD were extracted from the defined regions of interest and correlated to Pfirrmann grade.Both T2-weighted images and T2-maps displayed similar histogram features. Histograms of well-hydrated IVDs displayed two separate peaks, representing annulus fibrosus and nucleus pulposus. Degenerated IVDs displayed decreased peak separation, where the separation was shown to correlate strongly with Pfirrmann grade (P<0.05). In addition, some degenerated IVDs within the same Pfirrmann grade displayed diametrically different histogram appearances.Histogram features correlated well with IVD degeneration, suggesting that IVD histogram analysis is a suitable tool for objective and continuous IVD degeneration classification. As histogram analysis revealed IVD heterogeneity, it may be a clinical tool for characterization of regional IVD degeneration effects. To elucidate the usefulness of histogram analysis in patient management, IVD histogram features between asymptomatic and symptomatic individuals needs to be compared.
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