Browsing by Subject "Magnetic resonance imaging"

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  • Kaipainen, Aku L.; Pitkänen, Johanna; Haapalinna, Fanni; Jääskeläinen, Olli; Jokinen, Hanna; Melkas, Susanna; Erkinjuntti, Timo; Vanninen, Ritva; Koivisto, Anne M.; Lötjönen, Jyrki; Koikkalainen, Juha; Herukka, Sanna-Kaisa; Julkunen, Valtteri (2021)
    Purpose Automated analysis of neuroimaging data is commonly based on magnetic resonance imaging (MRI), but sometimes the availability is limited or a patient might have contradictions to MRI. Therefore, automated analyses of computed tomography (CT) images would be beneficial. Methods We developed an automated method to evaluate medial temporal lobe atrophy (MTA), global cortical atrophy (GCA), and the severity of white matter lesions (WMLs) from a CT scan and compared the results to those obtained from MRI in a cohort of 214 subjects gathered from Kuopio and Helsinki University Hospital registers from 2005 - 2016. Results The correlation coefficients of computational measures between CT and MRI were 0.9 (MTA), 0.82 (GCA), and 0.86 (Fazekas). CT-based measures were identical to MRI-based measures in 60% (MTA), 62% (GCA) and 60% (Fazekas) of cases when the measures were rounded to the nearest full grade variable. However, the difference in measures was 1 or less in 97-98% of cases. Similar results were obtained for cortical atrophy ratings, especially in the frontal and temporal lobes, when assessing the brain lobes separately. Bland-Altman plots and weighted kappa values demonstrated high agreement regarding measures based on CT and MRI. Conclusions MTA, GCA, and Fazekas grades can also be assessed reliably from a CT scan with our method. Even though the measures obtained with the different imaging modalities were not identical in a relatively extensive cohort, the differences were minor. This expands the possibility of using this automated analysis method when MRI is inaccessible or contraindicated.
  • FinnDiane Study Grp; Inkeri, Jussi; Tynjälä, Anniina; Forsblom, Carol; Liebkind, Ron; Tatlisumak, Turgut; Thorn, Lena M.; Groop, Per-Henrik; Shams, Sara; Putaala, Jukka; Martola, Juha; Gordin, Daniel (2021)
    Aims To determine if arterial functional and structural changes are associated with underlying cerebral small vessel disease in neurologically asymptomatic individuals with type 1 diabetes. Methods We enrolled 186 individuals (47.8% men; median age 40.0, IQR 33.0-45.0 years) with type 1 diabetes (median diabetes duration of 21.6, IQR 18.2-30.3 years), and 30 age- and sex-matched healthy controls, as part of the Finnish Diabetic Nephropathy (FinnDiane) Study. All individuals underwent a biochemical work-up, brain magnetic resonance imaging (MRI), ultrasound of the common carotid arteries and arterial tonometry. Arterial structural and functional parameters were assessed by carotid intima-media thickness (CIMT), pulse wave velocity and augmentation index. Results Cerebral microbleeds (CMBs) were present in 23.7% and white matter hyperintensities (WMHs) in 16.7% of individuals with type 1 diabetes. Those with type 1 diabetes and CMBs had higher median (IQR) CIMT 583 (525 - 663) mu m than those without 556 (502 - 607) mu m, p = 0.016). Higher CIMT was associated with the presence of CMBs (p = 0.046) independent of age, eGFR, ApoB, systolic blood pressure, albuminuria, history of retinal photocoagulation and HbA(1c). Arterial stiffness and CIMT were increased in individuals with type 1 diabetes and WMHs compared to those without; however, these results were not independent of cardiovascular risk factors. Conclusions Structural, but not functional, arterial changes are associated with underlying CMBs in asymptomatic individuals with type 1 diabetes.
  • Nousiainen, Katri Ilona; Mäkelä, Teemu Olavi; Peltonen, Juha (2022)
    Objective Phantoms are often used to estimate the geometric accuracy in magnetic resonance imaging (MRI). However, the distortions may differ between anatomical and phantom images. This study aimed to investigate the applicability of a phantom-based and a test-subject-based method in evaluating geometric distortion present in clinical head-imaging sequences. Materials and methods We imaged a 3D-printed phantom and test subjects with two MRI scanners using two clinical head-imaging 3D sequences with varying patient-table positions and receiver bandwidths. The geometric distortions were evaluated through nonrigid registrations: the displaced acquisitions were compared against the ideal isocenter positioning, and the varied bandwidth volumes against the volume with the highest bandwidth. The phantom acquisitions were also registered to a computed tomography scan. Results Geometric distortion magnitudes increased with larger table displacements and were in good agreement between the phantom and test-subject acquisitions. The effect of increased distortions with decreasing receiver bandwidth was more prominent for test-subject acquisitions. Conclusion Presented results emphasize the sensitivity of the geometric accuracy to positioning and imaging parameters. Phantom limitations may become an issue with some sequence types, encouraging the use of anatomical images for evaluating the geometric accuracy.
  • Vuorinen, Aino-Maija; Pakarinen, Sami; Jaakkola, Ilkka; Holmström, Miia; Kivisto, Sari; Kaasalainen, Touko (2019)
    Background Magnetic resonance imaging (MRI) in patients with cardiac pacing devices has become available despite previously being considered absolutely contraindicated. However, most institutional safety protocols have included several limitations on patient selection, leaving MRI unavailable for many patients. Purpose To evaluate the first 1000 MRI examinations conducted on patients with cardiac pacing devices at Helsinki University Hospital for any potential safety hazards and also to evaluate the long-term functionality of the safety protocol in "real-life" clinical practice. Material and Methods A total of 1000 clinically indicated MRI scans were performed with a 1.5-T MRI scanner according to the safety protocol. The following information was collected from the electronic medical record (EMR): patients' date of birth; sex; pacing device generator model; date of MRI scan; date of the latest pacing device generator implantation; and the body region scanned. The EMR of these patients was checked and especially searched for any pacing device related safety hazards or adverse outcomes during or after the MRI scan. Results Only one potentially dangerous adverse event was noted in our study group. In addition, patients with abandoned leads, temporary pacing devices, and newly implanted pacing device generators were scanned successfully and safely. Conclusion MRI scans can be performed safely in patients with cardiac pacing devices if the dedicated safety protocol is followed.
  • Saat, R.; Mahmood, G.; Laulajainen-Hongisto, A.; Lempinen, Laura; Aarnisalo, A. A.; Jero, J.; Markkola, Antti Thor Olavi (2016)
    To compare MR imaging features in patients with incidental mastoid T2-hyperintensity with those of clinical acute mastoiditis, to ascertain characteristic differences between them. MR images of 35 adult and paediatric patients with clinical acute mastoiditis and 34 consecutive age-matched controls without relevant middle ear pathology and with incidental T2-hyperintensity that covered >= 50 % of the mastoid were retrospectively analysed with regard to signal, diffusion, and enhancement characteristics, and presence of complications. Incidental mastoid T2-hyperintensity that covered >= 50 % of the mastoid volume was found in 4.6 % of reviewed MR scans (n = 2341), and associated significantly (p <0.05) less with the involvement of the tympanic cavity (38 % vs. 74 %) and mastoid antrum (56 % vs. 80 %), hypointense-to-CSF signal intensity on T2 FSE (6 % vs. 86 %), intramastoid diffusion restriction (0 % vs. 62 %), intense intramastoid enhancement (0 % vs. 51 %), periosteal enhancement (3 % vs. 69 %), perimastoid dural enhancement 3 % vs. 43 %), bone destruction (0 % vs 49 %), intratemporal abscess or cholesteatoma (0 % vs. 24 %), labyrinth involvement (0 % vs. 14 %), and extracranial abscesses (0 % vs. 20 %). Hypointense-to-CSF signal intensity on T2WI, restricted diffusion, intense intramastoid enhancement among other MR imaging characteristics favoured an acute mastoiditis diagnosis over clinically non-relevant incidental mastoid pathology. Intramastoid T2-hyperintensity alone is not a reliable sign for acute mastoiditis. In acute mastoiditis, intramastoid T2-weighted signal intensity is usually hypointense to CSF. Diffusion restriction and intense intramastoid enhancement are absent in incidental mastoid effusion. An ADC value >= 1.72 x 10 (-3) mm (2) /s contradicts the AM diagnosis.
  • Ruuth, Riikka; Kuusela, Linda; Mäkelä, Teemu; Melkas, Susanna; Korvenoja, Antti (2019)
    Aim and scope: A Gradient Echo Plural Contrast Imaging technique (GEPCI) is a post-processing method, which can be used to obtain quantitative T2* values and generate multiple synthetic contrasts from a single acquisition. However, scan duration and image reconstruction from k-space data present challenges in a clinical workflow. This study aimed at optimizing image reconstruction and acquisition duration to facilitate a post-processing method for synthetic image contrast creation in clinical settings. Materials and methods: This study consists of tests using the American College of Radiology (ACR) image quality phantom, two healthy volunteers, four mild traumatic brain injury patients and four small vessel disease patients. The measurements were carried out on a 3.0 T scanner with multiple echo times. Reconstruction from k-space data and DICOM data with two different coil-channel combination modes were investigated. Partial Fourier techniques were tested to optimize the scanning time. Conclusions: Sum of squares coil-channel combination produced artifacts in phase images, but images created with adaptive combination were artifact-free. The voxel-wise median signed difference of T2* between the vendor's adaptive channel combination and k-space reconstruction modes was 2.9 +/- 0.7 ms for white matter and 4.5 +/- 0.6 ms for gray matter. Relative white matter/gray matter contrast of all synthetic images and contrast-to-noise ratio of synthetic T1-weighted images were almost equal between reconstruction modes. Our results indicate that synthetic contrasts can be generated from the vendor's DICOM data with the adaptive combination mode without affecting the quantitative T2* values or white matter/gray matter contrast.
  • Kavaluus, Henna; Nousiainen, Katri; Kaijaluoto, Sampsa; Seppälä, Tiina; Saarilahti, Kauko; Tenhunen, Mikko (2021)
    Background and Purpose: Magnetic resonance imaging is increasingly used in radiotherapy planning; yet, the performance of the utilized scanners is rarely regulated by any authority. The aim of this study was to determine the geometric accuracy of several magnetic resonance imaging scanners used for radiotherapy planning, and to establish acceptance criteria for such scanners. Materials and Methods: The geometric accuracy of five different scanners was measured with three sequences using a commercial large-field-of-view phantom. The distortion magnitudes were determined in spherical volumes around the scanner isocenter and in cylindrical volumes along scanner z-axis. The repeatability of the measurements was determined on a single scanner with two quality assurance sequences with three single-setup and seven repeated-setup measurements. Results: For all scanners and sequences except one, the mean and median distortion magnitude was Conclusions: All tested scanners were geometrically accurate for their current use in radiotherapy planning. The acceptance criteria of geometric accuracy for regulatory inspections of a supervising authority could be set according to these results.
  • Kallankari, Hanna; Saunavaara, Virva; Parkkola, Riitta; Haataja, Leena; Hallman, Mikko; Kaukola, Tuula (2021)
    Background Very preterm birth can disturb brain maturation and subject these high-risk children to neurocognitive difficulties later. Objective The aim of the study was to evaluate the impact of prematurity on microstructure of frontostriatal tracts in children with no severe neurologic impairment, and to study whether the diffusion tensor imaging metrics of frontostriatal tracts correlate to executive functioning. Materials and methods The prospective cohort study comprised 54 very preterm children (mean gestational age 28.8 weeks) and 20 age- and gender-matched term children. None of the children had severe neurologic impairment. The children underwent diffusion tensor imaging and neuropsychological assessments at a mean age of 9 years. We measured quantitative diffusion tensor imaging metrics of frontostriatal tracts using probabilistic tractography. We also administered five subtests from the Developmental Neuropsychological Assessment, Second Edition, to evaluate executive functioning. Results Very preterm children had significantly higher fractional anisotropy and axial diffusivity values (P
  • Hietikko, Ronja; Kilpeläinen, Tuomas P; Kenttämies, Anu; Ronkainen, Johanna; Ijäs, Kirsty; Lind, Kati; Marjasuo, Suvi; Oksala, Juha; Oksanen, Outi; Saarinen, Tuomas; Savolainen, Ritja; Taari, Kimmo; Tammela, Teuvo L. J.; Mirtti, Tuomas; Natunen, Kari; Auvinen, Anssi; Rannikko, Antti (BioMed Central, 2020)
    Abstract Background The aim of this study is to investigate the potential impact of prostate magnetic resonance imaging (MRI) -related interreader variability on a population-based randomized prostate cancer screening trial (ProScreen). Methods From January 2014 to January 2018, 100 men aged 50–63 years with clinical suspicion of prostate cancer (PCa) in Helsinki University Hospital underwent MRI. Nine radiologists individually reviewed the pseudonymized MRI scans of all 100 men in two ProScreen trial centers. All 100 men were biopsied according to a histological composite variable comprising radical prostatectomy histology (N = 38) or biopsy result within 1 year from the imaging (N = 62). Fleiss’ kappa (κ) was used to estimate the combined agreement between all individual radiologists. Sample data were subsequently extrapolated to 1000-men subgroups of the ProScreen cohort. Results Altogether 89% men of the 100-men sample were diagnosed with PCa within a median of 2.4 years of follow-up. Clinically significant PCa (csPCa) was identified in 76% men. For all PCa, mean sensitivity was 79% (SD ±10%, range 62–96%), and mean specificity 60% (SD ±22%, range 27–82%). For csPCa (Gleason Grade 2–5) MRI was equally sensitive (mean 82%, SD ±9%, range 67–97%) but less specific (mean 47%, SD ±20%, range 21–75%). Interreader agreement for any lesion was fair (κ 0.40) and for PI-RADS 4–5 lesions it was moderate (κ 0.60). Upon extrapolating these data, the average sensitivity and specificity to a screening positive subgroup of 1000 men from ProScreen with a 30% prevalence of csPCa, 639 would be biopsied. Of these, 244 men would be true positive, and 395 false positive. Moreover, 361 men would not be referred to biopsy and among these, 56 csPCas would be missed. The variation among the radiologists was broad as the least sensitive radiologist would have twice as many men biopsied and almost three times more men would undergo unnecessary biopsies. Although the most sensitive radiologist would miss only 2.6% of csPCa (false negatives), the least sensitive radiologist would miss every third. Conclusions Interreader agreement was fair to moderate. The role of MRI in the ongoing ProScreen trial is crucial and has a substantial impact on the screening process.
  • Hietikko, Ronja; Kilpeläinen, Tuomas P.; Kenttämies, Anu; Ronkainen, Johanna; Ijäs, Kirsty; Lind, Kati; Marjasuo, Suvi; Oksala, Juha; Oksanen, Outi; Saarinen, Tuomas; Savolainen, Ritja; Taari, Kimmo; Tammela, Teuvo L. J.; Mirtti, Tuomas; Natunen, Kari; Auvinen, Anssi; Rannikko, Antti (2020)
    Background: The aim of this study is to investigate the potential impact of prostate magnetic resonance imaging (MRI) -related interreader variability on a population-based randomized prostate cancer screening trial (ProScreen). Methods: From January 2014 to January 2018, 100 men aged 50-63 years with clinical suspicion of prostate cancer (PCa) in Helsinki University Hospital underwent MRI. Nine radiologists individually reviewed the pseudonymized MRI scans of all 100 men in two ProScreen trial centers. All 100 men were biopsied according to a histological composite variable comprising radical prostatectomy histology (N = 38) or biopsy result within 1 year from the imaging (N = 62). Fleiss' kappa (kappa) was used to estimate the combined agreement between all individual radiologists. Sample data were subsequently extrapolated to 1000-men subgroups of the ProScreen cohort. Results: Altogether 89% men of the 100-men sample were diagnosed with PCa within a median of 2.4 years of follow-up. Clinically significant PCa (csPCa) was identified in 76% men. For all PCa, mean sensitivity was 79% (SD +/- 10%, range 62-96%), and mean specificity 60% (SD +/- 22%, range 27-82%). For csPCa (Gleason Grade 2-5) MRI was equally sensitive (mean 82%, SD +/- 9%, range 67-97%) but less specific (mean 47%, SD +/- 20%, range 21-75%). Interreader agreement for any lesion was fair (kappa 0.40) and for PI-RADS 4-5 lesions it was moderate (kappa 0.60). Upon extrapolating these data, the average sensitivity and specificity to a screening positive subgroup of 1000 men from ProScreen with a 30% prevalence of csPCa, 639 would be biopsied. Of these, 244 men would be true positive, and 395 false positive. Moreover, 361 men would not be referred to biopsy and among these, 56 csPCas would be missed. The variation among the radiologists was broad as the least sensitive radiologist would have twice as many men biopsied and almost three times more men would undergo unnecessary biopsies. Although the most sensitive radiologist would miss only 2.6% of csPCa (false negatives), the least sensitive radiologist would miss every third. Conclusions: Interreader agreement was fair to moderate. The role of MRI in the ongoing ProScreen trial is crucial and has a substantial impact on the screening process.
  • Urrila, Anna S.; Hakkarainen, Antti; Castaneda, Anu; Paunio, Tiina; Marttunen, Mauri; Lundbom, Nina (2017)
    Aim: This study used proton magnetic resonance spectroscopy (H-1 MRS) to evaluate the neurochemistry of the frontal cortex in adolescents with symptoms of sleep and depression. Methods: Nineteen non-medicated adolescent boys (mean age 16.0 years; 9 clinical cases with depression/sleep symptoms and 10 healthy controls) underwent H-1 MRS at 3 T. MR spectra were acquired from the anterior cingulate cortex (ACC), the dorsolateral prefrontal cortex, and frontal white matter. Concentrations of N-acetyl aspartate, total creatine, choline-containing compounds, total glutamine plus glutamate, and myo-inositol (mI) were compared in the 2 subgroups, and correlated with sleep and clinical measures in the total sample. Sleep was assessed with self-report questionnaires and ambulatory polysomnography recordings. Results: Concentrations of mI were lower in both frontal cortical regions among the depressed adolescents than in controls. No statistically significant differences in other metabolite concentrations were observed between the subgroups. Frontal cortex mI concentrations correlated negatively with depression severity, subjective daytime sleepiness, insomnia symptoms, and the level of anxiety, and correlated positively with total sleep time and overall psychosocial functioning. The correlations between mI in the ACC and total sleep time as well as daytime sleepiness remained statistically significant when depression severity was controlled in the analyses. Conclusion: Lower frontal cortex ml may indicate a disturbed second messenger system. Frontal cortical mI may thus be linked to the pathophysiology of depression and concomitant sleep symptoms among maturing adolescents. Short sleep and daytime sleepiness may be associated with frontal cortex mI independently from depression. (C) 2017 S. Karger AG, Basel
  • Jokela, Manu; Huovinen, Salina; Palmio, Johanna; Saukkonen, Anna-Maija; Penttila, Sini; Udd, Bjarne (2017)
  • Mäkitie, Riikka E.; Niinimaki, Tuukka; Nieminen, Miika T.; Schalin-Jantti, Camilla; Niinimaki, Jaakko; Makitie, Outi (2017)
    Background: WNT signaling plays a major role in bone and cartilage metabolism. Impaired WNT/beta-catenin signaling leads to early-onset osteoporosis, but specific features in bone and other tissues remain inadequately characterized. We have identified two large Finnish families with early-onset osteoporosis due to a heterozygous WNT1 mutation c.652T>G, p.C218G. This study evaluated the impact of impaired WNT/beta-catenin signaling on spinal structures. Methods: Altogether 18 WNT1 mutation-positive (age range 11-76 years, median 49 years) and 14 mutation negative subjects (10-77 years, median 43 years) underwent magnetic resonance imaging (MRI) of the spine. The images were reviewed for spinal alignment, vertebral compression fractures, intervertebral disc changes and possible endplate deterioration. The findings were correlated with clinical data. Results: Vertebral compression fractures were present in 78% (7/9) of those aged over 50 years but were not seen in younger mutation-positive subjects. All those with fractures had several severely compressed vertebrae. Altogether spinal compression fractures were present in 39% of those with a WNT1 mutation. Only 14% (2/14) mutation -negative subjects had one mild compressed vertebra each. The mutation-positive subjects had a higher mean spinal deformity index (4.0 +/- 7.3 vs 0.0 +/- 0.4) and more often increased thoracic kyphosis (Z-score > + 2.0 in 33% vs 0%). Further, they had more often Schmorl nodes (61% vs 36%), already in adolescence, and their intervertebral discs were enlarged. Conclusion: Compromised WNT signaling introduces severe and progressive changes to the spinal structures. Schmorl nodes are prevalent even at an early age and increased thoracic kyphosis and compression fractures become evident after the age of 50 years. Therapies targeting the WNT pathway may be an effective way to prevent spinal pathology not only in those harboring a mutation but also in the general population with similar pathology. (C) 2017 Elsevier Inc. All rights reserved.
  • Sairanen, Viljami; Ocampo-Pineda, Mario; Granziera, Cristina; Schiavi, Simona; Daducci, Alessandro (2022)
    A B S T R A C T The white matter structures of the human brain can be represented using diffusion-weighted MRI tractography. Unfortunately, tractography is prone to find false-positive streamlines causing a severe decline in its specificity and limiting its feasibility in accurate structural brain connectivity analyses. Filtering algorithms have been pro-posed to reduce the number of invalid streamlines but the currently available filtering algorithms are not suitable to process data that contains motion artefacts which are typical in clinical research. We augmented the Con-vex Optimization Modelling for Microstructure Informed Tractography (COMMIT) algorithm to adjust for these signals drop-out motion artefacts. We demonstrate with comprehensive Monte-Carlo whole brain simulations and in vivo infant data that our robust algorithm is capable of properly filtering tractography reconstructions despite these artefacts. We evaluated the results using parametric and non-parametric statistics and our results demonstrate that if not accounted for, motion artefacts can have severe adverse effects in human brain structural connectivity analyses as well as in microstructural property mappings. In conclusion, the usage of robust filtering methods to mitigate motion related errors in tractogram filtering is highly beneficial, especially in clinical stud-ies with uncooperative patient groups such as infants. With our presented robust augmentation and open-source implementation, robust tractogram filtering is readily available.
  • Mattila, Katariina A.; Aronniemi, Johanna; Salminen, Päivi; Rintala, Risto J.; Kyrklund, Kristiina (2020)
    Background Intra-articular venous malformations of the knee are an uncommon cause of unilateral knee pain in children. Timely diagnosis is important because lesions with intrasynovial involvement can lead to joint space hemorrhage and secondary cartilage damage. Objective To describe our tertiary center's experience of diagnostics and typical magnetic resonance imaging (MRI) findings. Materials and methods A retrospective review of all patients
  • Kaukinen, P.; Podlipska, J.; Guermazi, A.; Niinimaki, J.; Lehenkari, P.; Roemer, F. W.; Nieminen, M. T.; Koski, J. M.; Saarakkala, S.; Arokoski, J. P. A. (2017)
    Objective: The main aim was to investigate the associations between Magnetic Resonance Imaging (MRI)-defined structural pathologies of the knee and physical function. Design: A cohort study with frequency matching on age and sex with eighty symptomatic subjects with knee pain and suspicion or diagnosis of knee osteoarthritis (OA) and 57 asymptomatic subjects was conducted. The subjects underwent knee MRI, and the severity of structural changes was graded by MRI Osteoarthritis Knee Score (MOAKS) in separate knee locations. WOMAC function subscores were recorded and physical function tests (20-m and 5-min walk, stair ascending and descending, timed up & go and repeated sit-to-stand tests) performed. The association between MRI-defined structural pathologies and physical function tests and WOMAC function subscores were evaluated by linear regression analysis with adjustment for demographic factors, other MRI-features and pain with using effect size (ES) as a measure of the magnitude of an association. Results: Cartilage degeneration showed significant association with poor physical performance in TUG-, stair ascending and descending-, 20-m- and 5-min walk-tests (ESs in the subjects with cartilage degeneration anywhere between 0.134 [95%CI 0.037-0.238] and 0.224 [0.013-0.335]) and with increased WOMAC function subscore (ES in the subjects with cartilage degeneration anywhere 0.088 [0.012-0.103]). Also, lateral meniscus maceration and extrusion were associated with poor performance in stair ascending test (ESs 0.067 [0.008-0.163] and 0.077 [0.012-0.177]). Conclusions: After adjustments cartilage degeneration was associated with both decreased self-reported physical function and poor performance in the physical function tests. Furthermore, subjects with lateral meniscus maceration and extrusions showed significantly worse performance in stair ascending tests. (C) 2017 Osteoarthritis Research Society International. Published by Elsevier Ltd. All rights reserved.
  • Nousiainen, Katri; Mäkelä, Teemu (2020)
    Objective We aimed to develop a vendor-neutral and interaction-free quality assurance protocol for measuring geometric accuracy of head and brain magnetic resonance (MR) images. We investigated the usability of nonrigid image registration in the analysis and looked for the optimal registration parameters. Materials and methods We constructed a 3D-printed phantom and imaged it with 12 MR scanners using clinical sequences. We registered a geometric-ground-truth computed tomography (CT) acquisition to the MR images using an open-source nonrigid-registration-toolbox with varying parameters. We applied the transforms to a set of control points in the CT image and compared their locations to the corresponding visually verified reference points in the MR images. Results With optimized registration parameters, the mean difference (and standard deviation) of control point locations when compared to the reference method was (0.17 +/- 0.02) mm for the 12 studied scanners. The maximum displacements varied from 0.50 to 1.35 mm or 0.89 to 2.30 mm, with vendors' distortion correction on or off, respectively. Discussion Using nonrigid CT-MR registration can provide a robust and relatively test-object-agnostic method for estimating the intra- and inter-scanner variations of the geometric distortions.
  • Dudek, Mateusz; Canals, Santiago; Sommer, Wolfgang H.; Hyytiä, Petri (2016)
    The nonselective opioid receptor antagonist naltrexone is now used for the treatment of alcoholism, yet naltrexone's central mechanism of action remains poorly understood. One line of evidence suggests that opioid antagonists regulate alcohol drinking through interaction with the mesolimbic dopamine system. Hence, our goal here was to examine the role of the nucleus accumbens connectivity in alcohol reinforcement and naltrexone's actions using manganese enhanced magnetic resonance imaging (MEMRI). Following long-term free-choice drinking of alcohol and water, AA (Alko Alcohol) rats received injections of MnCl2 into the nucleus accumbens for activity-dependent tracing of accumbal connections. Immediately after the accumbal injections, rats were imaged using MEMRI, and then allowed to drink either alcohol or water for the next 24 h. Naltrexone was administered prior to the active dark period, and the second MEMRI was performed 24 h after the first scan. Comparison of signal intensity at 1 and 24 h after accumbal MnCl2 injections revealed an ipsilateral continuum through the ventral pallidum, bed nucleus of the stria terminalis, globus pallidus, and lateral hypothalamus to the substantia nigra and ventral tegmental area. Activation was also seen in the rostral part of the insular cortex and regions of the prefrontal cortex. Alcohol drinking resulted in enhanced activation of these connections, whereas naltrexone suppressed alcohol-induced activity. These data support the involvement of the accumbal connections in alcohol reinforcement and mediation of naltrexone's suppressive effects on alcohol drinking through their deactivation. (C) 2016 Elsevier B.V. and ECNP. All rights reserved.
  • Peltonen, Juha I; Mäkelä, Teemu; Salli, Eero (2018)
    Objective Quality assurance (QA) of magnetic resonance imaging (MRI) often relies on imaging phantoms with suitable structures and uniform regions. However, the connection between phantom measurements and actual clinical image quality is ambiguous. Thus, it is desirable to measure objective image quality directly from clinical images. Materials and methods In this work, four measurements suitable for clinical image QA were presented: image resolution, contrast-to-noise ratio, quality index and bias index. The methods were applied to a large cohort of clinical 3D FLAIR volumes over a test period of 9.5 months. The results were compared with phantom QA. Additionally, the effect of patient movement on the presented measures was studied. Results A connection between the presented clinical QA methods and scanner performance was observed: the values reacted to MRI equipment breakdowns that occurred during the study period. No apparent correlation with phantom QA results was found. The patient movement was found to have a significant effect on the resolution and contrast-to-noise ratio values. Discussion QA based on clinical images provides a direct method for following MRI scanner performance. The methods could be used to detect problems, and potentially reduce scanner downtime. Furthermore, with the presented methodologies comparisons could be made between different sequences and imaging settings. In the future, an online QA system could recognize insufficient image quality and suggest an immediate re-scan.
  • Sistonen, Heli J.; Aro, Katri; Atula, Timo; Jouhi, Lauri; Linden, Riikka; Tapiovaara, Laura; Loimu, Venla; Markkola, Antti (2021)
    Purpose To investigate clinical and radiological factors predicting worse outcome after (chemo)radiotherapy ([C]RT) in oropharyngeal squamous cell carcinoma (OPSCC) with a focus on apparent diffusion coefficient (ADC). Methods This retrospective study included 67 OPSCC patients, treated with (C)RT with curative intent and diagnosed during 2013-2017. Human papilloma virus (HPV) association was detected with p16 immunohistochemistry. Of all 67 tumors, 55 were p16 positive, 9 were p16 negative, and in 3 the p16 status was unknown. Median follow-up time was 38 months. We analyzed pretreatment magnetic resonance imaging (MRI) for factors predicting disease-free survival (DFS) and locoregional recurrence (LRR), including primary tumor volume and the largest metastasis. Crude and p16-adjusted hazard ratios were analyzed using Cox proportional hazards model. Interobserver agreement was evaluated. Results Disease recurred in 13 (19.4%) patients. High ADC predicted poor DFS, but not when the analysis was adjusted for p16. A break in RT (hazard ratio, HR = 3.972, 95% confidence interval, CI 1.445-10.917, p = 0.007) and larger metastasis volume (HR = 1.041, 95% CI 1.007-1.077, p = 0.019) were associated with worse DFS. A primary tumor larger than 7 cm(3) was associated with increased LRR rate (HR = 4.861, 1.042-22.667, p = 0.044). Among p16-positive tumors, mean ADC was lower in grade 3 tumors compared to lower grade tumors (0.736 vs. 0.883; p = 0.003). Conclusion Low tumor ADC seems to be related to p16 positivity and therefore should not be used independently to evaluate disease prognosis or to choose patients for treatment deintensification.