Quality control methods for magnetic resonance imaging in a multi-unit medical imaging organization

Quality control methods and test objects were developed and used for structural magnetic resonance imaging (MRI), functional MRI (fMRI) and diffusion-weighted imaging (DWI). Emphasis was put on methods that allowed objective quality control for organizations that use several MRI systems from different vendors, which had different field strengths. Notable increases in the numbers of MRI studies and novel MRI systems, fast development of MRI technology, and international discussion about the quality and safety of medical imaging have motivated the development of objective, quantitative and time-efficient methods for quality control. The quality control methods need to be up to date with the most modern MRI methods, including parallel imaging, parallel transmit technology, and new diffusion-weighted sequences. The methods need to be appropriate to those organizations that use MRI for quantitative measurements, or for the participation in multicenter studies. Two different test object methods for structural MRI were evaluated in a multi-unit medical imaging organization, these were: the Eurospin method and the American College of Radiology (ACR) method. The Eurospin method was originally developed as a part of European Concerted Action, and five standardized test objects were used to create a quality control protocol for six MRI systems. Automatic software was written for image analysis. In contrast, a single multi-purpose test object was used for the ACR method, and image quality for both standard and clinical imaging protocols were measured for 11 MRI systems. A previously published method for fMRI quality control was applied to the evaluation of 5 MRI systems and was extended for simultaneous electroencephalography (EEG) and fMRI (EEG fMRI). The test object results were compared with human data that were obtained from two healthy volunteers. A body-diameter test object was constructed for DWI testing, and apparent diffusion coefficient (ADC) values and level of artifacts were measured using conventional and evolving DWI methods. The majority of the measured MRI systems operated at an acceptable level, when compared with published recommended values for structural and functional MRI. In general, the measurements were repeatable. The study that used the test object revealed information about the extent of superficial artifacts (15 mm) and the magnitude of signal-to-noise ratio (SNR) reduction (15%) of the simultaneous EEG fMRI images. The observations were in accordance with the data of healthy human volunteers. The agreement between the ADC values for different methods used in DWI was generally good, although differences of up to 0.1 x10^-3 mm^2/s were observed between different acquisition options and different field strengths, and along the slice direction. Readout-segmented echo-planar imaging (EPI) and zoomed EPI in addition to efficient use of the parallel transmit technology resulted in lower levels of artifacts than the conventional methods. Other findings included geometric distortions at the edges of MRI system field-of-view, minor instability of image center-of-mass in fMRI, and an amplifier difference that affected the EEG signal of EEG fMRI. The findings showed that although the majority of the results were within acceptable limits, MRI quality control was capable of detecting inferior image quality and revealing information that supported clinical imaging. A comparison between the different systems and also with international reference values was feasible with the reported limitations. Automated analysis methods were successfully developed and applied in this study. The possible future direction of MRI quality control would be the further development of its relevance for clinical imaging.Magneettikuvaus on ydinmagneettiseen resonanssiin perustuva, nykytiedon valossa turvallinen lääketieteellinen kuvantamismenetelmä, jonka ensimmäiset sovellukset kehitettiin 1970-luvulla. Magneettikuvauksen kysyntä potilastutkimuksiin on jatkuvasti kasvanut. Myös magneettikuvauksen tekninen kehitys on ollut jatkuvaa ja nopeaa. Lääketieteellisen kuvantamisen turvallisuudesta ja laadusta on käyty vilkasta kansainvälistä keskustelua erityisesti 1990-luvulta lähtien. Kuvantamistutkimusten teknistä laatua on voitava mitata ja valvoa, jotta kuvantamisen kokonaislaadusta voidaan varmistua. Laadunvalvonnan menetelmien tulee kehittyä samassa tahdissa nopeasti kehittyvien laiteteknologian ja ohjelmistojen kanssa. Tässä väitöskirjatyössä kehitettiin ja sovellettiin käytäntöön laadunvalvontamenetelmiä organisaatiossa, joka koostui useista eri toimintayksiköstä ja jolla oli käytössään useita erilaisia magneettikuvauslaitteita. Menetelmiä tutkittiin erikseen anatomisen, funktionaalisen ja diffuusiopainotteisen kuvantamisen osalta. Anatomisen magneettikuvauksen laadunvalvontaa tutkittiin suorittamalla laajat laadunvalvontamittaukset kaikille organisaatiossa tutkimushetkellä käytössä olleille magneettikuvauslaitteille kahdella eri menetelmällä. Ensimmäinen tutkimus tehtiin Eurospin-testivälineillä kuudelle laitteelle ja toinen American College of Radiologyn (ACR) testikappaletta hyödyntäen 11 laitteelle. Funktionaalisen kuvantamisen laadunvalvonnan tutkimiseksi sovellettiin toisen tutkimusryhmän julkaisema menetelmä käyttöön viidelle magneettikuvauslaitteelle ja laajennettiin menetelmä tilanteeseen, jossa funktionaalinen magneettikuvaus suoritetaan samanaikaisesti elektroenkefalografiatutkimuksen (EEG) kanssa. Vartalon alueen diffuusiopainotteisen magneettikuvauksen laadun arvioimista varten rakennettiin suurikokoisen potilaan vartalon alueen mittoja vastaava testikappale. Sen sisälle asetettiin geelinäytteitä, joista mitattujen diffuusiovakioiden (ADC) arvot vastasivat tyypillisesti kehon kudoksista mitattavia arvoja. Tällä testikappaleella mitattiin myös uusien diffuusiokuvantamistekniikoiden avulla tuotettujen kuvien laatua ja ADC-arvoja. Automaattista laadunvalvontakuvien analyysia käytettiin Eurospin-testivälineiden tapauksessa, joille analyysiohjelma kirjoitettiin itse, sekä funktionaalisen magneettikuvauksen yhteydessä, jolloin käytettiin olemassa olevaa ohjelmistoa. Suurin osa mittaustuloksista oli vertailukelpoisia suositeltujen tai aiemmin raportoitujen arvojen kanssa. Samanaikaisen funktionaalisen magneettikuvauksen ja EEG:n tapauksessa voitiin mitata EEG-elektrodien aiheuttaman, signaalin puutoksena ilmenevän kuvanlaatuhäiriön syvyys (15 mm) sekä EEG-laitteiston aiheuttaman magneettikuvan signaali-kohinasuhteen aleneminen (15 %). Diffuusiopainotteisessa kuvantamisessa eri menetelmillä mitatut ADC-arvot vastasivat hyvin toisiaan. Uusilla diffuusiokuvantamistekniikoilla saatiin tuotettua kuvia, joissa arvioitiin olevan vähemmän kuvanlaatuhäiriöitä kuin vakiintunutta tekniikkaa käytettäessä. Mittauksissa saatiin useita pienempiä kuvanlaatuun liittyneitä havaintoja. Vaikka suurin osa magneettikuvauslaitteista toimi tarkoituksenmukaisella tavalla tuottaen kuvia joiden laatu oli hyväksyttävä, tässä työssä kehitettyjen ja sovellettujen laadunvalvontamenetelmien avulla voitiin havaita kuvanlaadun puutteita. Näistä havainnoista oli hyötyä myös potilastutkimusten kannalta. Tarkastelluilla menetelmillä laitteiden välinen vertailu oli tietyin rajoituksin mahdollista. Osa työssä saaduista laadunvalvontakuvista voitiin analysoida automaattisesti, osin itse kehitetyllä ohjelmalla. Nämä seikat olivat keskeisiä organisaatiossa, jossa oli käytössä useita erilaisia magneettikuvauslaitteita. Työssä saatiin potilastutkimusten kannalta hyödyllistä tietoa uusien ja kehittyvien magneettikuvaustekniikoiden kuvanlaadusta. Teknisten laadunvalvontamittausten ja potilaskuvausten välistä yhteyttä on mahdollista edelleen kehittää

A body-sized phantom for evaluation of diffusion-weighted MRI data using conventional, readout-segmented, and zoomed echo-planar sequences

Peer reviewe

Bile Reflux is a Common Finding in the Gastric Pouch After One Anastomosis Gastric Bypass

INTRODUCTION: Data on postoperative bile reflux after one anastomosis gastric bypass (OAGB) is lacking. Bile reflux scintigraphy (BRS) has been shown to be a reliable non-invasive tool to assess bile reflux after OAGB. We set out to study bile reflux after OAGB with BRS and endoscopy in a prospective series (RYSA Trial). METHODS: Forty patients (29 women) underwent OAGB between November 2016 and December 2018. Symptoms were reported and upper gastrointestinal endoscopy (UGE) was done preoperatively. Six months after OAGB, bile reflux was assessed in UGE findings and as tracer activity found in gastric tube and esophagus in BRS (follow-up rate 95%). RESULTS: Twenty-six patients (68.4%) had no bile reflux in BRS. Twelve patients (31.6%) had bile reflux in the gastric pouch in BRS and one of them (2.6%) had bile reflux also in the esophagus 6 months postoperatively. Mean bile reflux activity in the gastric pouch was 5.2% (1-21%) of total activity. De novo findings suggestive of bile reflux (esophagitis, stomal ulcer, foveolar inflammation of gastric pouch) were found for 15 patients (39.5%) in postoperative UGE. BRS and UGE findings were significantly associated (P = 0.022). Eight patients experienced de novo reflux symptoms at 6 months, that were significantly associated with BRS and de novo UGE findings postoperatively (P = 0.033 and 0.0005, respectively). CONCLUSION: Postoperative bile reflux in the gastric pouch after OAGB is a common finding in scintigraphy and endoscopy. The long-term effects of bile exposure will be analyzed in future reports after a longer follow-up. TRIAL REGISTRATION: Clinical Trials Identifier NCT02882685.Peer reviewe

Convolutional neural networks for detection of transthyretin amyloidosis in 2D scintigraphy images

Background Transthyretin amyloidosis (ATTR) is a progressive disease which can be diagnosed non-invasively using bone avid [Tc-99m]-labeled radiotracers. Thus, ATTR is also an occasional incidental finding on bone scintigraphy. In this study, we trained convolutional neural networks (CNN) to automatically detect and classify ATTR from scintigraphy images. The study population consisted of 1334 patients who underwent [Tc-99m]-labeled hydroxymethylene diphosphonate (HMDP) scintigraphy and were visually graded using Perugini grades (grades 0-3). A total of 47 patients had visual grade >= 2 which was considered positive for ATTR. Two custom-made CNN architectures were trained to discriminate between the four Perugini grades of cardiac uptake. The classification performance was compared to four state-of-the-art CNN models. Results Our CNN models performed better than, or equally well as, the state-of-the-art models in detection and classification of cardiac uptake. Both models achieved area under the curve (AUC) >= 0.85 in the four-class Perugini grade classification. Accuracy was good in detection of negative vs. positive ATTR patients (grade = 2, AUC > 0.88) and high-grade cardiac uptake vs. other patients (grade < 3 vs. grade 3, AUC = 0.94). Maximum activation maps demonstrated that the automated deep learning models were focused on detecting the myocardium and not extracardiac features. Conclusion Automated convolutional neural networks can accurately detect and classify different grades of cardiac uptake on bone scintigraphy. The CNN models are focused on clinically relevant image features. Automated screening of bone scintigraphy images using CNN could improve the early diagnosis of ATTR.Peer reviewe

Gastrointestinal Symptoms and Dopamine Transporter Asymmetry in Early Parkinson's Disease

Background The neurophysiological correlates of gastrointestinal symptoms (GISs) in Parkinson's disease (PD) are not well understood. It has been proposed that in patients with a gastrointestinal origin of PD dopaminergic neurodegeneration would be more symmetric. Objectives The aim is to assess the associations between GISs and asymmetry of nigrostriatal dopaminergic neurodegeneration in PD. Methods Ninety PD patients were assessed using motor and GIS scales and I-123-FP-CIT SPECT. We calculated the asymmetry index and the predominant side of motor symptoms and dopamine transporter (DAT) imaging defect and assessed their association with GISs. Results There were no significant differences in GISs between symmetric and asymmetric dopaminergic defect. Left predominant defect was related to more GIS and higher constipation scores. Conclusions GISs were associated with left predominant reduction in putaminal DAT binding but not asymmetry per se. It remains open whether left-sided DAT deficit is related to more pronounced GI involvement or symptom perception in PD. (c) 2022 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson Movement Disorder Society.Peer reviewe

Diagnostic accuracy of glabellar tap sign for Parkinson's disease

Glabellar tap or reflex (GR) is an old bedside clinical test used in the diagnostics of Parkinson's disease (PD), but its diagnostic value is unclear. This study examines the diagnostic validity and reliability of GR in PD in relation to brain dopaminergic activity. GR was performed on 161 patients with PD, 47 patients with essential tremor (ET) and 40 healthy controls immediately prior to dopamine transporter (DAT) [I-123]FP-CIT SPECT scanning. The binding ratios were investigated with consideration of the GR result (normal/abnormal). In addition, the consistency of the GR was investigated with 89 patients after a mean follow-up of 2.2 years. PD and ET patients had higher GR scores than healthy controls (p 0.36). Over follow-up, the GR changed from abnormal to normal in 20% of PD patients despite the presence of clinically typical disease. The sensitivity and specificity of GR for differentiating PD from ET were 78.3% and 36.2%, respectively. Although GR has been used by clinicians in the diagnostics of PD, it does not separate PD from ET. It also shows considerable inconsistency over time, and abnormal GR has no relationship with dopamine loss. Its usefulness should be tested for other clinical diagnostic purposes.Peer reviewe

Diagnostic value of micrographia in Parkinson's disease : a study with [I-123]FP-CIT SPECT

Micrographia is a common symptom of Parkinson's disease (PD), and it may precede other motor symptoms. Despite the high prevalence of micrographia in PD, its neurobiological mechanisms are not known. Given that levodopa may alleviate consistent micrographia and that nondopaminergic essential tremor (ET) is not associated with micrographia, micrographia could possibly be used as an ancillary diagnostic method that reflects nigrostriatal dopamine function. We evaluated the usefulness of micrographia as a simple one-sentence writing test in differentiating PD from ET. A total of 146 PD patients, 42 ET patients and 38 healthy controls provided writing samples and were scanned with brain [I-123]FP-CIT dopamine transporter (DAT) SPECT imaging with ROI-based and voxelwise analyses. The diagnostic accuracy of micrographia was evaluated and compared to that of DAT binding. Compared to ET and healthy controls, PD patients showed micrographia (consistent, 25.6% smaller area of handwriting sample in PD compared to ET, p = 0.002, and 27.2% smaller area of handwriting compared to healthy controls, p = 0.004). PD patients showed 133% more severe progressive micrographia compared with ET patients (median b = - 0.14 in PD, b = - 0.06 in ET, p = 0.021). In early unmedicated cognitively normal patients, consistent micrographia showed 71.2% specificity and 87.5% sensitivity in PD versus ET differentiation, but micrographia had no correlation with striatal or extrastriatal [I-123]FP-CIT binding in patients with PD. The one-sentence micrographia test shows moderately good accuracy in PD versus ET differentiation. The severity of micrographia has no relationship with DAT binding, suggesting nondopaminergic mechanism of micrographia in PD. ClinicalTrials.gov identifier: NCT02650843 (NMDAT study).Peer reviewe

Bioactive glass ions induce efficient osteogenic differentiation of human adipose stem cells encapsulated in gellan gum and collagen type I hydrogels

Background: Due to unmet need for bone augmentation, our aim was to promote osteogenic differentiation of human adipose stem cells (hASCs) encapsulated in gellan gum (GG) or collagen type I (COL) hydrogels with bioactive glass (experimental glass 2-06 of composition [wt-%]: Na2O 12.1, K2O 14.0, CaO 19.8, P2O5 2.5, B2O3 1.6, SiO2 50.0) extract based osteogenic medium (BaG OM) for bone construct development. GG hydrogels were crosslinked with spermidine (GG-SPD) or BaG extract (GG-BaG). Methods: Mechanical properties of cell-free GG-SPD, GG-BaG, and COL hydrogels were tested in osteogenic medium (OM) or BaG OM at 0, 14, and 21d. Hydrogel embedded hASCs were cultured in OM or BaG OM for 3, 14, and 21d, and analyzed for viability, cell number, osteogenic gene expression, osteocalcin production, and mineralization. Hydroxyapatite-stained GG-SPD samples were imaged with Optical Projection Tomography (OPT) and Selective Plane Illumination Microscopy (SPIM) in OM and BaG OM at 21d. Furthermore, Raman spectroscopy was used to study the calcium phosphate (CaP) content of hASC-secreted ECM in GG-SPD, GG-BaG, and COL at 21d in BaG OM. Results: The results showed viable rounded cells in GG whereas hASCs were elongated in COL. Importantly, BaG OM induced significantly higher cell number and higher osteogenic gene expression in COL. In both hydrogels, BaG OM induced strong mineralization confirmed as CaP by Raman spectroscopy and significantly improved mechanical properties. GG-BaG hydrogels rescued hASC mineralization in OM. OPT and SPIM showed homogeneous 3D cell distribution with strong mineralization in BaG OM. Also, strong osteocalcin production was visible in COL. Conclusions: Overall, we showed efficacious osteogenesis of hASCs in 3D hydrogels with BaG OM with potential for bone-like grafts.peerReviewe

Gastrointestinal Symptoms and Dopamine Transporter Asymmetry in Early Parkinson's Disease

Background: The neurophysiological correlates of gastrointestinal symptoms (GISs) in Parkinson's disease (PD) are not well understood. It has been proposed that in patients with a gastrointestinal origin of PD dopaminergic neurodegeneration would be more symmetric.Objectives: The aim is to assess the associations between GISs and asymmetry of nigrostriatal dopaminergic neurodegeneration in PD.Methods: Ninety PD patients were assessed using motor and GIS scales and 123 I-FP-CIT SPECT. We calculated the asymmetry index and the predominant side of motor symptoms and dopamine transporter (DAT) imaging defect and assessed their association with GISs.Results: There were no significant differences in GISs between symmetric and asymmetric dopaminergic defect. Left predominant defect was related to more GIS and higher constipation scores.Conclusions: GISs were associated with left predominant reduction in putaminal DAT binding but not asymmetry per se. It remains open whether left-sided DAT deficit is related to more pronounced GI involvement or symptom perception in PD. © 2022 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson Movement Disorder Society.</p

Diagnostic accuracy of glabellar tap sign for Parkinson's disease

Glabellar tap or reflex (GR) is an old bedside clinical test used in the diagnostics of Parkinson's disease (PD), but its diagnostic value is unclear. This study examines the diagnostic validity and reliability of GR in PD in relation to brain dopaminergic activity. GR was performed on 161 patients with PD, 47 patients with essential tremor (ET) and 40 healthy controls immediately prior to dopamine transporter (DAT) [123I]FP-CIT SPECT scanning. The binding ratios were investigated with consideration of the GR result (normal/abnormal). In addition, the consistency of the GR was investigated with 89 patients after a mean follow-up of 2.2 years. PD and ET patients had higher GR scores than healthy controls (p p = 0.09). There were no differences in the ratio of abnormal to normal GRs between the PD and ET groups (73% vs. 64% abnormal, respectively, p = 0.13) or in DAT binding between PD patients with abnormal and normal GRs (p > 0.36). Over follow-up, the GR changed from abnormal to normal in 20% of PD patients despite the presence of clinically typical disease. The sensitivity and specificity of GR for differentiating PD from ET were 78.3% and 36.2%, respectively. Although GR has been used by clinicians in the diagnostics of PD, it does not separate PD from ET. It also shows considerable inconsistency over time, and abnormal GR has no relationship with dopamine loss. Its usefulness should be tested for other clinical diagnostic purposes.</p