Reduction of Collimator Correction Artefacts with Bayesian Reconstruction in Spect

Poor resolution of single photon emission computed tomography (SPECT) has degraded its use in clinical practice. Collimator correction has been shown to improve the reconstructed resolution, but the correction can generate ringing artefacts, which lower image quality. This paper investigates whether Bayesian reconstruction methods could reduce these artefacts. We have applied and tested three Bayesian reconstruction methods: smoothing prior, median root prior, and anatomical prior. To demonstrate the efficacy of these methods, we compared their physical and visual performance both in phantom and patient studies. All the three Bayesian reconstruction methods reduced the collimator correction artefacts. Images reconstructed using the smoothing prior and the median root prior had slightly lower contrast than the standard reconstruction with collimator correction, whereas the anatomical prior produced images with good resolution and contrast

Variability in PET image quality and quantification measured with a permanently filled Ge-68-phantom : a multi-center study

BackgroundThis study evaluated, as a snapshot, the variability in quantification and image quality (IQ) of the clinically utilized PET [F-18]FDG whole-body protocols in Finland using a NEMA/IEC IQ phantom permanently filled with Ge-68.MethodsThe phantom was imaged on 14 PET-CT scanners, including a variety of models from two major vendors. The variability of the recovery coefficients (RCmax, RCmean and RCpeak) of the hot spheres as well as percent background variability (PBV), coefficient of variation of the background (COVBG) and accuracy of corrections (AOC) were studied using images from clinical and standardized protocols with 20 repeated measurements. The ranges of the RCs were also compared to the limits of the EARL F-18 standards 2 accreditation (EARL2). The impact of image noise on these parameters was studied using averaged images (AVIs).ResultsThe largest variability in RC values of the routine protocols was found for the RCmax with a range of 68% and with 10% intra-scanner variability, decreasing to 36% when excluding protocols with suspected cross-calibration failure or without point-spread-function (PSF) correction. The RC ranges of individual hot spheres in routine or standardized protocols or AVIs fulfilled the EARL2 ranges with two minor exceptions, but fulfilling the exact EARL2 limits for all hot spheres was variable. RCpeak was less dependent on averaging and reconstruction parameters than RCmax and RCmean. The PBV, COVBG and AOC varied between 2.3-11.8%, 9.6-17.8% and 4.8-32.0%, respectively, for the routine protocols. The RC ranges, PBV and COVBG were decreased when using AVIs. With AOC, when excluding routine protocols without PSF correction, the maximum value dropped to 15.5%.ConclusionThe maximum variability of the RC values for the [F-18]FDG whole-body protocols was about 60%. The RC ranges of properly cross-calibrated scanners with PSF correction fitted to the EARL2 RC ranges for individual sphere sizes, but fulfilling the exact RC limits would have needed further optimization. RCpeak was the most robust RC measure. Besides COVBG, also RCs and PVB were sensitive to image noise.Peer reviewe

Knowledge on and treatment practices of erosive tooth wear among Finnish dentists

Abstract Objectives: To investigate Finnish dentists’ knowledge on and means of recording, detecting and diagnosing erosive tooth wear (ETW). Treatment options and possible differences in treatment decisions between general and specialized dentists were also evaluated. Materials and methods: An electronic questionnaire was sent by e-mail to 3664 Finnish dentists. Respondents’ gender, age, work experience, field of specialty, and practice location were requested. The questionnaire also included a patient case where the dentists were asked about their choice of treatment. Statistical analyses were performed using means, proportions, and cross tabulations. Results: Response rate was 24% (n = 866). Almost all respondents (98.0%) recorded ETW in patient files, but only 4.1% used a detailed scoring system. Of the respondents, 64.4% usually found the cause of ETW. Use of carbonated beverages (84.3%), energy drinks (57.0%), and reflux disease (53.1%) were reported to be probable causes. The majority of the respondents (80.9%) usually assessed patient’s dietary history while 1.9% evaluated saliva secretion rate. When asked about treatment decisions of ETW patients, the differences between general dentists and specialized dentists were not as obvious as hypothesized. Conclusions: This study suggests that the Finnish dentists who participated in this survey are able to detect and/or diagnose erosive tooth wear, but there is variation in recording it. The differences in treatment decisions between general dentists and specialized dentists seem to be moderate. The treatment practices for ETW are not established and further research to create clinical guidelines seems to be needed

Erosiivisen kulumisen diagnosointi ja hoito Suomessa

Tiivistelmä Lähtökohdat: Eroosiovaurioiden esiintyvyys on lisääntynyt erityisesti teini-ikäisillä sekä nuorilla aikuisilla. Toistaiseksi ei ole tutkimustietoa siitä, kuinka suomalaiset hammaslääkärit diagnosoivat ja hoitavat eroosiota. Menetelmät: Tutkimusaineisto kerättiin Webrobol-kyselyllä, joka lähetettiin Suomen Hammaslääkäriseura Apolloniaan kuuluville hammaslääkäreille (n = 3 664). Kyselyssä kartoitettiin eroosion diagnosointia ja dokumentointia sekä näkemyksiä eroosion yleisyydestä ja aiheuttajista. Lisäksi tiedusteltiin hoitokeinoja erikseen esitettyyn potilastapaukseen. Kyselyyn vastasi 866 hammaslääkäriä (24 %). Tulokset: Lähes kaikki vastaajat (98 %) ilmoittivat kirjaavansa eroosiolöydökset potilasasiakirjoihin, mutta 62 % ei käyttänyt eroosion vakavuutta kuvaavia luokittelujärjestelmiä. Yli puolet (65 %) koki saavansa selville eroosiovaurioiden syyn; yleisimpinä syinä pidettiin virvoitus- (85 %) ja energiajuomia (60 %). Lähes puolet (45 %) selvitti aina eroosiopotilaan dieettihistorian. Näkemyksissä sen suhteen, millaisia neuvoja ja hoitoa potilastapauksen potilaalle pitäisi antaa, oli hajontaa, mutta kaikki vastaajat antaisivat ruoka- ja juomatottumuksiin liittyviä ohjeita. Johtopäätökset: Eroosiovaurioiden dokumentointiin, seurantaan ja hoitolinjauksiin kaivataan yhtenäistä ohjeistusta

Prevalence of erosive tooth wear and associated dietary factors among a group of Finnish adolescents

Abstract The aim of this study was to investigate the prevalence and severity of erosive tooth wear (ETW) among Finnish adolescents and to evaluate how frequency as well as amount of the use of erosive products are associated with ETW. The study population consisted of 328 voluntary, >15-year-old secondary school students (males 49.1%, females 50.9%) in three municipalities in Finland. Clinical examination to measure erosive tooth wear (BEWE index) was carried out by trained and calibrated dentists. Piloted questionnaires included questions on consumption of drinks, fruits and berries, as well as tooth brushing frequency. Means and medians of frequencies and amounts of consumed erosive products were calculated and associations with ETW severity were analysed by logistic regression models. One third (36.9%) of the participants were in need of at least preventive measures for ETW (BEWE sum score ≥ 3), but severe ETW (BEWE sum score > 9) was rare (2.1%). Boys had severe ETW significantly more frequently than girls (p < 0.001). Habitual consumption of erosive drinks was common especially among boys compared to girls (p = 0.001). ETW was significantly associated with the amount of consumed erosive drinks, fruits or berries. The prevalence of ETW among adolescences in Finland seems to be at the same level as in other Nordic and European countries. Consumption of erosive products is common and thus, the risk for tooth erosion is high, especially in boys. In addition to erosive drinks, also berries and fruits are associated with ETW and should be included in individual dietary counselling when early signs of ETW are clinically detected