Patient doses in ct, dental cone beam ct and projection radiography in Finland, with emphasis on paediatric patients

Diagnostic radiology represents the largest man-made contribution to population radiation doses in Europe. To be able to keep the diagnostic benefit versus radiation risk ratio as high as possible, it is important to understand the quantitative relationship between the patient radiation dose and the various factors which affect the dose, such as the scan parameters, scan mode, and patient size. Paediatric patients have a higher probability for late radiation effects, since longer life expectancy is combined with the higher radiation sensitivity of the developing organs. The experience with particular paediatric examinations may be very limited and paediatric acquisition protocols may not be optimised. The purpose of this thesis was to enhance and compare different dosimetric protocols, to promote the establishment of the paediatric diagnostic reference levels (DRLs), and to provide new data on patient doses for optimisation purposes in computed tomography (with new applications for dental imaging) and in paediatric radiography. Large variations in radiation exposure in paediatric skull, sinus, chest, pelvic and abdominal radiography examinations were discovered in patient dose surveys. There were variations between different hospitals and examination rooms, between different sized patients, and between imaging techniques; emphasising the need for harmonisation of the examination protocols. For computed tomography, a correction coefficient, which takes individual patient size into account in patient dosimetry, was created. The presented patient size correction method can be used for both adult and paediatric purposes. Dental cone beam CT scanners provided adequate image quality for dentomaxillofacial examinations while delivering considerably smaller effective doses to patient compared to the multi slice CT. However, large dose differences between cone beam CT scanners were not explained by differences in image quality, which indicated the lack of optimisation. For paediatric radiography, a graphical method was created for setting the diagnostic reference levels in chest examinations, and the DRLs were given as a function of patient projection thickness. Paediatric DRLs were also given for sinus radiography. The detailed information about the patient data, exposure parameters and procedures provided tools for reducing the patient doses in paediatric radiography. The mean tissue doses presented for paediatric radiography enabled future risk assessments to be done. The calculated effective doses can be used for comparing different diagnostic procedures, as well as for comparing the use of similar technologies and procedures in different hospitals and countries.Diagnostisen röntgensäteilyn osuus ihmisen aiheuttamasta väestön keskimääräisestä säteilyannoksesta on kaikkein suurin. Jotta diagnostisen hyödyn ja säteilyhaitan välinen suhde voidaan pitää mahdollisimman suurena, on tärkeää ymmärtää kvantitatiivisesti potilaan säteilyannoksen ja siihen vaikuttavien tekijöiden, kuten kuvausarvojen, kuvausmenetelmien ja potilaiden kokojen välinen suhde. Lapsipotilailla on aikuisia suurempi riski säteilyn myöhäisiin haittavaikutuksiin, mikä on seurausta pitkästä odotettavissa olevasta eliniästä sekä kehittyvien elinten korkeasta säteilyherkkyydestä. Henkilökunnan kokemus tietyissä lasten tutkimuksissa voi olla rajallinen eikä lasten kuvausmenetelmiä välttämättä ole optimoitu. Työn tarkoituksena oli kehittää ja vertailla eri annosmittausmenetelmiä tietokonetomografiatutkimuksissa (TT) ja lasten natiiviröntgentutkimuksissa, edistää lasten vertailutasojen käyttöönottoa sekä tuottaa uutta potilasannostietoa röntgentutkimusten optimointia varten. Potilasannoskartoituksissa todettiin suuria vaihteluita kuvaustekniikoissa eri sairaaloiden, tutkimushuoneiden ja eri kokoisten potilaiden välillä. Tutkimustekniikoiden vaihtelusta aiheutuneet erot potilasannoksissa osoittivat tarvetta kuvausmenetelmien optimoinnille sekä kansallisella, että kansainvälisellä tasolla. Tietokonetomografiatutkimuksia varten kehitettiin korjauskerroin, joka ottaa potilaan koon huomioon aikuisten ja lasten potilasannoksia määritettäessä. Tietokonetomografiatutkimuksissa lapset, naiset ja pienikokoiset potilaat absorboivat säteilyä suhteellisesti isokokoisia potilaita voimakkaammin. Hampaiston kuvantamisessa käytettävien rajoitetun kartiokeilan TT-laitteiden kuvanlaatu todettiin riittäväksi potilasannosten ollessa oleellisesti pienempiä kuin monileike-TT-laitteilla. Eri kartiokeila-TT-laitteiden potilasannoksissa oli kuitenkin suuria eroja kuvanlaadusta riippumatta, mikä osoitti tarvetta kuvaustekniikoiden jatkokehitykselle. Lasten keuhkokuvauksia varten annettiin graafiset vertailutasot, joiden avulla sairaalat voivat suoraan verrata eri kokoisten potilaiden säteilyannoksia vertailutasoon. Vertailutasot annettiin myös lasten nenän sivuontelokuvauksia varten. Yksityiskohtaiset tiedot kerätystä aineistosta, kuvausarvoista ja -menetelmistä antoivat työkalut potilasannosten vähentämiseksi lasten natiiviröntgentutkimuksissa. Kudoksiin absorboituvien annosten määrittäminen mahdollistaa jatkossa potilaskohtaiset riskiarvioinnit. Määritettyjä efektiivisiä annoksia voidaan käyttää diagnostisten menetelmien ja kuvaustekniikoiden vertailuun eri sairaaloiden ja valtioiden välillä

Lasten röntgentutkimusten vertailutasot

Euroopan Unionin direktiivi 97/43/Euratom ja Sosiaali- ja terveysministeriön asetus 423/2000 velvoittavat Säteilyturvakeskuksen antamaan diagnostiset vertailutasot yleisimmille röntgen- ja isotooppitutkimuksille. Lapsipotilas on radiologisissa tutkimuksissa erityisen huomion kohteena aikuisia korkeammasta säteilyriskistä johtuen. Tämän työn tarkoituksena oli selvittää aikaisemmat tiedot lasten röntgentutkimusten säteilyannoksista, esittää menetelmä lapsipotilaan koon huomioon ottamiseksi vertailutasoja asetettaessa ja arvioida röntgentutkimuksista aiheutuvaa säteilyriskiä. Lasten rintakehätutkimusten säteilyannoksia mitattiin kahdesta sairaalasta annosaineiston täydentämiseksi ja mittausmenetelmien soveltuvuuden varmistamiseksi. Pinta-annos (ESD) määritettiin säteilyntuottomittausten avulla ja annoksen ja pinta-alan tulo (DAP) DAP-mittarin avulla. PCXMC-annoslaskentaohjelman avulla laskettiin rintakehätutkimuksista keskimäärin aiheutuvat efektiiviset annokset, joiden avulla arvioitiin säteilyriskiä ikäryhmittäin. Tutkimuksessa käytetty aineisto koostui yhteensä kahdeksasta sairaalasta kerätyistä annostiedoista. Rintakehän röntgentutkimuksia oli 700, virtsateiden toiminnan läpivalaisututkimuksia (MCU) 100 ja muita natiiviröntgen sekä läpivalaisututkimuksia 10 - 30. Rintakehätutkimusten säteilyannokset olivat pienempiä kuin useissa muissa julkaistuissa tutkimuksissa. Yhdestä rintakehätutkimuksesta aiheutuvaksi efektiiviseksi annokseksi arvioitiin ikäryhmittäin 8 - 34 μSv. Pienten lasten muita korkeampi säteilyriski kompensoitui muita ikäryhmiä alhaisemmista säteilyannoksista johtuen. Rintakehän tutkimusten säteilyannokset kasvoivat eksponentiaalisesti potilaan koon kasvaessa, korrelaatiokertoimet säteilyannoksiin sovitetuille käyrille olivat 0,86 - 0,99. Vastaava eksponentiaalinen kasvu oli havaittavissa myös muissa tutkimuksissa, mutta niissä aineisto oli puutteellinen. Epävarmuusarvion perusteella toiminnanharjoittajat voivat määrittää potilasannoksiaan 20 %:n epävarmuudella. Iso-Britannian säteilysuojeluviranomaisen (NRPB) esittämän menetelmän lasten vertailutasojen asettamiseksi todettiin aiheuttavan lisää epävarmuutta (12 - 40 %) ja menetelmä oli työläs soveltaa. Vertailutasot lasten röntgentutkimuksille tulisi asettaa lineaarisena käyränä puolilogaritmisella asteikolla potilaan paksuuden funktiona. Tällä hetkellä annostietoja ei ole riittävästi vertailutasojen asettamiseksi, lisäksi käytettävissä oleva aineisto on osittain vanhentunutta. Vertailutasojen asettamiseksi annostietoja tulisi kerätä yli 20 sairaalasta keskittyen yliopistollisiin sairaaloihin ja keskussairaaloihin, joissa lasten röntgentutkimuksia tehdään eniten

Labour consumption models applied to motor-manual pre-commercial thinning in Finland.

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Effective radiation dose of a MSCT, two CBCT and one conventional radiography device in the ankle region

Peer reviewe

Comparative dosimetry of radiography device, MSCT device and two CBCT devices in the elbow region

The aim of the study was to estimate and to compare effective doses in the elbow region resulting from four different x-ray imaging modalities. Absorbed organ doses were measured using 11 metal oxide field effect transistor (MOSFET) dosimeters that were placed in a custom-made anthropomorphic elbow RANDO phantom. Examinations were performed using Shimadzu FH-21 HR radiography device, Siemens Sensation Open 24-slice MSCT-device, NewTom 5G CBCT device, and Planmed Verity CBCT device, and the effective doses were calculated according to ICRP 103 recommendations. The effective dose for the conventional radiographic device was 1.5 mu Sv. The effective dose for the NewTom 5G CBCT ranged between 2.0 and 6.7 mu Sv, for the Planmed Verity CBCT device 2.6 mu Sv and for the Siemens Sensation MSCT device 37.4 mu Sv. Compared with conventional 2D radiography, this study demonstrated a 1.4-4.6 fold increase in effective dose for CBCT and 25-fold dose for standard MSCT protocols. When compared with 3D CBCT protocols, the study showed a 6-19 fold increase in effective dose using a standard MSCT protocol. CBCT devices offer a feasible low-dose alternative for elbow 3D imaging when compared to MSCT.Peer reviewe

Dose monitoring in pediatric and young adult head and cervical spine CT studies at two emergency duty departments

PurposeAs the number of pediatric computed tomography (CT) imaging is increasing, there is a need for real-time radiation dose monitoring and evaluation of the imaging protocols. The aim of this study was to present the imaging data, patient doses, and observations of pediatric and young adult trauma—and routine head CT and cervical spine CT collected by a dose monitoring software.MethodsPatient age, study date, imaging parameters, and patient dose as volume CT dose index (CTDIvol) and dose length product (DLP) were collected from two emergency departments’ CT scanners for 2-year period. The patients were divided into four age groups (0–5, 6–10, 11–15, and 16–20 years) for statistical analysis and effective dose determination. The 75th percentile doses were evaluated to be used as local diagnostic reference levels (DRLs).ResultsSix hundred fifteen trauma head, 318 routine head, and 592 trauma cervical spine CT studies were assessed. All mean CTDIvol values were statistically lower in hospital B (40.3 ± 12.3, 30.03 ± 11.1, and 6.9 ± 3.1 mGy, respectively) than in hospital A (53.0 ± 12.9, 43.2 ± 8.7, and 18.3 ± 7.3 mGy, respectively). Statistically significant differences were observed on scanning length between hospitals and between CTDIvol values when protocol was updated. The 75th percentiles of trauma cervical spine in hospital B can be used as local DRL. Non-optimized protocols were also revealed in hospital A.ConclusionDose monitoring software offers a valuable tool for evaluating the imaging practices and finding non-optimized protocols.</div

Standardised spider (Arachnida, Araneae) inventory of Kilpisjarvi, Finland

Background A spider taxonomy and ecology field course was organised in Kilpisjarvi Biological Station, northern Finland, in July 2019. During the course, four 50 x 50 m plots in mountain birch forest habitat were sampled following a standardised protocol. In addition to teaching and learning about spider identification, behaviour, ecology and sampling, the main aim of the course was to collect comparable data from the Kilpisjarvi area as part of a global project, with the purpose of uncovering global spider diversity patterns. New information A total of 2613 spiders were collected, of which 892 (34%) were adults. Due to uncertainty of juvenile identification, only adults are included in the data presented in this paper. The observed adult spiders belong to 51 species, 40 genera and 11 families, of which the Linyphiidae were the most rich and abundant with 28 (55%) species and 461 (52%) individuals. Lycosidae had six species and 286 individuals, Gnaphosidae five species and 19 individuals, Thomisidae four species and 24 individuals, Theridiidae two species and 23 individuals. All other six families had one species and less than 40 individuals. The most abundant species were the linyphiid Agnyphantes expunctus (204) and the lycosids Pardosa eiseni (164) and Pardosa hyperborea (107).Peer reviewe

Characterization of MOSFET dosimeters for low-dose measurements in maxillofacial anthropomorphic phantoms

Peer reviewe

Bacteriophage Mu integration in yeast and mammalian genomes

Genomic parasites have evolved distinctive lifestyles to optimize replication in the context of the genomes they inhabit. Here, we introduced new DNA into eukaryotic cells using bacteriophage Mu DNA transposition complexes, termed ‘transpososomes’. Following electroporation of transpososomes and selection for marker gene expression, efficient integration was verified in yeast, mouse and human genomes. Although Mu has evolved in prokaryotes, strong biases were seen in the target site distributions in eukaryotic genomes, and these biases differed between yeast and mammals. In Saccharomyces cerevisiae transposons accumulated outside of genes, consistent with selection against gene disruption. In mouse and human cells, transposons accumulated within genes, which previous work suggests is a favorable location for efficient expression of selectable markers. Naturally occurring transposons and viruses in yeast and mammals show related, but more extreme, targeting biases, suggesting that they are responding to the same pressures. These data help clarify the constraints exerted by genome structure on genomic parasites, and illustrate the wide utility of the Mu transpososome technology for gene transfer in eukaryotic cells

Evaluation of Alpha-Therapy with Radium-223-Dichloride in Castration Resistant Metastatic Prostate Cancer—the Role of Gamma Scintigraphy in Dosimetry and Pharmacokinetics

Radium-223-dichloride (223RaCl2) is a new bone-seeking calcium analogue alpha-emitter, which has obtained marketing authorization for the treatment skeletal metastases of hormone-refractory prostate cancer. The current treatment regimen is based on six consecutive doses of 223RaCl2 at 4 week intervals and the administered activity dose, 50 kBq/kg per cycle is based on patient weight. We analyzed two patients using quantitative serial gamma imaging to estimate dosimetry in tumors and see possible pharmacokinetic differences in the treatment cycles. The lesions were rather well visualized in gamma scintigraphy in spite of low gamma activity (&lt;1.1% gamma radiation) at 0, 7 and 28 days using 30–60 min acquisition times. Both our patients analyzed in serial gamma imagings, had two lesions in the gamma imaging field, the mean counts of the relative intensity varied from 27.8 to 36.5 (patient 1), and from 37.4 to 82.2 (patient 2). The half-lives varied from 1.8 days to 4.5 days during the six cycles (patient 1), and from 1.5 days to 3.6 days (patient 2), respectively. In the lesion half-lives calculated from the imaging the maximum difference between the treatment cycles in the same lesion was 2.0-fold (1.8 vs. 3.6). Of these patients, patient 1 demonstrated a serum PSA response, whereas there was no PSA response in patient 2. From our data, there were maximally up to 4.0-fold differences (62.1 vs. 246.6 ) between the relative absorbed radiation doses between patients as calculated from the quantitative standardized imaging to be delivered in only two lesions, and in the same lesion the maximum difference in the cycles was up to 2.3-fold (107.4 vs. 246.6). Our recommendation based on statistical simulation analysis, is serial measurement at days 0–8 at least 3 times, this improve the accuracy significantly to study the lesion activities, half-lives or calculated relative absorbed radiation doses as calculated from the imaging. Both our patients had originally two metastatic sites in the imaging field; the former patient demonstrated a serum PSA response and the latter demonstrated no PSA response. In these two patients there was no significant difference in the lesion activities, half-lives or calculated relative absorbed radiation doses as calculated from the quantitative imaging. Our results, although preliminary, suggest that dose monitoring can be included as a part of this treatment modality. On the other hand, from the absorbed radiation doses, the response cannot be predicted because with very similar doses, only the former patient responded