Estimation of Radiation Dose and Image Quality in Pediatric and Young Adult Computed Tomography Studies

Computed tomography (CT) is currently the most important contributor to medical radiation exposure, and pediatric and young adult CT studies raise special concern. A young age and high cumulative effective doses due to repeated CT during follow-up increase the risk of detrimental effects of radiation. Thus, the radiation dose, image quality, and the effects of parameter changes to these two need to be estimated to optimize CT examinations. Thesis examines radiation doses as expressed by computed tomography dose index (CTDI), organ doses and effective doses among pediatric, adolescent and young adult patients. The influence of the CT scanner, patient size, and intravenous contrast agent were studied with regard to the radiation dose and image quality, and the effects of protocol parameter changes were studied to establish a more effective imaging protocol for the assessment of acute appendicitis. Radiation doses were evaluated by phantom measurements using dose monitoring software and dose calculation software. The image quality was evaluated by measuring the contrast to noise ratio and by visual assessment by radiologists. A wide deviation of CT doses was found, despite homogenous cohorts and similar imaging indications. The deviation resulted from differences in the CT devices and non-optimized protocols. High effective doses cumulated during the follow-up of patients with testicular cancer. In the assessment of acute appendicitis, the radiation dose may be reduced, without decreasing image quality, by appropriate protocol adjustments. The large variations in radiation doses and the high cumulative effective doses emphasize the need for setting parameters carefully and for harmonized practices. There is also a need for improved dose monitoring, which may uncover non-optimized protocols.Säteilyannoksen ja kuvan laadun arviointi lasten ja nuorten aikuisten tietokonetomografia tutkimuksissa Tietokonetomografia (TT) aiheuttaa nykyisin säteilyn lääketieteellisessä käytössä suurimman osan altistuksesta. Lasten ja nuorten TT-tutkimukset sekä seurannasta johtuvat toistuvat TT-tutkimukset ovat nousseet huolen aiheeksi, koska nuori ikä ja korkea kumulatiivinen efektiivinen annos ovat yhteydessä säteilyn haitallisiin vaikutuksiin. TT-tutkimusten optimoimiseksi säteilyannoksen suuruutta, kuvan laatua ja kuvausparametrien vaikutusta näihin pitää pystyä arvioimaan. Tässä tutkimuksessa arvioitiin vastasyntyneen keuhkojen, lasten ja nuorten aikuisten pään ja kaularangan sekä kivessyövän seurannan aikana tehtyjen TT-tutkimusten säteilyannoksia. Käytettävän TT-laitteen, potilaan koon ja varjoaineen vaikutusta säteilyannokseen arvioitiin ja kuvausparametrien vaikutusta kuvan laatuun ja säteilyannokseen arvioitiin tehokkaamman protokollan löytämiseksi akuuttiin appendisiittiin. Säteilyannoksia arvioitiin fantomimittauksilla sekä annosseuranta- ja laskentaohjelmalla. Kuvan laatua arvioitiin mittaamalla kontrasti-kohina suhdetta sekä visuaalisella arviolla. Tutkimuksessa paljastui suurta vaihtelua säteilyannoksissa huolimatta yhtenäisestä kohotista ja indikaatiosta. Vaihtelu johtui erilaisista laitteista sekä epäoptimaalisista protokollista. Lisäksi havaittiin korkeita kumulatiivisia annoksia kivessyövän seurannassa. Akuutin appendisiitin tutkimisessa säteilyannosta voidaan alentaa kuvan laadun kärsimättä sopivalla parametrien muutoksella. Annosten suuri vaihtelu ja korkeat kumulatiiviset annokset osoittavat tarvetta protokollien säätämiselle sekä yhtenäistämiselle. Myös annoksien seurannalle on tarve, jotta mahdolliset epäoptimaaliset kuvausprotokollat saadaan havaittua ja korjattua

Cancer Death Risk Related to Radiation Exposure from Computed Tomography Scanning Among Testicular Cancer Patients

Kivessyöpäpotilaiden tietokonekuvantamisen säteilyvaaraa voidaan vähentää tarkentamalla kuvantamiskäytäntöä ja uusimalla seurantasuosituksia. Tietokonekuvantamisen säteilyn aiheuttama syöpäkuoleman vaara oli suhteessa potilaan ikään: mitä nuorempi potilas sitä suurempi vaara oli. Nykyisellä kuvantamisella, mikä tarkoittaa 6-8 vatsan alueen tietokonekuvausta kuuden vuoden seuranta-aikana, vaara on kuitenkin kirjallisuuteen verrattaessa pienempi kuin aikaisempien seurantaohjelmien tiheämpään kuvantamiseen ja enemmän säteilyaltistusta aiheuttaneisiin laitteisiin nähden. Käytettäessä kansainvälisesti kehitettyä laskennallista UNSCEAR mallia arvioimme kuvantamissäteilyn lisäävän 2% säteilyn aiheuttaman syöpäkuoleman vaaraa. Nuorten kivessyöpäpotilaiden seurantaan hoitojen jälkeen on kuulunut paljon tietokonekuvauksia. Tietokonekuvantamiseen liittyvän säteilyaltistuksen tiedetään lisäävän syöpävaaraa etenkin lapsilla ja nuorilla. Tämän tietoisuuden myötä kivessyöpäpotilaiden tiheitä kuvantamisia on vähennetty. Selvitimme laskennallisesti minkälainen syöpäkuoleman vaara liittyy nykyisen käytännön mukaiseen kuvantamiseen. Tulokset osoittivat eri kuvantamislaitteisiin liittyvän eri suuruisen säteilyaltistuksen. Potilaat oli hoidettu ja kuvattu Varsinais-Suomen sairaanhoitopiirissä

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

Radiation-induced accelerated aging of the brain vasculature in young adult survivors of childhood brain tumors

Background. Cranial radiotherapy may damage the cerebral vasculature. The aim of this study was to understand the prevalence and risk factors of cerebrovascular disease (CVD) and white matter hyperintensities (WMHs) in childhood brain tumors (CBT) survivors treated with radiotherapy. Methods. Seventy CBT survivors who received radiotherapy were enrolled in a cross-sectional study at a median 20 years after radiotherapy cessation. The prevalence of and risk factors for CVD were investigated using MRI, MRA, and laboratory testing. Tumors, their treatment, and stroke-related data were retrieved from patients' files. Results. Forty-four individuals (63%) had CVD at a median age of 27 years (range, 16-43 years). The prevalence rates at 20 years for CVD, small-vessel disease, and large-vessel disease were 52%, 38%, and 16%, respectively. Ischemic infarcts were diagnosed in 6 survivors, and cerebral hemorrhage in 2. Lacunar infarcts were present in 7, periventricular or deep WMHs in 34 (49%), and mineralizing microangiopathy in 21 (30%) survivors. Multiple pathologies were detected in 44% of the participants, and most lesions were located in a high-dose radiation area. Higher blood pressure was associated with CVD and a presence of WMHs. Higher cholesterol levels increased the risk of ischemic infarcts and WMHs, and lower levels of high-density lipoprotein and higher waist circumference increased the risk of lacunar infarcts. Conclusions. Treating CBTs with radiotherapy increases the risk of early CVD and WMHs in young adult survivors. These results suggest an urgent need for investigating CVD prevention in CBT patients.Peer reviewe

Radiation-induced accelerated aging of the brain vasculature in young adult survivors of childhood brain tumors

Abstract Background: Cranial radiotherapy may damage the cerebral vasculature. The aim of this study was to understand the prevalence and risk factors of cerebrovascular disease (CVD) and white matter hyperintensities (WMHs) in childhood brain tumors (CBT) survivors treated with radiotherapy. Methods: Seventy CBT survivors who received radiotherapy were enrolled in a cross-sectional study at a median 20 years after radiotherapy cessation. The prevalence of and risk factors for CVD were investigated using MRI, MRA, and laboratory testing. Tumors, their treatment, and stroke-related data were retrieved from patients’ files. Results: Forty-four individuals (63%) had CVD at a median age of 27 years (range, 16–43 years). The prevalence rates at 20 years for CVD, small-vessel disease, and large-vessel disease were 52%, 38%, and 16%, respectively. Ischemic infarcts were diagnosed in 6 survivors, and cerebral hemorrhage in 2. Lacunar infarcts were present in 7, periventricular or deep WMHs in 34 (49%), and mineralizing microangiopathy in 21 (30%) survivors. Multiple pathologies were detected in 44% of the participants, and most lesions were located in a high-dose radiation area. Higher blood pressure was associated with CVD and a presence of WMHs. Higher cholesterol levels increased the risk of ischemic infarcts and WMHs, and lower levels of high-density lipoprotein and higher waist circumference increased the risk of lacunar infarcts. Conclusions: Treating CBTs with radiotherapy increases the risk of early CVD and WMHs in young adult survivors. These results suggest an urgent need for investigating CVD prevention in CBT patients