Establishing national clinical diagnostic reference levels and achievable doses for CT examinations in Brazil: A prospective study.

PURPOSE: Diagnostic reference levels (DRL) and achievable doses (AD) are important tools for radiation dose optimization. Therefore, a prospective study was performed which aimed to establish a multi-parametric, clinical indication based - DRL(DRLCI) and clinical indication - AD (ADCI) for adult CT in Brazil. METHODS: The prospective study included 4787 patients (50 ± 18 years old; male:female 2041:2746) at 13 Brazilian sites that have been submitted to head, paranasal sinus, cervical spine, chest, or abdomen-pelvis CT between January and October 2021 for 13 clinical indications. The sites provided the following information: patient age, gender, weight, height, body mass index[BMI], clinical indications, scanner information(vendor, model, detector configuration), scan parameters (number of scan phases, kV, mA, pitch) and dose-related quantities (CT dose index volume- CTDIvol, dose length product- DLP). Median(AD) and 75th(DRL) percentile CTDIvol and DLP values were estimated for each body region and clinical indications. Non-normal data were analyzed with the Kruskal-Wallis test. RESULTS: In majority of Brazilian sites, body region and clinical indications based DRLs were at or lower than the corresponding DRLs in the US and higher than Europe. Although radiation doses varied significantly for patients in different body mass index groups (p < 0.001), within each body region, there were no differences in radiation doses for different clinical indications (p > 0.1). Radiation doses for 7/13 clinical indications were higher using iterative reconstruction technique than for the filtered back projection. CONCLUSIONS: There was substantial variation in Brazil DRLCI across different institutions with higher doses compared to the European standards. There was also a lack of clinical indication-based protocol and dose optimization based on different clinical indications for the same body region.

Influence of partial k-space filling on the quality of magnetic resonance images.

OBJECTIVE: To study the influence that the scan percentage tool used in partial k-space acquisition has on the quality of images obtained with magnetic resonance imaging equipment. MATERIALS AND METHODS: A Philips 1.5 T magnetic resonance imaging scanner was used in order to obtain phantom images for quality control tests and images of the knee of an adult male. RESULTS: There were no significant variations in the uniformity and signal-to-noise ratios with the phantom images. However, analysis of the high-contrast spatial resolution revealed significant degradation when scan percentages of 70% and 85% were used in the acquisition of T1- and T2-weighted images, respectively. There was significant degradation when a scan percentage of 25% was used in T1- and T2-weighted in vivo images (p ≤ 0.01 for both). CONCLUSION: The use of tools that limit the k-space is not recommended without knowledge of their effect on image quality.

OBJETIVO: Estudar a influência da ferramenta scan percentage, usada para a aquisição parcial do espaço K na qualidade de imagens obtidas por ressonância magnética. MATERIAIS E MÉTODOS: Foi usado um equipamento de ressonância magnética Philips de 1,5 T para obter imagens de um objeto simulador e imagens in vivo do joelho de um adulto do sexo masculino. RESULTADOS: Com o objeto simulador, não ocorreram variações significativas quanto à avaliação da uniformidade e razão sinal-ruído. Entretanto, na análise da resolução espacial de alto contraste, houve significativa degradação nas imagens quando adotada a scan percentage a 70% e 85% em T1 e T2, respectivamente. Nas imagens in vivo comprovou-se a degradação somente quando adotada a scan percentage a 25% (p ≤ 0,01) em T1 e T2. CONCLUSÃO: Não é aconselhável adotar ferramentas que limitem o espaço K sem que haja conhecimento sobre sua influência na qualidade da imagem clinicamente gerada.

Determination of dosimetric quantities in pediatric abdominal computed tomography scans.

OBJECTIVE: Aiming at contributing to the knowledge on doses in computed tomography (CT), this study has the objective of determining dosimetric quantities associated with pediatric abdominal CT scans, comparing the data with diagnostic reference levels (DRL). MATERIALS AND METHODS: The study was developed with a Toshiba Asteion single-slice CT scanner and a GE BrightSpeed multi-slice CT unit in two hospitals. Measurements were performed with a pencil-type ionization chamber and a 16 cm-diameter polymethylmethacrylate trunk phantom. RESULTS: No significant difference was observed in the values for weighted air kerma index (CW), but the differences were relevant in values for volumetric air kerma index (CVOL), air kerma-length product (PKL,CT) and effective dose. CONCLUSION: Only the CW values were lower than the DRL, suggesting that dose optimization might not be necessary. However, PKL,CT and effective dose values stressed that there still is room for reducing pediatric radiation doses. The present study emphasizes the importance of determining all dosimetric quantities associated with CT scans.

OBJETIVO: Visando contribuir para o conhecimento das doses em tomografia computadorizada (TC), este trabalho teve o objetivo de quantificar grandezas dosimétricas associadas a exames do abdome em pacientes pediátricos, comparando-as com os níveis de referência em radiodiagnóstico (NRD). MATERIAIS E MÉTODOS: O estudo foi realizado em dois hospitais, em um tomógrafo Toshiba Asteion single-slice e um GE BrightSpeed multi-slice. Medidas foram feitas com uma câmara de ionização tipo lápis e um objeto simulador de tronco de polimetilmetacrilato de 16 cm de diâmetro. RESULTADOS: Os valores do índice ponderado de kerma no ar (CW) não apresentaram diferenças significativas, porém, para as grandezas índice de kerma no ar volumétrico (CVOL), produto kerma-comprimento (PKL,CT) e dose efetiva, as diferenças foram relevantes. CONCLUSÃO: Apenas o CW apresentou valores menores que os NRD, sugerindo que a otimização não seria necessária. Porém, os valores de PKL,CT e dose efetiva mostraram que há espaço para reduzir as doses de radiação pediátricas. Este trabalho ressalta a importância de avaliar todas as grandezas dosimétricas associadas aos exames por TC.

Influence of partial k-space filling on the quality of magnetic resonance images / Influência do preenchimento parcial do espaço K na qualidade da imagem de ressonância magnética

Abstract Objective: To study the influence that the scan percentage tool used in partial k-space acquisition has on the quality of images obtained with magnetic resonance imaging equipment. Materials and Methods: A Philips 1.5 T magnetic resonance imaging scanner was used in order to obtain phantom images for quality control tests and images of the knee of an adult male. Results: There were no significant variations in the uniformity and signal-to-noise ratios with the phantom images. However, analysis of the high-contrast spatial resolution revealed significant degradation when scan percentages of 70% and 85% were used in the acquisition of T1- and T2-weighted images, respectively. There was significant degradation when a scan percentage of 25% was used in T1- and T2-weighted in vivo images (p ≤ 0.01 for both). Conclusion: The use of tools that limit the k-space is not recommended without knowledge of their effect on image quality.

Resumo Objetivo: Estudar a influência da ferramenta scan percentage, usada para a aquisição parcial do espaço K na qualidade de imagens obtidas por ressonância magnética. Materiais e Métodos: Foi usado um equipamento de ressonância magnética Philips de 1,5 T para obter imagens de um objeto simulador e imagens in vivo do joelho de um adulto do sexo masculino. Resultados: Com o objeto simulador, não ocorreram variações significativas quanto à avaliação da uniformidade e razão sinal-ruído. Entretanto, na análise da resolução espacial de alto contraste, houve significativa degradação nas imagens quando adotada a scan percentage a 70% e 85% em T1 e T2, respectivamente. Nas imagens in vivo comprovou-se a degradação somente quando adotada a scan percentage a 25% (p ≤ 0,01) em T1 e T2. Conclusão: Não é aconselhável adotar ferramentas que limitem o espaço K sem que haja conhecimento sobre sua influência na qualidade da imagem clinicamente gerada.

Quantificação das grandezas dosimétricas em exames de tomografia computadorizada pediátricos do abdome / Determination of dosimetric quantities in pediatric abdominal computed tomography scans

Objetivo: Visando contribuir para o conhecimento das doses em tomografia computadorizada (TC), este trabalho teve o objetivo de quantificar grandezas dosimétricas associadas a exames do abdome em pacientes pediátricos, comparando-as com os níveis de referência em radiodiagnóstico (NRD). Materiais e métodos: O estudo foi realizado em dois hospitais, em um tomógrafo Toshiba Asteion single-slice e um GE BrightSpeed multi-slice. Medidas foram feitas com uma câmara de ionização tipo lápis e um objeto simulador de tronco de polimetilmetacrilato de 16 cm de diâmetro. Resultados: Os valores do índice ponderado de kerma no ar (CW) não apresentaram diferenças significativas, porém, para as grandezas índice de kerma no ar volumétrico (CVOL), produto kerma-comprimento (PKL,CT) e dose efetiva, as diferenças foram relevantes. Conclusão: Apenas o CW apresentou valores menores que os NRD, sugerindo que a otimização não seria necessária. Porém, os valores de PKL,CT e dose efetiva mostraram que há espaço para reduzir as doses de radiação pediátricas. Este trabalho ressalta a importância de avaliar todas as grandezas dosimétricas associadas aos exames por TC. .

Objective: Aiming at contributing to the knowledge on doses in computed tomography (CT), this study has the objective of determining dosimetric quantities associated with pediatric abdominal CT scans, comparing the data with diagnostic reference levels (DRL). Materials and methods: The study was developed with a Toshiba Asteion single-slice CT scanner and a GE BrightSpeed multi-slice CT unit in two hospitals. Measurements were performed with a pencil-type ionization chamber and a 16 cm-diameter polymethylmethacrylate trunk phantom. Results: No significant difference was observed in the values for weighted air kerma index (CW), but the differences were relevant in values for volumetric air kerma index (CVOL), air kerma-length product (PKL,CT) and effective dose. Conclusion: Only the CW values were lower than the DRL, suggesting that dose optimization might not be necessary. However, PKL,CT and effective dose values stressed that there still is room for reducing pediatric radiation doses. The present study emphasizes the importance of determining all dosimetric quantities associated with CT scans. .