RESUMO
In the context of the increasing spread of cardiac active implantable heart devices (CIEDs) in the population and of the wide diagnostic/therapeutic utility of magnetic resonance (MRI) examinations, the goal of this paper is to provide the experience of the Santa Maria Nuova Hospital of the USL Tuscany Center in Florence and to report an organizational proposal to perform, in the hospital settings, MRI examinations on patients carrying CIED. This report is intended to show the operational choices of a Radiology Department which organizes this activity in accordance with the new Italian regulatory framework in the field of safety of MR sites (Ministero della Salute in Decreto Ministeriale 10 agosto 2018 Determinazione degli standard di sicurezza e impiego per le apparecchiature a risonanza magnetica, 2018).
Assuntos
Abdome , Desfibriladores Implantáveis , Eletrodos Implantados , Imageamento por Ressonância Magnética/métodos , Marca-Passo Artificial , Abdome/diagnóstico por imagem , Adulto , Idoso , Idoso de 80 Anos ou mais , Articulação do Tornozelo/diagnóstico por imagem , Encéfalo/diagnóstico por imagem , Segurança de Equipamentos , Europa (Continente) , Humanos , Consentimento Livre e Esclarecido , Itália , Legislação Médica , Imageamento por Ressonância Magnética/estatística & dados numéricos , Pessoa de Meia-Idade , Modelos Organizacionais , Pelve/diagnóstico por imagem , Medição de Risco , Coluna Vertebral/diagnóstico por imagem , Coxa da Perna/diagnóstico por imagemRESUMO
PURPOSE: To propose a magnetic resonance imaging (MRI) quality assurance procedure that can be used for multicenter comparison of different MR scanners for quantitative diffusion-weighted imaging (DWI). MATERIALS AND METHODS: Twenty-six centers (35 MR scanners with field strengths: 1T, 1.5T, and 3T) were enrolled in the study. Two different DWI acquisition series (b-value ranges 0-1000 and 0-3000 s/mm(2) , respectively) were performed for each MR scanner. All DWI acquisitions were performed by using a cylindrical doped water phantom. Mean apparent diffusion coefficient (ADC) values as well as ADC values along each of the three main orthogonal directions of the diffusion gradients (x, y, and z) were calculated. Short-term repeatability of ADC measurement was evaluated for 26 MR scanners. RESULTS: A good agreement was found between the nominal and measured mean ADC over all the centers. More than 80% of mean ADC measurements were within 5% from the nominal value, and the highest deviation and overall standard deviation were 9.3% and 3.5%, respectively. Short-term repeatability of ADC measurement was found <2.5% for all MR scanners. CONCLUSION: A specific and widely accepted protocol for quality controls in DWI is still lacking. The DWI quality assurance protocol proposed in this study can be applied in order to assess the reliability of DWI-derived indices before tackling single- as well as multicenter studies.
Assuntos
Imagem de Difusão por Ressonância Magnética/instrumentação , Imagem de Difusão por Ressonância Magnética/normas , Interpretação de Imagem Assistida por Computador/instrumentação , Interpretação de Imagem Assistida por Computador/normas , Garantia da Qualidade dos Cuidados de Saúde/normas , Imagem de Difusão por Ressonância Magnética/métodos , Desenho de Equipamento , Análise de Falha de Equipamento , Interpretação de Imagem Assistida por Computador/métodos , Itália , Imagens de Fantasmas , Garantia da Qualidade dos Cuidados de Saúde/métodos , Reprodutibilidade dos Testes , Sensibilidade e EspecificidadeRESUMO
PURPOSE: The purpose of this multicenter phantom study was to exploit an innovative approach, based on an extensive acquisition protocol and unsupervised clustering analysis, in order to assess any potential bias in apparent diffusion coefficient (ADC) estimation due to different scanner characteristics. Moreover, we aimed at assessing, for the first time, any effect of acquisition plan/phase encoding direction on ADC estimation. METHODS: Water phantom acquisitions were carried out on 39 scanners. DWI acquisitions (b-value = 0-200-400-600-800-1000 s/mm2) with different acquisition plans (axial, coronal, sagittal) and phase encoding directions (anterior/posterior and right/left, for the axial acquisition plan), for 3 orthogonal diffusion weighting gradient directions, were performed. For each acquisition setup, ADC values were measured in-center and off-center (6 different positions), resulting in an entire dataset of 84 × 39 = 3276 ADC values. Spatial uniformity of ADC maps was assessed by means of the percentage difference between off-center and in-center ADC values (Δ). RESULTS: No significant dependence of in-center ADC values on acquisition plan/phase encoding direction was found. Ward unsupervised clustering analysis showed 3 distinct clusters of scanners and an association between Δ-values and manufacturer/model, whereas no association between Δ-values and maximum gradient strength, slew rate or static magnetic field strength was revealed. Several acquisition setups showed significant differences among groups, indicating the introduction of different biases in ADC estimation. CONCLUSIONS: Unsupervised clustering analysis of DWI data, obtained from several scanners using an extensive acquisition protocol, allows to reveal an association between measured ADC values and manufacturer/model of scanner, as well as to identify suboptimal DWI acquisition setups for accurate ADC estimation.
Assuntos
Imagem de Difusão por Ressonância Magnética , Análise por Conglomerados , Difusão , Imagens de Fantasmas , Reprodutibilidade dos TestesRESUMO
The aim of the work relies on the adjustment of scanning parameters, kV and mAs, in multislice computed tomography (MSCT) to reduce paediatric patient dose whilst keeping the same reference image quality. Only abdomen examinations are employed in this study. The measurement of noise in a region of interest (ROI) inside the liver in a reference adult man has been chosen as an image quality parameter. Paediatric patients are categorised according to the width and thickness of abdomen trunk. A relationship between patient size, image quality and dose reduction has been obtained. The study has been performed at the Meyer Children Hospital (1300 CT paediatric patient/year).
Assuntos
Tomografia Computadorizada por Raios X/métodos , Fenômenos Biofísicos , Biofísica , Tamanho Corporal , Criança , Humanos , Imagens de Fantasmas , Controle de Qualidade , Doses de Radiação , Interpretação de Imagem Radiográfica Assistida por Computador/normas , Radiografia Abdominal/métodos , Radiografia Abdominal/normas , Tomografia Computadorizada por Raios X/normasRESUMO
PURPOSE: To propose an MRI quality assurance procedure that can be used for routine controls and multi-centre comparison of different MR-scanners for quantitative diffusion-weighted imaging (DWI). MATERIALS AND METHODS: 44 MR-scanners with different field strengths (1â¯T, 1.5â¯T and 3â¯T) were included in the study. DWI acquisitions (b-value range 0-1000â¯s/mm2), with three different orthogonal diffusion gradient directions, were performed for each MR-scanner. All DWI acquisitions were performed by using a standard spherical plastic doped water phantom. Phantom solution ADC value and its dependence with temperature was measured using a DOSY sequence on a 600â¯MHz NMR spectrometer. Apparent diffusion coefficient (ADC) along each diffusion gradient direction and mean ADC were estimated, both at magnet isocentre and in six different position 50â¯mm away from isocentre, along positive and negative AP, RL and HF directions. RESULTS: A good agreement was found between the nominal and measured mean ADC at isocentre: more than 90% of mean ADC measurements were within 5% from the nominal value, and the highest deviation was 11.3%. Away from isocentre, the effect of the diffusion gradient direction on ADC estimation was larger than 5% in 47% of included scanners and a spatial non uniformity larger than 5% was reported in 13% of centres. CONCLUSION: ADC accuracy and spatial uniformity can vary appreciably depending on MR scanner model, sequence implementation (i.e. gradient diffusion direction) and hardware characteristics. The DWI quality assurance protocol proposed in this study can be employed in order to assess the accuracy and spatial uniformity of estimated ADC values, in single- as well as multi-centre studies.
Assuntos
Imagem de Difusão por Ressonância Magnética/instrumentação , Difusão , Imagens de Fantasmas , Controle de QualidadeRESUMO
The aim of this study was to assess the patient dosimetric impact of endovascular abdominal aortic aneurysm repair (EVAR), both in an operating theatre (OR) and in an angiosuite (AS), with the facility of Dynamic CT (Dyna CT, Siemens AG, Berlin, Germany). One hundred and forty-six consecutive EVAR procedures dating from May 2011 to March 2013 were analysed. These were performed either in an OR (n = 97) using a mobile C-arm or in an AS (n = 49) equipped with a ceiling-mounted angiography system. Air kerma area product (P(KA)) and total air kerma at reference point (K(a,r)) values were reported for all procedures and Dyna CT. Radiation exposure during EVAR was quite low in the majority of patients but nearly 50 % higher if performed in AS vs. OR. Median Dyna CT K(a,r) was the same as an entire EVAR procedure in OR. The higher patient's radiation exposure recorded in the AS should be balanced with the technical advantages given to the EVAR procedure.