Optimization of CT procedures in two radiology departments

Autor: M. Al-Amin, V. Stoinova, I. Dyakov, V. Groudeva, Jenia Vassileva, V. Hadjidekov
Rok vydání: 2014
Předmět:
Zdroj: Physica Medica. 30:e17
ISSN: 1120-1797
DOI: 10.1016/j.ejmp.2014.07.063
Popis: s / Physica Medica 30 (2014) e16ee44 e17 [4] Eller, Achim, et al. “Attenuation-based automatic kilovolt selection in abdominal computed tomography: effects on radiation exposure and image quality.”Investigative radiology 47.10 (2012): 559-565. OPTIMIZATION OF CT PROCEDURES IN TWO RADIOLOGY DEPARTMENTS I. Dyakov , M. Alamin , V. Groudeva , J. Vassileva , V. Stoinova , V. Hadjidekov . National Centre of Radiobiology and Radiation Protection, Bulgaria; b “Aleksandrovska” University Hospital, Sofia, Bulgaria; c “St. Ekaterina” University Hospital, Sofia, Bulgaria Technical advances allowed utilization of computed tomography (CT) modality in differentmedical applications. With the increase in complexity of CT scanners staff education, proper CT adjustment and optimization of CT procedures are becoming of higher importance. The purpose of this study was to improve the practice in two radiology departments through implementation of optimized CT protocols. Image quality and patient dose in CT urography (CTU) and cardiac CT were compared when replacing the standard protocol with low-kV protocols. Our study was performed with a 64-row detector and a 320-row detector CT systems, both of Toshiba medical systems. Three groups of patients examined with different kV in urography phase standard 120; 100 and 80 kV protocols were included in the study. CTDIvol and DLP were recorded and effective dose was calculated using CT Expo 2.1 software. Image noise, signal to noise ratio (SNR), contrast to noise ratio (CNR) and figure of merit (FOM) were estimated based on measurements in clinical and phantom images. Image quality in phantom showed more than 50% reduction of SNR, CNR and FOM when using 80 kV CTU protocol. Clinical image quality of low-kV patient images was clinically acceptable. Higher than 47 % reduction of patient CTDIvol when using 100 kV andmore than 60 % when using 80 kV CTU protocol was achieved. Effective dose was reduced by more than 60 % with introduction of 80 kV CTU protocol. Cardiac CT is routinely acquired with retrospective ECG-gating which leads to increased patient dose, since data is acquired at the entire cardiac cycle, and not all data is used for post-processing or reconstruction. For selected patients prospective ECG-gating was applied. Further implementationwas made of low-kV cardiac protocol into practice. More than 56% reduction of DLP was achieved with the implementation of prospective cardiac protocol. The preliminary results indicated significant dose reduction when using low-kV cardiac protocol by keeping the adequate diagnostic quality of clinical images. EDGE-ENHANCING DIFFUSION NOISE REDUCTION IN DUAL-ENERGY CT Georgios Vlachopoulos, Spyros Skiadopoulos, Andreas Petropoulos, Anna Karahaliou, Lena Costaridou. Department of Medical Physics, School of Medicine, University of Patras, Patras, Greece Background: Dual-Energy Computed Tomography (DECT) is an evolving field in radiology. DECT offers material decomposition by exploiting spectral information of low and high kV energies. Furthermore, DECT allows for increased identification of iodinated structures and improved differentiation from other high-density substances (e.g. calcium). This study investigates the effect of an Edge-Enhancing Diffusion (EED) noise reduction method on the quality of DECT images, derived by varying the weighting factor (w) of the two spectra (w1⁄40.1 up to 0.9, in 0.1 step). Materials and methods: A material equivalent head CT phantom (Mini CT QC phantom, Gammex) was scanned with a Dual-Source CT system (Somatom Definition, Siemens) in dual-energy mode. Dual-energy headangio analysis incorporated in the CT system was performed, using a clinical image acquisition protocol (80kV/213mAs and 140kV/50mAs). An EED parameter selection procedure was considered by means of quantitative image quality evaluation and qualitative assessment of edge preservation of the 80 kV images. The EED algorithm incorporating the selected parameters is then used to reduce noise toweighted images of thematerial equivalent CT phantom. The quality of EED-filtered weighted images was quantitatively assessed by means of Contrast, Signal-to-Noise Ratio (SNR) and Contrast-to-Noise Ratio (CNR) measured on regions of interest of phantom images corresponding to 14 mg/ml iodine concentration and bone equivalent material. The quality of EED-filtered weighted images was also compared to the quality of median-filtered weighted images. Results: EED filtering improved significantly the quality of DECT weighted images, performing better as compared to median filtering. Using original DECT weighted images as a reference, the average image quality improvement of the filtered weighted images was: SNR1⁄460.1% and CNR1⁄482.4% for EED filtering and SNR1⁄415.3% and CNR1⁄418.7% for median filtering. Discussion: Results demonstrate that EED improved significantly the quality of DECT weighted images, suggesting the method potential in establishing low-dose image acquisition protocols. 5 YEARS CONTINUOUS PATIENT DOSE SURVEY IN INTERVENTIONAL CARDIOLOGY: LESSONS LEARNED AND FUTURE POTENTIAL O. Dragusin , N. Oumohand , P. Frambach , D. Wagner , J. Beissel . a F ed eration des Hopitaux Luxembourgeois, Luxembourg; b INCCI, Haerz Zenter, Luxembourg INCCI is the Luxembourgish national institute for cardiac surgery and interventional cardiology. It has 2 catheterization laboratories equipped with X-ray flat panel detectors. About 10 interventional cardiologists are performing diagnostic and therapeutic procedures (including electrophysiology interventions). The number of interventions is around 3000 per year. All patient doses are registered in the medical file. The purpose of the work is to present the evolution of patient doses in last five years. Yearly reports are generated and discussed with the medical staff in order to assess current practice in our center. The interventional cardiology procedures are performed in adults. We distinguish 3 categories of procedures: diagnostic (coronary angiography), therapeutic (percutaneous coronary interventions) and electrophysiology studies. Following information is available for each patient: radiation dose (total air kerma-area product KAP, fluoroscopy time, dose at interventional reference point, number of cine acquisitions); personal data (age, body mass index); procedural details (intervention, number of segments or stent dilated/implanted, type of access to the lesion, cardiologist that performed the intervention). Our analysis is focused on two directions. Firstly, determination of local reference dose levels for each group of procedures (considering the 75% percentile of dose and fluoroscopy time) and identification of potentially patients overexposed to radiation (cumulative dose for 3 months that exceed 20000 Gycm). Secondly, analyze of patient doses per cardiologist and how they report to the local reference dose levels. In this way, we are able to identify eventually deviations and find the corrective solutions. For example, table 1 shows the yearly variation of local reference values for diagnostic procedures (CA) and therapeutic (PCI) in terms of KAP and fluoroscopy time. Procedure Reference values year year year year year 2009 201
Databáze: OpenAIRE
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