A CT deep learning reconstruction algorithm: Image quality evaluation for brain protocol at decreasing dose indexes in comparison with FBP and statistical iterative reconstruction algorithms.

PURPOSE: To characterise the impact of Precise Image (PI) deep learning reconstruction algorithm on image quality, compared to filtered back-projection (FBP) and iDose4 iterative reconstruction for brain computed tomography (CT) phantom images. METHODS: Catphan-600 phantom was acquired with an Incisive CT scanner using a dedicated brain protocol, at six different dose levels (volume computed tomography dose index (CTDIvol): 7/14/29/49/56/67 mGy). Images were reconstructed using FBP, levels 2/5 of iDose4, and PI algorithm (Sharper/Sharp/Standard/Smooth/Smoother). Image quality was assessed by evaluating CT numbers, image histograms, noise, image non-uniformity (NU), noise power spectrum, target transfer function, and detectability index. RESULTS: The five PI levels did not significantly affect the mean CT number. For a given CTDIvol using Sharper-to-Smoother levels, the spatial resolution for all the investigated materials and the detectability index increased while the noise magnitude decreased, slightly affecting noise texture. For a fixed PI level increasing the CTDIvol the detectability index increased, the noise magnitude decreased. From 29 mGy, NU values converged within 1 Hounsfield Unit from each other without a substantial improvement at higher CTDIvol values. CONCLUSIONS: The improved performances of intermediate PI levels in brain protocols compared to conventional algorithms seem to suggest a potential reduction of CTDIvol.

"Image quality evaluation of the Precise image CT deep learning reconstruction algorithm compared to Filtered Back-projection and iDose4: a phantom study at different dose levels".

PURPOSE: To characterize the performance of the Precise Image (PI) deep learning reconstruction (DLR) algorithm for abdominal Computed Tomography (CT) imaging. METHODS: CT images of the Catphan-600 phantom (equipped with an external annulus) were acquired using an abdominal protocol at four dose levels and reconstructed using FBP, iDose4 (levels 2,5) and PI ('Soft Tissue' definition, levels 'Sharper','Sharp','Standard','Smooth','Smoother'). Image noise, image non-uniformity, noise power spectrum (NPS), target transfer function (TTF), detectability index (d'), CT numbers accuracy and image histograms were analyzed. RESULTS: The behavior of the PI algorithm depended strongly on the selected level of reconstruction. The phantom analysis suggested that the PI image noise decreased linearly by varying the level of reconstruction from Sharper to Smoother, expressing a noise reduction up to 80% with respect to FBP. Additionally, the non-uniformity decreased, the histograms became narrower, and d' values increased as PI reconstruction levels changed from Sharper to Smoother. PI had no significant impact on the average CT number of different contrast objects. The conventional FBP NPS was deeply altered only by Smooth and Smoother levels of reconstruction. Furthermore, spatial resolution was found to be dose- and contrast-dependent, but in each analyzed condition it was greater than or comparable to FBP and iDose4 TTFs. CONCLUSIONS: The PI algorithm can reduce image noise with respect to FBP and iDose4; spatial resolution, CT numbers and image uniformity are generally preserved by the algorithm but changes in NPS for the Smooth and Smoother levels need to be considered in protocols implementation.

X-ray population exposure from projection radiology and computed tomography in Emilia-Romagna from 2001 to 2010: comparison of ICRP 60 and ICRP 103 weighting factors.

PURPOSE: This paper shows the trends from 2001 to 2010 of per caput and collective effective dose (S) to the Emilia-Romagna population due to radiation exposure from projection radiology (PR) and computed tomography (CT), calculated according to both ICRP60 and ICRP103 tissue weighting factors. MATERIALS AND METHODS: The frequency of examinations and dose calculations were based on data provided directly by Emilia-Romagna Health Trusts. In particular, effective doses were evaluated using the tissue weighting (w T) factors reported both in ICRP60 (w T,60) and in ICRP103 (w T,103). RESULTS: A decrease in the frequency of PR skull examinations and an increase in the frequency of mammography, CT of the abdomen, chest, and head-neck were found during the decade. In 2010, the PR/CT procedures contributed 75.4 %/24.6 % to examination frequency and approximately 10 %/90 % to dose; S was 6,169.2 man Sv when w T,60 was used and 5,855.1-6,665.5 man Sv when w T,103 in two different mathematical models was utilised. CONCLUSIONS: Dose estimates pre- and post-ICRP103 must be compared carefully, because changes due to different radiological practices could be confused with changes due to the use of different w T's. In general, dose evaluations with the use of w T,60 until 2007 and w T,103 from 2008 seem to be consistent and coherent.

Calculation of conversion factors for effective dose for various interventional radiology procedures.

PURPOSE: To provide dose-area-product (DAP) to effective dose (E) conversion factors for complete interventional procedures, based on in-the-field clinical measurements of DAP values and using tabulated E/DAP conversion factors for single projections available from the literature. METHODS: Nine types of interventional procedures were performed on 84 patients with two angiographic systems. Different calibration curves (with and without patient table attenuation) were calculated for each DAP meter. Clinical and dosimetric parameters were recorded in-the-field for each projection and for all patients, and a conversion factor linking DAP and effective doses was derived for each complete procedure making use of published, Monte Carlo calculated conversion factors for single static projections. RESULTS: Fluoroscopy time and DAP values for the lowest-dose procedure (biliary drainage) were approximately 3-fold and 13-fold lower, respectively, than those for the highest-dose examination (transjugular intrahepatic portosystemic shunt, TIPS). Median E/DAP conversion factors from 0.12 (abdominal percutaneous transluminal angioplasty) to 0.25 (Nephrostomy) mSvGy(-1) cm(-2) were obtained and good correlations between E and DAP were found for all procedures, with R(2) coefficients ranging from 0.80 (abdominal angiography) to 0.99 (biliary stent insertion, Nephrostomy and TIPS). The DAP values obtained in this study showed general consistency with the values provided in the literature and median E values ranged from 4.0 mSv (biliary drainage) to 49.6 mSv (TIPS). CONCLUSIONS: Values of E/DAP conversion factors were derived for each procedure from a comprehensive analysis of projection and dosimetric data: they could provide a good evaluation for the stochastic effects. These results can be obtained by means of a close cooperation between different interventional professionals involved in patient care and dose optimization.

Survey of the interventional cardiology procedures in Italy.

Interventional cardiology procedures are increasing because they offer many advantages to patients compared with other techniques: therefore the Italian National Institution for Insurance against Accidents at Work decided to start a survey for monitoring the state-of-the-art regarding the professionals involved in those procedures. The survey covered six cardiology and medical physics Italian departments. Each centre was asked to record 10 examinations for five types of procedures: coronary angiography (CA), electrophysiology studies (ES), pacemaker implantation (PI), percutaneous transluminal coronary angioplasty (PTCA) and radiofrequency catheter ablation (RA). For each examination all the centres were requested to fill in a questionnaire containing information regarding the operator performing the examination, the patient and the procedure. A total of 290 examinations were recorded: 103 CA, 14 ES, 68 PI, 79 PTCA and 26 RA. As occupational doses are strongly related to patient doses, both patients and operators radiation dose data are reported. Ratios of maximum to minimum mean patient doses across the hospitals surveyed were 2.0, 3.9, 7.0, 1.8 and 1.4 for CA, ES, PI, PTCA and RA, respectively. The calculated rounded mean dose-area product values across all participating hospitals were comparable with other values reported in the literature. In general, specific radiation protection tools were used by all operators performing different procedures in all hospitals. A major issue in this survey was the absence of information about correlation between staff and patient doses in a single procedure: future studies could be more aimed to prospective goals where occupational exposures per procedure are monitored specifically.

Effective and equivalent organ doses in patients undergoing coronary angiography and percutaneous coronary intervention.

PURPOSE: Recent recommendations of the International Commission on Radiological Protection state that the use of effective dose (E) for assessing patient exposure has severe limitations, though it can be kept for dose comparisons. In cardiology procedures, the equivalent dose (H(T)) is one of the most appropriate dose quantity to be evaluated for risk-benefit assessment. In this study, both E and H(T) values for ten critical organs in coronary angiography (CA) and percutaneous coronary interventions (PCI) were derived from in-the-field dose-area-product (DAP) measurements in order to provide a database for doses in those procedures. METHODS: Conversion factors E/DAP calculated by Monte Carlo methods in two different mathematical human phantoms were applied to DAP values measured on 193 patients (118 CA and 75 PCI). Partial DAP values were recorded in-the-field for each projection and for all patients. The partial effective doses of all projections were summed up to calculate the E of the entire procedure. Similarly, equivalent doses for ten critical organs/tissues (bone, colon, heart, liver, lung, esophagus, red bone marrow, skin, stomach, and thyroid) were derived from H(T)/DAP conversion factors for different projections calculated by Monte Carlo method. RESULTS: All parameters related to the patient dose, i.e., fluoroscopy times, number of images, DAP, effective doses, and equivalent doses, show a wide range of values depending on the complexity of the patient case and the experience of the cardiologist. The mean fluoroscopy time, DAP, and E values for coronary angiography patients were approximately threefold lower than those for PCI patients; the number of images for CA was half that for PCI. The correlation between effective dose and DAP was excellent for both CA and PCI. The equivalent doses values were in good correlations with DAP values in CA examinations, with Pearson's coefficients ranging from 0.87 (stomach) to 0.99 (skin) and r(mean) = 0.94. The same analysis was performed for PCI procedures. In this case, the trends were only slightly worse because "r" ranged from 0.70 (stomach) to 0.92 (bone) and r(mean) = 0.85. Simple conversion coefficients to estimate equivalent doses to ten critical organs/tissues from DAP values, for both CA and PCI, were provided for avoiding the need to carry out detailed in-the-field analysis for all projections and for all patients. CONCLUSIONS: Measurements in-the-field of DAP values were carried out for two common cardiology procedures and effective doses were derived for each technique from detailed analysis of dose and projection data, using conversion factors provided by two different theoretical models. Equivalent doses to organs/tissues were also calculated using conversion factors proposed in the literature for different projections and cumulative conversion factors (H)T/DAP for ten organs/tissues were estimated.