Reliability of radiomics features due to image reconstruction using a standardized T2 -weighted pulse sequence for MR-guided radiotherapy: An anthropomorphic phantom study.

PURPOSE: To prospectively investigate the impact of image reconstruction on MRI radiomics features. METHODS: An anthropomorphic phantom was scanned at 1.5 T using a standardized sequence for MR-guided radiotherapy under SENSE and compressed-SENSE reconstruction settings. A total of 93 first-order and texture radiomics features in 10 volumes of interest were assessed based on (1) accuracy measured by the percentage deviation from the reference, (2) robustness on reconstruction in all volumes of interest measured by the intraclass correlation coefficient, and (3) repeatability measured by the coefficient of variance over the repetitive acquisitions. Finally, reliable and unreliable radiomics features were comprehensively determined based on their accuracy, robustness, and repeatability. RESULTS: Better accuracy and robustness of the radiomics features were achieved under SENSE than compressed-SENSE reconstruction. The feature accuracy under SENSE reconstruction was more affected by acceleration factor than direction, whereas under compressed-SENSE reconstruction, accuracy was substantially impacted by the increasing denoising levels. Feature repeatability was dependent more on feature types than on reconstruction. A total of 45 reliable features and 13 unreliable features were finally determined for SENSE, compared with 22 reliable and 26 unreliable features for compressed SENSE. First-order and gray-level co-occurrence matrix features were generally more reliable than other features. CONCLUSION: Radiomics features could be substantially affected by MRI reconstruction, so precautions need to be taken regarding their reliability for clinical use. This study helps the guidance of the preselection of reliable radiomics features and the preclusion of unreliable features in MR-guided radiotherapy.

Intrasession and Intersession Repeatability of Diffusion Tensor Imaging in Healthy Human Liver.

OBJECTIVE: The aim of this study was to evaluate the effect of signal to noise ratio (SNR) and number of gradient directions (NGD) on intra- and intersession repeatability of liver diffusion tensor imaging (DTI) metrics. METHODS: At each of 3 liver DTI scan sessions, liver diffusion was assessed in 5 healthy volunteers using a 6-direction DTI scan performed 9 separate times (ie, number of signal averages [NSA]). In addition, 4 combinations of NSA and NGD were acquired (NSA/NGD = 1/30, 3/10, 3/12, and 5/6) to determine the combined effect to DTI metrics, which was based on intersubject variability and intrasession (Vintra) and intersession (Vinter) repeatability. RESULTS: Intersubject variability was less than 20%, whereas Vintra and Vinter repeatability were less than 5% and less than 10%, respectfully. Vinter was not affected by the NGD used. Decreases in Vinter(FA), Vinter(λ1), Vinter(RD), and Vinter(MD) were observed with increasing NSA, and hence SNR. CONCLUSION: Increased SNR may improve intrasession and intersession repeatability of liver DTI metrics. Scan repeatability was not influenced by NGD.

The Enhanced Workflow and Efficiency of the Wireless Local Area Network (WLAN)-Based Direct Digital Radiography (DDR) Portable Radiography.

With the implementation of the PACS in the hospital, there is an increasing demand from the clinicians for immediate access and display of radiological images. Recently, our hospital has installed the first wireless local area network (WLAN)-based direct digital radiography (DDR) portable radiography system. The DDR portable radiography system allows wireless retrieval of modality worklist and wireless transmission of portable X-ray image on the console to the Picture Archiving and Communication System (PACS), via WLAN connection of wireless fidelity (Wi-Fi). The aim of this study was to analyze the workflow and performance between the WLAN-based DDR portable radiography system and the old practice using conventional portable X-ray machine with computed radiography (CR) system. A total of 190 portable chest X-ray examinations were evaluated and timed, using the conventional portable X-ray machine with CR from March to April of 2012 and using the new DDR portable radiography system on December of 2012 (n = 97 for old system and n = 93 for DDR portable system). The time interval of image becoming available to the PACS using the WLAN-based DDR portable radiography system was significantly shorter than that of the old practice using the conventional portable X-ray machine with CR (6.8 ± 2.6 min for DDR portable system; 23 ± 10.2 min for old system; p < 0.0001), with the efficiency improved by 70 %. The implementation of the WLAN-based DDR portable radiography system can enhance the workflow of portable radiography by reduction of procedural steps.

Striatal dopamine synthesis capacity and its association with negative symptoms upon resolution of positive symptoms in first-episode schizophrenia and delusional disorder.

RATIONALE: How striatal dopamine synthesis capacity (DSC) contributes to the pathogenesis of negative symptoms in first-episode schizophrenia (SZ) and delusional disorder (DD) has seldom been explored. As negative symptoms during active psychotic episodes can be complicated by secondary influences, such as positive symptoms, longitudinal investigations may help to clarify the relationship between striatal DSC and negative symptoms and differentiate between primary and secondary negative symptoms. OBJECTIVE: A longitudinal study was conducted to examine whether baseline striatal DSC would be related to negative symptoms at 3 months in first-episode SZ and DD patients. METHODS: Twenty-three first-episode age- and gender-matched patients (11 DD and 12 SZ) were consecutively recruited through an early intervention service for psychosis in Hong Kong. Among them, 19 (82.6%) patients (9 DD and 10 SZ) were followed up at 3 months. All patients received an 18F-DOPA PET/MR scan at baseline. RESULTS: Baseline striatal DSC (Kocc;30-60) was inversely associated with negative symptoms at 3 months in first-episode SZ patients (rs = - 0.80, p = 0.010). This association remained in SZ patients even when controlling for baseline negative, positive, and depressive symptoms, as well as cumulative antipsychotic dosage (ß = - 0.69, p = 0.012). Such associations were not observed in first-episode DD patients. Meanwhile, the severity of negative symptoms at 3 months was associated with more positive symptoms in DD patients (rs = 0.74, p = 0.010) and not in SZ patients. CONCLUSIONS: These findings highlight the role of striatal DSC in negative symptoms upon resolution of active psychotic episodes among first-episode SZ patients. Baseline striatal dopamine activity may inform future symptom expression with important treatment implications.

Key Performance Indicators for Comparing the Performance of Portable Radiography: Direct Digital Radiography versus Conventional Machine Computed Radiography-A Study in a Nonacute Hospital.

INTRODUCTION: Portable radiography traditionally has been performed with a conventional portable x-ray unit with computed radiography (CR) system (conventional-CR combo), and off-site processing of the exposed CR cassettes was time-consuming. The direct digital radiography (DDR) portable x-ray system, with the digital image immediately available for review and wireless transmission as the key merits, is newly installed for portable radiography. Thus, the work flow of portable radiography is changed. This study was performed to quantitatively investigate the performance of portable radiography using the DDR portable x-ray system and conventional-CR combo in terms of efficiency and work flow enhancement. METHODS: One hundred ninety portable x-ray examinations were timed for each procedural step using conventional-CR combo (n=97) and the DDR portable x-ray system. The following key performance indicators were designed for measuring the performance of portable radiography quantitatively: "examination duration," "time for image becoming available in PACS," "postacquisition processing time," and "manpower deployment time." RESULTS: Productivity was raised by 96% using the DDR portable x-ray system. "Examination duration" using the DDR portable system was significantly faster (P < .0001), with a mean calculated time of 13.4 ± 7.6 minutes for the DDR portable system and 25.2 ± 10.9 minutes for conventional-CR combo. The "time for image becoming available in PACS" was significantly shorter than that of conventional-CR combo (P < .0001), with a mean time of 6.8 ± 2.6 minutes for the DDR portable system and 19.2 ± 9.7 minutes for conventional-CR combo. The "postacquisition processing time" was measured with slight differences, with a mean time of 2.2 ± 1.1 minutes for the DDR portable system and 1.9 ± 1.0 minutes for conventional-CR combo (P = .1064). Because more portable x-ray examinations could be performed when using the DDR portable x-ray system in each round of service, the mean "manpower deployment time" when using the DDR portable x-ray system was longer (ie, 82.6 ± 46.8 minutes for the DDR portable system and 24.5 ± 11.9 minutes for conventional-CR combo). CONCLUSIONS: By using the new DDR portable x-ray system with work flow changes, the performance of portable radiography was improved in efficiency and work flow was enhanced. Furthermore, the four defined key performance indicators in this study may help provide a framework for measuring the performance of portable radiography in other institutions.