Methods for measuring fluoroscopic skin dose.
Ontology highlight
ABSTRACT:
SUBMITTER: Balter S
PROVIDER: S-EPMC2663643 | biostudies-other | 2006 Sep
REPOSITORIES: biostudies-other
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Project description:Modern fluoroscopes used for image-based guidance in interventional procedures are complex X-ray machines, with advanced image acquisition and processing systems capable of automatically controlling numerous parameters based on defined protocol settings. This study evaluated and compared approaches to technique factor modulation and air kerma rates in response to simulated patient thickness variations for four state-of-the-art and one previous-generation interventional fluoroscopes. A polymethyl methacrylate (PMMA) phantom was used as a tissue surrogate for the purposes of determining fluoroscopic reference plane air kerma rates, kVp, mA, and variable copper filter thickness over a wide range of simulated tissue thicknesses. Data were acquired for each fluoroscopic and acquisition dose curve within each vendor's default abdomen or body imaging protocol. The data obtained indicated vendor- and model-specific variations in the approach to technique factor modulation and reference plane air kerma rates across a range of tissue thicknesses. However, in the imaging protocol evaluated, all of the state-of-the-art systems had relatively low air kerma rates in the fluoroscopic low-dose imaging mode as compared to the previous-generation unit. Each of the newest-generation systems also employ Cu filtration within the selected protocol in the acquisition mode of imaging; this is a substantial benefit, reducing the skin entrance dose to the patient in the highest dose-rate mode of fluoroscope operation. Some vendors have also enhanced the radiation output capabilities of their fluoroscopes which, under specific conditions, may be beneficial; however, these increased output capabilities also have the potential to lead to unnecessarily high dose rates. Understanding how fluoroscopic technique factors are modulated provides insight into the vendor-specific image acquisition approach and may provide opportunities to optimize the imaging protocols for clinical practice.
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Project description:There is a growing concern regarding the dose delivered during x-ray fluoroscopy guided procedures, particularly in interventional cardiology and neuroradiology, and in real-time tumor tracking radiotherapy and radiosurgery. Many of these procedures involve long treatment times, and as such, there is cause for concern regarding the dose delivered and the associated radiation related risks. An insufficient dose, however, may convey less geometric information, which may lead to inaccuracy and imprecision in intervention placement. The purpose of this study is to investigate a method for achieving the required tracking uncertainty for a given interventional procedure using minimal dose.A simple model is used to demonstrate that a relationship exists between imaging dose and tracking uncertainty. A feedback framework is introduced that exploits this relationship to modulate the tube current (and hence the dose) in order to maintain the required uncertainty for a given interventional procedure. This framework is evaluated in the context of a fiducial tracking problem associated with image-guided radiotherapy in the lung. A particle filter algorithm is used to robustly track the fiducial as it traverses through regions of high and low quantum noise. Published motion models are incorporated in a tracking test suite to evaluate the dose-localization performance trade-offs.It is shown that using this framework, the entrance surface exposure can be reduced by up to 28.6% when feedback is employed to operate at a geometric tracking uncertainty of 0.3 mm.The analysis reveals a potentially powerful technique for dynamic optimization of fluoroscopic imaging parameters to control the applied dose by exploiting the trade-off between tracking uncertainty and x-ray exposure per frame.
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Project description:In this article, we present GE Healthcare's design philosophy and implementation of X-ray imaging systems with dose management for pediatric patients, as embodied in its current radiography and fluoroscopy and interventional cardiovascular X-ray product offerings. First, we present a basic framework of image quality and dose in the context of a cost-benefit trade-off, with the development of the concept of imaging dose efficiency. A set of key metrics of image quality and dose efficiency is presented, including X-ray source efficiency, detector quantum efficiency (DQE), detector dynamic range, and temporal response, with an explanation of the clinical relevance of each. Second, we present design methods for automatically selecting optimal X-ray technique parameters (kVp, mA, pulse width, and spectral filtration) in real time for various clinical applications. These methods are based on an optimization scheme where patient skin dose is minimized for a target desired image contrast-to-noise ratio. Operator display of skin dose and Dose-Area Product (DAP) is covered, as well. Third, system controls and predefined protocols available to the operator are explained in the context of dose management and the need to meet varying clinical procedure imaging demands. For example, fluoroscopic dose rate is adjustable over a range of 20:1 to adapt to different procedure requirements. Fourth, we discuss the impact of image processing techniques upon dose minimization. In particular, two such techniques, dynamic range compression through adaptive multiband spectral filtering and fluoroscopic noise reduction, are explored in some detail. Fifth, we review a list of system dose-reduction features, including automatic spectral filtration, virtual collimation, variable-rate pulsed fluoroscopic, grid and no-grid techniques, and fluoroscopic loop replay with store. In addition, we describe a new feature that automatically minimizes the patient-to-detector distance, along with an estimate of its dose reduction potential. Finally, two recently developed imaging techniques and their potential effect on dose utilization are discussed. Specifically, we discuss the dose benefits of rotational angiography and low frame rate imaging with advanced image processing in lieu of higher-dose digital subtraction.
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Project description:BackgroundRadiographic images in adolescent idiopathic scoliosis (AIS) have a potential radiation-induced oncogenic effect; thus lowering radiation dose by using fluoroscopic imaging technique of low-dose fluoroscopic technique (LFT) which might be relevant for clinical evaluation.PurposeTo compare radiographs of LFT with gold standard radiographs for AIS ordinary radiographic technique (ORT).Material and methodsImage quality was evaluated for LTF and ORT of a child phantom and two 3D-printed models (3DPSs) of AIS. We measured the primary physical characteristics of noise, contrast, spatial resolution, signal-to-noise ratio, and contrast-to-noise ratio. Three independent evaluators assessed the radiographs by observer-based methods of image criteria (ICS) and visual grading analysis(VGAS). Radiation doses were evaluated by the dose-area-product (DAP) of the 25 phantom radiographs. Reliability and agreement of Cobb's angle (CA) and other radiographic parameters were evaluated on the 3DPSs and reliability on 342 LFT.ResultsThe average noise and contrast were approximately 15-fold higher for LFT. SNR and CNR were similar. Overall, ICS and VGAS were 3-fold higher for ORT than for LFT for L3 and similar for Th6. Reliability and agreement were good for the experimental LFT, and the interclass correlation coefficient for CA was 0.852 for the clinical LFT. The average DAP and effective dose for LFT were 8-fold lower than those for ORT.ConclusionIn conclusion, LFT is reliable for CA measurements and is thus useful for clinical outpatient follow-up evaluation. Even though the image quality is lower for LFT than ORT, the merits are the substantially reduced radiation and a lowered malignancy risk without compromising the measurement of Cobb's angle, thus following the principles of ALARA.
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Project description:BACKGROUND:The patient's perspective of their facial scar after skin cancer surgery influences perception of care and quality of life (QoL). Appearance satisfaction after surgery is also an important but often overlooked treatment outcome. OBJECTIVES:To report the psychometric validation of the FACE-Q Skin Cancer Module consisting of five scales, measuring appearance satisfaction (Satisfaction with Facial Appearance, Appraisal of Scars), QoL (Cancer Worry, Appearance-related Psychosocial Distress) and the patient experience (Satisfaction with Information: Appearance). METHODS:Participants underwent Mohs surgery for facial basal or squamous cell carcinoma or excision of early facial melanoma. Cohort 1 received a set of scales before and after surgery. Cohort 2 received the scales on two occasions in the postoperative period for test-retest reliability. Rasch measurement theory was used to select (item-reduce) the most clinically meaningful items for the scales. Reliability, validity, floor and ceiling effects and responsiveness were also analysed. RESULTS:Of 334 patients, 209 (response rate 62·6%) were included. Rasch analysis reduced the total scale items from 77 to 41. All items had ordered thresholds and good psychometric fit. Reliability was high (Person separation index and Cronbach's ? ? 0·90) and scales measuring similar constructs were correlated. High floor and ceiling effects were seen for the scales. The Cancer Worry scale demonstrated responsiveness (P = 0·004). CONCLUSIONS:The FACE-Q Skin Cancer Module meet the requirements of the Rasch model providing linearized measurement. Discriminating between patients with minimal appearance or worry impairment may be a limitation. The scales can be used for larger validation studies, clinical practice and research.
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Project description:INTRODUCTION:To prove objective effect of using mechanical device for immobilization of pediatric patient during voiding cystourethrogram (VCUG) compare immobilization by hand-holding. METHODS:This study included 77 patients, who underwent VCUG in our center from April to October 2017, who had a clinically suspicious urinary tract infection. Patients were classified into one of two groups based on whether examination was done before (Group A) or after (Group B) adaptation of immobilization device. Patient-related data, image quality related score and dose-related data were collected and compared between two groups. RESULTS:Group A included 36 patients and group B included 41. Patient related data including mean age, sex, body weight and height didn't show significant difference between two groups (p > 0.05 for all). Among the image quality scoring, overall image quality, motion artifact, showed significant difference between two groups with improved inadequate timing and centering after adaptation of immobilization device. Dose related data showed significantly decreased shot number, mean fluoroscopic time with decreased mean dose area product (DAP) value and effective dose after adaptation of immobilization device (p < 0.05 for all). CONCLUSION:Adaptation of immobilization device can improve overall image quality with decreased motion artifact and improved centering and timing with even shot number, mean fluoroscopic time with decreased mean DAP value and effective dose.
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