William Pavlicek - Academia.edu (original) (raw)

Papers by William Pavlicek

Examinations of the skeletal system have historically used 'detail' x-ray film screen com... more Examinations of the skeletal system have historically used 'detail' x-ray film screen combinations having film-lightbox image quality that is challenging to replicate in a soft- copy environment. A review of the basic diagnostic imaging tasks for this sub-specialty is presented, including resolution and gray scale requirements for visualization of subtle fractures, bone mineral loss, implant loosening, and soft tissue disease.

CONCLUSION The spectral error causes ghost-like artifacts and leads uncertainty or misclassificat... more CONCLUSION The spectral error causes ghost-like artifacts and leads uncertainty or misclassification in DECT material decomposition. The proposed technique removed such artifacts and produced better material differentiation by improving SNR as well as CNR in phantom and patient studies. BACKGROUND We recently proposed a noisy-pixel detection scheme for dual-energy computed tomography (DECT), based on the fact that the attenuation of a higher density material decreases more rapidly as X-ray energy increases. We called it spectral error of DECT if a CT value pair of low and high energy images deviates from the expected trend. After the analysis of DECT images, we identified three major sources of the spectral error: misregistration, water-reference offset error, and random noise. In this paper, we propose a new image enhancement method for DECT, which consists of three steps: water-reference offset correction, spectral-error correction, and anti-correlated noise reduction (ACNR). EVAL...

Journal of Applied Clinical Medical Physics

The current work describes an anthropomorphic beating heart phantom constructed as a tool for the... more The current work describes an anthropomorphic beating heart phantom constructed as a tool for the assessment of technological advances in cardiac x-ray computed tomography (CT). The phantom is comprised of a thorax, a compressor system, an ECG system, a beating heart with tortuous coronary arteries, and the option to add or remove pathologies such as aberrant beats, stents, and plaques. Initial trials with the phantom have shown its utility to assess temporal resolution, spatial resolution, radiation dose, iodine contrast, stents, and plaques.

BACKGROUND Excessive Z axis coverage with CT imaging can be a source of unnecessary radiation exp... more BACKGROUND Excessive Z axis coverage with CT imaging can be a source of unnecessary radiation exposure to patients. Using a tracking database that receives the DICOM Dose Structured Report (containing the CTDIvol and DLP) and a RIS HL7 feed (containing the patient height, weight, anterior-posterior/AP dimensions and lateral/LAT dimensions), a prediction model was constructed to automatically monitor the Z axis coverage. This model was incorporated into the tracking database as a web tool to be used for quality reviews of Z axis coverage. CONCLUSION Excessive Z axis coverage provides an opportunity for significant radiation dose reduction. The ability to automate Z axis coverage review for the abdomen pelvis CT Exam will be helpful in educating technologists, particularly if the performing technologist is recorded as part of the data. This approach can be applied to protocol specific measurement of Z axis coverage including CT colonography, urography and other limited scan length stu...

PURPOSE/AIM To introduce the critical components of an ALARA program, including: protocol setting... more PURPOSE/AIM To introduce the critical components of an ALARA program, including: protocol setting optimization, physician operator education, and automated radiation dose monitoring. CONTENT ORGANIZATION + Protocol Specific Dose Control Settings - Evaluate and determine optimized dose settings for imaging task. - Set equipment default settings. + Personnel Education and Training - Utilize didactic and table-side training modules for physician operators. - Train technologists on procedure specific protocols. + Radiation Dose Monitoring - Establish calculation for protocol specific patient skin dose. - Automate reports for patient skin dose. SUMMARY Subspecialty based ALARA programs focus personnel on radiation dose parameters most relevant to their specific practice, which increases retention of key ALARA concepts. + Targeted ALARA program content increases acceptance of best radiation practices. + Radiation dose monitoring is possible with automated systems and reports.

CONCLUSION Conclusion: DIT and the PSD Toolkit can be used to accurately capture skin dose inform... more CONCLUSION Conclusion: DIT and the PSD Toolkit can be used to accurately capture skin dose information over multiple exams. It can be easily deployed as a tool for medical professionals in the healthcare environment. BACKGROUND Background: Skin damage from medical x-ray undergoes biological repair, yet damage can be cumulative, which has implications for patients having repeated fluoroscopically-guided interventions (FGI). Both the FDA (since 1994) and Joint Commission (since 2006) have specified that skin exposures from fluoroscopy be routinely monitored as a quality assurnace (QA) metric, including peak skin dose (PSD) arising from multiple episodes of care. We have developed an Excel-based PSD toolkit to generate skin dose map based on the information from Digital Imaging and Communications in Medicine (DICOM) tags including data from DICOM structured dose report. We further enhanced this toolkit by quering the information for repeated exams and correcting the PSD via a time-dose...

CONCLUSION Our study found iDEM permits accurate analysis of efficiency data for imaging equipmen... more CONCLUSION Our study found iDEM permits accurate analysis of efficiency data for imaging equipment located in different departments or hospitals. BACKGROUND The Center for Medicare and Medicaid Services (CMS) has specified efficiency for devices costing more than 1M (PET, CT, and MRI) using self-reporting and on-site review of a small sample of imaging centers. A method to automatically provide accurate and standardized efficiency reports has been developed. Formal definitions of fundamental metrics of efficiency are proposed: Table Utilization (%), Exam Duration Time (min), Inter-Patient Time (min), Inter-Series Time (min) and Appointment Interval Time (min). These metrics use time stamps from DICOM compliant PACs. The actual use of imaging devices is recorded without disrupting patient exams - standardized and continuously available by administrative staff. EVALUATION A database uses a parser to capture all DICOM image data when archived via PACS. The images are deleted while the ...

Journal of applied clinical medical physics / American College of Medical Physics, 2013

The purpose of this study is to evaluate a direct measure of calcium burden by using dual-energy ... more The purpose of this study is to evaluate a direct measure of calcium burden by using dual-energy computed tomography (DECT) during contrast-enhanced coronary imaging, potentially eliminating the need for an extra noncontrast X-ray acquisition. The ambiguity of separation of calcium from contrast material on contrast-enhanced images was solved by using virtual noncontrast images obtained by DECT. A new threshold CT number was required to detect the calcium carrying potential risk for adverse coronary events on virtual noncontrast images. Two methods were investigated to determine the 130 HU threshold for DECT scoring. An in vitro anthropomorphic phantom with 29 excised patient calcium plaques inserted was used for both a linear and a logistic regression analysis. An IRB approved in vivo prospective study of six patients was also performed to be used for logistic regression analysis. The threshold found by logistic regression model to define the calcium burden on virtual noncontrast i...

CONCLUSION Single energy reconstructions can accurately assess vessel stenosis in CCTA exams but ... more CONCLUSION Single energy reconstructions can accurately assess vessel stenosis in CCTA exams but are unable to provide diagnostic confidence in arteries with high levels of calcium. Dual energy reconstructions provide better visualization of vessel stenosis by reducing calcium blurring. BACKGROUND Coronary Computed Tomography Angiography (CCTA) uses iodine to identify possible stenosis in an artery. Stenosis occurring as a result of soft plaques can be confidently visualized and quantified. The presence of dense calcified plaques can cause blurring that hinders the ability to diagnose stenosis and/or assess surrounding soft plaque composition. EVALUATION The proposed work evaluates the use of single energy CCTA to visualize and quantify soft plaque stenosis. There is also discussion on the use of monochromatic energy images and two material basis images for improved visualization of iodine patency with reduced calcium blur in coronary angiograms. DISCUSSION Measurements were taken o...

Medical Imaging 2011: Image Processing, 2011

Nonalcoholic steatohepatitis (NASH) is a liver disease that occurs in patients that lack a histor... more Nonalcoholic steatohepatitis (NASH) is a liver disease that occurs in patients that lack a history of the well-proven association of alcohol use. A major symptom of NASH is increased fat deposition in the liver. Gemstone Spectral Imaging (GSI) with fast kVp-switching enables projection-based material decomposition, offering the opportunity to accurately characterize tissue types, eg, fat and healthy liver tissue, based on their energy-sensitive material attenuation and density. We describe our pilot efforts to apply GSI to locate and quantify ...

Radiology, 2014

Computed tomography (CT) is an imaging test that is widely used worldwide to establish medical di... more Computed tomography (CT) is an imaging test that is widely used worldwide to establish medical diagnoses and perform image-guided interventions. More recently, concern has been raised about the risk of carcinogenesis from medical radiation, with a focus on CT. The purpose of this article is to (a) describe the importance of educating radiology personnel, patients, and referring clinicians about the concerns over CT radiation, (b) describe commonly used CT parameters and radiation units, (c) discuss the importance of establishing a dedicated radiology team to manage CT radiation, and (d) describe specific CT techniques to minimize radiation while providing diagnostic examinations. q RSNA, 2014

2007 6th International Special Topic Conference on Information Technology Applications in Biomedicine, 2007

Numerous studies based on the spectral analysis of diastolic sounds showed an increase in the hig... more Numerous studies based on the spectral analysis of diastolic sounds showed an increase in the high frequency portion of the spectrum for patients with coronary artery disease (CAD) compared with normal patients. The overall goal of this study is to detect the presence of coronary artery disease in patients using a noninvasive and inexpensive approach. A commercially available electronic stethoscope

IEEE J. Biomed. Health Inform., 2014

Coronary heart disease (CHD) is the most prevalent cause of death worldwide. Atherosclerosis whic... more Coronary heart disease (CHD) is the most prevalent cause of death worldwide. Atherosclerosis which is the condition of plaque buildup on the inside of the coronary artery wall is the main cause of CHD. Rupture of unstable atherosclerotic coronary plaque is known to be the cause of acute coronary syndrome. Vulnerability of atherosclerotic plaque has been related to a large lipid core covered by a fibrous cap. Non-invasive assessment of plaque characterization is necessary due to prognostic importance of early stage identification. The purpose of this study is to use the additional attenuation data provided by dual energy computed tomography (DECT) for plaque characterization. We propose to train supervised learners on pixel values recorded from DECT monochromatic X-ray and material basis pairs images, for more precise classification of fibrous and lipid plaques. The interaction of the pixel values from different image types is taken into consideration, as single pixel value might not be informative enough to separate fibrous from lipid. Organic phantom plaques scanned in a fabricated beating heart phantom were used as ground truth to train the learners. Our results show that support vector machines, artificial neural networks and random forests provide accurate results both on phantom and patient data.

Medical Imaging 2010: Computer-Aided Diagnosis, 2010

Hypodense metastases are not always completely distinguishable from benign cysts in the liver usi... more Hypodense metastases are not always completely distinguishable from benign cysts in the liver using conventional Computed Tomography (CT) imaging, since the two lesion types present with overlapping intensity distributions due to similar composition as well as other factors including beam hardening and patient motion. This problem is extremely challenging for small lesions with diameter less than 1 cm. To accurately characterize such lesions, multiple follow-up CT scans or additional Positron Emission Tomography or Magnetic Resonance Imaging exam are often conducted, and in some cases a biopsy may be required after the initial CT finding. Gemstone Spectral Imaging (GSI) with fast kVp switching enables projection-based material decomposition, offering the opportunity to discriminate tissue types based on their energy-sensitive material attenuation and density. GSI can be used to obtain monochromatic images where beam hardening is reduced or eliminated and the images come inherently pre-registered due to the fast kVp switching acquisition. We present a supervised learning method for discriminating between cysts and hypodense liver metastases using these monochromatic images. Intensity-based statistical features extracted from voxels inside the lesion are used to train optimal linear and nonlinear classifiers. Our algorithm only requires a region of interest within the lesion in order to compute relevant features and perform classification, thus eliminating the need for an accurate segmentation of the lesion. We report classifier performance using M-fold cross-validation on a large lesion database with radiologist-provided lesion location and labels as the reference standard. Our results demonstrate that (a) classification using a single projection-based spectral CT image, i.e., a monochromatic image at a specified keV, outperforms classification using an image-based dual energy CT pair, i.e., low and high kVp images derived from the same fast kVp acquisition and (b) classification using monochromatic images can achieve very high accuracy in separating benign liver cysts and metastases, especially for small lesions.

Medical Imaging 2009: Physics of Medical Imaging, 2009

Dual energy x-ray CT images are computed using either image or projection data. The latter is tho... more Dual energy x-ray CT images are computed using either image or projection data. The latter is thought to be preferable for two-material decomposition. Nonetheless, using effective energies of polychromatic x-ray beams at separated kVp values, material decomposition and pseudo-monochromatic reconstruction can be performed from reconstructed images. This image-based approach generates added noise which should benefit from applying processing for noise

International journal of computer assisted radiology and surgery, 2015

Dual-energy computed tomography (DECT) images can undergo a two-material decomposition process wh... more Dual-energy computed tomography (DECT) images can undergo a two-material decomposition process which results in two images containing material density information. Material density images obtained by that process result in images with increased pixel noise. Noise reduction in those images is desirable in order to improve image quality. A noise reduction algorithm for material density images was developed and tested. A three-level wavelet approach combined with the application of an anisotropic diffusion filter was used. During each level, the resulting noise maps are further processed, until the original resolution is reached and the final noise maps obtained. Our method works in image space and, therefore, can be applied to any type of material density images obtained from any DECT vendor. A quantitative evaluation of the noise-reduced images using the signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR) and 2D noise power spectrum was done to quantify the improvements. The n...

Medical Imaging 2010: Physics of Medical Imaging, 2010

Coronary CT Angiography (CTA) is limited in patients with calcified plaque and stents. CTA is una... more Coronary CT Angiography (CTA) is limited in patients with calcified plaque and stents. CTA is unable to confidently differentiate fibrous from lipid plaque. Fast switched dual energy CTA offers certain advantages. Dual energy CTA removes calcium thereby improving visualization of ...

Skeletal Radiology, 2009

Introduction Despite recent advances in CT technology, metal orthopedic implants continue to caus... more Introduction Despite recent advances in CT technology, metal orthopedic implants continue to cause significant artifacts on many CT exams, often obscuring diagnostic information. We performed this prospective study to evaluate the effectiveness of an experimental metal artifact reduction (MAR) image reconstruction program for CT.

Radiology, 2013

To assess the accuracy and initial clinical use of a software tool that automatically maps and re... more To assess the accuracy and initial clinical use of a software tool that automatically maps and records values of skin dose, including peak skin dose (PSD), administered to patients undergoing fluoroscopically guided interventional procedures. In this retrospective study, the institutional review board determined that this HIPAA-compliant study met the criteria as a quality assurance investigation. Informed consent was waived. After the initial validation and accuracy tests, distributed skin dose and PSD estimates were obtained for fluoroscopically guided interventional procedures performed in the radiology, cardiology, and gastroenterology practice areas between January and October 2011. A total of 605 procedures were performed in 520 patients (64% men; age range, 20-95 years). The accuracy of a skin dose tool to estimate patient dose distribution was verified with phantom studies by using an external dosimeter and direct exposure film. PSD distribution, PSD according to procedure type, and PSD for individual physician operators were assessed. Calculated PSD values agreed within ±9% of that measured by using film dosimetry under the condition of matched-phantom geometry. The area receiving the highest dose (greater than 95% of peak) agreed within ±17%. Of 605 patient procedures, 15 demonstrated PSD greater than 2 Gy, with a maximum PSD of 5.6 Gy. Knowledge of the patient skin dose can help direct treatment of patients who were administered relatively high skin dose and may be used to plan future procedures. http://radiology.rsna.org/lookup/suppl/doi:10.1148/radiol.12112295/-/DC1.