Dan Kadrmas

• Phd
• Professor Emeritus at University of Utah

e16285 Background: Neuroendocrine tumors (NETs) may be imaged for theranostics with somatostatin receptor (SSTR)-PET/CT like Cu64- or Ga68-dotatate-PET/CT. NETs may also be imaged with 18F-Fluorodeoxyglucose (FDG)-PET/CT based on disease state and insurance coverage. FDG+ and SSTR- disease predicts poor response to Lu177-dotatate therapy, making bo...

p> Purpose Respiratory motion during positron emission tomography (PET) scans can be a major detriment to image quality in oncological imaging, leading to loss of quantification accuracy and false negative findings. The impact of motion on lesion quantification and detectability can be assessed using anthropomorphic phantoms with realistic anatomy...

Background Positron emission tomography (PET) with prostate specific membrane antigen (PSMA) have shown superior performance in detecting metastatic prostate cancers. Relative to [¹⁸F]fluorodeoxyglucose ([¹⁸F]FDG) PET images, PSMA PET images tend to visualize significantly higher-contrast focal lesions. We aim to evaluate segmentation and reconstru...

Background Prostate specific membrane antigen (PSMA) PET images have shown superior performance in detecting metastatic prostate cancers. Relative to [¹⁸F]FDG PET images, PSMA PET images tend to visualize significantly higher-contrast focal lesions. We aim to evaluate segmentation and reconstruction algorithms in this emerging context. Specifically...

Purpose Respiratory motion during positron emission tomography (PET) scans can be a major detriment to image quality in oncological imaging. The impact of motion on lesion quantification and detectability can be assessed using phantoms with realistic anatomy representation and motion modeling. In this work, we develop an anthropomorphic phantom for...

p> Purpose Respiratory motion during positron emission tomography (PET) scans can be a major detriment to image quality in oncological imaging, leading to loss of quantification accuracy and false negative findings. The impact of motion on lesion quantification and detectability can be assessed using anthropomorphic phantoms with realistic anatomy...

p> Purpose Respiratory motion during positron emission tomography (PET) scans can be a major detriment to image quality in oncological imaging, leading to loss of quantification accuracy and false negative findings. The impact of motion on lesion quantification and detectability can be assessed using anthropomorphic phantoms with realistic anatomy...

Point-Spread Function (PSF) modelling offers the capability to account for resolution degrading phenomena within the PET reconstruction framework. PSF modelling improves resolution and enhances contrast, but at the same time significantly alters image noise properties and induces edge overshoot effect. Thus, studying the effect of PSF modelling on...

Positron emission tomography (PET) images are typically reconstructed with an in-plane pixel size of approximately 4 mm for cancer imaging. The objective of this work was to evaluate the effect of using smaller pixels on general oncologic lesion-detection. A series of observer studies was performed using experimental phantom data from the Utah PET...

Multi-tracer positron emission tomography (PET) can image two or more tracers in a single scan, characterizing multiple aspects of biological functions to provide new insights into many diseases. The technique uses dynamic imaging, resulting in time-activity curves that contain contributions from each tracer present. The process of separating and r...

Background: Metastatic renal cell carcinoma has a poor prognosis and an intrinsic resistance to standard treatment. Sunitinib is an oral receptor tyrosine kinase inhibitor that has been used as a first-line targeted therapy in metastatic renal cell carcinoma. While computed tomography (CT) is currently the gold standard for response assessment in...

Iterative reconstruction has become the standard for routine clinical PET imaging. However, iterative reconstruction is computationally expensive, especially for time-of-flight (TOF) data. Block-iterative algorithms such as ordered-subsets expectation maximization (OSEM) are commonly used to accelerate the reconstruction. There is a tradeoff betwee...

Positron emission tomography (PET) can image a wide variety of functional and physiological parameters in vivo using different radiotracers. As more is learned about the molecular basis for disease and treatment, the potential value of molecular imaging for characterizing and monitoring disease status has increased. Characterizing multiple aspects...

Purpose: Kinetic modeling is widely used to analyze dynamic imaging data, estimating kinetic parameters that quantify functional or physiologic processes in vivo. Typical kinetic models give rise to nonlinear solution equations in multiple dimensions, presenting a complex fitting environment. This work generalizes previously described separable no...

Rapid multi-tracer PET aims to image two or more tracers in a single scan, simultaneously characterizing multiple aspects of physiology and function without the need for repeat imaging visits. Using dynamic imaging with staggered injections, constraints on the kinetic behavior of each tracer are applied to recover individual-tracer measures from th...

Positron emission tomography (PET) images are typically reconstructed with an in-plane pixel size of ∼4mm for cancer imaging. The objective of this work was to evaluate the use of smaller pixels for the task of detecting focal warm lesions in a noisy structured background. Experimental phantom data from the Utah PET Lesion Detection Database was us...

Lesion-detection performance in oncologic PET depends in part upon count statistics, with shorter scans having higher noise and reduced lesion detectability. However, advanced techniques such as time-of-flight (TOF) and point spread function (PSF) modeling can improve lesion detection. This work investigates the relationship between reducing count...

This paper uses the method of integration by parts to convert a differentiation equation into an equation that does not contain any derivatives. A linear estimation model is set up and a closed-form estimation solution is obtained.

Dynamic emission computed tomographic imaging with compartment modeling can quantify in vivo physiologic processes, eliciting more information regarding underlying molecular disease processes than is obtained from static imaging. However, estimation of kinetic rate parameters for multi-compartment models can be computationally demanding and problem...

Background Compared with static imaging, dynamic emission computed tomographic imaging with compartment modeling can quantify in vivo physiologic processes, providing useful information about molecular disease processes. Dynamic imaging involves estimation of kinetic rate parameters. For multi-compartment models, kinetic parameter estimation can be...

The objective was to compare F-fluorodeoxyglucose (FDG) and F-fluorothymidine (FLT) PET in differentiating radiation necrosis from recurrent glioma. Visual and quantitative analyses were derived from static FDG PET and static and dynamic FLT PET in 15 patients with suspected recurrence of treated grade 2 glioma or worse with a new focus of Gd contr...

Dynamic emission computed tomographic imaging with compartment modeling can quantify in vivo physiologic processes, eliciting more information regarding underlying molecular disease processes than can be obtained from static imaging. However, estimation of kinetic rate parameters for multi-compartment models can be computationally demanding and pro...

Rapid multi-tracer PET aims to image two or more tracers in a single scan, thereby characterizing multiple aspects of function. Using dynamic imaging with tracers staggered in time, constraints on the kinetic behavior of each tracer can be applied to predict the makeup of the multi-tracer PET signal. Signal-separation algorithms can then be applied...

In a dedicated cardiac single photon emission computed tomography (SPECT) system, the detectors are focused on the heart and the background is truncated in the projections. Reconstruction using truncated data results in biased images, leading to inaccurate kinetic parameter estimates. This paper has developed a closed-form kinetic parameter estimat...

Lesion-detection performance in oncologic PET depends in part upon count statistics, with shorter scans having higher noise and reduced lesion detectability. However, advanced techniques such as time-of-flight (TOF) and point spread function (PSF) modeling can improve lesion detectability. This work investigates the relationship between reducing co...

The introduction of fast scintillators with good stopping power for 511-keV photons has renewed interest in time-of-flight (TOF) PET. The ability to measure the difference between the arrival times of a pair of photons originating from positron annihilation improves the image signal-to-noise ratio (SNR). The level of improvement depends upon the ex...

Task-based assessment of image quality is a challenging but necessary step in evaluating advancements in PET instrumentation, algorithms, and processing. We have been developing methods of evaluating observer performance for detecting and localizing focal warm lesions using experimentally-acquired whole-body phantom data designed to mimic oncologic...

Iterative statistical algorithms offer desirable properties; however, the maximum likelihood solution provides sub-maximal performance for detecting focal lesions unless noise effects are regularized. Typical approaches include stopping the algorithm prior to convergence, penalizing objective functions, or post-reconstruction filtering. The width o...

Rapid multi-tracer PET, where two to three PET tracers are rapidly scanned with staggered injections, can recover certain imaging measures for each tracer based on differences in tracer kinetics and decay. We previously showed that single-tracer imaging measures can be recovered to a certain extent from rapid dual-tracer ⁶²Cu-PTSM (blood...

Time-of-flight (TOF) PET uses very fast detectors to improve localization of events along coincidence lines-of-response. This information is then utilized to improve the tomographic reconstruction. This work evaluates the effect of TOF upon an observer's performance for detecting and localizing focal warm lesions in noisy PET images. An advanced an...

The objective of this work was to evaluate the lesion detection performance of four fully-3D positron emission tomography (PET) reconstruction schemes using experimentally acquired data. A multi-compartment anthropomorphic phantom was set up to mimic whole-body (18)F-fluorodeoxyglucose (FDG) cancer imaging and scanned 12 times in 3D mode, obtaining...

The objective of this work was to evaluate the lesion detectability performance of four fully-3D PET reconstruction schemes using experimentally acquired data. A multi-compartment anthropomorphic phantom was setup to mimic whole-body FDG cancer imaging and scanned twelve times in 3D mode. Eight of the scans had twenty-six 68Ge "shell-less" lesions...

Noninvasive medical imaging procedures play a central and increasingly important role in cancer diagnosis, staging, re-staging, assessment of prognosis, treatment planning, therapy monitoring, and evaluation for recurrence. The dominant modality for imaging tumor physiology in vivo is positron emission tomography (PET). In PET, a pharmaceutical or...

Model-independent analysis with B-spline regularization has been used to quantify myocardial blood flow (perfusion) in dynamic contrast-enhanced cardiovascular magnetic resonance (CMR) studies. However, the model-independent approach has not been extensively evaluated to determine how the contrast-to-noise ratio between blood and tissue enhancement...

One of the greatest challenges facing iterative fully-3-D positron emission tomography (PET) reconstruction is the issue of long reconstruction times due to the large number of measurements for 3-D mode as compared to 2-D mode. A rotate-and-slant projector has been developed that takes advantage of symmetries in the geometry to compute volumetric p...

We are developing methods for imaging multiple PET tracers in a single scan with staggered injections, where imaging measures for each tracer are separated and recovered using differences in tracer kinetics and radioactive decay. In this work, signal separation performance for rapid dual-tracer (62)Cu-PTSM (blood flow) + (62)Cu-ATSM (hypoxia) tumor...

Rapid multi-tracer PET, where two to three PET tracers are rapidly scanned with staggered injections, can recover certain imaging measures for each tracer based on differences in tracer kinetics and decay. We previously showed that single-tracer imaging measures can be recovered to a certain extent from rapid dual-tracer ⁶²Cu-PTSM (blood...

Quantification of myocardial blood flows at rest and stress using 13N-ammonia PET is an established method; however, current techniques require a waiting period of about 1 h between scans. The objective of this study was to test a rapid dual-injection single-scan approach, where 13N-ammonia injections are administered 10 min apart during rest and a...

Blood flow and hypoxia are interrelated aspects of physiology that affect cancer treatment and response. Cu-PTSM and Cu-ATSM are related PET tracers for blood flow and hypoxia, and the ability to rapidly image both tracers in a single scan would bring several advantages over conventional single-tracer techniques. Using dynamic imaging with staggere...

Positron emission tomography (PET) can characterize different aspects of tumor physiology using various tracers. PET scans are usually performed using only one tracer since there is no explicit signal for distinguishing multiple tracers. We tested the feasibility of rapidly imaging multiple PET tracers using dynamic imaging techniques, where the si...

Positron emission tomography (PET) can characterize different aspects of tumor physiology using various tracers. PET is usually limited to one tracer since there is no explicit signal for distinguishing multiple tracers. We tested the feasibility of rapidly imaging two PET tracers using dynamic imaging techniques, where the signals from each tracer...

Iterative statistical reconstruction methods are becoming the standard in positron emission tomography (PET). Conventional maximum-likelihood expectation-maximization (MLEM) and ordered-subsets (OSEM) algorithms act on data which have been pre-processed into corrected, evenly-spaced histograms; however, such pre-processing corrupts the Poisson stat...

Hybrid PET gamma cameras with coincidence detection electronics are commonly equipped with parallel slat collimators in order to reduce detection of singles and scattered photons, and create a pseudo-2D imaging geometry. The objective of this work was to survey a broad range of parallel slat collimator designs using a series of Monte Carlo simulate...

Parallel slat collimators are often employed in hybrid positron emission tomography (PET) to reduce the scatter fraction, decrease singles rates, and create a pseudo 2-D imaging geometry. Similar collimators or inter-slice septa may be used with newer classes of large-area dedicated PET cameras. While conventional parallel slat collimators are adeq...

The lesion detectability performance of 6 PET imaging platforms has been compared using a highly reproducible whole-body phantom and localization receiver operating characteristic (LROC) analysis. A realistic whole-body phantom consisting of brain, thorax with lungs and liver, and pelvis with bladder was assembled and outfitted with 27 semipermanen...

The lesion detectability performance of 6 PET imaging platforms has been compared using a highly reproducible whole-body phantom and localization receiver operating characteristic (LROC) analysis. Methods: A realistic whole-body phantom consisting of brain, thorax with lungs and liver, and pelvis with bladder was assembled and outfitted with 27 sem...

Hybrid PET cameras have a number of hardware compromises that degrade image quality relative to dedicated PET. Such degradation is primarily caused by poor detection efficiency given by Nal scintillation crystals, limited count-rate culpabilities, multi-head as opposed to full-ring camera geometry, and so on. The count-rate limitation is exacerbate...

Hybrid PET scanners offer the possibility of obtaining myocardial viability information from coincidence imaging of the positron emitter (18)F-FDG and perfusion measurements from a single-photon tracer-potentially simultaneously. This new approach is less costly and more readily available than dedicated PET and offers potential for improved FDG res...

A 4D ordered-subsets maximum a posteriori (OSMAP) algorithm for dynamic SPECT is described which uses a temporal prior that constrains each voxel's behaviour in time to conform to a compartmental model. No a priori limitations on kinetic parameters are applied; rather, the parameter estimates evolve as the algorithm iterates to a solution. The esti...

Cardiac SPECT is typically performed clinically with static imaging protocols and visually assessed for perfusion defects based upon the relative intensity of myocardial regions. Dynamic imaging, however, has the potential to provide quantitative measures of flow, possibly improving diagnosis. The objective of this study was to compare the informat...

Di Bella EVR, Ross SG, Kadrmas DJ, et al. Compartmental modeling of technetium-99m-labeled teboroxime with dynamic single-photon emission computed tomography: Comparison with static thallium-201 in a canine model. Invest Radiol 2001;36:178-185. A compartmental modeling approach to deriving kinetic parameters from a time series of single-photon emis...

Tc-99m-teboroxime is a perfusion tracer with high myocardial extraction, fast washin and washout kinetics, and excellent imaging properties. The fast kinetics pose some problems for static imaging, but they also allow for back-to-back stress/rest studies to be performed very quickly. Furthermore, such fast kinetics are ideally suited for dynamic im...

Kinetic parameters and static images from dynamic SPECT imaging of (99m)Tc-teboroxime have been shown to reflect blood flow in dogs and in humans at rest and during adenosine stress. When compartment modeling is used, steady-state physiological conditions are assumed. With standard adenosine stress protocols, imaging of teboroxime would likely invo...

The objective of this project was to comparatively evaluate the image quality of rotating slant-hole (RSH) SPECT versus parallel beam SPECT. RSH collimators provide a means for increasing SPECT sensitivity at a volume of interest (VOI), such as the breast or heart. However RSH has an asymmetric geometric response function (GRF) and requires fully-3...

Clinically, cardiac SPECT is performed with static imaging protocols and visually assessed for perfusion defects based upon the relative intensity of myocardial regions. Dynamic imaging, however, has the potential to provide quantitative measures of flow, possibly improving diagnosis. The objective of this study was to compare the information conte...

There are a number of factors that affect the intensity of the apical region in cardiac SPECT images, which sometime lead to apparent defects in this region. In some patient studies, images reconstructed with non-uniform attenuation correction appear to have a significant decrease of apical intensity, whereas images reconstructed without such corre...

Dynamic SPECT is a relatively new technique that may potentially benefit many imaging applications. Though similar to dynamic PET, the accuracy and precision of dynamic SPECT parameter estimates are degraded by factors that differ from those encountered in PET. In this work we formulate a methodology for analytically studying the propagation of err...

Simultaneous acquisition of dual-isotope SPECT data offers a number of advantages over separately acquired data; however, simultaneous acquisition can result in cross-contamination between isotopes. In this work we propose and evaluate two frameworks for iterative model-based compensation of cross-contamination in dual-isotope SPECT. The methods we...

Tc-99m-teboroxime is a perfusion tracer with high myocardial extraction, fast washin and washout kinetics, and excellent imaging properties. The fast kinetics pose some problems for static imaging, but they also allow for back-to-back stress/rest studies to be performed very quickly. Furthermore, such fast kinetics are ideally suited for dynamic im...

The quality and quantitative accuracy of SPECT images are degraded by effects of attenuation, scatter, noise, geometric response, septal penetration and intrinsic crystal resolution. The geometric response has a significant degrading effect on spatial resolution, and can introduce spatial distortions because it is non-stationary. In this study the...

Kinetic parameters and static images from dynamic SPECT imaging of 99mTc-teboroxime have been shown to reflect blood flow in dogs and in humans at rest and during adenosine stress. When compartment modeling is used, steady-state physiological conditions are assumed. With standard adenosine stress protocols, imaging of teboroxime would likely involv...

Scatter compensation in Tl-201 single photon emission computed tomography (SPECT) presents an interesting challenge because of the multiple emission energies and relatively large proportion of scattered photons. In this paper, the authors present a simulation study investigating reconstructed image noise levels arising from various implementations...

The presence of scatter in single-photon emission computed tomography(SPECT) data can lead to degraded contrast and inaccurate quantitation in reconstructed images. A promising approach to compensate for these effects is to model the process of scatter during the image reconstruction process. Such reconstruction-based scatter compensation (RBSC) ha...

Accurate scatter compensation in SPECT can be performed by modelling the scatter response function during the reconstruction process. This method is called reconstruction-based scatter compensation (RBSC). It has been shown that RBSC has a number of advantages over other methods of compensating for scatter, but using RBSC for fully 3D compensation...

A variety of effects may make the apical region appear colder than it actually is when performing cardiac SPECT image reconstructions. For some of the patient data, the apical regions of the images reconstructed with only attenuation correction have lower relative intensities to the rest of the heart than those of the images reconstructed without a...

A 4D ordered-subsets maximum a posteriori (OSMAP) algorithm for dynamic SPECT is described. It uses a temporal prior that constrains each voxel's behavior in time to obey a compartmental model. No a priori limitations on kinetic parameters are applied; rather, the parameter estimates evolve as the algorithm iterates to a solution. The estimated par...

Since scattered photons carry degraded spatial information, scatter is typically considered a source of contamination in SPECT. However, with the advent of scatter modelling methods and reconstruction-based scatter compensation (RBSC), it may be possible to utilize scattered data in a productive manner. In this work we analyse the reconstructibilit...

Two of the most formidable challenges when diagnosing cardiac disease are detecting blood perfusion defects and ascertaining whether those defects are ischemic and viable myocardial tissue or infarcted tissue. Current medical imaging techniques can help answer these important clinical questions through imaging of the mechanical, electrical, and phy...

Results from clinical trials have suggested no improvement in lesion detection with parallel hole SPECT scintimammography (SM) with Tc-99m over parallel hole planar SM. In this initial investigation, we have elucidated some of the unique requirements of SPECT SM. With these requirements in mind, we have begun to develop practical data acquisition a...

Scatter compensation in Tl-201 SPECT presents an interesting challenge because of the multiple emission energies and relatively large proportion of scattered photons. Reconstruction-based scatter compensation (RBSC), in which the scatter response function is modeled during the reconstruction, can improve quantitative accuracy and contrast while mai...

In this work singular value decomposition (SVD) techniques are used to investigate how the use of low energy photons and multiple energy windows affects the noise properties of Tc-99m SPECT imaging. We have previously shown that, when modeling scatter in the projector and backprojector of iterative reconstruction algorithms, simultaneous reconstruc...

Transmission computed tomography (TCT) has been shown to be an accurate method of acquiring non-uniform attenuation maps for single-photon emission computed tomography (SPECT) attenuation compensation. One commonly encountered problem, especially for convergent beam geometries, is image truncation. We describe two methods for reducing associated tr...

A Ge-68 (t(1/2) = 271 d) source is normally used to produce transmission images for PET studies. New PET scanners utilize two or three 10-15 mCi Ge-68 sources for this purpose. V-48 (t(1/2) = 15.98 d) has been investigated as an alternative to Ge-68 for routine transmission scanning in PET. A target system has been developed to produce nearly homog...

We have proposed to use tellurium-123m line sources to determine attenuation maps for image reconstruction of technetium-99m radionuclide imaging. To experimentally evaluate the performance of the transmission line source for the fast sequential approach for emission and transmission data acquisition, a prototype tellurium-123m line source is manuf...

The convergent beam geometry of fan beam (FB) transmission computed tomography (TCT) often results in image truncation; producing ring artifacts, distorted body contours, and erroneously high pixel values in filtered-backprojection reconstructed images. A method is described which reduces the degree of truncation by performing two patient-shifted F...

Hybrid positron emission tomography (PET) with coincidence-detection gamma cameras has a potential role in cardiac viability imaging with 18 F-fluorodeoxyglucose. The feasibility of hybrid PET perfusion imaging was evaluated for short-lived generator-produced tracers 82 Rb and 62 Cu-pyruvaldehyde-bis-(4N- thiosemicarbazone) (PTSM). Methods Normal v...

In this work singular value decomposition (SVD) techniques are used to investigate how the use of low energy photons and multiple energy windows affects the noise properties of SPECT reconstructions. The authors have previously shown that, when modeling scatter in the projector of iterative reconstruction algorithms, simultaneous reconstruction fro...