The imaging biomarkers EmphysemaPresence and NoduleSpiculation are crucial inputs for most models aiming to predict the risk of indeterminate pulmonary nodules detected at CT screening. To increase reproducibility and to accelerate screening workflow it is desirable to assess these biomarkers automatically. Validation on NLST images indicates that standard histogram measures are not sufficient to assess EmphysemaPresence in screenees. However, automatic scoring of bulla-resembling low attenuation areas can achieve agreement with experts with close to 80% sensitivity and specificity. NoduleSpiculation can be automatically assessed with similar accuracy. We find a dedicated spiculi tracing score to slightly outperform generic combinations of texture features with classifiers.
Microwave ablation (MWA) has become a recommended treatment modality for interventional cancer treatment.
Compared with radiofrequency ablation (RFA), MWA provides more rapid and larger-volume tissue heating. It
allows simultaneous ablation from different entry points and allows users to change the ablation size by controlling
the power/time parameters. Ablation planning systems have been proposed in the past, mainly addressing the needs
for RFA procedures. Thus a planning system addressing MWA-specific parameters and workflows is highly
desirable to help physicians achieve better microwave ablation results. In this paper, we design and implement an
automated MWA planning system that provides precise probe locations for complete coverage of tumor and margin.
We model the thermal ablation lesion as an ellipsoidal object with three known radii varying with the duration of the
ablation and the power supplied to the probe. The search for the best ablation coverage can be seen as an iterative
optimization problem. The ablation centers are steered toward the location which minimizes both un-ablated tumor
tissue and the collateral damage caused to the healthy tissue. We assess the performance of our algorithm using
simulated lesions with known "ground truth" optimal coverage. The Mean Localization Error (MLE) between the
computed ablation center in 3D and the ground truth ablation center achieves 1.75mm (Standard deviation of the
mean (STD): 0.69mm). The Mean Radial Error (MRE) which is estimated by comparing the computed ablation radii
with the ground truth radii reaches 0.64mm (STD: 0.43mm). These preliminary results demonstrate the accuracy
and robustness of the described planning algorithm.
The multimodal fusion of spatially tracked real-time ultrasound (US) with a prior CT scan has demonstrated clinical
utility, accuracy, and positive impact upon clinical outcomes when used for guidance during biopsy and radiofrequency
ablation in the treatment of cancer. Additionally, the combination of CT-guided procedures with positron emission
tomography (PET) may not only enhance navigation, but add valuable information regarding the specific location and
volume of the targeted masses which may be invisible on CT and US. The accuracy of this fusion depends on reliable,
reproducible registration methods between PET and CT. This can avoid extensive manual efforts to correct registration
which can be long and tedious in an interventional setting. In this paper, we present a registration workflow for
PET/CT/US fusion by analyzing various image metrics based on normalized mutual information and cross-correlation,
using both rigid and affine transformations to automatically align PET and CT. Registration is performed between the
CT component of the prior PET-CT and the intra-procedural CT scan used for navigation to maximize image
congruence. We evaluate the accuracy of the PET/CT registration by computing fiducial and target registration errors
using anatomical landmarks and lesion locations respectively. We also report differences to gold-standard manual
alignment as well as the root mean square errors for CT/US fusion. Ten patients with prior PET/CT who underwent
ablation or biopsy procedures were selected for this study. Studies show that optimal results were obtained using a crosscorrelation
based rigid registration with a landmark localization error of 1.1 +/- 0.7 mm using a discrete graphminimizing
scheme. We demonstrate the feasibility of automated fusion of PET/CT and its suitability for multi-modality
ultrasound guided navigation procedures.
Live three dimensional (3D) transesophageal echocardiography (TEE) provides real-time imaging of cardiac
structure and function, and has been shown to be useful in interventional cardiac procedures. Its application in
catheter based cardiac procedures is, however, limited by its limited field of view (FOV). In order to mitigate
this limitation, we register pre-operative magnetic resonance (MR) images to live 3D TEE images. Conventional
multimodal image registration techniques that use mutual information (MI) as the similarity measure use
statistics from the entire image. In these cases, correct registration, however, may not coincide with the global
maximum of MI metric. In order to address this problem, we present an automated registration algorithm that
balances a combination global and local edge-based statistics. The weighted sum of global and local statistics is
computed as the similarity measure, where the weights are decided based on the strength of the local statistics.
Phantom validation experiments shows improved capture ranges when compared with conventional MI based
methods. The proposed method provided robust results with accuracy better than 3 mm (5°) in the range of
-10 to 12 mm (-6 to 3°), -14 to 12 mm (-6 to 6°) and -16 to 6 mm (-6 to 3°) in x-, y-, and z- axes respectively.
We believe that the proposed registration method has the potential for real time intra-operative image fusion
during percutaneous cardiac interventions.
Radiofrequency ablation (RFA) is a minimally invasive procedure used for the treatment of small-to-moderate sized
tumors most commonly in the liver, kidney and lung. An RFA procedure for successfully treating large or complex
shape tumors may require many ablations, in a non-obvious pattern. Tumor size > 3cm predisposes to incomplete
treatment [1] and potential recurrence, therefore RFA is less often successful and less often used for treating large
tumors.
A mental solution is the current clinical practice standard, but is a daunting task for defining the complete 3D
geometrical coverage of a tumor and margin (planned target volume, PTV) with the fewest ellipsoidal ablation volumes,
while also minimizing collateral damage to healthy tissue. In order to generate a repeatable and reliable result, a solution
must quantify precise locations.
A new interactive planning system with an automated coverage algorithm is described. The planning system allows the
interventional radiologist to segment the potentially complex PTV, select an RFA needle (which determines the specific
3D ablation shape), and identify the skin entry location that defines the shape's orientation. The algorithm generates a
cluster of overlapping ablations from the periphery of the PTV, filling toward the center. The cluster is first tightened
toward the center to reduce the overall number of ablations and collateral damage, and then pulled toward optimal
attractors to further reduce the number of ablations. For most clinical applications, computation requires less than 15
seconds.
This fast ablation planning enables rapid scenario assessment, including proper probe selection, skin entry location,
collateral damage and procedure duration. The plan can be executed by transferring target locations to a navigation
system.
Imaging techniques try to identify patients who may respond to cardiac resynchronization therapy (CRT). However, it
may be clinically more useful to identify patients for whom CRT would not be beneficial as the procedure would not be
indicated for this group. We developed a novel, clinically feasible and technically-simple echocardiographic
dyssynchrony index and tested its negative predictive value. Subjects with standard indications for CRT had echo preand
post-device implantation. Atrial-ventricular dyssynchrony was defined as a left ventricular (LV) filling time of
<40% of the cardiac cycle. Intra-ventricular dyssynchrony was quantified as the magnitude of LV apical rocking. The
apical rocking was measured using tissue displacement estimates from echo data. In a 4-chamber view, a region of
interest was positioned within the apical end of the middle segment within each wall. Tissue displacement curves were
analyzed with custom software in MATLAB. Rocking was quantified as a percentage of the cardiac cycle over which the
displacement curves showed discordant behavior and classified as non-significant for values <35%. Validation in 50
patients showed that absence of significant LV apical rocking or atrial-ventricular dyssynchrony was associated with
non-response to CRT. This measure may therefore be useful in screening to avoid non-therapeutic CRT procedures.
We present and validate image-based speckle-tracking calipers for quantification of tissue deformation and rotation
in dynamic cardiovascular phantom models. Lagrangian strain was computed from the change in distance
between caliper regions-of-interest (ROIs) positioned within the wall of a pulsatile phantom and compared with
reference measurements derived from cardiac CT imaging. In a torsion phantom, rotational tissue excursion
in a 2D plane was estimated and compared with reference values from CT-scan data. Tissue deformation and
rotation measurements correlated well with their respective reference measurements. Our algorithm is capable
of estimating strain and rotation from distinct tissue regions without requiring explicit cardiac border detection,
a step which can be especially challenging in patients with poor acoustic windows.
This work presents an integrated system for multimodality image guidance of minimally invasive medical procedures.
This software and hardware system offers real-time integration and registration of multiple image streams with
localization data from navigation systems. All system components communicate over a local area Ethernet network,
enabling rapid and flexible deployment configurations. As a representative configuration, we use X-ray fluoroscopy
(XF) and ultrasound (US) imaging. The XF imaging system serves as the world coordinate system, with gantry geometry
derived from the imaging system, and patient table position tracked with a custom-built measurement device using linear
encoders. An electromagnetic (EM) tracking system is registered to the XF space using a custom imaging phantom that
is also tracked by the EM system. The RMS fiducial registration error for the EM to X-ray registration was 2.19 mm,
and the RMS target registration error measured with an EM-tracked catheter was 8.81 mm. The US image stream is
subsequently registered to the XF coordinate system using EM tracking of the probe, following a calibration of the US
image within the EM coordinate system. We present qualitative results of the system in operation, demonstrating the
integration of live ultrasound imaging spatially registered to X-ray fluoroscopy with catheter localization using
electromagnetic tracking.
KEYWORDS: Modulation transfer functions, LCDs, Radiology, Diagnostics, Bone, Medical imaging, Projection systems, Large screens, Electronics, Medical devices
Radiology has readily made the transition to the digital reading room. One commodity left behind when moving to digital displays however is display real estate. Even with multiple monitors radiologists cannot display numerous images as they did on a film alternator. We evaluated a large-screen rear-projection display (Philips Electronics) for potential use in radiology. Resolution was 1920 x 1080 with a 44-inch diagonal size and it was a color display. For comparison we used the IBM 9 Mpixel color display (22-inch diagonal) set to a comparable resolution and maximum luminance. Diagnostic accuracy with a series of bone images with subtle fractures and six observers was comparable (F = 0.3170, p = 0.5743) to traditional computer monitor. Viewing time, however, was significantly shorter (t = 6.723, p < 0.0001) with the large display for both normal and fracture images. On average, readers sat significantly closer (t = 5.578, p = 0.0026) to the small display than the large display. Four of the 6 radiologists preferred the smaller display, judging it to yield a sharper image. Half of the readers thought the black level was better with the large display and half with the small display. Most of the radiologists thought the large-screen display has potential for use in conferencing situations or those in which multiple viewers need to see images simultaneously.
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