Dataset Information

Collimator design for a dedicated molecular breast imaging-guided biopsy system: proof-of-concept.

ABSTRACT: Molecular breast imaging (MBI) is a dedicated nuclear medicine breast imaging modality that employs dual-head cadmium zinc telluride (CZT) gamma cameras to functionally detect breast cancer. MBI has been shown to detect breast cancers otherwise occult on mammography and ultrasound. Currently, a MBI-guided biopsy system does not exist to biopsy such lesions. Our objective was to consider the utility of a novel conical slant-hole (CSH) collimator for rapid (<1 min) and accurate monitoring of lesion position to serve as part of a MBI-guided biopsy system.An initial CSH collimator design was derived from the dimensions of a parallel-hole collimator optimized for MBI performed with dual-head CZT gamma cameras. The parameters of the CSH collimator included the collimator height, cone slant angle, thickness of septa and cones of the collimator, and the annular areas exposed at the base of the cones. These parameters were varied within the geometric constraints of the MBI system to create several potential CSH collimator designs. The CSH collimator designs were evaluated using Monte Carlo simulations. The model included a breast compressed to a thickness of 6 cm with a 1-cm diameter lesion located 3 cm from the collimator face. The number of particles simulated was chosen to represent the count density of a low-dose, screening MBI study acquired with the parallel-hole collimator for 10 min after a ∼150 MBq (4 mCi) injection of Tc-99m sestamibi. The same number of particles was used for the CSH collimator simulations. In the resulting simulated images, the count sensitivity, spatial resolution, and accuracy of the lesion depth determined from the lesion profile width were evaluated.The CSH collimator design with default parameters derived from the optimal parallel-hole collimator provided 1-min images with error in the lesion depth estimation of 1.1 ± 0.7 mm and over 21 times the lesion count sensitivity relative to 1-min images acquired with the current parallel-hole collimator. Sensitivity was increased via more vertical cone slant angles, larger annular areas, thinner cone walls, shorter cone heights, and thinner radiating septa. Full width at half maximum trended in the opposite direction as sensitivity for all parameters. There was less error in the depth estimates for less vertical slant angles, smaller annular areas, thinner cone walls, cone heights near 1 cm, and generally thinner radiating septa.A Monte Carlo model was used to demonstrate the feasibility of a CSH collimator design for rapid biopsy application in molecular breast imaging. Specifically, lesion depth of a 1-cm diameter lesion positioned in the center of a typical breast can be estimated with error of less than 2 mm using circumferential count profiles of images acquired in 1 min.

SUBMITTER: Weinmann AL

PROVIDER: S-EPMC3537760 | biostudies-other | 2013 Jan

REPOSITORIES: biostudies-other

ACCESS DATA

Similar Datasets

Project description:Research and discovery of novel radiopharmaceuticals and targets thereof generally involves initial studies in cell cultures, followed by animal studies, both of which present several inherent limitations. The objective of this work was to develop a tissue bioreactor (TBR) enabling modulation of the microenvironment and to integrate the TBR with a small-animal PET scanner to facilitate imaging biomarker research and discovery and validation of radiopharmaceuticals.The TBR chamber is a custom-blown, water-jacketed, glass vessel enclosed in a circulating perfusion bath powered by a peristaltic pump, which is integrated within the field of view of the PET scanner. The chamber is in series with a gas exchanger and a vessel for degassing the system during filling. Dissolved oxygen/temperature probes and septa for injection or sampling are located at the inlet and outlet of the cell chamber. A pH probe is located at the chamber outlet. Effluent is collected in the fraction collector as mixed-cup samples. In addition, both medium and tissue chamber can be sampled to investigate tissue and secretory products through multiscale analysis. As a proof of concept, we studied the effects of lipids on glucose uptake using HepG2 cells. To that end, we varied the nutrient substrate environment over a period of approximately 27 d, before and after the addition of lipids, and studied the effects of pioglitazone, a peroxisome proliferator-activated receptor ? agonist, on lipid and glucose uptake. In parallel, the TBR was imaged by PET in conjunction with (11)C-palmitate in the presence and absence of lipids to characterize (11)C-palmitate uptake.The O2 consumption, glucose consumption, lactate production, and free fatty acid consumption and production rates were consistent in demonstrating the effects of lipids on glucose uptake. Pioglitazone exhibited improved glucose uptake within 3 d of treatment. Semiquantitative analysis suggested that lipids induced greater (11)C-palmitate uptake.The integrated TBR offers a platform to monitor and modulate the tissue microenvironment, thus facilitating tissue-specific imaging and therapeutic biomarkers of disease, identification of molecular diagnostic markers, and validation of radiopharmaceuticals in both rodent and human cell lines.

Project description:The purpose of this article is to present the first imaging experiments to demonstrate the functional equivalence between a conventional rotational gantry and a fixed-beam imaging geometry, and the feasibility of an iterative image-reconstruction technique under gravitational deformation.Experiments were performed using an Elekta Axesse with Agility MLC and XVI, a custom-built rotating phantom stage, a Catphan QA phantom, and a porcine heart. For the imaging equivalence, a conventional cone beam computed tomography (CBCT) of the Catphan was acquired, as well as a set of 660 x-ray projections with a static gantry and rotating Catphan. Both datasets were reconstructed with the Feldkamp-Davis-Kress (FDK) algorithm, and the resultant volumetric images were compared using standard metrics. For imaging under gravitational deformation, a conventional CBCT of the Catphan and a set of 660 x-ray projections with a static gantry and rotating Catphan were also acquired with a porcine heart. The conventional CBCT was reconstructed using FDK. The projections that were acquired with the heart rotating were sorted into angular bins and reconstructed with prior image constrained compressed sensing using a deformation-blurred FDK prior. Deformation was quantified with B-spline transformation-based deformable image registration.For imaging equivalence, the difference between the two Catphan images was consistent with Poisson noise. For imaging under gravitational deformation, the conventional CBCT porcine heart image (ground truth at 0 degrees) matched the static gantry, rotating heart reconstruction with a mean magnitude of <3 mm and maximum magnitude of <5 mm of the deformation vector field. The mean deformation of the rotating heart was 3.0 to 8.9 mm, up to 16.1 mm maximum deformation. Deformation was mainly observed in the direction of gravity.We have demonstrated imaging equivalence in cone beam CT reconstructions between rigid phantom images acquired with a conventional rotating gantry and with a fixed-gantry and rotating phantom. We have presented a method for image reconstruction under a fixed-beam imaging geometry using a deformable phantom.

Project description:Molecular breast imaging (MBI) is a nuclear medicine technology that uses dual-head cadmium zinc telluride (CZT) gamma cameras to image functional uptake of a radiotracer, Tc-99m sestamibi, in the breast. An important factor in adoption of MBI in the screening setting is reduction of the necessary administered dose of Tc-99m sestamibi from the typically used dose of 740 MBq to approximately 148 MBq, such that MBI's whole-body effective dose is comparable to that of screening mammography. Methods that increase MBI count sensitivity may allow a proportional reduction in the necessary administered dose. Our objective was to evaluate the impact of two count sensitivity improvement methods on image quality by evaluating count sensitivity, spatial resolution, and lesion contrast in phantom simulations.Two dual-head CZT-based MBI systems were studied: LumaGem and Discovery NM 750b. Two count sensitivity improvement methods were implemented: registered collimators optimized for dedicated breast imaging and widened energy acceptance window optimized for use with CZT. System sensitivity, spatial resolution, and tumor contrast-to-noise ratio (CNR) were measured comparing standard collimation and energy window setting [126-154 keV (+10%, -10%)] with optimal collimation and a wide energy window [110-154 keV (+10%, -21%)].Compared to the standard collimator designs and energy windows for these two systems, use of registered optimized collimation and wide energy window increased system sensitivity by a factor of 2.8-3.6. Spatial resolution decreased slightly for both systems with new collimation. At 3 cm from the collimator face, LumaGem's spatial resolution was 4.8 and 5.6 mm with standard and optimized collimation; Discovery NM 750b's spatial resolution was 4.4 and 4.6 mm with standard and optimized collimation, respectively. For both systems, at tumor depths of 1 and 3 cm, use of optimized collimation and wide energy window significantly improved CNR compared to standard settings for tumors 8.0 and 9.2 mm in diameter. At the closer depth of 1 cm, optimized collimation and wide energy window also significantly improved CNR for 5.9 mm tumors on Discovery NM 750b.Registered optimized collimation and wide energy window yield a substantial gain in count sensitivity and measurable gain in CNR, with some loss in spatial resolution compared to the standard collimator designs and energy windows used on these two systems. At low-count densities calculated to represent doses of 148 MBq, this tradeoff results in adequate count density and lesion contrast for detection of lesions ≥8 mm in the middle of a typical breast (3 cm deep) and lesions ≥6 mm close to the collimator (1 cm deep).

Dataset Information

Collimator design for a dedicated molecular breast imaging-guided biopsy system: proof-of-concept.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets