Advances in Vascular Diagnostics using Magnetic Particle Imaging (MPI) for Blood Circulation Assessment

Rapid and accurate assessment of conditions characterized by altered blood flow, cardiac blood pooling, or internal bleeding is crucial for diagnosing and treating various clinical conditions. While widely used imaging modalities such as magnetic resonance imaging (MRI), computed tomography (CT), and ultrasound offer unique diagnostic advantages, they fall short for specific indications due to limited penetration depth and prolonged acquisition times. Magnetic particle imaging (MPI), an emerging tracer-based technique, holds promise for blood circulation assessments, potentially overcoming existing limitations with reduction in background signals and high temporal and spatial resolution, below the millimeter scale. Successful imaging of blood pooling and impaired flow necessitates tracers with diverse circulation half-lives optimized for MPI signal generation. Recent MPI tracers show potential in imaging cardiovascular complications, vascular perforations, ischemia, and stroke. The impressive temporal resolution and penetration depth also position MPI as an excellent modality for real-time vessel perfusion imaging via functional MPI (fMPI). This review summarizes advancements in optimized MPI tracers for imaging blood circulation and analyzes the current state of pre-clinical applications. This work discusses perspectives on standardization required to transition MPI from a research endeavor to clinical implementation and explore additional clinical indications that may benefit from the unique capabilities of MPI.

Total-Body PET/CT Applications in Cardiovascular Diseases: A Perspective Document of the SNMMI Cardiovascular Council

Digital PET/CT systems with a long axial field of view have become available and are emerging as the current state of the art. These new camera systems provide wider anatomic coverage, leading to major increases in system sensitivity. Preliminary results have demonstrated improvements in image quality and quantification, as well as substantial advantages in tracer kinetic modeling from dynamic imaging. These systems also potentially allow for low-dose examinations and major reductions in acquisition time. Thereby, they hold great promise to improve PET-based interrogation of cardiac physiology and biology. Additionally, the whole-body coverage enables simultaneous assessment of multiple organs and the large vascular structures of the body, opening new opportunities for imaging systemic mechanisms, disorders, or treatments and their interactions with the cardiovascular system as a whole. The aim of this perspective document is to debate the potential applications, challenges, opportunities, and remaining challenges of applying PET/CT with a long axial field of view to the field of cardiovascular disease.

Tumor Thrombus within the Superior Sagittal Sinus Detected on FDG PET Venography

Early detection of cereberal venous sinus thrombosis is important to prevent complication. Here we present an interstecting case of tumor thrombsosis of the superior sagittal venous sinus in a follow up case of adenocarcinoma esophagus, highlighting the feasibility for FDG PET venography for detection of the same.

Biologically-Based Mathematical Modeling of Tumor Vasculature and Angiogenesis via Time-Resolved Imaging Data

Tumor-associated vasculature is responsible for the delivery of nutrients, removal of waste, and allowing growth beyond 2-3 mm3. Additionally, the vascular network, which is changing in both space and time, fundamentally influences tumor response to both systemic and radiation therapy. Thus, a robust understanding of vascular dynamics is necessary to accurately predict tumor growth, as well as establish optimal treatment protocols to achieve optimal tumor control. Such a goal requires the intimate integration of both theory and experiment. Quantitative and time-resolved imaging methods have emerged as technologies able to visualize and characterize tumor vascular properties before and during therapy at the tissue and cell scale. Parallel to, but separate from those developments, mathematical modeling techniques have been developed to enable in silico investigations into theoretical tumor and vascular dynamics. In particular, recent efforts have sought to integrate both theory and experiment to enable data-driven mathematical modeling. Such mathematical models are calibrated by data obtained from individual tumor-vascular systems to predict future vascular growth, delivery of systemic agents, and response to radiotherapy. In this review, we discuss experimental techniques for visualizing and quantifying vascular dynamics including magnetic resonance imaging, microfluidic devices, and confocal microscopy. We then focus on the integration of these experimental measures with biologically based mathematical models to generate testable predictions.

Usefulness of dynamic fluorodeoxyglucose positron emission tomography/computed tomography in diagnosing pulmonary arteriovenous malformation mimicking a lung tumour

A 61-year-old male patient with known kidney dysfunction who underwent a non-contrast thorax CT and was then referred to our department for metabolic assessment of solitary pulmonary nodule (SPN). The patient underwent dynamic FDG PET/CT to differentiate benign from malignant SPN. This case illustrates the usefulness of dynamic FDG PET/CT imaging when assessing SPN especially in patients with suspicion for pulmonary arterio-venous malformation accompanying renal failure or contrast allergy.

Potential Cardiovascular Applications of Total-body PET Imaging

Cardiovascular conditions can exist as part of a systemic disorder (eg, sarcoidosis, amyloidosis, or vasculitis) or have systemic consequences as a result of the cardiovascular insult (eg, myocardial infarction). In other circumstances, multisystem evaluation of metabolism and blood flow might be key for evaluation of multisystemic syndromes or conditions. Long axial field-of-view PET/computed tomography systems hold the promise of transforming the investigation of such systemic disorders. This article aims at reviewing some of the potential cardiovascular applications of this novel instrumentation device.

Early-Dynamic Positron Emission Tomography (PET)/Computed Tomography and PET Angiography for Endoleak Detection After Endovascular Aneurysm Repair

PURPOSE

To propose a positron emission tomography (PET)/computed tomography (CT) protocol including early-dynamic and late-phase acquisitions to evaluate graft patency and aneurysm diameter, detect endoleaks, and rule out graft or vessel wall inflammation after endovascular aneurysm repair (EVAR) in one examination without intravenous contrast medium.

TECHNIQUE

Early-dynamic PET/CT of the endovascular prosthesis is performed for 180 seconds immediately after intravenous injection of F-18-fluorodeoxyglucose. Data are reconstructed in variable time frames (time periods after tracer injection) to visualize the arterial anatomy and are displayed as PET angiography or fused with CT images. Images are evaluated in view of vascular abnormalities, graft configuration, and tracer accumulation in the aneurysm sac. Whole-body PET/CT is performed 90 to 120 minutes after tracer injection.

CONCLUSION

This protocol for early-dynamic PET/CT and PET angiography has the potential to evaluate vascular diseases, including the diagnosis of complications after endovascular procedures.

F-18 Choline PET angiography of the pelvic arteries: evaluation of image quality and comparison with contrast-enhanced CT

PURPOSE

The purpose was to show the feasibility of F-18 choline positron emission tomography (PET) angiography for the evaluation of abdominal and iliac arteries.

METHODS

Thirty-five patients were examined and image quality was scored. Findings were correlated with contrast-enhanced computed tomography.

RESULTS

Image quality was best in the aorta and common iliac arteries (100% and 93% of vessels). Negative predictive values of PET angiography were excellent (100%), and positive predictive values were impaired by disease overestimation.

CONCLUSION

PET angiography is technically feasible and of good image quality in large arteries. In selected cases, it may become an alternative to established angiographic methods.

Multimodal imaging of aortoiliac occlusive disease with three-dimensional postprocessing of PET angiography and CT

Two patients with aortoiliac occlusive disease underwent dynamic and late-static positron emission tomography/computed tomography (PET/CT) acquisitions with 257 and 244 MBq F-18 FDG (CT scan parameters 50 mAs, 120 kV, pitch 1.25). Three-dimensional reconstructions revealed an occluded aortic stent and a high-grade aortic stenosis and demonstrated the relations of vascular pathologies to adjacent structures. Early-dynamic PET can be performed without additional radioactive tracer and may be valuable for evaluation and intervention planning in patients with contraindications to other angiographic modalities.