Animal Imaging: Overview

Animal Imaging
Overview
Members

Animal Imaging: Overview

Share
Share

9.4T Magnetic Resonance Imaging and Spectroscopy and 7T duel modality PET/MRI

The MR core facility currently utilizes a 9.4T 20-cm bore magnet imaging/spectroscopy system for proton imaging experiments alongside a 7T/30 scanner. Ultra high-resolution ex vivo MRI can also be performed with a 11.7T micro MRI scanner. The core has a PET/MRI insert that allows simultaneous co-registered acquisition of both in vivo PET/MR imaging in mouse and sequential PET/MR acquisition for rats. We provide a wide array of non-invasive, high-resolution, quantitative imaging-based capabilities for metabolic characterization of tumors and their microenvironment in small-animals. We perform MRI phenotypic screening of tumor incidence, progression and therapy-induced regression in xenograft models and transgenic/knock-out models; detection and localization of tumor hypoxia and re-oxygenation; evaluation of tumor cellularity, vascularity and the its response under treatment.

In addition, in vivo metabolite quantitation using x-nuclei in vivo MR spectroscopy imaging is available after custom setup. This allows monitoring of drugs with labels that are MR visible. Other labels, including iron and gadolinium which are MR detectable through relaxation effect, are used as MR contrast agents. These have potential for tagging of compounds and cells for in vivo tracing.

Techniques Available and Services Provided

  • In vivo acquisition and reconstruction of high-resolution images in small animals
  • In vivo and Ex vivo diffusion imaging
  • In vivo cine cardiac imaging
  • Off-line Image processing.
  • Ex vivo imaging and analysis of tissues.
  • Metabolite quantitation of both perfused cells and animals.
  • In vivo drug and organ metabolism.
  • Estimates of tumor perfusion.

microPET, microCT, X-SPECT, Ultrasound and Optical Imaging and External-Beam Radiation Therapy

The Focus 120 microPET and Inveon microPET/microCT are dedicated high-resolution-animal PET scanners (the latter with an integrated CT scanner for transparent registration of functional PET and anatomic CT image sets). Both systems provide isotropic PET resolution of 1-2 mm FWHM or better and absolute activity quantitation (e.g., in %ID/gm). PET data are collected in list mode, with resulting unlimited flexibility in binning of dynamic frames. 

The Core’s PET imaging capability will soon be supplemented with a state-of-the-art Super Argus 6R PET/CT (installation scheduled for the third quarter of 2025).  The NanoSPECT/CT Plus is a dedicated small-animal SPECT/CT scanner for non-invasive, ultra-high-resolution (~1 mm) imaging in vivo of single photon-emitting radiotracers (with absolute activity quantitation [e.g., in %ID/gm]) and high-resolution (~100 microns) CT scans of anatomy. It can image multiple photopeaks for simultaneous imaging of multiple radiotracers. The cone-beam CT sub-systems of both the Inveon microPET/microCT, and the NanoSPECT/CT Plus, and the new Super Argus 6R can be operated in a “CT-only” mode; both provide spatial resolution of ~100 microns or better depending on the user-selectable parameters.  Optical in vivo imaging is a widely used, highly sensitive modality for tracking genetically modified (i.e., luciferase- or -fluorophore-expressing) immune cells, cancer cells, and infectious agents. The optics of the Core’s Ivis Lumina II, Spectrum, and Spectrum CT optical imaging systems, with cryo-cooled (~-100 °C) charged-coupled detector (CCD) cameras, are optimized for low background and high sensitivity and can detect as few as ~10,000 luminescent cells. In addition, the Spectrum’s and Spectrum CT’s proprietary “spectral un-mixing” capability effectively “subtracts” tissue autofluorescence to yield high-contrast images of the in vivo distribution of a wide range of selected fluorophores. 

The Core’s Vevo 2100 small-animal US scanner was recently upgraded to a Vevo F2 US scanner (FujiFil/VisualSonics), a compact, full-function small-animal (rodent) US imaging system combining ultra-high-frequency US imaging in a turn-key all-in-one platform with an integrated touch screen-controlled Windows PC running the proprietary FUJIFILM VisualSonics data acquisition and processing software.  The Vevo F2 includes the 29-MHz UHFx series transducer for near-full-depth rat imaging and the 57-MHz UHFx series transducer for ultra-high-resolution (down to 30 mm) mouse imaging. 

The Core’s Microirradiator, the X-RAD 225Cx Image-Guided Biological Irradiator (Precision X-Ray) was upgraded to a state-of-the-art X-RAD SmartPlus Irradiator (also Precision X-Ray).  Like the X-RAD 225Cx, the SmartPlus  provides image (i.e., CT) -guided delivery of dose distributions of orthovoltage x-rays with an accuracy of 1 mm or better. Its isocentric design and integrated cone-beam CT allow accurate, real-time delineation of the targeted 3D volume and avoidance of normal structures and requires less than ~5 minutes to deliver absorbed doses of up to 10 Gy. It includes a laser isocenter locator to direct the beam in 3D to the center of the targeted volume; multiple treatment collimators (applicators) for defining circular or rectangular treatment fields (TFs) from 1 to 40 mm; a user-configurable collimator (applicator) for defining irregularly shaped TFs; a dosimeter for measurement of dose within the TF for tumor-specific treatment planning; and a DICOM image registration software package for integration of multi-modality imaging (i.e., PET, MRI, etc.) for guidance in dose delivery.

Techniques Available and Services Provided

  • Acquisition and reconstruction of planar, SPECT, and PET images of single-photon- and positron-emitting radiotracer distributions, microCT imaging, and optical (bioluminescent and fluorescent) imaging of mice and rats.
  • Image processing (digital filtering, ROI analysis, etc.) and computer storage.
  • Mathematical analysis (e.g., curve-fitting, compartmental modeling) of time-activity data.
  • Harvesting of tissues at necropsy and scintillation well-counting ex vivo of radioactivity in blood and tissue samples.
  • Phosphor plate-based quantitative autoradiography of tissue sections (with harvesting, freezing, and sectioning of tissue samples using the facility’s cryostatic microtome).
  • Consultation on experimental design, including choice of the radiotracer, handling of radioactivity, and compliance with associated institutional and regulatory requirements.