Practical method for radioactivity distribution analysis in small-animal PET cancer studies

Abstract

We present a practical method for radioactivity distribution analysis in small-animal tumors and organs using positron emission tomography imaging with a calibrated source of known activity and size in the field of view. We reconstruct the imaged mouse together with a source under the same conditions, using an iterative method, Maximum Likelihood Expectation-Maximization with System Modeling, capable of delivering high resolution images. Corrections for the ratios of geometrical efficiencies, radioisotope decay in time and photon attenuation are included in the algorithm. We demonstrate reconstruction results for the amount of radioactivity within the scanned mouse in a sample study of osteolytic and osteoblastic bone metastasis from prostate cancer xenografts. Data acquisition was performed on the small-animal PET system which was tested with different radioactive sources, phantoms and animals to achieve high sensitivity and spatial resolution. Our method uses high resolution images to determine the volume of organ or tumor and the amount of their radioactivity, has the possibility of saving time, effort and the necessity to sacrifice animals. This method has utility for prognosis and quantitative analysis in small-animal cancer studies, and will enhance the assessment of characteristics of tumor growth, identifying metastases, and potentially determining the effectiveness of cancer treatment. The possible application for this technique could be useful for the organ radioactivity dosimetry studies.

Site Specific Discrete PEGylation of 124I-Labeled mCC49 Fab′ Fragments Improves Tumor MicroPET/CT Imaging in Mice

“…Radioactivity intensity of each tumor (SUV) 58 is shown in Figure 4 right bars, right axis (and Tables S3 and S4), 124 I-Fab′-A demonstrated the highest intensity in the tumors at all time points from 5 to 72 h, followed by 124 I-Fab′-NEM, 124 I-Fab′-B, and 124 I-Fab′-C. Table S3 shows that all of the molecules demonstrated high intensity in tumors, but 124 I-Fab′-A was significantly higher than that of 124 I-Fab′-B, 124 I-Fab′-NEM, and 124 I-Fab′-C: at 24 h SUV were 0.39 ± 0.08 vs 0.16 ± 0.10, 0.15 ± 0.04, 0.12 ± 0.04, p < 0.01). This is also true at 72 h except that 124 I-Fab′-NEM was not determined (0.17 ± 0.05 vs 0.05 ± 0.02, 0.06 ± 0.02, p < 0.01)).…”

“…These data were compared with the actual blood curves generated by radioactivity counting of extracted blood samples (vide infra). Standardized Uptake Values (SUV) were calculated using a formula, 58 SUV = Measure radioactivity in ROI in MBq/mL divided by ID/g in MBq/g-Body weight. Tumor to background ratio (T/B) values were calculated as SUV-Tumor/SUV-Arm.…”

Targeting murine heart and brain: visualisation conditions for multi-pinhole SPECT with 99mTc- and 123I-labelled probes

“…In preclinical research, multi-pinhole SPECT is developing into a complement to PET as a tool for in vivo imaging of pharmacodynamics and pharmacokinetics of receptor ligands [ 11 ], tracers of metabolic processes [ 12 , 13 ] and physiological properties in healthy and diseased small animals [ 3 , 14 – 17 ]. Dedicated SPECT and PET systems can provide sufficient spatial and temporal resolution for quantitative observation of such processes even in mouse models.…”

High-Resolution Photon Counting Using a Lens-Coupled EMCCD Gamma Camera

“…This method was improved by using a list-mode high-resolution algorithm for system matrix modeling [23], an image de-blurring procedure [24], and realistic resolution modeling [25]. Details of this EMSMD reconstruction method can be found in our previous publication [26]. Fig.…”