Abstract
ObjectivesThe purpose of this study was to assess the feasibility of dual-energy CT-based material decomposition using dual-X-ray spectra information to determine local concentrations of holmium microspheres in phantoms and in an animal model.Materials and methodsA spectral calibration phantom with a solution containing 10 mg/mL holmium and various tube settings was scanned using a third-generation dual-energy CT scanner to depict an energy-dependent and material-dependent enhancement vectors. A serial dilution of holmium (microspheres) was quantified by spectral material decomposition and compared with known holmium concentrations. Subsequently, the feasibility of the spectral material decomposition was demonstrated in situ in three euthanized rabbits with injected (radioactive) holmium microspheres.ResultsThe measured CT values of the holmium solutions scale linearly to all measured concentrations and tube settings (R2 = 1.00). Material decomposition based on CT acquisitions using the tube voltage combinations of 80/150 Sn kV or 100/150 Sn kV allow the most accurate quantifications for concentrations down to 0.125 mg/mL holmium.ConclusionDual-energy CT facilitates image-based material decomposition to detect and quantify holmium microspheres in phantoms and rabbits.Key Points• Quantification of holmium concentrations based on dual-energy CT is obtained with good accuracy.• The optimal tube-voltage pairs for quantifying holmium were 80/150 Sn kV and 100/150 Sn kV using a third-generation dual-source CT system.• Quantification of accumulated holmium facilitates the assessment of local dosimetry for radiation therapies.
Highlights
In the 1970s and 1980s, dual-energy CT (DECT) technology demonstrated improved tissue characterization; the technique was not widely applied due to limitations like noise in low-kilo voltage images, acquisition time, and image registration difficulties [1,2,3,4,5]
Quantification of accumulated holmium facilitates the assessment of local dosimetry for radiation therapies
Since only a very small fraction of holmium-165 is converted to holmium166 after neutron activation during production, no difference is expected in X-ray attenuation between radioactive and non-radioactive microspheres
Summary
In the 1970s and 1980s, dual-energy CT (DECT) technology demonstrated improved tissue characterization; the technique was not widely applied due to limitations like noise in low-kilo voltage (kV) images, acquisition time, and image registration difficulties [1,2,3,4,5]. DECT technology is clinically established as a result of fast technological developments, such as detectors with fully integrated electronics minimizing electronic noise, improved spectral separation using optimized beam pre-filtration, increased scan speed, and improved post processing techniques [6,7,8,9,10,11]. Experimental studies suggest the use of nonapproved CM with spectral properties that could be utilized for CTA or cancer theranostics
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