Scientific Research

ABK Biomedical Scientific Research

ABK Biomedical is committed to improving every aspect of Y90 radioembolization treatment and patient follow-up.

We are dedicated to improving patient outcomes; from engineering microsphere technology and delivery systems for optimal imaging and tumor targeting to ensuring physicians know the cutting-edge advantages of Eye90 microspheres Precision Dosimetry™.

Eye90 microspheres Precision Dosimetry™

Precision Dosimetry involves a CT-based approach to calculating the post-treatment absorbed dose. The benefits of Precision Dosimetry include significantly enhanced spatial resolution of the dose distribution and a more accurate estimation of dose heterogeneity.

Current Y90 microsphere technology lacks sufficient radiopacity for CT-based dosimetry to be feasible.

Eye90 microspheres™ are engineered to be radiopaque, permitting Precision Dosimetry with CT-based imaging to be utilized. The clinical potential of Eye90 microspheres Precision Dosimetry™ has been demonstrated in a pre-clinical model and published in a well-respected peer-reviewed journal.

Y90 radioembolization

Eye90 microspheres Precision Dosimetry™ in a rabbit model. a–c Axial, sagittal, and coronal views of CT-based dose distribution.  d–f Axial, sagittal, and coronal views of traditional PET-based dose distribution showing inferior resolution.

From Henry et al. EJNMMI Physics (2022) 9:21

Scientific Presentations

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Purpose :
Perform a comparison of PET- and CT-based approaches to dosimetry in Yttrium-90 (90Y) radioembolization (RE) following the administration of 90Y-infused radiopaque microspheres (MS) in a rabbit liver model.
Materials & Methods :
An experimental calibration phantom (Figure 1.A) containing multiple cylinders varying in diameter and MS concentration was designed to quantify the correlation between CT Hounsfield units (HU) and MS concentration. Mean HU were extracted from CT volumes-of-interest placed within 15 mm-diameter cylinders containing nominal MS concentrations of 0.5 mg/mL, 5.0 mg/mL, and 25.0 mg/mL. A calibration curve was determined through a linear least squares fit of the data (Figure 1.B). PET and CT imaging of a rabbit liver was performed following the intra-arterial administration of activated 90Y MS. CT voxel values [HU] were transformed into 90Y activity [Bq] through the application of the calibration curve and three scale factors: CT voxel volume [mL], MS number per milligram [MS/mg], and specific activity [Bq/MS]. PET and CT activity distributions were convolved with 90Y dose-voxel kernels generated with the GATE Monte Carlo toolkit to produce PET- and CT-based dose distributions, dd_PET and dd_CT, respectively. Within the liver, the mean dose ± standard deviation (Dµ ± σ) and dose maxima (Dmax) were compared between dd_PET and dd_CT.
Results :
The calibration curve demonstrated strong linearity (r2 > 0.999) between HU and MS concentration. Axial, sagittal, and coronal slices through a high-dose region in dd_CT and dd_PET are shown in Figure 2. In dd_PET, Dmax = 309 Gy and Dµ = 68 ± 63 Gy. In dd_CT, Dmax = 1230 Gy and Dµ = 45 ± 65 Gy. These statistics suggest that Dµ can be ascertained with reasonable confidence independent of the imaging modality while the true range of dose values is better characterized through CT-based dosimetry.
Conclusions :
CT imaging of radiopaque MS distributions in 90Y RE can provide increased confidence in characterizing the dose heterogeneity – relative to PET-based dosimetry – by capturing the true range of dose values within the tumour and healthy liver tissue. The accurate and precise knowledge of the dose distribution is essential in identifying undertreated tumour volumes, identifying radiation toxicity in adjacent liver tissue, and improving our estimates of dose metrics used in establishing a viable dose-response

CT-based Dosimetry in Yttrium-90 Radioembolization Performed in a Rabbit Liver Model. Dr E. Courtney Henry, Dalhousie University

Global Embolization Symposium and Technologies Annual Meeting 2021

  • The poor spatial resolution encountered with Y90 PET and SPECT dosimetry underestimates the true dose heterogeneity following radioembolization.
  • Improved estimates of distribution can be obtained with higher resolution dosimetry to accurately quantify dose-response and identify areas at risk of recurrence.
  • The steep dose gradients observed with CT-based dosimetry are highly correlated with radioembolized vasculature because it is directly derived from the microspheres implanted distribution.
  • The strong positive correlation between radiopaque microspheres and CT-based dosimetry may help physicians with dose-response relationships and improve future patient outcomes.
Read the abstract!
Purpose :
The purpose of this study was to develop a novel hepatic tumor vascular model (TVM) for investigating the embolic characteristics of Y-90 microspheres (MS) during radioembolization (RE). The microscale features of this model enables quantification of attributes not practical in animal models, and may offer new perspectives on the mechanics of embolization.
Materials & Methods :
The TVM was designed to represent a 4.5cm (48cc) tumor in a 1400cc liver with a total hepatic flow of 160mL/min. The TVM flow rate was calculated to be 20mL/min using a two compartment model with a T/N ratio of 4. Thus with a mean inlet pressure of 90mmHg, the TVM must have a fluid resistance of 270PRU (mmHg·s/mL). The TVM was designed to branch from an inlet diameter of 1mm to four microfluidic trees which further branch down to a total of 6400 outlet arterioles. These arterioles were designed to be 180μm long and taper from 30μm to 18μm wide. Fabricated using a silicone soft-lithography technique, the TVM was attached to a 3D-printed hepatic vascular system consisting of a proper hepatic artery (PHA), left/right hepatic arteries (LHA/RHA), and 16 outlets 1mm in diameter; one of which feeds the TVM. The PHA was perfused with a glycerin-water mixture (3.5cP viscosity) at a pressure of 140/60mmHg and a rate of 160mL/min. A 2.9F Cook Cantata (0.027in ID) microcatheter (Cook Medical, Bloomington, IN) was placed distal to the RHA origin into a 2mm caliber artery feeding the TVM and two additional arteries. A syringe pump was used to inject glass MS (20-30μm diameter) through the catheter at a concentration of 50mg/mL and a rate of 0.3mL/s. MS were delivered in two 1.5mL aliquots separated by a pause of 180s. Following delivery, the TVM was disconnected from the vascular system and imaged.
Results :
The actual TVM flow rate measured was 23.5mL/min giving a resistance of 230PRU. Within 15% of the 270PRU target, this shows good agreement between the design methodology and fabrication. A series of 2 TVM were embolized and imaged. TVM flow rates measured after embolization revealed an 88% reduction to 2.5mL/min and 3.0mL/min for the two trials. Image analysis showed the glass MS penetrated a distance of 100μm (95th percentile) into the outlet arterioles.
Conclusions :
The TVM—through image analysis and flow measurements—can yield information about the MS deposition that would otherwise be difficult to obtain using animal models. This has demonstrated its potential to bring a new perspective to Y-90 technological development.

Novel Hepatic Tumor Microvascular Model for Evaluating the Microembolic Characteristics of Y-90 Microspheres. Dr. Sam Miller, NC State University.

Global Embolization Symposium and Technologies Annual Meeting 2021

  • Attributes of Y90 distribution in tumors are difficult to observe through in vivo models. This is the first published in vitro model simulating HCC tumors down to the arteriole level (18µm).
  • This study compared in vitro microsphere distribution between the ABK dual-syringe delivery system (DS) a typical glass Y90 bolus delivery system (BD).
  • The use of the ABK DS system resulted in greater a greater number of microspheres penetrating distally compared to BD.
  • A more uniform distribution of microspheres was also observed with ABK DS vs BD.
  • This study demonstrated that the mode of microsphere delivery affects penetration and uniformity of deposition, and may bring a new perspective to Y90 technology development.

Peer-Reviewed Publications

A

Precision dosimetry in yttrium‑90 radioembolization through CT imaging of radiopaque microspheres in a rabbit liver model

Henry et al. EJNMMI Physics (2022) 9:21 

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Quantification of the inherent radiopacity of glass microspheres for precision dosimetry in yttrium-90 radioembolization.

Henry et al 2019 Biomed. Phys. Eng. Express 5 055011

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Post-administration dosimetry in yttrium-90 radioembolization through micro-CT imaging of radiopaque microspheres in a porcine renal model

Henry et al 2021 Phys. Med. Biol. 66 095011

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