Chapter 4
Equira™ (VoxelPHITS): Democratising Precision Radiopharmaceutical Therapy for Global Cancer Care
Basri Johan Jeet Abdullah1*, Shalaine Sana Tatu2, Yin How Wong2,
Azahari Kasbollah3, Subapriya Suppiah4, S. Cheenu Kappadath5,
and Chai Hong Yeong2
1Department of Radiology, Hospital PICASO, Malaysia
2School of Medicine, Faculty of Health and Medical
Sciences, Taylors University, Malaysia
3Medical Technology Division, Malaysian Nuclear Agency, Malaysia
4Department of Radiology, Faculty of Medicine and Health Sciences,
Universiti Putra Malaysia
5Department of Imaging Physics, The University of Texas MD Anderson
Cancer Center, United States of America
Abstract
Radiopharmaceutical therapy is an essential option for cancers such as hepatocellular carcinoma, metastatic prostate cancer, and neuroendocrine tumours, delivering radiation internally via targeted radiolabelled compounds. Yet, most patients are still treated with empirical, fixed-dose protocols, with limited knowledge of the absorbed dose to tumours and organs-at-risk (OARs), driving variability in outcomes and avoidable toxicity.
Equira, developed from the VoxelPHITS platform, offers a practical, scalable solution to personalised dosimetry. The open-source, vendor-neutral software converts standard CT (anatomy/tissue density) and SPECT/PET (radioactivity) into patient-specific 3D dose maps using Monte Carlo simulation and pre-computed dose-voxel kernels for speed. It accepts routine DICOM inputs, runs on Windows and Linux, and is designed for deployment in both high- and low-resource settings without specialised infrastructure. Outputs include isodose overlays, dose-volume histograms (DVHs, and tabulated dose metrics (e.g. Dmean, D95, Vx) suitable for pre-treatment planning and post-therapy verification.
By aligning treatment decisions with measured dose rather than surrogates, Equira can improve safety, efficacy, and equity in radionuclide therapy. Its development supports a broader shift toward accessible precision medicine, enabling centres worldwide to deliver the right dose, first time and to standardise protocol optimisation with interpretable task-based metrics.
Keywords: Radiopharmaceutical therapy, Voxel-based dosimetry, Monte Carlo simulation, Personalised dosing, VoxelPHITS
Introduction
Precision medicine in radiopharmaceutical therapy requires not only locating tumours but also quantifying the absorbed dose to tumours and organs-at-risks (OARs). For radionuclides such as Yttrium-90 (Y-90), Samarium-153 (Sm-153), Lutetium-177 (Lu-177), and Holmium-166 (Ho-166), internal dosimetry is essential to balance efficacy against toxicity1-7. Yet, according to the European Association of Nuclear Medicine (EANM) Dosimetry Committee surveys, about 70% of radiopharmaceutical therapies worldwide still use empirical dosing, contributing to variability in outcomes and elevated toxicity risks8-10. A key barrier is the limited availability of practical, accessible tools for personalised dosimetry11.
Equira, built on the modular VoxelPHITS platform, addresses this gap by transforming routine CT (anatomy/tissue density) and SPECT/PET (radioactivity) into patient-specific 3D dose maps. Leveraging the PHITS Monte Carlo software with pre-computed dose-voxel kernels, it delivers high-fidelity voxel-based dosimetry on standard Windows/Linux workstations, avoiding the need for specialised computing infrastructure or advanced physics expertise12. Dosimetry outputs, such as isodose overlays, DVHs, and tabulated dose metrics, are integrated into familiar clinical workflow for pre-treatment planning and post-therapy verification.
By providing an open, vendor-neutral, and easily deployable platform, EquiraTM offers a practical route to personalised dosing across both high- and low-resource settings.
Results and Discussion
Platform capability and robustness
Equira is designed to be easily accessible, adaptable, and technically robust. It runs on Windows or Linux, accepts standard Digital Imaging and Communications in Medicine (DICOM) inputs from any imaging modalities, and installs locally within hospital networks to comply with patient data privacy requirements while still allowing secure remote updates. A modular framework supports multiple radionuclides, voxel sizes, and tissue models. Built with open-source tools such as Python and FORTRAN on the VoxelPHITS core, the platform reduces dependence on costly commercial software and supports long-term scalability and maintainability. Figure 1 shows the overview of the EquiraTM workflow.
Figure 1: Overview of VoxelPHITS workflow.
Clinical utility
Equira quantifies absorbed dose to tumours and OARs, improving therapeutic confidence for both pre-treatment planning (to verify target coverage and OAR sparing) and post-therapy verification (to evaluate delivered dose). This aligns with modern theranostics, integrating imaging and therapy to enable patient-specific decision-making. Figure 2 illustrates a Y-90 selective internal radiation therapy (SIRT) case with baseline imaging, isodose mapping, follow-up response, and DVHs of a liver metastasis patient. Figure 3 shows multi-planar dose map visualisations generated by EquiraTM.
Implementation considerations and adoption
To support rapid adoption across diverse centres, Equira emphasises usability and trust: an intuitive interface requiring minimal training; colour-coded dose maps and location options for international use; and commercial-grade packaging (documentation, verification cases, and user support) even though the software is open-source.
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Figure 2: Personalised dosimetry for Y-90 selective internal radiation therapy (SIRT) of liver tumours. (A) Baseline CT prior to SIRT. (B) SPECT/CT with overlaid dose map demonstrating tumour and normal liver dose distribution. (C) Follow-up CT acquired at 80 days post-SIRT, revealing significant shrinkage of tumour. (D) Dosevolume histogram (DVH) for tumour and normal liver. (E) Volumetric response analysis. (Adapted from Abbott et al.13). |
A sustainable deployment model is proposed: sites manage local installation and data control, while receiving secure online updates. A central support hub provides training materials, FAQs, peer discussion forums, and regular online training to encourage standardised practice and shared learning. Engagement with key opinion leaders (KOLs) will further strengthen credibility and accelerate clinical implementation.
Sustainability and governance
The project operates under a not-for-profit model supported by institutional partnerships and research grants, aligning the platform with global health-equity goals. Governance includes visioned radionuclide libraries, checksum-verified builds, and a minimal QA set (phantom cases, periodic checks) to ensure consistent performance across sites.
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Figure 3: Cross sectional (axial, coronal and sagittal) views of a Y-90 SIRT 3D dose maps produced in EquiraTM. |
Roadmap
Planned enhancements include AI-assisted organ segmentation, a cloud research mode (where policy permits), adaptations for paediatric and rare-disease protocols, and health-economic modules to inform policy and budget decisions. These additions aim to deepen clinical utility while keeping the system deployable in both high- and low-resource settings.
Conclusion
Equira represents a breakthrough in nuclear medicine dosimetry. By making personalised dosimetry accessible and affordable, it can improve safety, efficacy, and consistency of radiopharmaceutical therapy across diverse care settings. Our broader aim is clear: to advance precision care for every patient, irrespective of geography or socioeconomic status.
Acknowledgements
We acknowledge the support of Taylors University, the Malaysian Nuclear Agency, the Philippine Nuclear Research Institute, and the Japan Atomic Energy Agency (JAEA). The project is funded by the Prototype Research Grant Scheme (PRGS/1/2023/SKK01/TAYLOR/01/1) under the Ministry of Higher Education, Malaysia, and partially supported by the DOST-HRDP Scholarship Programme.
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