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Advances in Radiotherapy
& Nuclear Medicine Software impact in Ho dosimetry
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The absorbed dose estimation to different organs and based on the CT scan. Tumor VOIs were segmented
target lesions, such as tumors, include the assessment of using contrast-enhanced CT images for better guidance
the activity distribution within the patient’s body, which is and validated by both nuclear medicine and radiology
attained through activity quantification and its conversion physicians. The maximum dose limits for the whole-liver
to dose using Monte Carlo simulations, MIRD calculations and lungs were set at 60 Gy and 30 Gy, respectively. The
or by application of dose point kernels (DPK). 14 ideal minimum absorbed tumor dose was set to 150 Gy.
Using these different dosimetric objectives and constraints,
The aim of this study was to estimate the dose to
the whole-liver and tumor after the treatment phase the potential range of activity to be administered in the
therapy was achieved, along with the corresponding
administration using two different software Hermia Voxel mean doses for each VOI. The patients proceeded to the
Dosimetry 1.1 (Hermes Medical Solutions AB) and therapy phase when all these inclusion criteria were met.
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Q-Suite 2.1 (developed by Quirem Medical B.V.) and The optimal therapeutic activity was determined by the
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compare the results.
multidisciplinary team, which include a Medical Physics
2. Materials and methods Expert who assists in assessing both dosimetric data and
the patient’s clinical status.
2.1. Clinical workflow
The treatment was performed approximately 2 weeks
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In this study, Ho-TARE may be offered as a treatment after the scout procedure. As a standard practice, the post-
option for patients with hepatocellular carcinoma in stages therapy SPECT was conducted within 18–24 h after the
0 (Very Early), A (Early), or B (Intermediate) as per the day of treatment. Dosimetric post-treatment verification
2022 Barcelona clinic liver cancer Guidelines and for was then carried out using the two different software tools
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liver-confined metastasis (usually arising from primary (Hermia Voxel Dosimetry 1.1 and Q-Suite 2.1). Once
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neuroendocrine tumor or colorectal cancer) presenting the results from both software were obtained, they were
with contraindications for other locoregional therapies analyzed and then compared for further assessment.
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(e.g., ablation). These criteria were used to guide patient
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selection for Ho-TARE. 2.2. Therapeutic absorbed dose calculation
After patient clinical selection, each patient underwent 2.2.1. Hermia voxel dosimetry
a preparatory angiography and, immediately after, For dose distribution map estimation and dosimetry
administration of the 166 Ho scout activity. On the same using Hermes software, the workflow used is presented
day, a post-scout SPECT/CT was acquired. These images in Figure 1. The first step was performing the SPECT/CT
were acquired in a Siemens Symbia Intevo Bold (Siemens reconstruction of the patient through Hybrid Recon 4.0
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Healthcare, Erlangen, Germany) SPECT/CT system. (Hermes Medical Solutions AB) using a pre-determined
Written informed consent was obtained from all patients CF of 15 cps/MBq (which was calculated using a
before undergoing the therapeutic procedure. uniformly filled Jaszczak phantom ), which resulted in a
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The imaging parameters were set as follows: a non- representation of the activity distribution in MBq/mL.
circular step-and-shoot 360° orbit with 60 views per head, Next, the SPECT/CT reconstruction was inputted into
each view lasting 20 seconds, matrix size of 128 × 128 and the Hermia Voxel Dosimetry 1.1 application (Hermes
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a pixel size of 4.8 mm. The photopeak energy window Medical Solutions AB), along with the administered
was centered on the 80.6 keV with a width of 15%, while activity (in MBq) and the time to first scan (duration in
the scatter energy window was centered at 118 keV with hours from the injection of the radiopharmaceutical to the
a width of 12% to account for scatter from higher energy start of the first scan). This program performs voxel-by-
gamma emissions and Bremsstrahlung. Medium energy voxel integration of the time activity curve and conducts
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low penetration collimators were used to reduce the absorbed dose simulations using a semi-MC method,
impact of Bremsstrahlung radiation and optimize image which assumes that electrons are primarily absorbed locally,
quality. The CT scans were conducted before the SPECT and employs accelerated MC simulations specifically for
acquisition. A CT tube voltage of 110 keV and a tube photons. 19,20 After Voxel Dosimetry calculations, a dose
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current-time product of 40 mAs were used. All SPECT/ map was obtained.
CT acquisitions performed throughout this study followed The mean doses for the tumor and liver, along with their
these parameters.
respective dose-volume histograms (DVH) for each patient,
The treatment planning phase was exclusively were determined through delineation of the tumor and
conducted using the Q-Suite software. The lungs, whole, liver VOIs using the Affinity (Hermes Medical Solutions
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and target liver volume of interest (VOIs) were delineated AB). The liver VOI was delineated through manual

Volume 3 Issue 3 (2025) 57 doi: 10.36922/ARNM025220023