Page 12 - ARNM-1-2

Advances in Radiotherapy
& Nuclear Medicine Advancements and challenges in radioactive iodine-125

94.64 ± 1.43% vs. 93.35 ± 2.45%, 91.21 ± 1.59% vs. 89.35 i. Fully manual insertion, where surgery proceeds
± 3.21%, 65.01 ± 5.78% vs. 63.40 ± 6.36%, and 46.67 ± without any robotics assistance
21.87% vs. 46.60 ± 22.85%, respectively) . This indicates ii. Manual-assisted steering, in which robotics provide
[17]
that 3D-printed personalized templates can provide better sensor feedback to the surgeon
repeatability in the treatment of immobilized malignant iii. Semi-automated steering, requiring surgeon-in-loop
tumors, facilitating the achievement of dose parameters control
outlined in the pre-operative plan. Moreover, the study iv. Fully automated steering surgery, where no surgeon
showed a mean needle entrance deviation of 0.090 cm assistance is necessary.
(95% confidence interval: 0.081 – 0.098) and consistent The main approaches for controlling needle insertion
intraoperative needle depth and angle with the planned involve pushing the needle into the tissue and rotating it
values in patients with recurrent/metastatic head-and- around its shaft to control the direction. Manual-assisted
neck cancer, demonstrating the improved accuracy of steering mainly offers additional information about the
3D-printed personalized template-guided I-125 interstitial
brachytherapy for recurrent/metastatic head-and-neck inner needle and tissue without direct intervention.
cancer . This approach has the potential to become a The surgeon can decide whether to follow calculated
[18]
standardized and easily reproducible procedure in the recommendations based on their surgical experience.
future. The utilization of fiducial markers can further The assisted system can be categorized into visual
enhance this process by linking the pretreatment plan with devices and haptic device systems. Seifabadi et al. first
real-time operations [19,20] . proposed a teleoperation needle steering system that
[31]
While accurate needle layout is achieved, the utilize MRI and a needle with a tracking coil . The high-
movement of prelocalized seeds from their predesigned resolution images provided by MRI, along with its high
[30]
positions remains a challenge when using loose seeds. precision, garner significant attention from researchers .
This movement, known as seed migration, is often However, this system did not address the challenge of real‐
a consequence of the changing tumor volume and time imaging, which remains a limitation in most current
microenvironment due to the necrosis and apoptosis of MRI devices. In semi-automated steering systems, the
the tumor cells driven by I-125 radiation. This can result needle’s rotation or lateral movement is controlled, but the
in suboptimal dosimetry due to seed migration or seed surgeon still maintains a dominant position in the control
loss . In addition to impacting dosimetry, seed migration loop. Salcudean et al. proposed a four-degree freedom
[21]
[32]
can lead to adverse clinical outcomes and complications, robot for prostate brachytherapy , which allowed the
including pulmonary or cardiac seed embolism . To surgeon to retain control over the insertion procedure
[22]
accurately quantify local seed migration during the while benefiting from robotic accuracy. This approach also
30-day period following I-125 brachytherapy, assess seed mitigated ethical concerns related to responsibility. Fully
loss/migration, and identify the locations from which automated steering robotics perform all insertion and
seeds have migrated, researchers conducted an analysis rotation actions according to specified insertion points
of seed displacement in 62 patients who underwent and target locations, thereby reducing the risk of damage
brachytherapy using stranded I-125 seeds. The analysis to normal tissue. However, the use of a fully automated
revealed that local seed migration and loss were minimal surgical system raises serious ethical questions. Therefore,
and mainly occurred near the inferior-lateral sides of the most fully automated steering systems currently exist only
prostate . One strategy to overcome seed migration and in laboratory settings.
[23]
enhance retention is the use of stranded seeds. Several
clinical trials have developed custom-linked seeds for 3. Radiobiology in the context of radiation
intraoperative use in prostate cancer treatment. Compared therapy
to loose seeds, stranded seeds exhibit a reduced risk of I-125 decays through the emission of a cascade of Auger
migration, and there is also lower biochemical evidence electrons, depositing energy within the tissue over a mean
of disease [24-26] . path length well below 10 μm. This results in a high linear
[33]
Robot-assisted systems have been widely studied and energy transfer (LET) ranging from 4 to 26 keV/μm .
applied in various surgical fields [27-29] . Recent developments When I-125 seeds are deposited in close proximity to
in the applications of robotics in the field of prostate the cell nucleus, this high LET of I-125 contributes to a
I-125 brachytherapy are paving the way for a potentially significant radiobiological effect, which could increase
fully automated prostate brachytherapy surgery. Current the fraction of lethal DNA damage and limit the impact
surgical robotics can be categorized into four levels of of hypoxia and cell cycle dynamics on destroying cancer
automation : cells . Much of the data concerning brachytherapy
[30]
[34]
Volume 1 Issue 2 (2023) 4 https://doi.org/10.36922/arnm.0914