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

Brachytherapy offers several advantages compared the clinical implementation and evaluation of innovative
to EBRT, including superior dose localization within brachytherapy devices and applications. With the
the target volume, enhanced sparing of normal tissue, introduction of 3D printing, studies have indicated that
and cost-effectiveness. Guidelines for brachytherapy there is comparability between the dosimetric parameters of
dosimetry and source calibration have been established pre-operative and post-operative planning for D90, V100,
by organizations such as the American Association of and V200 in 3D printing-guided I-125 brachytherapy for
Physicists in Medicine (AAPM) and the Groupe Européen recurrent high-grade gliomas .
[61]
de Curiethérapie-European Society for Radiotherapy When comparing I-125 LDR brachytherapy to HDR
and Oncology. These guidelines, as exemplified in the brachytherapy for prostate cancer, a randomized trial
AAPM Task Group 43 report, recommend specific dose suggested that the D90, V100, and V150 values of the
parameters, including D90>100%, V100>90%~95%, and LDR brachytherapy group were significantly higher than
V150<50%~60% [19,54] . A comparative study evaluated the those of the HDR brachytherapy group. In addition, the
dosimetric parameters of I-125 brachytherapy for lung urethral D10, D30, and rectal D10 values of the LDR
cancer between intraoperative and pre-operative planning, brachytherapy group were significantly higher than those
revealing the superiority of intraoperative planning. of the HDR brachytherapy group . Therefore, while
[62]
Intraoperative planning demonstrated significantly higher both I-125 LDR brachytherapy and HDR brachytherapy
V100, V150, and V200 values compared to pre-operative can offer effective dose coverage, I-125 brachytherapy
planning . In addition, intraoperative planning exhibited tends to result in slightly higher doses to the urethra
[55]
improved coverage, conformity, and quality indices, along and rectum, potentially contributing to the occurrence
with reduced dose uniformity indices compared to pre- of genitourinary and gastrointestinal toxicity in LDR
operative planning . brachytherapy. In addition, a retrospective analysis
[55]
Ensuring accurate dose delivery is crucial for of 25 patients with pancreatic cancer indicated that
therapeutic efficacy in radiotherapy. A key component 3D-printed personalized templates-assisted I-125
for accurate dose delivery with brachytherapy sources is brachytherapy provided dosimetric advantages in terms of
the ability to determine the absolute radiation output at a V100 when compared to manual implantation. In essence,
reference point. For photon sources, this is usually achieved current brachytherapy, guided by CT scans and assisted
by correlating the radiation output to air-Kerma strength by 3D-printed personalized templates, has achieved a
(SK) in the U.S. and reference air-kerma rate in Europe. perfect match between post-operative dose verification
A primary calibration standard for low-energy LDR I-125 and pre-operative planning. The pre-operative planning
brachytherapy sources was developed at the National and post-operative dose verification demonstrated no
Bureau of Standards (the former name for NIST) in 1984 significant difference in multiple dosimetric parameters,
by Loftus, using the Ritz free air ionization chamber . with accuracy improved by over 90%. The incorporation
[56]
However, discrepancies in source measurements arose, of 3D-printed personalized templates proves beneficial
with the 1999 value for a given I-125 source differing from in achieving individualized treatment and reducing
the 1998 standard by 3%. Subsequently, all source models dependence on operator experience.
underwent reevaluation in 2000, revealing discrepancies In recent years, several scholars have explored the
ranging from 2% to 7% in 1999. To address these application of single photon emission CT/CT for detecting
variations, the AAPM mandates that brachytherapy source the radioactive concentration distribution following
manufacturers annually compare their in-house standard particle implantation and utilizing it to evaluate the
to the NIST standard for low-energy sources and, every therapeutic effect. This novel approach warrants further
2 years, with a primary standards dosimetry laboratory- investigation [63,64] . It is worth noting that, in contrast to HDR
traceable standard for high-energy sources [57,58] . brachytherapy, I-125 brachytherapy has some drawbacks,
The Task Group 56 report provides guidelines for such as potential radiation exposure to clinical personnel
quality control and quality assurance in brachytherapy during the procedure and subsequent exposure to patients’
procedures . Detailed information on the use of robotics family members and the general public. Nonetheless,
[59]
in brachytherapy for source delivery can be found in studies have indicated that the radiation dose carried
the TG-192 report . However, when it comes to the by patients after prostate cancer particle implantation
[60]
dosimetric requirements of innovative brachytherapy is minimal, approaching levels observed in the general
devices or the implementation of new clinical applications, population. Apart from some limitations, like prolonged
there is a limited availability of guidelines. Therefore, the child-carrying restrictions, patients can generally lead a
role of medical physicists becomes even more critical in normal daily life without significant disruption .
[65]

Volume 1 Issue 2 (2023) 6 https://doi.org/10.36922/arnm.0914