Page 101 - ARNM-3-2

Advances in Radiotherapy
& Nuclear Medicine A dosimetric research on iodine-125 seed implantation

cases. The use of iodine-125 seeds has demonstrated Radio Nuclear (USA). (Positron Emission Tomography–
1
effective therapeutic outcomes in the treatment of early Computed Tomography [PET-CT]; DiscoveryCT750HD,
NSCLC, particularly in resection margin supplementary GE Healthcare, USA) was used for imaging. The
radiotherapy, radical treatment, advanced NSCLC radioactive iodine-125 particles (Model 6711-99, Beijing
management, and palliative care for extrapulmonary Zhibo Company, China) possessed a length of 4.8 mm,
metastases. Accurate target delineation is essential for a diameter of 0.6 – 0.8 mCi, an energy of 27 – 35 keV,
2-5
ensuring the efficacy of radiotherapy and plays a critical and a half-life of 59.4 days. For the activity meter, the
6,7
role in iodine-125 seed implantation. Traditionally, target RM-905a well-type ionization chamber (China Institute of
delineation for seed implantation involves clinicians Metrology) was employed. The negative pressure vacuum
manually outlining the tumor as the clinical target. However, pad (Zibo Tianchen Medical Instrument Factory, China),
this approach is susceptible to subjective biases from dimension of size is 120 cm × 80 cm × 4 cm.
the operator and variations in scanning time and image
quality, which can lead to inaccurate target delineation. 2.3. Seed implantation
Such inaccuracies may adversely affect the effectiveness One week before surgery, a routine enhanced CT scan
of seed implantation and contribute to tumor recurrence. with a slice thickness of 5 mm, was performed for
Stereotactic body radiotherapy (SBRT) demonstrates localization. The CT images were imported into the TPS
favorable outcomes with a comparatively lower recurrence planning system. The CTV and organs at risk (OARs) were
rate in the treatment of early-stage NSCLC. 8-10 This study delineated according to the International Commission on
compares the dosimetric impact of target delineation Radiation Units and Measurement Report No.83. The
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standards between transitional particle implantation using prescribed dose was 140 Gy, with a particle activity of 0.6
SBRT and traditional clinical target volume (CTV) methods, – 0.8 mCi. The number of particles required and the dose
aiming to explore how target delineation influences the to OARs were calculated using the TPS planning system.
efficacy of iodine-125 seed treatment for NSCLC.
Particle implantation was performed using an 18G
2. Materials and methods disposable implantation needle under real-time CT
2.1. Patient data guidance to avoid critical organs. Post-implantation CT
scanning was conducted to evaluate particle distribution.
Thirty-one patients with NSCLC who received iodine-125 If dose cold spots or underdosed regions were identified,
seed implantation at Radioactive Seeds Implantation additional particles were implanted as needed.
Diagnosis and Treatment Center, Shijiazhuang, China,
between January 2018 and January 2023, were retrospectively After surgery, the last intraoperative CT scan image
analyzed. All patients met the following criteria before the was uploaded to the TPS planning system to evaluate
operation: (1) No major organ dysfunction and a general parameters including target volume (Vol), minimum
condition score (PS) ≤3; (2) pathological confirmation peripheral dose received by 90% of the target volume
of NSCLC via biopsy. Following multidisciplinary (D ), percentage of target volume covered by 100% of the
90
discussion, the patients were deemed ineligible for surgical prescription dose (V ), percentage of target Vol covered
100
resection or multiple-line treatment and consented to seed by 150% of the prescription dose (V ), and percentage of
150
implantation; (3) routine blood tests, biochemical analysis, target Vol covered by 200% of the prescription dose (V ).
200
coagulation function assessments, and evaluations of heart, For target area expansion, the gross target Vol (GTV)
lung, liver, and kidney functions can indicate tolerance to was automatically expanded by 5 mm (CTV 5mm ) and
the procedure; (4) An estimated survival time of more than 1 cm (CTV 1mm ) using the TPS software to assess changes
3 months. The exclusion criteria were: (1) Severe organ in Vol, D , V , V , and V . Follow-up assessments
150
100
90
200
dysfunction, such as severe heart failure or significant were conducted monthly for the first 6 months post-
lung, liver, or kidney dysfunction; (2) severe coagulation implantation and every 3 months thereafter. Treatment
dysfunction; (3) an estimated survival time of <3 months. efficacy was compared with previous evaluations, and
This study was approved by the Medical Ethics Committee adverse events were recorded.
of Hebei General Hospital.
2.4. Observation indexes
2.2. Main reagents and instruments Efficacy was assessed based on the response evaluation
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The computerized three-dimensional treatment planning criteria in solid tumors version 1.1. The complete
system (TPS) from Prowess Panther Brachy V5.0 (United remission (CR) category was assigned when all target
States) was used. The 18G implant needle (J820-C) and lesions disappeared, with the short diameter of any
Mick200-TPV applicator gun were purchased from Mick pathological lymph node (whether a target lesion or not)

Volume 3 Issue 2 (2025) 93 doi: 10.36922/arnm.8512