1.L-Point Entry, Juxtapedicular, and Endplate-Parallel Trajectory (L-JET) Screw Fixation: A Novel Technique in Thoracic Spinal Tumor Surgery
Seunghoon LEE ; Young Rak KIM ; Chang-Hyun LEE ; Jungbo SIM ; Woojin KIM ; Ho Sung MYEONG ; Hangeul PARK ; Jun-Hoe KIM ; Chi Heon KIM
Journal of Minimally Invasive Spine Surgery and Technique 2026;11(1):6-13
Objective:
Thoracic pedicle screw fixation is technically demanding because of the natural variability in pedicle anatomy, a challenge that is further exacerbated in patients with spinal tumors who often have compromised pedicles. The L-point entry, juxtapedicular, and endplate-parallel trajectory (L-JET) technique was developed to provide a uniform entry point, a predictable screw trajectory, and the capacity to accommodate larger-diameter screws at levels T3–10. This study aimed to evaluate the safety and feasibility of the L-JET technique in comparison with the conventional transpedicular method.
Methods:
A comparative analysis of consecutively collected data was performed to evaluate outcomes associated with the L-JET technique in patients undergoing surgery for thoracic extradural spinal tumors. The L-point was defined as the intersection of a vertical line along the lateral margin of the facet joint and a horizontal line along the upper edge of the transverse process. The screw trajectory was planned with 30° of medial convergence in the axial plane, creating a juxtapedicular path, and a straightforward trajectory in the sagittal plane. Primary outcome measures included screw diameter, screw length, cortical breach rate, and the need for revision surgery, as assessed using computed tomography scans and medical records.
Results:
A total of 108 screws were placed in 22 patients using the L-JET technique, while 98 screws were placed in 18 patients using the conventional technique. The L-JET group used significantly larger-diameter screws (6.06±0.65 mm) than the conventional group (5.74±0.80 mm, p=0.02), with no significant difference observed in screw length between groups. Medial cortical breach occurred in one screw in each group, and no supra- or infrapedicular breaches were identified. No screw-related neurovascular complications or revision surgeries occurred in either group.
Conclusion
The L-JET technique enables consistent screw placement with larger-diameter screws, even in compromised pedicles associated with thoracic spinal tumors, without increasing the risk of complications or the need for revision surgery.
2.Role of HIF-1α in the Responses of Tumors to Radiotherapy and Chemotherapy
Chang W SONG ; Hyunkyung KIM ; Mi-Sook KIM ; Heon J PARK ; Sun-Ha PAEK ; Stephanie TEREZAKIS ; L Chinsoo CHO
Cancer Research and Treatment 2025;57(1):1-10
Tumor microenvironment is intrinsically hypoxic with abundant hypoxia-inducible factors-1α (HIF-1α), a primary regulator of the cellular response to hypoxia and various stresses imposed on the tumor cells. HIF-1α increases radioresistance and chemoresistance by reducing DNA damage, increasing repair of DNA damage, enhancing glycolysis that increases antioxidant capacity of tumors cells, and promoting angiogenesis. In addition, HIF-1α markedly enhances drug efflux, leading to multidrug resistance. Radiotherapy and certain chemotherapy drugs evoke profound anti-tumor immunity by inducing immunologic cell death that release tumor-associated antigens together with numerous pro-immunological factors, leading to priming of cytotoxic CD8+ T cells and enhancing the cytotoxicity of macrophages and natural killer cells. Radiotherapy and chemotherapy of tumors significantly increase HIF-1α activity in tumor cells. Unfortunately, HIF-1α effectively promotes various immune suppressive pathways including secretion of immune suppressive cytokines, activation of myeloid-derived suppressor cells, activation of regulatory T cells, inhibition of T cells priming and activity, and upregulation of immune checkpoints. Consequently, the anti-tumor immunity elevated by radiotherapy and chemotherapy is counterbalanced or masked by the potent immune suppression promoted by HIF-1α. Effective inhibition of HIF-1α may significantly increase the efficacy of radiotherapy and chemotherapy by increasing radiosensitivity and chemosensitivity of tumor cells and also by upregulating anti-tumor immunity.
3.Role of HIF-1α in the Responses of Tumors to Radiotherapy and Chemotherapy
Chang W SONG ; Hyunkyung KIM ; Mi-Sook KIM ; Heon J PARK ; Sun-Ha PAEK ; Stephanie TEREZAKIS ; L Chinsoo CHO
Cancer Research and Treatment 2025;57(1):1-10
Tumor microenvironment is intrinsically hypoxic with abundant hypoxia-inducible factors-1α (HIF-1α), a primary regulator of the cellular response to hypoxia and various stresses imposed on the tumor cells. HIF-1α increases radioresistance and chemoresistance by reducing DNA damage, increasing repair of DNA damage, enhancing glycolysis that increases antioxidant capacity of tumors cells, and promoting angiogenesis. In addition, HIF-1α markedly enhances drug efflux, leading to multidrug resistance. Radiotherapy and certain chemotherapy drugs evoke profound anti-tumor immunity by inducing immunologic cell death that release tumor-associated antigens together with numerous pro-immunological factors, leading to priming of cytotoxic CD8+ T cells and enhancing the cytotoxicity of macrophages and natural killer cells. Radiotherapy and chemotherapy of tumors significantly increase HIF-1α activity in tumor cells. Unfortunately, HIF-1α effectively promotes various immune suppressive pathways including secretion of immune suppressive cytokines, activation of myeloid-derived suppressor cells, activation of regulatory T cells, inhibition of T cells priming and activity, and upregulation of immune checkpoints. Consequently, the anti-tumor immunity elevated by radiotherapy and chemotherapy is counterbalanced or masked by the potent immune suppression promoted by HIF-1α. Effective inhibition of HIF-1α may significantly increase the efficacy of radiotherapy and chemotherapy by increasing radiosensitivity and chemosensitivity of tumor cells and also by upregulating anti-tumor immunity.
4.Role of HIF-1α in the Responses of Tumors to Radiotherapy and Chemotherapy
Chang W SONG ; Hyunkyung KIM ; Mi-Sook KIM ; Heon J PARK ; Sun-Ha PAEK ; Stephanie TEREZAKIS ; L Chinsoo CHO
Cancer Research and Treatment 2025;57(1):1-10
Tumor microenvironment is intrinsically hypoxic with abundant hypoxia-inducible factors-1α (HIF-1α), a primary regulator of the cellular response to hypoxia and various stresses imposed on the tumor cells. HIF-1α increases radioresistance and chemoresistance by reducing DNA damage, increasing repair of DNA damage, enhancing glycolysis that increases antioxidant capacity of tumors cells, and promoting angiogenesis. In addition, HIF-1α markedly enhances drug efflux, leading to multidrug resistance. Radiotherapy and certain chemotherapy drugs evoke profound anti-tumor immunity by inducing immunologic cell death that release tumor-associated antigens together with numerous pro-immunological factors, leading to priming of cytotoxic CD8+ T cells and enhancing the cytotoxicity of macrophages and natural killer cells. Radiotherapy and chemotherapy of tumors significantly increase HIF-1α activity in tumor cells. Unfortunately, HIF-1α effectively promotes various immune suppressive pathways including secretion of immune suppressive cytokines, activation of myeloid-derived suppressor cells, activation of regulatory T cells, inhibition of T cells priming and activity, and upregulation of immune checkpoints. Consequently, the anti-tumor immunity elevated by radiotherapy and chemotherapy is counterbalanced or masked by the potent immune suppression promoted by HIF-1α. Effective inhibition of HIF-1α may significantly increase the efficacy of radiotherapy and chemotherapy by increasing radiosensitivity and chemosensitivity of tumor cells and also by upregulating anti-tumor immunity.
5.Developing standardized informed consent for hysterectomy and vulva cancer surgery
Soohyun OH ; Geonwoo LEE ; Kwang-Beom LEE ; Min-Sun KYUNG ; Myounghwan KIM ; Mi-Kyung KIM ; Jaeman BAE ; Min Jong SONG ; Heon Jong YOO ; Dae-Hyung LEE ; Sang-Hun LEE ; Ha Kyun CHANG ; Jae-Weon KIM ; Sang-Yoon PARK
Journal of Gynecologic Oncology 2025;36(6):e107-
Informed consent is a fundamental aspect of surgical care, designed to reinforce patient autonomy, promote shared decision-making, and potentially mitigate legal conflicts by ensuring the provision of comprehensive and consistent information in clinical practice. The Korean Society of Gynecologic Oncology (KSGO) previously published detailed informed consent documents for cervical, endometrial, and ovarian cancer surgery. However, standardized consent forms remain relatively lacking for laparoscopic-robotic hysterectomy performed for non-malignant indications, as well as for vulvar cancer surgery. Hence, the KSGO subcommittee collected, reviewed, and discussed consent forms from domestic medical institutions and subsequently developed informed consent for laparoscopic-robotic hysterectomy and vulvar cancer surgery, aiming to build patient trust and understanding.
6.Why large language models cannot possess consciousness: an integrated information theory perspective
Dong Ah SHIN ; Pyung Goo CHO ; Gyu Yeul JI ; Sang Hyuk PARK ; Soo Heon KIM ; Yoo Jin CHOO ; Min Cheol CHANG
Journal of Yeungnam Medical Science 2025;42(1):79-
Background:
The question of whether large language models (LLMs) possess consciousness has been increasingly debated. Integrated information theory (IIT) offers a quantitative framework for assessing consciousness through a measure of integrated information.
Methods:
This study applied IIT principles to the architecture of transformer-based LLMs, focusing on causal integration, temporal persistence, and system irreducibility. Ablation experiments on Generative Pretrained Transformer 2 (GPT-2) were performed, selectively removing individual attention heads and measuring changes in perplexity as a behavioral proxy for integrated information to empirically approximate the measure of integrated information.
Results:
The ablation study of a single attention head produced minimal or negative changes in perplexity in four out of five representative sentences, indicating redundancy or noise. Only one sentence revealed a significant increase in perplexity change (ΔPPL +11.29), reflecting a localized but nonessential contribution. A comparison with biological systems demonstrated that LLMs meet the IIT criterion of differentiation, but fail to meet the criteria of integration, causal closure, and temporal persistence. These findings confirm that LLMs are architecturally decomposable, lack persistent internal states, and do not sustain global causal irreducibility. Philosophical considerations, including Searle’s Chinese Room argument, further support the idea that the linguistic fluency of LLMs arises from syntactic manipulation rather than semantic understanding.
Conclusion
Current LLMs do not satisfy the structural and informational requirements of consciousness under IIT. Although capable of simulating intelligent language, LLMs remain unconscious systems with a negligible amount of integrated information, underscoring the distinction between linguistic competence and conscious experience.
7.Clinical Applications of Thermoplastic Sheets as Patient-Specific Gonadal Shields During Computed Tomography Simulation
Jin JEGAL ; Hyojun PARK ; Seonghee KANG ; Chang Heon CHOI ; Jung-in KIM
Progress in Medical Physics 2024;35(4):172-177
Purpose:
Conventional gonadal shields are manufactured in standardized sizes and shapes and do not conform to individual testicular contours, causing discomfort. We developed a novel patientspecific gonadal shield using thermoplastic sheets and tested its feasibility through dosimetric evaluations.
Methods:
During the computed tomography simulation, custom lead shields were fabricated using thermoplastic sheets that were molded to the testicular shape of the patient. The shielding efficacy was evaluated using optically stimulated luminescent dosimeters (OSLDs) for point dose measurements.
Results:
The thermoplastic sheet was molded to fit closely to the skin with a minimal air gap of approximately 8.4 cm³, providing comfort to the patient during treatment. The patient-specific shield effectively reduced the surface dose from 28 cGy to less than 15 cGy. By combining the OSLDs located in the same row and calculating the mean dose value, a shielding effect was achieved with a maximum dose reduction of 56.1%.
Conclusions
Customized gonadal shields were successfully created using thermoplastic sheets to minimize patient discomfort during application. However, further improvements in lead shield fabrication are needed to ensure full conformity.
8.Evaluation of the Dosimeter Volume Effect on Small-Field Dosimetry Using the Elekta Harmony Pro Linear Accelerator
Hyojun PARK ; Jin JEGAL ; Yoonsuk HUH ; Inbum LEE ; Sung Hyun LEE ; Chang Heon CHOI ; Jung-In KIM ; Seonghee KANG
Progress in Medical Physics 2024;35(4):89-97
Purpose:
This study investigated the dose perturbation according to the size of the sensitive volume in the dosimeter in small-field dosimetry.
Methods:
The dose profiles with different field sizes were measured using three different dosimeters: the CC13, Razor ion chamber, and Edge solid-state detector. Both the open and wedged beams with different field sizes were employed in the measurement. The profiles were measured in a water phantom at maximum dose depths of 5, 10, and 20 cm. The penumbra and width of the open-beam profiles were compared according to the types of the dosimeters and beam. The dose fall-off between the peak and 20% dose was evaluated for the wedged beam profiles.
Results:
In the open-beam measurement, the fall-off of the profile was steeper with the Edge detector, which has the smallest sensitive volume. Meanwhile, the dose in the out-of-field region was the smallest with the Edge detector. The widths of the penumbra were 6.10, 4.47, and 4.03 mm for the profile of the 3×3 cm 2 field measured by the CC13 chamber, Razor chamber, and Edge detector, respectively. The width of the profile was not changed even if different dosimeters were used in the measurement. The wedged beam profiles showed more clear peaks at the field edge when a smaller dosimeter was used.
Conclusions
The results demonstrate the necessity of dosimeters with a small sensitive volume for measuring a small-field beam or a steep dose gradient.
9.Evaluation of Methods for Characterizing Kilovoltage Beam Quality from the Varian TrueBeam STx
Inbum LEE ; Yoonsuk HUH ; Jin JEGAL ; Hyojun PARK ; Chang Heon CHOI ; Jung-in KIM ; Seonghee KANG
Progress in Medical Physics 2024;35(4):98-105
Purpose:
This study evaluated various methods for determining the half-value layer (HVL) of kilovoltage (kV) beams produced by the Varian TrueBeam STx on-board imager. By comparing these methods with the standard ionization chamber approach, the study aimed to identify practical solutions for HVL determination and dosimetric characterization of kV beams, particularly in resource-limited settings.
Methods:
HVLs for kV beams (40–140 kVp) were measured using an Exradin A12 ionization chamber and a Piranha MULTI meter. The ionization chamber measurements adhered to American Association of Physicists in Medicine Task Group 61 guidelines and served as the reference standard. Additionally, HVL values were calculated using two model-based approaches: SpekPy (a Python-based tool) and Monte Carlo (MC) simulations using Geant4 and GATE. The results from these methods were compared to assess consistency and reliability.
Results:
Deviations across all methods were generally below 4%. At 40 kV, the most significant discrepancies were attributed to lower signal levels from the ionization chamber. The consistency between the model-based methods and experimental measurements demonstrates the reliability of these alternative approaches for HVL determination.
Conclusions
Although the ionization chamber remains the gold standard, the Piranha MULTI meter and model-based methods, i.e., SpekPy and MC simulations, have shown promise as viable alternatives, especially in resource-constrained settings. These in silico approaches also offer advantages in convenience and accuracy, supporting their potential for broader future applications.
10.A Commissioning Report on the Magnetic ResonanceCompatible Geneva Brachytherapy Applicator
Yoonsuk HUH ; Hyojun PARK ; Jin JEGAL ; Inbum LEE ; Jaeman SON ; Seonghee KANG ; Chang Heon CHOI ; Jung-in KIM ; Hyeongmin JIN
Progress in Medical Physics 2024;35(4):116-124
Purpose:
Brachytherapy is essential for treating gynecological cancers as it offers precise radiation delivery to tumors while minimizing radiation exposure to surrounding healthy tissues. The Geneva applicator, introduced in 2020 as a replacement for older models like the Utrecht applicator, enhances MRI-based brachytherapy with improved imaging capabilities and more accurate applicator placement. In 2021, updates to non-reimbursement policies in Korea for MRI-based 3D brachytherapy planning further promoted the adoption of advanced techniques such as the Geneva applicator. This study aims to commission the Geneva applicator, focusing on wall thickness, dummy marker positions, and source dwell positions to ensure accurate dose delivery and safety.
Methods:
The commissioning process involved measuring wall thickness in both the longitudinal and transverse directions for the tandem and lunar-shaped ovoid tubes and comparing thesemeasurements with the manufacturer’s specifications. Dummy marker positions were verifiedusing CT imaging, with a focus on alignment tolerances of ±1 mm. Source dwell positions were planned using the Oncentra treatment planning system, with measurements taken using EBT4 film and analyzed with RIT software.
Results:
Wall thickness measurements and dummy marker positions were within the specified tolerance ranges, confirming their accuracy. The source dwell positions, measured and analyzedthrough multiple tests, were all within the ±1 mm tolerance, ensuring the applicator’s reliability.
Conclusions
The Geneva applicator met all standards for safe and effective use in brachytherapy.The use of a 3D-printed holder was crucial for precise alignment and measurement. With updated reimbursement policies in Korea for MRI-based brachytherapy, the Geneva applicator is expected to significantly impact the future of advanced brachytherapy treatments and research.

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