• Progress in Medical Physics
• /
• v.33 no.4
• /
• pp.37-52
• /
• 2022

Over the past decades, radiation therapy combined with imaging modalities that ensure optimal image guidance has revolutionized cancer treatment. The two major purposes of using imaging modalities in radiotherapy are to clearly delineate the target prior to treatment and set up the patient during radiation delivery. Image guidance secures target position prior to and during the treatment. High quality images provide an accurate definition of the treatment target and the possibility to reduce the treatment margin of the target volume, further lowering radiation toxicity and improving the quality of life of cancer patients. In this review, the various types of image guidance modalities used in radiation therapy are distinguished into ionized (kilovoltage and megavoltage image) and nonionized imaging (magnetic resonance image, ultrasound, surface imaging, and radiofrequency). The functional aspects, advantages, and limitation of imaging using these modalities are described as a subsection of each category. This review only focuses on the technological viewpoint of these modalities and any clinical aspects are omitted. Image guidance is essential, and its importance is rapidly increasing in modern radiotherapy. The most important aspect of using image guidance in clinical settings is to monitor the performance of image quality, which must be checked during the periodic quality assurance process.

• Radiation Oncology Journal
• /
• v.38 no.1
• /
• pp.18-25
• /
• 2020

Purpose: This study was aim to evaluate the patterns of failure according to radiotherapy (RT) target volume for cervical lymph nodes in metastases of unknown primary origin in head and neck region (HNMUO). Materials and Methods: Sixty-two patients with HNMUO between 1998 and 2016 were retrospectively reviewed. We analyzed the clinical outcomes and primary site failure depending on the radiation target volume. The target volume was classified according to whether the potential head and neck mucosal sites were included and whether the neck node was treated involved side only or bilaterally. Results: Potential mucosal site RT (mucosal RT) was done to 23 patients and 39 patients did not receive mucosal RT. Mucosal RT showed no significant effect on overall survival (OS) and locoregional recurrence (LRR). The location of primary site failure encountered during follow-up period was found to be unpredictable and 75% of patients with recurrence received successful salvage therapies. No significant differences in OS and LRR were found between patients treated to unilateral (n = 35) and bilateral neck irradiation (n = 21). Treatment of both necks resulted in significantly higher mucositis. Conclusions: We found no advantages in OS and LRR of patients with HNMUO when mucosal sites and bilateral neck node were included in the radiation target volume.

• Progress in Medical Physics
• /
• v.33 no.4
• /
• pp.121-128
• /
• 2022

Purpose: This study evaluated the quality of plans based on magnetic resonance-guided radiotherapy (MRgRT) tri-Co-60, linac, and conventional linac-based volumetric modulated arc therapy (linac-VMAT) for prostate cancer. Methods: Twenty patients suffering from prostate cancer with intermediate risk who were treated by MAT were selected. Additional treatment plans (primary and boost plans) were generated based on MRgRT-tri-Co-60 and MRgRT-linac. The planning target volume (PTV) of MRgRT-based plans was created by adding a 3 mm margin from the clinical target volume (CTV) due to high soft-tissue contrast and real-time motion imaging. On the other hand, the PTV of conventional linac was generated based on a 1 cm margin from CTV. The targets of primary and boost plans were prostate plus seminal vesicle and prostate only, respectively. All plans were normalized to cover 95% of the target volume by 100% of the prescribed dose. Dosimetric characteristics were evaluated for each of the primary, boost, and sum plans. Results: For target coverage and conformity, the three plans showed similar results. In the sum plans, the average value of V_65Gy of the rectum of MRgRT-linac (2.62%±2.21%) was smaller than those of MRgRT tri-Co-60 (9.04%±3.01%) and linac-VMAT (9.73%±7.14%) (P<0.001). In the case of bladder, the average value of V_65Gy of MRgRT-linac was also smaller. Conclusions: In terms of organs at risk sparing, MRgRT-linac shows the best value while maintaining comparable target coverage among the three plans.

• Biomolecules & Therapeutics
• /
• v.22 no.5
• /
• pp.371-383
• /
• 2014

The nematode Caenorhabditis elegans (C. elegans) offers a unique opportunity for biological and basic medical researches due to its genetic tractability and well-defined developmental lineage. It also provides an exceptional model for genetic, molecular, and cellular analysis of human disease-related genes. Recently, C. elegans has been used as an ideal model for the identification and functional analysis of drugs (or small-molecules) in vivo. In this review, we describe conserved oncogenic signaling pathways (Wnt, Notch, and Ras) and their potential roles in the development of cancer stem cells. During C. elegans germline development, these signaling pathways regulate multiple cellular processes such as germline stem cell niche specification, germline stem cell maintenance, and germ cell fate specification. Therefore, the aberrant regulations of these signaling pathways can cause either loss of germline stem cells or overproliferation of a specific cell type, resulting in sterility. This sterility phenotype allows us to identify drugs that can modulate the oncogenic signaling pathways directly or indirectly through a high-throughput screening. Current in vivo or in vitro screening methods are largely focused on the specific core signaling components. However, this phenotype-based screening will identify drugs that possibly target upstream or downstream of core signaling pathways as well as exclude toxic effects. Although phenotype-based drug screening is ideal, the identification of drug targets is a major challenge. We here introduce a new technique, called Drug Affinity Responsive Target Stability (DARTS). This innovative method is able to identify the target of the identified drug. Importantly, signaling pathways and their regulators in C. elegans are highly conserved in most vertebrates, including humans. Therefore, C. elegans will provide a great opportunity to identify therapeutic drugs and their targets, as well as to understand mechanisms underlying the formation of cancer.

• Asian Pacific Journal of Cancer Prevention
• /
• v.15 no.11
• /
• pp.4717-4721
• /
• 2014

Background: Dosimetric comparison of two dimensional (2D) radiography and three-dimensional computed tomography (3D-CT) based dose distributions with high-dose-rate (HDR) intracavitry radiotherapy (ICRT) for carcinoma cervix, in terms of target coverage and doses to bladder and rectum. Materials and Methods: Sixty four sessions of HDR ICRT were performed in 22 patients. External beam radiotherapy to pelvis at a dose of 50 Gray in 27 fractions followed by HDR ICRT, 21 Grays to point A in 3 sessions, one week apart was planned. All patients underwent 2D-orthogonal and 3D-CT simulation for each session. Treatment plans were generated using 2D-orthogonal images and dose prescription was made at point A. 3D plans were generated using 3D-CT images after delineating target volume and organs at risk. Comparative evaluation of 2D and 3D treatment planning was made for each session in terms of target coverage (dose received by 90%, 95% and 100% of the target volume: D90, D95 and D100 respectively) and doses to bladder and rectum: ICRU-38 bladder and rectum point dose in 2D planning and dose to 0.1cc, 1cc, 2cc, 5cc, and 10cc of bladder and rectum in 3D planning. Results: Mean doses received by 100% and 90% of the target volume were $4.24{\pm}0.63$ and $4.9{\pm}0.56$ Gy respectively. Doses received by 0.1cc, 1cc and 2cc volume of bladder were $2.88{\pm}0.72$, $2.5{\pm}0.65$ and $2.2{\pm}0.57$ times more than the ICRU bladder reference point. Similarly, doses received by 0.1cc, 1cc and 2cc of rectum were $1.80{\pm}0.5$, $1.48{\pm}0.41$ and $1.35{\pm}0.37$ times higher than ICRU rectal reference point. Conclusions: Dosimetric comparative evaluation of 2D and 3D CT based treatment planning for the same brachytherapy session demonstrates underestimation of OAR doses and overestimation of target coverage in 2D treatment planning.

• The Journal of Korean Society for Radiation Therapy
• /
• v.12 no.1
• /
• pp.20-25
• /
• 2000

The accuracy of the target localization was evaluated by conventional and spiral CT in stereotactic radiosurgerv. Conventional and spiral CT images were obtained with geometrical phantom, which was designed to produce exact three-dimensional coordinates of several objects within 0.1mm error range. Geometrical phantom was attached by BRW headframe, intermediate head ring, and CT localizer. Twentv-seven slices of conventional CT image were scanned at 3 mm slice thickness. Spiral CT images were scanned at 3 mm slice thickness from the pitch value 1 to 3, and twenty-seven slices of image were obtained per each the pitch value. These CT images were transferred to a treatment planning system(X-knife, Radionics) by ethernet, Three-dimensional coordinates of these images measured from the treatment planning system were compared to known values of geometrical phantom. The mean localization error of the target localization of conventional CT was 1.4mm. In case of spiral CT, the error of the target localization was within 1.6mm from the pitch value 1 to 1.3, but was more than 30mm above the pitch value 1.5. In conclusion, as the localization error of spiral CT was increased in high pitch value compared to conventional CT, the application of spiral CT will be with caution in stereotactic radiosurgery.

• Progress in Medical Physics
• /
• v.17 no.4
• /
• pp.192-200
• /
• 2006

We evaluated the positional accuracy of the delivered beams to the target in a phantom by simulating the whole process of the radiation treatments Including CT scanning, planning and beam exposures with MLCs. For this purpose, a phantom was made to calibrate the alignment between the CT and the attached laser system. A new, convenient method was also devised to align the setup lasers in the treatment room. Film was used for the Identification of the delivered beam and analyzed with a homemade computer program. The positional differences between the target and the beam centers varied with the couch rotations. The accelerator we used showed a maximum discrepancy of 2.0 mm at the table angle of $295^{\circ}$. The same measurements based on the new isocenter from the Winston-Lutz test resulted in the maximum of 1.35 mm for all rotation angles. The evaluation of the differences between the target and the beam centers is useful for the treatment planning.

• Progress in Medical Physics
• /
• v.27 no.4
• /
• pp.220-223
• /
• 2016

Generally, it is recommended that the dosimetric effect of carbon fiber couch should be considered especially for an intensity-modulated therapy with a large portion of monitor units from posterior angles. Even a flattening filter free (FFF) beam has been used for stereotactic body radiation therapy (SBRT), the effect of carbon fiber couch for FFF beam is not well known. This work is an effort to evaluate the dosimetric effect of carbon fiber couch for flattened and FFF beam of Elekta linac empirically. The absorbed doses were measured with Farmer type chamber and water-equivalent phantoms with and without couch. And differences of the absorbed doses between with and without couch defined as "couch effect". By comparing calculated dose in treatment planning system (TPS) with measured dose, the optimal density of couch was evaluated. Finally, differences on patient's skin dose and target dose by couch were evaluated in TPS. As a result, the couch effect for 6 and 10 MV flattened beam were -2.71% and -2.32%, respectively. These values were agreed with provided data by vendor within 0.5%. The couch effect for 6 and 10 MV FFF beam were -3.75% and -2.80%, respectively. The patient's skin dose was increased as 18.6% and target dose was decreased as 0.87%, respectively. It was realized that the couch effect of FFF beam was more severe than that of flattened beam. Patient's skin dose and target dose were changed by the couch effect.

• Radiation Oncology Journal
• /
• v.30 no.1
• /
• pp.36-42
• /
• 2012

Purpose: To evaluate the radial displacement of clinical target volume in the patients with node negative head and neck (H&N) cancer and to quantify the relative positional changes compared to that of normal healthy volunteers. Materials and Methods: Three node-negative H&N cancer patients and five healthy volunteers were enrolled in this study. For setup accuracy, neck thermoplastic masks and laser alignment were used in each of the acquired computed tomography (CT) images. Both groups had total three sequential CT images in every two weeks. The lymph node (LN) level of the neck was delineated based on the Radiation Therapy Oncology Group (RTOG) consensus guideline by one physician. We use the second cervical vertebra body as a reference point to match each CT image set. Each of the sequential CT images and delineated neck LN levels were fused with the primary image, then maximal radial displacement was measured at 1.5 cm intervals from skull base (SB) to caudal margin of LN level V, and the volume differences at each node level were quantified. Results: The mean radial displacements were 2.26 (${\pm}1.03$) mm in the control group and 3.05 (${\pm}1.97$) in the H&N cancer patients. There was a statistically significant difference between the groups in terms of the mean radial displacement (p = 0.03). In addition, the mean radial displacement increased with the distance from SB. As for the mean volume differences, there was no statistical significance between the two groups. Conclusion: This study suggests that a more generous radial margin should be applied to the lower part of the neck LN for better clinical target coverage and dose delivery.

• Progress in Medical Physics
• /
• v.22 no.4
• /
• pp.206-215
• /
• 2011

The purpose of this was to investigate the measurement of fluence dose map for the specific patient quality assurance. The measurement of fluence map was performed using 2D matrixx detector. The absorbed dose was measured by a glass detector, Gafchromic film and ion chamber in Hybrid Optimized VMAT Phantom (HOVP). For 2D Matrixx, the results of comparison were average passing rate $85.22%{\pm}1.7$ (RT_Target), $89.96%{\pm}2.15$ (LT_Target) and $95.14%{\pm}1.18$ (G4). The dose difference was $11.72%{\pm}0.531$, $-11.47%{\pm}0.991$, $7.81%{\pm}0.857$, $-4.14%{\pm}0.761$ at the G1, G2, G3, G4. In HOVP, the results of comparison for film were average passing rate (3%, 3 mm) $93.64%{\pm}3.87$, $90.82%{\pm}0.99$. We were measured an absolute dose in steep gradient area G1, G2, G3, G4 using the glass detector. The difference between the measurement and calculation are 8.3% (G1), -5.4% (G2), 6.1% (G3), 7.2% (G4). The using an Ion-chamber were an average relative dose error $-1.02%{\pm}0.222$ (Rt_target), $0.96%{\pm}0.294$ (Lt_target). Though we need a more study using a transmission detector. However, a measurement of real-time fluence map will be predicting a dose for real-time specific patient quality assurance in volume modulated arc therapy.