• Journal of radiological science and technology
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• v.34 no.2
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• pp.105-116
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• 2011

In this study, we present the measurements of effective dose from CT of head & neck region. A series of dose measurements in anthropomorphic Rando phantom was conducted using a radio photoluminescent glass rod dosimeter to evaluate effective doses of organs of head and neck region from the patient. The experiments were performed with respect to four anatomic regions of head & neck: optic nerve, pons, cerebellum, and thyroid gland. The head & neck CT protocol was used in the single scan (Brain, 3D Facial, Temporal, Brain Angiography and 3D Cervical Spine) and the multiple scan (Brain+Brain Angiography, Brain+3D Facial, Brain+Temporal, Brain+3D Cervical spine, Brain+3D Facial+Temporal, Brain+3D Cervical Spine+Brain Angiography). The largest effective dose was measured at optic nerve in Brain CT and Brain Angiography. The largest effective dose was delivered to the thyroid grand in 3D faical CT and 3D cervical spine, and to the pons in Temporal CT. In multiple scans, the higher effective dose was measured in the thyroid grand in Brain+3D Facial, Brain+3D Cervical Spine, Brain+3D Facial+Temporal and Brain+3D Cervical Spine+Brain Angiography. In addition, the largest effective dose was delivered to the cerebellum in Brain CT+Brain Angiography CT and higher effective dose was delivered to the pons in Brain+Temporal CT. The results indicate that in multiple scan of Brain+3D Cervical Spine+Brain Angiography, effective dose was 2.52 mSv. This is significantly higher dose than the limitation of annual effective dose of 1 mSv. The effective dose to the optic nerve was 0.31 mSv in Brain CT, which shows a possibility of surpassing the limitation of 1 mSv by furthre examination. Therefore, special efforts should be made in clinical practice to reduce dose to the patients.

• Progress in Medical Physics
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• v.11 no.1
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• pp.59-71
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• 2000

It is possible to obtain a fast CT scan during breath holding with spiral technique. But the risk of radiation is increased due to detailed and repeated scans. However, the limitation of X-ray doses is not fully specified on CT, yet. Therefore, the purpose of the present study is to define the limitation of X-ray doses on CT The CT unit was somatom plus 4. Alderson Rando phantom, Solenoid water phantom, TLD, and reader were used. For determining adequate position and size of organs, the measurement of distance(${\pm}$2mm) from the midline of vertebral body was performed in 40 women(20~40 years). On the brain scan for 8:8(8mm slice thickness, 8mm/sec movement velocity of the table) and 10:10(10mm slice thickness, 10mm/sec movement velocity of the table) methods, the absorption doses of exposed area of the 10:10 were slightly higher than those of 8:8. The doses of unexposed uterus were negligible on the brain scan for both 8:8 and 10:10. On the chest scan for 8:8, 8:10(8mm slice thickness, 10mm/sec movement velocity of the table), 10:10, 10:12(10mm slice thickness, 12mm/sec movement velocity of the table) and 10:15(10mm slice thickness, 15mm/sec movement velocity of the table) methods, 8:8 method of the absorption doses of exposure area was the most highest and 10:15 method was the most lowest. The absorption doses of 8:10 method was relatively lower than those of the other methods. In conclusion, the 8:10 method is the most suitable to give a low radiation burden to patient without distorting image quality.

• Journal of the Korean Society of Radiology
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• v.6 no.5
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• pp.365-371
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• 2012

The radiation therapy treatment technique is developed from 3D-CRT, IMRT to Tomotherapy. and these three technique was most widely using methods. We find out a comparison normal tissue doses and tumor dose of 3D-CRT, IMRT(Linac Based), and Tomotherapy on Head and Neck Cancer. We achieved radiological image used the Human model phantom (Anthropomorphic Phantom) and it was taken CT simulation (Slice Thickness : 3mm) and GTV was nasopharngeal region and PTV(including set-up margin) was GTV plus 2mm area. and transfer those images to the radiation planning system (3D-CRT - ADAC-Pinnacle3, Tomotherapy - Tomotherapy Hi-Art System). The prescription dose was 7020 cGy and measuring PTV's dose and nomal tissue (parotid gland, oral cavity, spinal cord). The PTV's doses was Tomotherapy, Linac Based - IMRT, 3D-CRT was 6923 cGy, 6901 cGy and 6718 cGy its dose value was meet TCP because its value was up to the 95% based on 7020 cGy, Nomal tissue (parotid gland, oral cavity, spinal cord) was 1966 cGy(Tomotherapy), 2405 cGy(IMRT), 2468 cGy(3D-CRT)[parotid gland], 2991 cGy(Tomotherapy), 3062 cGy(IMRT), 3684 cGy (3D-CRT)[oral cavity], 1768 cGy(Tomotherapy), 2151 cGy(IMRT), 4031 cGy(3D-CRT)[spinal cord] its value did not exceeded NTCP. All the treatment techniques are equated with tumor and nomal tissue doses. The 3D-CRT was worse than other techniques on dose distribution, but it is reasonable in terms of TCP and NTCP baseline Tomotherapy, IMRT -dose distribution was relatively superior- was hard to therapy to claustrophobic patients and patients with respiratory failure. Particularly, in case on Tomotherapy, it take MVCT before treatment so dose measurement will be unnecessary radiation exposure to patients. Conclusion, Tomotherapy was the best treatment technique and 2nd was IMRT, and 3rd 3D-CRT. But applicable differently depending on the the patient's condition even though dose not matter.

• Progress in Medical Physics
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• v.17 no.2
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• pp.89-95
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• 2006

The purpose of this study was to evaluate the radiation doses during CT transmission scan by changing tube voltage and tube current, and to estimate the radiation dose during our clinical whole body $^{137}Cs$ transmission scan and high quality CT scan. Radiation doses were evaluated for Philips GEMINI 16 slices PET/CT system. Radiation dose was measured with standard CTDI head and body phantoms in a variety of CT tube voltage and tube current. A pencil ionization chamber with an active length of 100 mm and electrometer were used for radiation dose measurement. The measurement is carried out at the free-in-air, at the center, and at the periphery. The averaged absorbed dose was calculated by the weighted CTDI ($CTDI_w=1/3CTDI_{100,c}+2/3CTDI_{100,p}$) and then equivalent dose were calculated with $CTDI_w$. Specific organ dose was measured with our clinical whole body $^{137}Cs$ transmission scan and high quality CT scan using Alderson phantom and TLDs. The TLDs used for measurements were selected for an accuracy of ${\pm}5%$ and calibrated in 10 MeV X-ray radiation field. The organ or tissue was selected by the recommendations of ICRP 60. The radiation dose during CT scan is affected by the tube voltage and the tube current. The effective dose for $^{137}Cs$ transmission scan and high qualify CT scan are 0.14 mSv and 29.49 mSv, respectively. Radiation dose during transmission scan in the PET/CT system can measure using CTDI phantom with ionization chamber and anthropomorphic phantom with TLDs. further study need to be peformed to find optimal PET/CT acquisition protocols for reducing the patient exposure with same image qualify.

• Radiation Oncology Journal
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• v.12 no.2
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• pp.233-241
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• 1994

Purpose : This study was performed to verify dose distribution with the tissue compensator which is used for uniform dose distribution in total body irradiation(TBI). Materials and methods : The compensators were made of lead(0.8mm thickness) and aluminum(1mm or 5mm thickness) plates. The humanoid phantom of adult size was made of paraffin as a real treatment position for bilateral total body technique. The humanoid phantom was set at 360cm of source-axis distance(SAD) and irradiated with geographical field size(FS) $144{\times}144cm^2(40{\times}40cm^2$ at SAD 100cm) which covered the entire phantom. Irradiation was done with 10MV X-ray(CLINAC 1800, Varian Co., USA) of linear accelerator set at Department of Therapeutic Radiology, Chonnam University Hospital. The midline absorbed dose was checked at the various regions such as head, mouth, mid-neck, sternal notch, mid-mediastinum, xiphoid, umbilicus, pelvis, knee and ankle with or without compensator, respectively. We used exposure/exposure rate meter(model 192, Capintec Inc., USA) with ionization chamber(PR 05) for dosimetry, For the dosimetry of thorax region TLD rods of $1x1x6mm^3$ in volume(LiF, Harshaw Co., Netherland) was used at the commercially available humanoid phantom. Results : The absorbed dose of each point without tissue compensator revealed significant difference(from $-11.8\%\;to\;21.1\%$) compared with the umbilicus dose which is a dose prescription point in TBI. The absorbed dose without compensator at sternal notch including shoulder was $11.8\%$ less than the dose of umbilicus. With lead compensator the absorbed doses ranged from $+1.3\%\;to\;-5.3\%$ except mid-neck which revealed over-compensation($-7.9\%$). In case of aluminum compensator the absorbed doses were measured with less difference(from $-2.6{\%}\;to\;5.3\%$) compared with umbilicus dose. Conclusion : Both of lead and aluminum compensators applied to the skull or lower leg revealed a good compensation effect. It was recognized that boost irradiation or choosing reference point of dose prescription at sternal notch according to the lateral thickness of patient in TBI should be considered.

• Journal of radiological science and technology
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• v.30 no.2
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• pp.139-145
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• 2007

Dose evaluation for small field such as stereotactic radiosurgery was performed using $Gafchromic^{(R)}$ EBT film. Every film which irradiated 6MV photon beam was scanned and obtained the optical density(OD) by flat bed scanner after 24 hours of irradiation. This study compared dose from diode in water and Gafchromic $EBT^{(R)}$ film in acrylic phantom to verify the reliability of the film, and to evaluate the SRS in clinical dose distributions from calculation and measurement in the region of virtual target in humanoid and cylindrical phantoms were compared. The Gafchromic $EBT^{(R)}$ film was found to be linear up to 9Gy. The $D_{max}$ for 6 MV was measured at 1.5 cm from the surface by both of diode and the film. As the depth is deeper, the error was measured within $2{\sim}3%$ at $10{\sim}20\;cm$ depth. Comparing between distribution from calculation and measurement, we found that there is 5% error at 90% isodose line. We found that given dose could be measured accurately by using the phantoms. It was feasible to use the Gafchromic $EBT^{(R)}$ film in quality assurance of SRS.

• Radiation Oncology Journal
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• v.16 no.4
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• pp.399-408
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• 1998

Purpose : This study was designed to demonstrate the potential therapeutic advantage of 3-dimensional (3-D) treatment planning over the conventional 2-dimensional (2-D) approach in patients with carcinoma of the nasopharynx. Materials and Methods : The two techniques were compared both qualitatively and quantitatively for the boost portion of the treatment (19.8 Gy of a total 70.2 Gy treatment schedule) in patient with T4. The comparisons between 2-D and 3-D plans were made using dose statistics, dose-volume histogram, tumor control probabilities, and normal tissue complication probabilities. Results : The 3-D treatment planning improved the dose homogeneity in the planning target volume. In addition, it caused the mean dose of the planning target volume to increase by 15.2$\%$ over 2-D planning. The mean dose to normal structures such as the temporal lobe, brain stem, parotid gland, and temporomandibular joint was reduced with the 3-D plan. The probability of tumor control was increased by 6$\%$ with 3-D treatment planning compared to the 2-D planning, while the probability of normal tissue complication was reduced. Conclusion : This study demonstrated the potential advantage of increasing the tumor control by using 3-D planning. but prospective studies are required to define the true clinical benefit.

• Journal of the Korean Society of Radiology
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• v.16 no.7
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• pp.843-849
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• 2022

In this study, the probability of secondary carcinogenesis was analyzed by measuring the exposure dose of surrounding normal organs during radiosurgery using a gamma knife. A pediatric phantom (Model 706-G, CIRS, USA) composed of human tissue-equivalent material was set to four tumor volumes of 0.25 cm³, 0.51 cm³, 1.01 cm³, and 2.03 cm³, and the average dose was 18.4 ± 3.4 Gy. After installing the Rando phantom on the table of the gamma knife surgical equipment, the OSLD nanoDot dosimeters were placed in the right eye, left eye, thyroid, thymus gland, right lung, and left lung to measure each exposure dose. The probability of cancer occurrence due to radiation exposure of surrounding normal organs during gamma knife radiosurgery for acoustic schwannoma disease was 4.08 cancers per 100,000 at a tumor volume of 2.03 cm³. This study is expected to be used as useful data in relation to stochastic effects in the future by studying the risk of secondary radiation exposure that can occur during stereotactic radiosurgery.

• Journal of the Korean Society for Nondestructive Testing
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• v.16 no.1
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• pp.19-28
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• 1996

This study has investigated the optimization of NDT method and the minimum detectable defect size for complex structures such as the solid propellant rocket motor using real time X-ray imaging system. Test specimens were made of steel plates with various defect size, and installed with proper thickness for which solid propellant, rubber, and case converted to the steel equivalent thickness according to the radiographic equivalent theory. As the results, this examination obtained optimum magnification and X-ray energy, dose rate according to steel equivalent thickness, also, obtained the relationship between minimum detectable defect size and the ratio(defect depot/object thickness). Thus, this simulated test is the preliminary procedure before performing NDT for real objects, and is possibly applied for NDT of other complex structures.

• Journal of Radiation Protection and Research
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• v.24 no.4
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• pp.195-203
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• 1999

It is difficult to determine dosimetric characteristics for small field photon beams since such small fields do not achieve complete lateral electronic equilibrium and have steep dose gradients. Dosimetric characteristics of small field 4, 6, and 10 MeV photon beams have been measured in water with a diamond detector and compared to measurements using small volume cylindrical and plane parallel ionization chambers. Percent depth dose (PDD) and beam profiles for 6 and 10 MeV photon beams were measured with diamond detector and cylindrical ion chamber for small fields ranging from $1{\times}1\;to\;4{\times}4cm^2$. Total scatter factors($S_{c,p}$) for 4, 6, and 10 MeV photon beams were measured with diamond detector, cylindrical and plane parallel ion chambers for small fields ranging from $1{\times}1\;to\;4{\times}4cm^2$. The $S_{c,p}$ factors obtained with three detectors for 4, 6, and 10 MeV photon beams agreed well ($\pm1.2%$) for field sizes greater than $2{\times}2,\;2.5{\times}2.5,\;and\;3{\times}3\;cm^2$, respectively. For smaller field sizes, the cylindrical and plane parallel ionization chambers measure a smaller $S_{c,p}$ factor, as a result of the steep dose gradients across their sensitive volumes. The PDD values obtained with diamond detector and cylindrical ionization chamber for 6 and 10MeV photon beams agreed well ($\pm1.5%$) for field sizes greater than $4{\times}4\;cm^2$. For smaller field sizes, diamond detector produced a depth-dose curve which had a significantly shallower falloff than that obtained from the measurements of relative depth-dose with a cylindrical ionization chamber. For the measurements of beam profiles, a distortion in terms of broadened penumbra was observed with a cylindrical ionization chamber since diamond detector exhibited higher spatial resolution. The diamond detector with small sensitive volume, near water equivalent, and high spatial resolution is suitable detector compared to ionization chambers for the measurements of small field photon beams.