SUMMARY Objectives: to describe the clinical and subclinical symptoms and evaluate the response after recurrent lymph node dissection of differentiated thyroid cancer patients after 131I treatment. Subjects: 50 differentiated thyroid cancer patients after 131I treatment, recurrence for the first time. Study methods: Retrospective and prospective description, data collection through patients’ medical records. Results: the mean age of the study patients was: 43.5 ± 12.6, the most common age is <55 years old with the rate of 80%, the female/ male ratio=3.5/1. The group of patients with Tg < 1 ng/ml accounted for the majority with 33/50 patients (66%). The median Tg before and after surgery was 2.02 ng/ml and 0.35 ng/ml, respectively. After surgery, response achieved in 98% of patients, mainly complete response and incomplete response in biochemical, accounted for 40%, 36%. Lymph node dissection reduced Tg in 78% of patients. Reccurent lymph nodes mainly observed in group IV, group III and group VI. The recurrence of lymph nodes was mainly in the central and cervical regions on the same side of the primary tumor. Conclusion: Surgery is the preferred first-line treatment for the reccurrent lymph node thyroid cancer patients. It changes response assessment, improve prognosis for reccurence patients after 131I treatment. Keywords: Differentiated thyroid cancer, response after recurrent lymph node dissection, Tg

SUMMARY Background: Ultrasonic-guided fine needle aspiration cytology is a minimally invasive diagnostic technique with the highest accuracy and sensitivity in the diagnosis of lymph node metastasis. Objectives: The study consists of 2 objectives: 1) Describe clinical and subclinical characteristics in treated patients with differentiated thyroid cancer; Evaluation of the role of ultrasound-guided fine needle aspiration cytology in the diagnosis of lymph node metastasis in patients with differentiated thyroid cancer. Materials and methods: A cross-sectional descriptive study design was conducted on 89 patients diagnosed with differentiated thyroid cancer and found that the cervical lymph nodes were potentially malignant under ultrasonography and indicated fine-needle aspiration cytology under ultrasound guidance. Results: Among 89 research subjects, small cell aspiration of lymph node groups, group IV and VI lymph nodes with suspicion of malignancy accounted for the highest proportion of 25/89 nodes (28.1%) fine needle aspiration cytology, in which positive accounts for 30.1%. Sensitivity, specificity, negative predictive value, false positive rate, false negative rate, and cytology accuracy were 90%; 100%; 100%; 52.9%.0%, 10.1%, 91.01%. Conclusion: Ultrasonic-guided fine needle aspiration cytology for the diagnosis of lymph node metastasis in differentiated thyroid cancer has a low false-positive rate, high accuracy, accurately reflecting the presence or absence of underlying cervical lymph node metastasis. Avoid complications and thoroughly treat metastatic disease for patients. Keywords: Ultrasonic-guided fine needle aspiration cytology, metastatic lymph nodes, differentiated thyroid cancers

SUMMARY Background: 18F-FDG PET/CT is method with high sensitivity and specificity in the diagnosis of recurrent lesions in patients with radioiodine refractory differentiated thyroid cancer ((RAI-R- DTC). The aim of this study was to evaluate the relationship between Tg, Tg – DT and rucurrent/metastatic lessions detected in 18F-FDG PET/CT imaging in RAI-R DTC patients. Methods: 119 RAI-R DTC patients underwent 18F-FDG PET/CT. At least two consecutive Tg measurements under the thyroid hormone replacement therapy (TSH ≤ 0,1 uIU/ml) to calculate Tg - DT before 18F-FDG PET/CT scan. We analyzed the relationship between PET/CT imaging and clinical characteristics, risk of recurrence, Tg and Tg – DT. Results : 18F-FDG PET/CT imaging detected recurrent lesions in 88 patients (73,9 %) and distant metastasis in 29 patient (24,3 %). Tg-DT was significantly lower in the positive PET/CT group compared to negative PET/CT group (median 12.9 vs 166 months, p< 0.001). Serum Tg concentration in the patients with distant metastasis was higher than those without distant metastasis (334 ng/ml vs 114.6 ng/ml, p < 0.001). In univariate and multivariate logistic regression analysis, Tg-DT was an independent predictor of positive PET/CT and serum Tg concentration was a predictor of distant metastasis. The ROC curve determines the optimal threshold of Tg - DT in predicting positive PET/CT is 34.75 months and Tg level at 218.1 ng/ml predicting distant metastasis Conclusion: Tg - DT is reliable value in predicting positive 18F - FDG PET/CT and serum Tg concentration is valuable for predicting the outcome of distant metastasis in RAI – R DTC patients. Keywords : thyroglobulin, thyroglobulin doubling time, differentiated thyroid carcinoma, 18F - FDG PET/CT.

SUMMARY This study applies the Monte Carlo simulation method EGSnrc Code with two dedicated codes: BEAMnrc code is used to simulate the beam emitted from the accelerator head and DOSXYZnrc code is used to calculate the dose emitted from the accelerator. From there, evaluate the beam attenuation of radiation emitted from the accelerator through the layers of shielding material. Initial study results showed that dose limited at staff area (area Control) is 0,11 mSv/ week (5,5 mSv / year) and in the public area (area Uncontrol) is 0,022 mSv/week (1,1 mSv/year). Initial research results show that the effectiveness of the application of the EGSnrc simulation program with two specialized codes, BEAMnrc and DOSXYZnrc, shows that the radiation dose in the study area for medical staff is safe, within the allowable limits. Keywords: Accelerator, Radiation Safety, MCNP, EGSnrc, DOSXYZnrc, and BEAMnrc

SUMMARY Background: Ultrasound is a minimally invasive diagnostic technique with the highest accuracy and sensitivity in the diagnosis of lymph node metastasis. Objectives: The study consists of objectives: Describe the ultrasound imaging characteristics of cervical lymph nodes in treated patients with differentiated thyroid cancer. Materials and methods: A cross-sectional descriptive study design was conducted on 89 patients diagnosed with differentiated thyroid cancer and found that the cervical lymph nodes were potentially malignant under ultrasonography and indicated fine-needle aspiration cytology under ultrasound guidance. Results: Among 89 study subjects, the main reason for admission was lymphadenopathy, accounting for 95.5%. The results of papillary pathology accounted for 96.6%. Time after thyroid surgery when cervical lymph node metastasis is detected is 1-3 years (27%). The time after thyroid surgery when cervical lymph node metastasis was detected was 6-36 months (38.2%). Oval shape on ultrasound has 73%, cortex on ultrasound accounts for 65.2%, decreased lymph node on ultrasound accounts for 64%, loss of hilar lymph nodes on ultrasound accounts for 62.9%. Conclusion: Ultrasound plays an important role in diagnosing the stage of the disease, fully and accurately describing the lesions and stage of the disease, helping to increase the effectiveness of treatment. Keywords: ultrasonic imaging, lymph nodes, differentiated thyroid cancers.

SUMMARY Purpose: Describe imaging characteristics and evaluate the role of 18FDG-PET/CT in the diagnosis of cervical lymph nodes in nasopharyngeal cancer patients. Subjects and methods: Prospective description of 60 patients with nasopharyngeal carcinoma identified by biopsy and histopathology and untreated (in which 55 patients with undifferentiated carcinoma and 5 patients with squamous cell carcinoma), were taken with 18FDG PET/CT and compared with ultrasound and done FNA lymph nodes respectively, from June 2018 to July 2019 to K Central Hospital, Tan Trieu campus. All 18FDG-PET/CT films were read and compared with their respective locations on ultrasound and lymph node FNA before treatment. Results: In total 60 patients common age is 52.3±11.1, male/female ≈ 5/1; A total of 379 bilateral cervical lymph nodes on PET/CT, 195 lymph nodes in the left neck are common (51.5%), the most common lymph node location in group II (96.7% of patients and 61% of total lymph nodes). There are 322/379 (85%) lymph nodes with structural loss on ultrasound, there is a correlation between lymph node size and lymph node absorption on 18FDG-PET/CT with r=0.6, cervical lymph node groups 322/379 Structural abnormal lymph nodes with SUVmax = 9.5 ± 4.6 (nearly 4 times higher than 57/379 normal lymph nodes with SUVmax = 2.6 ± 2.5). In a total of 379 lymph nodes over 60 patients, there was a close agreement between the lymph nodes with loss of umbilical fat structure on ultrasound with SUVmax>2.5 threshold of 92.9% (kappa=0.67) and better at the threshold. SUVmax>3.5 was 92.9% (Cohen's kappa=0.75) on PET/CT. In addition, cytology was positive in 60/89 lymph nodes undergoing FNA, which was in close concordance with ultrasonography of loss of hilar fat structure and cytological diagnosis of 83.4% (Cohen's kappa = 0.62). ). The cytological diagnosis was mild with increased uptake with SUVmax>2.5 threshold of 75.3% (Cohen's kappa = 0.3), but there was a strong correlation when the lymph node imaging was increased. Absorption with SUVmax >2.5 on PET/CT and loss of umbilical cord fat on ultrasound with cytological diagnosis was 87.6% (Cohen's kappa = 0.69). In particular, out of a total of 340/379 lymph nodes with threshold SUVmax>2.5 on PET/CT are considered as metastatic nodes, changing the stage of 25/60 patients (41.67%); in which 17 patients increased and 8 patients decreased stage N compared with staging by other imaging methods before having PET/CT. Conclusion: 18FDG-PET/CT scan is an imaging method with accurate diagnostic value in diagnosing cervical lymph nodes in patients with cervical cancer, useful for treatment planning. Key words: lymph nodes, nasopharyngeal cancer, 18FDG-PET/CT lymph nodes on nasopharngeal cancer.

SUMMARY Purpose: Evaluation the survival of the patients with hepatocellular carcinoma (HCC) who underwent transcatheter arterial chemoembolization (TACE). Subjects and methods: Retrospective study on transcatheter arterial chemoembolization in patients with hepatocellular carcinoma from July 2017 to July 2020 at Radiology Center - Bach Mai Hospital. Results:. 70 patients including 64 men (92.9%) and 6 women (7.1%) had a confirmed diagnosis of HCC with a mean age of 61.5 ± 11.34 years (from 32 to 83 years). The mean number of treatment sessions were 4.5±0.4 lần (1-16). Progression-free survival after initial TACE and overall survival median was 29.7±3.3 months, 43.3±2.5 months, respectively. Cumulative survival time at 1 year, 2 years, 3 years and 5 years is 91.4%, 77.1%, 63.7% and 29.4%, respectively. Patients treated with cTACE were 67.1% and Deb-TACE were 32.9%. mRECIST after the first TACE: complete response, partial response, stable disease and advanced disease were 30.0%, 55.7%, 4.3%, 10.0%, respectivel. Patients with objective response had a survival of 47.8±2.3 months, and patients with poor response had a survival of 12.2±2.7 months, respectively (p = 0.001). mRECIST response predicted survival among the patients on univariate analysis (HR=15.13, p=0.000). The independent predictors for survival were mRECIST response (p=0.001). Conclusion : Use of TACE in intermediate stage HCC patients gives a significant survival advantage when objective response is achieved as per mRECIST. Key words: TACE, Progression-free survival, overall survival..

SUMMARY PET (positron emission tomography) techniques and radiopharmaceutical tracers are becoming increasingly common. Since 1991, 3’-deoxy-3’-18Fluorine-Fluorothymidine (18F-FLT) has been studied as a PET tracer for tumor proliferation assessment. The purpose of this study was to assess tracer uptake (%ID/g) in tumor-bearing mice. Materials and methods: Two cell lines (4T1 and LLC) were inoculated into BALB/c mice. The radiotracer was then injected, and tumor resection and organ samples were performed at 20, 40, 60, 90 and 120 minutes later. A gamma-ray spectrometer was used to calculate uptake values. Results: The data show that the tumor’s %ID/g were 3.68 ± 0.29 and 5.30 ± 0.44 at 60-minute post-injection for the 4T1 and LLC tumors, respectively. In other organs, the high uptake was observed in the kidneys, spleen, and bone marrow, but a low level of tracer was seen in the brain. Keywords: 3’-deoxy-3’-18Fluorine-Fluorothymidine, positron emission tomography, tumor-bearing mice.