[Papillary Thyroid Cancer Metastasizing Anterior Mediastinal Lymph Node with Extra-nodal Invasion to the Lung:Report of a Case].

We describe a 79-year-old female with a prior history of two times of mitral valve surgery and pacemaker implantation. She was transferred to our hospital presenting bloody sputum with dyspnea. Chest enhanced computed tomography (CT) showed a large anterior mediastinal mass of 64×52 mm in size. She underwent surgery for the mediastinal tumor through third time median sternotomy approach. As the tumor was suspected of infiltrating to the lung, combined resection of right upper lobe was additionally performed. Histological examination revealed papillary thyroid carcinoma metastasizing anterior mediastinal lymph node with extra-nodal invasion to the lung. After surgery, echography detected primary lesion in the left lobe of thyroid gland, and the patient was finally diagnosed as papillary thyroid cancer metastasizing mediastinal lymph node. Two months later, she underwent total thyroidectomy.

PHANTOM STUDY OF THE ENTRANCE SURFACE DOSE OF A NEW CT SCOUT ACQUISITION THAT ALSO SERVES AS A TUBE WARM-UP.

We determined the effect of a new scout image acquisition technique ('smart scout'), which also serves as a tube warm-up, on radiation dose and automatic exposure control (AEC) mA settings. The entrance surface dose (ESD) of a chest phantom with and without the smart scout was measured. A conical AEC phantom was scanned in the setting for abdominal CT, and AEC curves were generated. ESD when the smart scout was not used was 0.75 mGy at 120 kV, 50 mA. ESD when using the smart scout was 0.24 mGy for a body habitus setting of 'Less', 0.54 mGy for 'Moderate' and 0.95 mGy for 'More'. When the diameter of the subject was ≥32 cm, the mA setting became lower in 'Less'. The smart scout reduced exposure at the 'Less' and Moderate' settings compared to the conventional scout scan.

[Calculation of Lens Exposure Reduction Using Organ-effective Modulation in Pediatric Head CT].

PURPOSE: Using a pediatric head phantom constructed in our department, we examined a method to reduce exposure by using organ-effective modulation (OEM; Toshiba Medical Systems Corporation, Tochigi) to tilt the gantry during pediatric head computed tomography (CT) scanning. METHOD: The radiation reduction and CT image standard deviation (SD) were measured at gantry angles at which the orbit was slightly irradiated, partially irradiated, and completely irradiated. The OEM incident surface dose reduction rate was measured using an automatic exposure control (AEC) phantom with a diameter of 6-18 cm. RESULTS: The lens surface dose reduction rate using OEM was 21.2%. When the gantry was tilted and the orbit was completely out of the scanning range, the rate of reduction was 47.8%. OEM incident surface dose reduction rates were 27.4% for a phantom diameter of 18 cm, 22.0% for that of 16 cm, 17.8% for that of 14 cm, 17.2% for that of 12 cm, 8.4% for that of 10 cm, and 0% for that of 8 cm and 6 cm. OEM effectiveness decreased with decreasing phantom diameter. The use of OEM increased the rate of change of SD by 1.25´ when the gantry inclination was 0°, 1.27´ when the gantry inclination was 10°, and 1.27´ when the gantry inclination was 20°in the 12 o'clock position. CONCLUSION: The degree of reduction in exposure dose to the lens in pediatric head CT imaging was 47.8% by completely removing the lens from the irradiation range using gantry tilt and 21.2% by using OEM. The effect of OEM changed in proportion to tube current. The exposure reduction effect of the OEM decreases with decreasing head size, indicating its reduced effectiveness in head CT scans of smaller infants.