Usefulness of Stereotactic Radiotherapy Using CyberKnife for Recurrent Lymph Node Metastasis of Differentiated Thyroid Cancer

A woman in her 60s presented with a recurrent lymph node metastasis from a papillary thyroid carcinoma in the right parapharyngeal space. She had already undergone total thyroidectomy, five resections for cervical lymph node metastases, and right carotid rebuilding. Surgical resection of the current metastasis was impossible. 131I-radioiodine therapy (RIT) with 3.7 GBq 131I was not effective; therefore, stereotactic radiation therapy (SRT) using a CyberKnife radiotherapy system was scheduled. The prescription dose was 21 Gy, and a dose covering 95% of the planning target volume (PTV) in three fractions was administered. The PTV was 4,790 mm3. Follow-up magnetic resonance imaging conducted 3 and 12 months after the SRT demonstrated a remarkable and gradual reduction of the recurrent lymph node metastasis in the right parapharyngeal space and no evidence of recurrence. For multidisciplinary therapy of unresectable and/or RIT unresponsive locoregional lymph node metastases and recurrences of DTC, SRT using the CyberKnife system should be considered

Improvement of a skeleton segmentation model of bone scintigrams with a transformer and component tree loss function

International audienc

Subcutaneous Extravasation of Sr-89: Usefulness of Bremsstrahlung Imaging in Confirming Sr-89 Extravasation and in the Decision Making for the Choice of Treatment Strategies for Local Radiation Injuries Caused by Sr-89 Extravasation

A male patient in his 20s presented at our clinic with pain caused by bone metastases of the primitive neuroectodermal tumor, and Sr-89 was administrated to palliate the pain. After receiving the injection, the patient complained of a slight burning pain at the catheterized area. Slight reddening and small circular swelling (diameter, 0.5 cm) were observed at the catheterized area. Sr-89 extravasation was suspected. To estimate the amount of subcutaneous Sr-89 leakage, bremsstrahlung imaging was immediately performed. We speculated that the skin-absorbed dose from the subcutaneous Sr-89 leakage was 1.78 Gy. The mildest clinical sign of local radiation injury was erythema. The received dose was higher than 3 Gy, and the time of onset was from 2 to 3 weeks. In our patient, local radiation injuries (LRIs) did not occur. Though requiring further verification, subsequent bremsstrahlung imaging and estimation of the skin-absorbed dose from the subcutaneous Sr-89 leakage are useful in confirming Sr-89 extravasation and in the decision making for the choice of treatment strategies for LRIs caused by Sr-89 extravasation