124I PET: Pretherapeutic Staging, Detection of Recurrent Thyroid Cancer and Dosimetry

Radioiodine therapy (RIT) is an integral component in the treatment of differentiated thyroid cancer (DTC). Patients usually undergo RIT as initial therapy or later in the case of recurrent or persistent disease. The most important requirement for a successful RIT is the ability of metastases and thyroid (remnant) tissue to accumulate radioiodine. In order to calculate the achievable absorbed radiation dose for a lesion, volume and iodine kinetics in the lesion need to be determined. Pretherapeutic imaging and dosimetry with 124I PET provide the methodology to answer these questions

Radioembolization with Y-90 Glass Microspheres: Do We Really Need SPECT-CT to Identify Extrahepatic Shunts?

Selective Internal Radiation Therapy (SIRT) with 90yttrium (Y-90) is an increasingly used therapeutic option for unresectable liver malignancies. Nontarget embolization of extrahepatic tissue secondary to vascular shunting can lead to SIRT associated complications. Our aim was to assess whether extrahepatic shunts can reliably be diagnosed based on hepatic digital subtraction angiography (DSA) or whether subsequent SPECT/CT data can provide additional information.825 patients with hepatocellular carcinoma (n = 636), hepatic metastases (n = 158) or cholangiocellular carcinoma (n = 31) were retrospectively analyzed. During hepatic DSA 128 arteries causing shunt flow to gastrointestinal tissue were coilembolized (right gastric artery n = 63, gastroduodenal artery n = 29; branches to duodenum / pancreas n = 36). Technectium-99m-labeled human serum albumin (HSA) was injected in all 825 patients. SPECT/CT data was used to identify additional or remaining shunts to extrahepatic tissue.An unexpected uptake of HSA in extrahepatic tissue was found by SPECT/CT in 54/825 (6.5%) patients (located in stomach n = 13, duodenum n = 26, distal bowel segments n = 12, kidney n = 1, diaphragm n = 2). These patients underwent repeated DSA and newly identified shunt vessels were coilembolized in 22/54 patients, while in 12/54 patients a more distal catheter position for repeat injection of HSA was chosen. In 20/54 patients the repeated SPECT/CT data still revealed an extrahepatic HSA uptake. These patients did not receive SIRT.Most extrahepatic shunts can be identified on DSA prior to Y-90 therapy. However, SPECT-CT data helps to identify additional shunts that were initially not seen on DSA

65 year-old male patient.

<p>The right gastric artery (Fig 1a; arrow) was identified and coilembolized (Fig 1b). SPECT/CT (Fig 1c) did not reveal extrahepatic tracer deposition.</p

41 year-old female patient.

<p>Initial DSA did not reveal any shunt vessels (Fig 2a). However, 99mTc-HSA scan revealed extrahepatic tracer uptake at the gastroduodenal junction (Fig 2b). A shunt vessel was identified during repeated DSA and occluded (Fig 2c) and no extrahepatic 99mTc-HSA deposition was seen anymore (Fig 2d).</p

47 year old male patient.

<p>During the initial DSA the gastroduodenal artery and right gastric artery were occluded. However, a small branch to the small bowel arising from the right hepatic artery was missed (Fig 3a) resulting in an extrahepatic 99mTc-HSA deposition in the small bowel wall (Fig 3b). During repeated angiography the microcatheter was positioned in a more distal part of the right hepatic artery (Fig 3c). Subsequent SPECT/CT did not reveal any extrahepatic tracer accumulation (Fig 3d).</p