Therasphere Part Deux

Our first patient, who has a long standing history of hepatocellular carcinoma (HCC), was excluded as a surgical candidate to remove the tumour in the right lobe of the liver because the patient suffers from portal hypertension and low platelets.  The alternative consideration was for transcatheter arterial chemoembolization (TACE) to treat the tumour,  however somehow this patient ended up in the trial study of Yittrium-90 Theraspheres at our facility (click on link for further reading)

A mesenteric angiography and embolization was performed as the first step of the selective internal radiation therapy.  The reasoning is to ensure the blood flow localizes into the tumour site while sparing normal healthy sites when the Y-90 is delivered.   The mircocatheters where inserted through the right femoral artery and threaded to the right hepatic and left hepatic arteries for the arteriography.  The right gastric artery, which arose from proximal left hepatic artery, was embolized with vortex coils.  Furthermore the gastroduodenal artery was emoblized as well, leaving patent the common hepatic artery, the left and right hepatic arteries.

Fig. 1  Infusion of contrast through the right hepatic artery.  Note the embolization coils below.

Fig. 2  Infusion of contrast through the right hepatic artery, outlining the tumour in the right lobe.

Fig. 3  The right lobe tumour is now fully visualized, with limited shunting.  However there is still extraneous vascularity.  Thus the lung shut fraction is calculated to quantitate the amount.

After the embolization process, Tc-99m MAA was injected through the microcatheter for the lung shunt study.  After the injection, the patient was stabilzed for transport to Nuclear Medicine, and the following images were taken.

Fig. 4  Anterior and posterior images were taken to determine any major shunting of blood to the lungs or stomach.

Fig.  5  Regions of interest were drawn over the lungs and liver and a geometric mean was calculated to determine the lung shunt fraction (LSF).

Lung shunt fraction was calculated to be 3.0%.  There is no cut off with regards to the LSF value to be excluded from the treatment.  However it is the discretion of the interventional radiologist who will be administering the Y-90 to determine the patient's inclusion within the treatment study.

Two weeks after the initial angiography and embolization, the Y-90 theraspheres were adminstered.  Based on the size and volume of the tumour which the interventional radiologist calculated prior to the administration, we wanted to give approximately 2.5Gbq of Y-90 to deliver 120Gy to the tumour site.

Nordion which supplies the theraspheres, has an excel worksheet to help with the ordering of the Y-90 dose to ensure the proper calibration of the actual dose.
In the end, the amount that we calculated (approximation) of the dose delivered to the tumour site was about 2.49GBq, based on a 1.7% residual activity remaining in the Y-90 administration vial.  Overall the tumour received 120.7Gy with the lungs receiving approximately 3.73Gy, based on the LSF value.

Having worked through our first patient it is important to address the fact that most Nuclear Medicine technologists are accustomed to working with radioactive materials.  However the interventional radiology (IR) technologists and some IR doctors do not.  The dose rate is quite high with respect to the Y-90 vial.... but we normally do not tell them how high it really is.  Thus it is a good idea that you get them on board with respect to working with radioactive materials and how to handle these materials without causing too much of a mess.  The reason why, is that they are most likely going to set up the Y-90 administration set, since they have much more experience than Nuclear Medicine technologists in a sterile field.  Plus it will be the IR doctors (at least at our site), that will be injecting the Y-90.

Fig. 6  An unassembled administration set.  Everything is performed in a sterile field.  I will endeavour to update this image, once everything is connected together, when our next patient arrives.  Which should be in 2 weeks time.