TITLE:
SIRT and Its Unresolved Problems—Is Imaging the Solution? A Review
AUTHORS:
Franziska Schulz, Michael Friebe
KEYWORDS:
Selective Internal Radiation Therapy (SIRT), Radioembolization, Yttrium 90, Holmium 166, Liver Tumors
JOURNAL NAME:
Journal of Cancer Therapy,
Vol.7 No.7,
July
12,
2016
ABSTRACT: Selective Internal Radiation Therapy (SIRT) is used as a treatment option
for unresectable liver tumors. In SIRT, microspheres, which have a radioactive
substance as an integral component, are placed via image guided catheters into
the hepatic artery. The ionizing radiation is directly delivered to the tumor.
Currently used commercially available microspheres are based on Yttrium 90, a β-emitter, which has been shown to be
safe and to produce good clinical results. The technical features of Y90, their
applications and their limitations are presented. Image guidance and intraoperative
depiction of Yttrium 90 microspheres are restricted, which is currently one of
the main limitations in SIRT. Therapy planning and control is currently based
on pre- and post-operative images to evaluate the placement of the microspheres
respectively. Holmium 166, another possible nuclide integrated into the
microspheres emits a higher amount of secondary γ-radiation (Bremsstrahlung) than Yttrium 90. This enables an
improved depiction of the microspheres inside the patient during and
immediately after application, but comes with other shortfalls. Imaging of
delivery and verification of the microsphere placement could solve many of the
identified problems with SIRT. The different technologies are reviewed and an
outlook in future developments is given particularly on image guidance and
therapy control.