“Hot spot” in Nuclear Medicine

Dr. WU Kwan Kit, Sam

Specialist in Nuclear Medicine

In my daily routine in nuclear medicine, I often come across oncology patients in need of radionuclide imaging, PET/CT or radionuclide therapy. In most examinations, radioactive tracer is given intravenously to patients before scanning to observe organ uptake. For easier understanding, the image results are often explained to patients in terms of “hot spot”. “Hot spot” means any abnormal update or accumulation of the tracer in certain regions, while “no hot spot” represents no abnormal uptake. Patients often interpret the presence of “hot spot” as bad news; on the contrary, “hot spot” sometimes could mean a treatable condition.

Take Radionuclide Therapy as an example. A therapeutic radionuclide is given to oncology patients orally or intravenously, which then accumulates and kills tumour cells with the emission of alpha and beta (α/β) particles. Prior to treatment, patients are required to undergo radionuclide imaging to confirm and access the tumour uptake. For example, F-18 or Ga-68 PSMA PET/CT is used to evaluate the PSMA expression status in tumors of prostate cancer patients. If the tumors show up as “hot spots”, it implies good tracer accumulation and the patient would be eligible for consideration of radionuclide therapy (Lu-177 PSMA treatment).

The concept behind radionuclide therapy is personalised treatment: the metabolic characteristics and presence of “targets” are firstly evaluated by radionuclide imaging. Then, corresponding radionuclide therapy can be given to the specific “targets” that are detected in the tumors. Subsequently, radionuclide imaging and and PET/CT can effectively monitor the disease progress and detect drug-resistant tumours in a timely manner.

With advances in radionuclide therapy, I look forward to more cancer-specific treatment options and better clinical outcomes.