Dr. Mohit Seth

Ga-68 FAPI PET/CT images fibroblast activation protein, which is expressed by cancer-associated fibroblasts in the tumour's supporting tissue, whereas 18F-FDG PET/CT images glucose metabolism. Because FAPI targets the tumour stroma rather than glucose uptake, it can show lesions clearly in settings where FDG is limited — including tumours with low glucose avidity and areas of inflammation where FDG is less specific.

In our prospective study of lung cancer patients being evaluated for surgery, Ga-68 FAPI PET/CT was more sensitive than 18F-FDG PET/CT for nodal staging (84.6% vs 61.5%), with the same specificity. Read the published abstract →

¹⁷⁷Lu-PSMA is a radioligand therapy for metastatic castration-resistant prostate cancer, in which lutetium-177 is attached to a molecule that binds prostate-specific membrane antigen on prostate cancer cells. It delivers beta radiation directly to PSMA-expressing deposits throughout the body while largely sparing surrounding tissue.

Patients are selected using a Ga-68 PSMA PET/CT scan first — treatment is only appropriate where the scan confirms sufficient PSMA expression at sites of disease.

Peptide receptor radionuclide therapy, or PRRT, treats neuroendocrine tumours by attaching lutetium-177 to a somatostatin analogue that binds somatostatin receptors on tumour cells. It is given as a series of infusions, typically four cycles spaced roughly eight weeks apart.

As with PSMA therapy, eligibility is confirmed on imaging first — a Ga-68 DOTANOC or DOTATATE PET/CT scan must show adequate receptor expression.

Radioiodine therapy uses I-131, taken orally as a capsule or liquid, to treat differentiated thyroid cancer and some overactive thyroid conditions. Thyroid tissue naturally concentrates iodine, so the radioactive iodine is absorbed by remaining thyroid or thyroid-cancer cells and destroys them from within.

Because patients emit low levels of radiation afterwards, higher-dose treatment involves a short stay in a dedicated isolation room, followed by a whole-body scan a few days later to confirm where the iodine has localised.

Nuclear medicine images function — how tissue behaves biologically — while conventional radiology largely images structure. A CT or MRI shows the size and shape of a lesion; a PET or SPECT scan shows whether it is metabolically active or expressing a particular molecular target.

Nuclear medicine is also therapeutic: the same specialty that performs the scan administers targeted radionuclide treatment, which is what distinguishes it from purely diagnostic imaging.