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Dr Ankur Pruthi
Consultant & Head, Nuclear Medicine and PET CT,
Manipal Hospital

Advances In Molecular Imaging

In the last decade, rapid strides have been made in the branch of nuclear medicine with the introduction of newer hybrid imaging equipment, radiotracers, and targeted radionuclide therapies. Hybrid imaging equipment such as PET CT, PET MR, time-of flight PET CT, digital PET, and digital SPECT systems are a significant advance over conventional imaging techniques such as ultrasound, CT, or MRI because they provide both functional and anatomical information regarding diseased organs and tissues. Newer molecular imaging tracers have been introduced, which provide functional biological information, such as substrate metabolism, receptor expression, antigen expression, amyloid or inclusion body deposition, angiogenesis, hypoxia, apoptosis, and the like, which help in selection of personalized targeted therapies. In addition, newer radionuclide therapies target affected diseased organs or tissues with high specificity.

Advances in molecular imaging equipment. With the introduction of PET CT in early 1990s, a huge void in oncology imaging was filled and PET CT became the most ordered investigation for cancer patients to assess the spread of disease and treatment-response evaluation. Since then, a lot of research has happened in improving image quality of these scanners. Several new technical innovations, like time-of-flight (TOF-PET), better scintillator crystals, semiconductor detectors, addition of rings of PET detectors, and multi-slice CT have significantly improved the image quality.

In 2018, India’s first digital PET had been installed, which utilizes semiconductor technology as compared to scintillator crystal technology. This has improved the resolution of image manifold.

The future appears bright as more and more research is being done by major manufacturers, such as GE Healthcare, Philips, and Siemens. The newer manufacturers such as United Imaging from China have the potential to cause major disruption in the imaging equipment market by offering cheaper prices compared to European and American companies. It will be a win-win for hospitals, patients, and ultimately the molecular imaging branch as a whole.

Advances in radiotracers. Theranostics (Therapeutics+ Diagnostics) is a new field of medicine where a specific targeted therapy is selected for a patient, based on results of targeted diagnostic tests. The theranostics paradigm involves using nanoscience to unite diagnostic and therapeutic applications to form a single agent, allowing for diagnosis, drug delivery, and treatment-response monitoring. In the last decade, theranostic agents have been developed for neuroendocrine tumors and prostate cancers.

Radionuclide generators and medical cyclotrons. Newer radiotracers, such as Ga-68 octreotide analogues (DOTANOC) and Ga-68 PSMA, are used to assess extent of disease and tracer avidity in neuroendocrine tumors and prostate cancers. The production of these radiotracers requires Germanium 68 – gallium 68 radionuclide generator. These generators are currently imported from countries, such as Germany, Austria, South Africa, and some others.

Also, these generators are used for production of therapeutic radiopharmaceuticals, such as Lutetium-177 Dotatate and Lutetium-PSMA, which are used for treatment of these diseases.

Medical cyclotrons. These are basically mini nuclear detectors, which are required for the production of multiple radioisotopes of nuclear medicine utility. New tracers, like fluorine-18-labelled PSMA, fluorine-18-labelled chlorine and fluorine-labelled fluorodopa, have important applications in oncology and neurology. The first medical cyclotron was installed in India in BARC in 2001. Since then, medical cyclotrons have been installed mainly in government facilities owing to their higher cost of installation, maintenance, and strict government regulations.

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