A new breed of high-tech body scanner is revolutionizing nuclear medicine, bringing better patient care, a better patient experience, and a more efficient use of health care resources: a big win-win-win.
Nuclear Medicine is an impactful field of medicine that uses tracers to image and diagnose a wide range of medical diseases, including cancer, cardiac disease, and many more. The tracers are called radiopharmaceuticals and have 2 properties, a molecule with a specific physiologic property such as seeking and binding to cancer, and a tiny radioactive component that emits energy detected by scanners, creating an image of the distribution of the tracer in the body. While the past several years have seen major advances in other pillars of Nuclear Medicine – Positron Emission Tomography (PET) scanning, and radioisotope therapy – the scanners used for most Nuclear Medicine tests had changed little in many years. However, a new state-of-the-art class of scanners has been developed, raising the bar to a new level.
A PARADIGM SHIFT IN NUCLEAR MEDICINE SCANNING
Dr. Steven Burrell MD, FRCPC Head of Nuclear Medicine QEII Health Sciences Centre Halifax, Nova Scotia,
A new breed of high-tech body scanner is revolutionizing nuclear medicine, bringing better patient care, a better patient experience, and a more efficient use of health care resources: a big win-win-win.
Nuclear Medicine is an impactful field of medicine that uses tracers to image and diagnose a wide range of medical diseases, including cancer, cardiac disease, and many more. The tracers are called radiopharmaceuticals and have 2 properties, a molecule with a specific physiologic property such as seeking and binding to cancer, and a tiny radioactive component that emits energy detected by scanners, creating an image of the distribution of the tracer in the body. While the past several years have seen major advances in other pillars of Nuclear Medicine – Positron Emission Tomography (PET) scanning, and radioisotope therapy – the scanners used for most Nuclear Medicine tests had changed little in many years. However, a new state-of-the-art class of scanners has been developed, raising the bar to a new level. There are two such scanners, the StarGuide by GE and the Veriton by Spectrum Dynamics. In June 2024, with the support of donors and the QEII Foundation, we installed the first of 2 planned StarGuide scanners in our department, immediately ushering in improvements in diagnostic accuracy and confidence, patient experience, and departmental efficiencies.
TECHNOLOGICAL ADVANCES
At the core of the scanners are 2 major innovations. One is the arrangement of the detectors in a 360° ring-configuration around the patient (Figure 1B). Traditional Nuclear Medicine scanners have always had a flat-panel of detectors, which created 2-dimensional (2-D) images of individual organs or the whole body. Those scanners could be slowly rotated around the patient to create 3-D images, known as SPECT scanning (Single Photon Emission Computed Tomography).
However, this took time and was often impractical to add to the 2-D images for large portions of the body. With the ring-detector approach all images are automatically acquired as 3-D images of the body, providing more precise assessment. The second major advantage is the use of high-tech detectors comprised of Cadmium-Zinc-Teluride (CZT). CZT is much more efficient at detecting the energy emitted by the radiopharmaceuticals, allowing excellent quality images to be obtained in less time or with a lower amount of radiopharmaceutical.
While CZT detectors are not new, they were previously used in only a small number of Nuclear Medicine scanners, and not in a ring-detector configuration. Another important technological consideration, although this is not unique to the new scanners, is that they have a built in Computed Tomography (CT) scanner. CT scans are the workhorse of advanced medical imaging, providing assessment of anatomy in fine detail. By combining a Nuclear Medicine scanner with a CT scanner, this “hybrid imaging” provides simultaneous assessment of disease processes (Nuclear Medicine) and anatomy (CT), a powerful construct (Figure 2B).
FASTER SCANNING BRINGS MULTIPLE BENEFITS
Nuclear Medicine scans take a considerable amount of time to acquire, many close to a half hour, and some an hour or even more. With the StarGuide scan times are significantly reduced for many types of studies, due to the 2 major technological advances discussed above. The CZT detectors are more efficient than conventional detectors, creating images of comparable quality in significantly less time. Further, acquiring 3-D images shortens the overall scan time in some studies that traditionally would acquire both 2-D and 3-D images. Shorter scan times means patients better tolerate the scans, particularly patients with pain or claustrophobia. This also means there is less patient motion during the imaging, leading to better quality scans and therefore more accurate diagnoses. Finally, the shorter scan times means that more patients can be scanned in a day, which is critical in a time of limited health care resources including Nuclear Medicine technologist staffing. This in turn leads to shorter wait lists for these important scans.
OVERALL PATIENT EXPERIENCE
In addition to less time in the scanner, patients often find the ring-detector configuration less claustrophobic than conventional scanners. At our centre, patients who have had scans on both types of scanners have stated they prefer their experience in the StarGuide. A further advantage is that, because of the greater sensitivity of the CZT detectors, a lower amount of radiopharmaceutical can be used, resulting in a lower radiation exposure to the patient, as well as to the Nuclear Medicine staff.
MORE DIAGNOSTIC SCANS ACROSS A WIDE RANGE OF MEDICAL CONDITIONS
Ultimately the main purpose of the test is to obtain the most diagnostic scan possible, and that is achieved with the StarGuide. Greater sensitivity and 3-D imaging lead to more accurate diagnoses, made with greater confidence, across a wide variety of scans and disease states. At our centre the greatest change has been in bone scans obtained to assess the spread of cancer (metastases) to bone. These scans are now obtained fully in 3-D, with anatomic correlation through the simultaneous CT, resulting in a more diagnostic scan. With the additional detail they take more time for our Nuclear Medicine physicians to interpret them, but the improved accuracy in cancer assessment warrants it. Bone scans are also commonly obtained to assess more localized bone abnormalities such as fractures or infection, and the 3-D assessment is fast and precise.
In cardiac imaging, myocardial perfusion studies with 99mTc-Sesta-MIBI have long made major contributions to the management of patients with known or suspected heart disease. Images obtained with the StarGuide are highly diagnostic, and obtained more quickly: these detailed heart assessments are particularly affected by patient motion during the scan, so the faster scan times are important. Highest level image quality is also obtained with 99mTc-PYP scans used to diagnose a form of amyloidosis in the heart, reliably distinguishing activity in the heart muscle from activity in the blood pool.
The advantages of the new scanning paradigm have also been realized in lung Ventilation-Perfusion scans to assess for blood clots, a potentially fatal condition, and in 111Indium-labelled white blood cells scans to assess for infection. In neurology, very high-quality scans of brain perfusion are obtained with 99mTc-HMPAO to assess epilepsy, and of dopamine transporters with 123I-ioflupane to assess for Parkinsonism. The neck is imaged in exquisite detail on StarGuide with 99mTc-Sesta-MIBI to identify parathyroid adenomas in patients with hyperparathyroidism, with greater sensitivity than before, and there is more.
NEW APPLICATIONS: CORONARY FLOW RESERVE
So far we have reviewed the advantages the StarGuide has brought to existing Nuclear Medicine tests. However, the state-of-the-art technological advances also bring new capabilities. This includes the measurement of coronary flow reserve. This is an adjunct to the well-established myocardial perfusion studies performed with 99mTc-Sesta-MIBI mentioned above. Although uncommon, a limitation of the existing studies is an underestimation of heart disease through visual assessment alone in patients with widespread coronary artery disease. CZT scanners can perform a flow reserve analysis in these patients, effectively detecting and quantifying such multi-focal disease, a further contribution of the new technology.
PUSHING THE BOUNDARIES: THERANOSTICS
Theranostics is a rapidly expanding field of Nuclear Medicine wherein molecules have been designed which bind to certain types of cancer and are labelled with radioisotopes that are then imaged in a scanner showing the distribution of the tumours throughout the body, or deliver treatment radiation to those tumours (“theranostics” = therapeutic + diagnostic). Recent radiopharmaceutical cancer treatments include Lutathera™ for neuroendocrine tumours and Pluvicto™ for prostate cancer. This paradigm has proven so effective that many more theranostic radiopharmaceuticals are under development for other cancers. The therapeutic dose of these treatments is accurately imaged with the StarGuide hours or days after it has been administered in the patient, depicting the distribution of the treatment in tumour sites within the body, a unique and powerful concept in cancer treatment. This allows confirmation that the treatment has gone to all sites of known disease, and monitoring of the disease throughout the course of therapy (Figure 2). The technological advances of the new breed of scanners does this accurately and efficiently, in many cases better than with conventional scanners. It also facilitates dosimetry, calculating how much of the therapeutic radiopharmaceutical goes to each tumour site and to normal tissue, which is exploited in some centres to deliver patient-individualized doses, a form of personalized medicine.
In our centre our Interventional Radiology team treats liver tumours with Therasphere™, glass microspheres labelled with radioactive 90Yttrium delivered through a catheter in an artery to the liver. To ensure it will be safe to deliver the planned dose, a mock treatment is performed in advance, injecting a non-therapeutic radiopharmaceutical 99mTc-MAA. The patient is then imaged in the StarGuide scanner to assess whether the tracer has gone to organs which might be damaged when the treatment dose is administered. As with the other theranostics discussed above, accurate quantitative measurements with the StarGuide can contribute to individual patient dosimetry.
CONCLUSION
The new breed of scanners has revolutionized the imaging of many diseases, with accurate and more efficient imaging leading to better patient care and a more effective use of health care resources. Along with recent major advancements in the other pillars of Nuclear Medicine, PET and radioisotope therapies, the new scanners are solidifying Nuclear Medicine as a state-of-the-art, impactful, specialty contributing to best patient care.
