Highlights included the application of PET for determining a patient's response to cancer treatments, the use of multimodality imaging such as PET/CT and SPECT/CT to detect and assess disease, and examples of how these techniques could eventually provide patient-friendly alternatives to existing invasive diagnostic regimes. Here is a selection of some of the key developments presented at the conference.
• Early metabolic imaging with PET can accurately identify a patient's response to neoadjuvant chemotherapy for oesophageal cancer, according to research presented by the Technical University Munich in Germany. The MUNICON trial, which examined 110 patients with fluorodeoxyglucose (FDG)-PET after two weeks of treatment, is said to be the first study to apply PET-based early metabolic-response assessment to clinical decision-making when treating common solid tumours.
"The outcome for metabolic responders turned out to be remarkably favourable compared to metabolic nonresponders," explained Ken Herrmann, a resident in the Technical University's department of nuclear medicine. "Our results show that PET helps select patients who are benefiting from chemotherapy. Based on our early response assessment, the course is set for tailoring multimodality treatment on the basis of tumour biology."
• According to a study at the University of California, Los Angeles, PET imaging with the radiotracer fluorothymidine (FLT) can determine brain-tumour patients' response to drugs within one or two weeks of treatment initiation.
The researchers used FLT-PET to assess the metabolic response of 19 patients with recurrent malignant gliomas. The patients that responded to drug treatment (nine subjects) survived twice as long as the nonresponders. When comparing responses determined via PET with those measured using MRI (the technique traditionally used to assess tumour response), PET provided a more significant prediction of overall survival - as well as a much earlier response.
• Researchers from Cedars-Sinai Medical Center and the Cardiovascular Medical Group of Southern California (Los Angeles, CA) have shown that combined functional and anatomical imaging can increase the accuracy of coronary-artery disease diagnosis. The team used myocardial perfusion SPECT to provide physiological images of blood flow to the heart muscle, plus 64-slice CT angiography to produce high-resolution anatomical images of the coronary arteries.
Data were obtained on separate scanners at different times and specialized software employed to fuse the images together in 3D space. In the patient data sets examined, diagnosis using fused images identified more lesions than either method alone. The authors suggest that this image fusion can be used selectively for patients who undergo SPECT or CT angiography with inconclusive results.
"This combination could also be accomplished by specialized hybrid scanners," noted Piotr Slomka, a research scientist at Cedars-Sinai. "However, our software approach is more flexible since the combination is required only in a subset of cases. We can use the best possible CT angiography equipment and SPECT at much lower cost than the dedicated combined scanner."
• PET/CT using a novel CT contrast agent can detect high-risk atherosclerotic plaque that could lead to heart attacks and strokes, say researchers at the Mount Sinai Hospital and Mount Sinai School of Medicine (New York, NY).
The study, performed using an animal model of atherosclerosis, used multidetector CT imaging with N1177 (a macrophage-specific nanoparticulate contrast agent) to determine the size of the plaque, whether it was causing arterial narrowing and whether any inflammatory cells were involved. An FDG-PET scan, meanwhile, provided information as to the degree of inflammation of the plaque and the likelihood of it causing future problems.
The researchers note that additional research on patients with heart disease and stroke could determine whether this approach can provide more information than the traditional diagnostic technique of invasive X-ray coronary angiography.
• Graft infection is a rare but potentially severe complication following prosthetic vascular reconstruction. A study at Rambam Health Care Campus in Haifa, Israel, has shown that PET/CT imaging can be used to effectively diagnose graft infection and differentiate it from infection affecting only the surrounding soft tissue.
The distinction is critical - removing an infected graft involves complex surgery while soft-tissue infection is generally treated with antibiotics - but clinically it's challenging. The researchers examined 39 patients with 69 prosthetic vascular grafts. FDG-PET/CT exhibited a sensitivity of 93% and a specificity of 92% for diagnosis of vascular graft infection.
"Ours is the first study to use the hybrid imaging technology of PET/CT in order to provide a solution for this difficult diagnostic problem," said Ora Israel, director of nuclear medicine and research operations at Rambam. "PET/CT provides accurate detection and precise localization of vascular graft-related infections."
• A multicentre study undertaken as part of the Australian PET Data Collection Project has demonstrated the value of PET/CT for the management of patients with suspected recurrent ovarian carcinoma. The researchers examined 90 women with suspected recurrent ovarian carcinoma using FDG-PET/CT plus standard abdominal and pelvic CT imaging.
At least 168 sites of disease (both within and outside the abdomen) in 61 patients were identified by PET/CT but not seen using conventional imaging. The referring doctors assessed the impact of the PET/CT data on patient management; in 59% of cases, the results influenced their treatment decisions. PET/CT could also identify those patients whose disease was more likely to progress within 12 months.
The authors point out that their findings suggest an opportunity to replace routine abdominal and pelvic CT with PET/CT.
• PET/CT is invaluable for noninvasively monitoring Crohn's disease, according to a study by scientists at the Centre Hospitalier Universitaire in Liège, Belgium. Crohn's disease - a chronic inflammatory disease of the gastrointestinal tract - is characterized by periods of clinical relapses and remissions. It's therefore important to determine the activity of the disease before administering treatment.
Twenty two patients with Crohn's disease were examined using FDG-PET/CT and ileocolonoscopy. While endoscopic evaluation is the gold standard for assessing the activity of this disease, ileocolonoscopy is invasive, unpleasant and cannot always reach all relevant segments.
All bowel areas that showed severe endoscopic lesions were correctly identified by PET/CT. There were no cases in which the ileocolonoscopy showed severe lesions and PET/CT showed normal metabolic activity. The authors deduce that when the PET/CT is negative, the disease is not active and there is no need to perform the endoscopy.
• See also Multimodal vision, higher definition and Time-of-flight speeds PET scans on medicalphysicsweb.