Image Quality and Diagnostic Performance of a Digital PET Prototype in Patients with Oncologic Diseases: Initial Experience and Comparison with Analog PET

Abstract

We report our initial clinical experience for image quality and diagnostic performance of a digital PET prototype scanner with time-of-flight (DigitalTF), compared with an analog PET scanner with time-of-flight (GeminiTF PET/CT). Methods: Twenty-one oncologic patients, mean age 58 y, first underwent clinical 18 F-FDG PET/CT on the GeminiTF. The scanner table was then withdrawn while the patient remained on the table, and the DigitalTF was inserted between the GeminiTF PET and CT scanner. The patients were scanned for a second time using the same PET field of view with CT from the GeminiTF for attenuation correction. Two interpreters reviewed the 2 sets of PET/CT images for overall image quality, lesion conspicuity, and sharpness. They counted the number of suggestive 18 F-FDG-avid lesions and provided the TNM staging for the 5 patients referred for initial staging. Standardized uptake values (SUVs) and SUV gradients as a measure of lesion sharpness were obtained. Results: The DigitalTF showed better image quality than the GeminiTF. In a side-by-side comparison using a 5-point scale, lesion conspicuity (4.3 ± 0.6), lesion sharpness (4.3 ± 0.6), and diagnostic confidence (3.4 ± 0.7) were better with DigitalTF than with GeminiTF (P , 0.01). In 52 representative lesions, the lesion maximum SUV was 36% higher with DigitalTF than with GeminiTF, lesion-toblood-pool SUV ratio was 59% higher, and SUV gradient was 51% higher, with good correlation between the 2 scanners. Lesions less than 1.5 cm showed a greater increase in SUV from GeminiTF to DigitalTF than those lesions 1.5 cm or greater. In 5 of 21 patients, DigitalTF showed an additional 8 suggestive lesions that were not seen using GeminiTF. In the 15 restaging patients, the true-negative rate was 100% and true-positive rate was 78% for both scanners. In the 5 patients for initial staging, DigitalTF led to upstaging in 2 patients and showed the same staging in the other 3 patients, compared with GeminiTF. Conclusion: DigitalTF provides better image quality, diagnostic confidence, and accuracy than GeminiTF. DigitalTF may be the most beneficial in detecting small tumor lesions and disease staging. PETcont inues to play a significant role in molecular imaging.Steady improvements in detector design and architecture as well as the implementation of time-of-flight (TOF) technology have created significant improvements in image quality and greater flexibility in reducing radiotracer dose and scanning time (1-4).The current trend in molecular imaging places emphasis on accurate, quantitative PET imaging for improved lesion characterization and treatment monitoring (5). A new type of scintillation detector, digital photon counters (DPC), was recently developed by Philips Healthcare (6-8). The key innovation of the new digital PET system is the replacement of conventional photomultipliers with high-performance digital detectors and the implementation of singlephoton avalanche photodiodes with low-voltage complementary metal-oxide semiconductor (CMOS) logic on the same silico...

18F-FDG silicon photomultiplier PET/CT: A pilot study comparing semi-quantitative measurements with standard PET/CT

“…These findings are aligned to results showed by Nguyen et al [18] who identified 8 additional 18 F-FDG avid lesions comparing digital to standard PET/CT in 5 of 21 patients.…”

“…Similar results were assessed by Nguyen et al [18], who evaluated a prototype of digital technology PET/CT scanner and found a 36% increase in SUV max in 52 avid FDG lesions from standard PET/CT to digital PET/CT.…”

124I PET/CT to Predict the Outcome of Blind 131I Treatment in Patients with Biochemical Recurrence of Differentiated Thyroid Cancer: Results of a Multicenter Diagnostic Cohort Study (THYROPET)

“…Even though this dosage is higher than in most published studies (23-64 MBq) (25,27,30,31,(36)(37)(38), Ho et al recently reported the use of 222 MBq of 124 I in patients with metastatic DTC refractory to radioiodine (39). Additionally, it is unclear whether improved PET scan technology (scanner design (40) or 124 I reconstruction protocols) will improve 124 I PET performance to a clinically relevant extent in this context. If in vitro data support the notion that detectability significantly improves by such innovations or higher 124 I dosages, the current study should be repeated.…”

Does simplified quantitative analysis of 18F-FDG PET in cardiac inflammatory disease work?

“…24 The improved detector sensitivity and time-of-flight resolution implemented in the latest digital PET systems could also contribute to improved signal-to-noise ratio as suggested by preliminary results. 25 Trends are evolving toward using the most relevant metrics available in PET quantification and evidence is gathering toward preferring dynamic imaging for this purpose. Yet, for diseases presenting with low incidence rates, such as cardiac inflammatory processes making the proof of an added clinical value of the more advanced quantification tools using dynamic imaging will take a tremendous amount of time.…”