Standardized image quality for 68Ga-DOTA-TATE PET/CT

Abstract

Background: Positron emission tomography (PET) imaging with 68 Gallium labeled somatostatin analogues (68 Ga-DOTA-SSA) plays a key role in neuroendocrine tumor management. The impact of patient size on PET image quality is not well known for PET imaging with 68 Ga-DOTA-SSA. The aim of this study is to propose a dose regimen based on patient size that optimizes image quality and yields sufficient image quality for diagnosis. Methods: Twenty-one patients (12 males, 9 females) were prospectively included for 68 Gallium-DOTA-Tyr3-Octreotate (68 Ga-DOTA-TATE) PET/CT, which was acquired in whole body list mode using 6 min per bed position (mbp). The list-mode events were randomly sampled to obtain 1 to 6 mbp PET reconstructions. For semiquantitative assessment of image quality, the signal-to-noise ratio (SNR) was measured in the liver. The SNR normalized (SNRnorm) for administered activity and mbp was correlated with body mass, length, body mass index, body mass/length, and lean body mass. Three experienced nuclear medicine physicians visually graded image quality using a 4-point scale, and categorically scored the number of somatostatin-receptor positive lesions for each reconstruction. To investigate the impact of image quality on lesion quantification, the mean, maximum, and peak standardized uptake values (SUVs) of one abdominal lesion were measured in the 1 to 6 mbp PET reconstructions. Results: Of all patient-dependent parameters, body mass showed the strongest correlation (R 2 = 0.6) with SNRnorm. Lesion detectability analysis showed no significant difference for 3-5 mbp compared with the complete 6 mbp PET reconstruction. The SUV measurements showed no significant (p > 0.05) differences across the reconstructions. Visual assessment revealed that an SNR of 6.2 results in PET scans with moderate to good image quality. A non-linear expression was derived to calculate the required (dose × acquisition time) product (DTP) for the chosen SNR level of 6.2 that would yield a more constant image quality. Conclusion: Body mass can be used to predict 68 Ga-DOTA-TATE PET image quality. The proposed non-linear dose regimen based on body mass standardizes the image quality while maintaining sufficient image quality for diagnosis.

Can the BMI-based dose regimen be used to reduce injection activity and to obtain a constant image quality in oncological patients by 18F-FDG total-body PET/CT imaging?

“…The fits of SNR norm with different parameters showed that both the quadric and linear fitting with BMI had the highest R 2 (0.68 and 0.69, respectively). Other parameters, such as the body mass, height, body mass per height, lean body mass, fat mass and body surface area showed a lower value of R 2 than the parameters discussed in previous studies [15,16]. Based on the results, a linear fit with BMI was selected.…”

“…If the SNR in the liver is normalized by the square root of the DTP, it can be assumed to be independent of the injected activity and the acquisition time (Eq. 5) [16]. Therefore, SNR norm can be regarded as a function of various patientdependent parameters and investigated in the study.…”

A Randomized, Factorial Phase II Study to Determine the Optimal Dosing Regimen for 68Ga-Satoreotide Trizoxetan as an Imaging Agent in Patients with Gastroenteropancreatic Neuroendocrine Tumors

“…This ideally provides the opportunity for an activity range of 68 Ga-satoreotide trizoxetan (100-200 MBq) to be prescribed, regardless of body weight. By contrast, 68 Ga-labelled SSTR2 agonists require dosing per body mass (10,11,16). In a recent prospective study from the Netherlands conducted among 21 patients with NETs who underwent whole-body 68 Ga-DOTATATE PET/CT, Cox and colleagues reported that, of all patient-dependent parameters, body mass showed the strongest correlation (coefficient of determination of 0.60) with normalised signal-to-noise ratio (16).…”

“…By contrast, 68 Ga-labelled SSTR2 agonists require dosing per body mass (10,11,16). In a recent prospective study from the Netherlands conducted among 21 patients with NETs who underwent whole-body 68 Ga-DOTATATE PET/CT, Cox and colleagues reported that, of all patient-dependent parameters, body mass showed the strongest correlation (coefficient of determination of 0.60) with normalised signal-to-noise ratio (16). Importantly, the absence of a weight-dependent effect represents a practical advantage for 68 Ga-satoreotide trizoxetan, as an administered activity within a predetermined range instead of a weight-based administered activity is not only more convenient but also reduces the possibility of dosing errors.…”

Feasibility of Low-Dose 68Ga-DOTATATE With Short Acquisition Time Using Total-Body PET/CT in Patients With Neuroendocrine Tumor

“…And ultra-low dose (0.37 MBq/kg) injected activity of 18 F-FDG could achieve relevant kinetic metrics and comparable image quality compared with that of full-activity imaging [11]. Besides, using conventional dose-regimen, the acquisition time could be significantly shorter within 2 min for a sufficient image quality of 18 F-FDG PET/CT [12].…”