Variability in lutetium-177 SPECT quantification between different state-of-the-art SPECT/CT systems

Background: Quantitative SPECT imaging in targeted radionuclide therapy with lutetium-177 holds great potential for individualized treatment based on dose assessment. The establishment of dose-effect relations requires a standardized method for SPECT quantification. The purpose of this multi-center study is to evaluate quantitative accuracy and inter-system variations of different SPECT/CT systems with corresponding commercially available quantitative reconstruction algorithms. This is an important step towards a vendor-independent standard for quantitative lutetium-177 SPECT. Methods: Four state-of-the-art SPECT/CT systems were included: Discovery™ NM/CT 670Pro (GE Healthcare), Symbia Intevo™, and two Symbia™ T16 (Siemens Healthineers). Quantitative accuracy and inter-system variations were evaluated by repeatedly scanning a cylindrical phantom with 6 spherical inserts (0.5 – 113 ml). A sphere-to-background activity concentration ratio of 10:1 was used. Acquisition settings were standardized: medium energy collimator, body contour trajectory, photon energy window of 208 keV (± 10%), adjacent 20% lower scatter window, 2 × 64 projections, 128 × 128 matrix size, and 40 s projection time. Reconstructions were performed using GE Evolution with Q.Metrix™, Siemens xSPECT Quant™, Siemens Broad Quantification™ or Siemens Flash3D™ algorithms using vendor recommended settings. In addition, projection data were reconstructed using Hermes SUV SPECT™ with standardized reconstruction settings to obtain a vendor-neutral quantitative reconstruction for all systems. Volumes of interest (VOI) for the spheres were obtained by applying a 50% threshold of the sphere maximum voxel value corrected for background activity. For each sphere, the mean and maximum recovery coefficient (RCmean and RCmax) of three repeated measurements was calculated, defined as the imaged activity concentration divided by the actual activity concentration. Inter-system variations were defined as the range of RC over all systems. Re

Impact of uptake time on image quality of [68 Ga]Ga-PSMA-11 PET/CT

Background: With the introduction of prostate specific membrane antigen (PSMA) PET/CT, the detection rate of prostate cancer metastases has improved significantly, both for primary staging and for biochemical recurrence. EANM/SNMMI guidelines recommend a 60 min time interval between [ 68Ga]Ga-PSMA administration and acquisition. Purpose: This study evaluates the possibility of a shorter time interval by investigating the dynamic change in image quality measures. Method: We retrospectively analyzed 10 consecutive prostate cancer patients who underwent a dynamic whole body [ 68Ga]Ga-PSMA-11 PET/CT of 75 min from skull vertex to mid-thigh using Siemens FlowMotion. PET images were acquired directly after injection of 1.5 MBq/kg [ 68Ga]Ga-PSMA-11. Image quality measures included lesion maximum standardized uptake value corrected for lean body mass (SUL max), tumor-to-background ratio (TBR), and contrast-to-noise ratio (CNR). Quantitative analysis of image quality in dynamic PET was performed using PMOD (version 4.2). Regions of interest (ROIs), drawn included different types of prostate lesions (primary tumor, lymph nodes, and bone metastasis), organ tissue (liver, spleen, lacrimal gland, submandibular gland, parotid gland, urinary bladder, kidneys blood pool [ascending aorta], left ventricle), bone tissue (4th lumbar vertebral body [L4]) and muscle tissue (gluteus maximus). To further investigate image quality four 10 min multi-frame reconstructions with clinical parameters were made at different post-injection times (15, 30, 45, and 60 min). A nuclear medicine physician performed a blinded lesion detectability evaluation on these multi-frame reconstructions for different prostate cancer lesions. Results: Six primary prostate tumors in seven patients with prostate in situ, 13 lymph node metastases in six patients and up to 12 bone metastases in three patients were found. The different prostate lesion types (lymph nodes metastases, bone metastases, and primary prostate tumor) all show an increase in average SUL max, TBR, and CNR over time during the scan. The normalized average SUL max, TBR, and CNR of the combined prostate lesions at 15, 30, and 45 min post-injection scans were all significant p < 0.05 lower from the 60 min post-injection [ 68Ga]Ga-PSMA-11 PET/CT (9.5 ± 4.5, 12.7 ± 6.2, and 41.8 ± 24.5, respectively). At patient level, the reader concluded the same regarding the presence/absence of primary prostate cancer recurrence, lymph node metastases, and/or bone metastases on all <60 min post-injection [ 68Ga]Ga-PSMA-11 PET/CT's in comparison to the reference scan (60 min post-injection). At lesion level, all bone metastases seen on the reference scan were also seen on all <60 min post-injection [ 68Ga]Ga-PSMA-11 PET/CT's but there were some lymph nodes (n = 2) metastases missed on the 15, 30, and 45 min post-injection scans. One lymph node metastasis on both the 15 and 30 min post-injection [ 68Ga]Ga-PSMA-11 PET/CT's was missed and one lymph node metastasis was missed, only on the 45 min post-injection [ 68Ga]Ga-PSMA-11 PET/CT. Conclusion: Shorter post-injection times (15, 30, and 45 min) compared to the recommended post-injection time of 60 min are not optimal. However, the impact of a shorter time interval of 45 min instead of 60 min between [ 68Ga]Ga-PSMA-11 administration and the start of PET/CT acquisition on both image quality (SUL max, TBR, and CNR) and lesion detection, while significant, is small

An international multi-center investigation on the accuracy of radionuclide calibrators in nuclear medicine theragnostics

Background: Personalized molecular radiotherapy based on theragnostics requires accurate quantification of the amount of radiopharmaceutical activity administered to patients both in diagnostic and therapeutic applications. This international multi-center study aims to investigate the clinical measurement accuracy of radionuclide calibrators for 7 radionuclides used in theragnostics: 99mTc, 111In, 123I, 124I, 131I, 177Lu, and 90Y. Methods: In total, 32 radionuclide calibrators from 8 hospitals located in the Netherlands, Belgium, and Germany were tested. For each radio

Correction to: Variability in lutetium-177 SPECT quantification between different state-of-the-art SPECT/CT systems

Following publication of the original article [1], it was reported that the sphere volumes defined in the original article should be adjusted. The correct inner diameters (and volumes) of the spherical inserts were: 9.9mm (0.5 ml), 15.4mm (2.0 ml), 19.8 mm (4.0 ml), 24.8mm (8.0 ml), 31.3mm (16.0 ml) and 60mm (113 ml). Figures 3, 5 and 6 have been adjusted accordingly. The original article has been updated.</p

Correction to: [18F]mFBG PET‑CT for detection and localisation of neuroblastoma: a prospective pilot study (European Journal of Nuclear Medicine and Molecular Imaging, (2023), 50, 4, (1146-1157), 10.1007/s00259-022-06063-6)

The article [ 18F]mFBG PET‑CT for detection and localisation of neuroblastoma: a prospective pilot study, written by Atia Samim, Thomas Blom, Alex J. Poot, Albert D. Windhorst, Marta Fiocco, Nelleke Tolboom, Arthur J. A. T. Braat, Sebastiaan L. Meyer Viol, Rob van Rooij, Max M. van Noesel, Marnix G. E. H. Lam, Godelieve A. M. Tytgat, and Bart de Keizer, was originally published Online First without Open Access. After publication in volume 50, issue 4, page 1146 - 1157 the author decided to opt for Open Choice and to make the article an Open Access publication

[18F]mFBG PET-CT for detection and localisation of neuroblastoma: a prospective pilot study

Purpose: Meta-[ 18F]fluorobenzylguanidine ([ 18F]mFBG) is a positron emission tomography (PET) radiotracer that allows for fast and high-resolution imaging of tumours expressing the norepinephrine transporter. This pilot study investigates the feasibility of [ 18F]mFBG PET-CT for imaging in neuroblastoma. Methods: In a prospective, single-centre study, we recruited children with neuroblastoma, referred for meta-[ 123I]iodobenzylguanidine ([ 123I]mIBG) scanning, consisting of total body planar scintigraphy in combination with single-photon emission computed tomography-CT (SPECT-CT). Within two weeks of [ 123I]mIBG scanning, total body PET-CTs were performed at 1 h and 2 h after injection of [ 18F]mFBG (2 MBq/kg). Detected tumour localisations on scan pairs were compared. Soft tissue disease was quantified by number of lesions and skeletal disease by SIOPEN score. Results: Twenty paired [ 123I]mIBG and [ 18F]mFBG scans were performed in 14 patients (median age 4.9 years, n = 13 stage 4 disease and n = 1 stage 4S). [ 18F]mFBG injection was well tolerated and no related adverse events occurred in any of the patients. Mean scan time for [ 18F]mFBG PET-CT (9.0 min, SD 1.9) was significantly shorter than for [ 123I]mIBG scanning (84.5 min, SD 10.5), p < 0.01. Most tumour localisations were detected on the 1 h versus 2 h post-injection [ 18F]mFBG PET-CT. Compared to [ 123I]mIBG scanning, [ 18F]mFBG PET-CT detected a higher, equal, and lower number of soft tissue lesions in 40%, 55%, and 5% of scan pairs, respectively, and a higher, equal, and lower SIOPEN score in 55%, 30%, and 15% of scan pairs, respectively. On average, two more soft tissue lesions and a 6-point higher SIOPEN score were detected per patient on [ 18F]mFBG PET-CT compared to [ 123I]mIBG scanning. Conclusion: Results of this study demonstrate feasibility of [ 18F]mFBG PET-CT for neuroblastoma imaging. More neuroblastoma localisations were detected on [ 18F]mFBG PET-CT compared to [ 123I]mIBG scanning. [ 18F]mFBG PET-CT shows promise for future staging and response assessment in neuroblastoma. Trial registration: Dutch Trial Register NL8152