Image reconstruction using small-voxel size improves small lesion detection for positron emission tomography

Background. PET/CT imaging is widely used in oncology and provides both metabolic and anatomic information. Because of the relatively poor spatial resolution of PET, the detection of small lesions is limited. The low spatial resolution introduces the partial-volume effect (PVE) which negatively affects images both qualitatively and quantitatively. The aim of the study was to investigate the effect of small-voxel (2 mm in-line pixel size) vs. standard-voxel (4 mm in-line pixel size) reconstruction on lesion detection and image quality in a range of activity ratios. Materials and methods. The National Electrical Manufacturers Association (NEMA) body phantom and the Micro Hollow-Sphere phantom spheres were filled with a solution of [18F]fluorodeoxyglucose ([18F]FDG) in sphere-to-background ratios of 2:1, 3:1, 4:1 and 8:1. In all images reconstructed with 2 mm and 4 mm in-line pixel size the visual lesion delineation, contrast recovery coefficient (CRC) and contrast-to-noise ratio (CNR) were evaluated. Results. For smaller (≤ 13 mm) phantom spheres, significantly higher CRC and CNR using small-voxel reconstructions were found, also improving visual lesion delineation. CRC did not differ significantly for larger (≥ 17 mm) spheres using 2 mm and 4 mm in-line pixel size, but CNR was significantly lowerhowever, lower CNR did not affect visual lesion delineation. Conclusions. Small-voxel reconstruction consistently improves precise small lesion delineation, lesion contrast and image quality

Detection and localization of hyperfunctioning parathyroid glands on [18F]fluorocholine PET/CT using deep learning – model performance and comparison to human experts

In the setting of primary hyperparathyroidism (PHPT), [18F]fluorocholine PET/CT (FCH-PET) has excellent diagnostic performance, with experienced practitioners achieving 97.7% accuracy in localising hyperfunctioning parathyroid tissue (HPTT). Due to the relative triviality of the task for human readers, we explored the performance of deep learning (DL) methods for HPTT detection and localisation on FCH-PET images in the setting of PHPT. Patients and methods. We used a dataset of 93 subjects with PHPT imaged using FCH-PET, of which 74 subjects had visible HPTT while 19 controls had no visible HPTT on FCH-PET. A conventional Resnet10 as well as a novel mPETResnet10 DL model were trained and tested to detect (present, not present) and localise (upper left, lower left, upper right or lower right) HPTT. Our mPETResnet10 architecture also contained a region-of-interest masking algorithm that we evaluated qualitatively in order to try to explain the model’s decision process. Results. The models detected the presence of HPTT with an accuracy of 83% and determined the quadrant of HPTT with an accuracy of 74%. The DL methods performed statistically worse (p < 0.001) in both tasks compared to human readers, who localise HPTT with the accuracy of 97.7%. The produced region-of-interest mask, while not showing a consistent added value in the qualitative evaluation of model’s decision process, had correctly identified the foreground PET signal. Conclusions. Our experiment is the first reported use of DL analysis of FCH-PET in PHPT. We have shown that it is possible to utilize DL methods with FCH-PET to detect and localize HPTT. Given our small dataset of 93 subjects, results are nevertheless promising for further researc

Best practice for the nuclear medicine technologist in CT-based attenuation correction and calcium score for nuclear cardiology

Abstract The use of hybrid systems is increasingly growing in Europe and this is progressively important for the final result of diagnostic tests. As an integral part of the hybrid imaging system, computed tomography (CT) plays a crucial role in myocardial perfusion imaging diagnostics. Throughout Europe, a variety of equipment is available and also different university curricula of the nuclear medicine technologist are observed. Hence, the Technologist Committee of the European Association of Nuclear Medicine proposes to identify, through a bibliographic review, the recommendations for best practice in computed tomography applied to attenuation correction and calcium score in myocardial perfusion imaging, which courses in the set of knowledge, skills, and competencies for nuclear medicine technologists. This document aims at providing recommendations for CT acquisition protocols and CT image optimization in nuclear cardiology

VLOGA SPECT/CT SCINTIGRAFIJE PRI LOKALIZACIJI OBŠČITNIČNIH ADENOMOV

Parathyroid scintigraphy is based on the different accumulation and distribution of radiopharmaceutical 99mTc-MIBI (MIBI) in parathyroid and adjacent tissues. Different scintigraphic techniques can be used: subtraction scintigraphy is a combination of MIBI and 99mTc-pertehnetate (pertehnetate) scintigraphySPECT can be performed after intravenous injection of MIBI or in the combination with low-dose computerized tomography (SPECT/CT) which allows precise anatomical localization of enlarged parathyroid glands (EPG). The objectives of our study were: to assess diagnostic performance of preoperative localization of EPG (adenomas and hyperplasia) of the early, delayed and combined SPECT/CT and of subtraction scintigraphy in patients with biochemically proven primary hyperparathyroidism (PHP)to determine whether size of EPG, serum parathyroid hormone (PTH), calcium (Ca) and phosphate (P) correlate with successful localizationto assess radiation exposure of patients with early and late SPECT/CT and subtraction scintigraphy The study included 41 patients in whom early, delay SPECT/CT and subtraction scintigraphy were performed. For all scintigraphic methods sensitivity, specificity, positive predictive value, negative predictive value and accuracy were calculated. Receiver Operating Characteristic analysis was used to express relationship between scintigraphy results and size of the EPG and serum Ca, P and PTH levels. ImPACT CT Patient Dosimetry Calculator and weighting factors for radiopharmaceuticals (MIBI and pertechnetate) were used for calculating patient expose dose. Sensitivity and specificity were 51.1% and 98.3 for subtraction scintigraphy, 65.1% and 97.5% for early SPECT/CT and 65.1% and 95.5% for delay SPECT/CT. In combined early and delay SPECT/CT sensitivity and specificity were 74.4% and 95.1%.Only size of the EPG correlated with successful localization in our study (AUC of 0.791-0.810). The highest average ED per patient had subtraction scintigraphy (7.37±0.40 mSv), which was statistically significant higher in comparison to combined early and delayed SPECT/CT (6.81±0.44 mSv). The most sensitive and most accurate method of preoperative localization of EPG in patients with PHP is combined early and delayed SPECT/CT. Only size of the EPG correlates with successful localization. The highest radiation exposure is after subtraction scintigraphy.Scintigrafija obščitnic temelji na različnih akumulacijah in distribuciji radiofarmaka 99mTc-MIBI (MIBI) v obščitnicah in v sosednjih tkivih. Možnih je več različnih scintigrafskih tehnik: odštevna scintigrafija je kombinacija scintigrafije z MIBI in scintigrafije z 99mTc-pertehnetatom (pertehnetatom)SPECT lahko uporabimo samostojno po aplikaciji MIBI ali v kombinaciji z nizko-dozno računalniško tomografijo (SPECT/CT), ki omogoča natančno anatomsko lokalizacijo povečanih obščitnic (PO). Cilji raziskave so bili: oceniti diagnostično uspešnost predoperativne lokalizacije PO (adenom ali hiperplazija) pri zgodnjem, kasnem in kombiniranem SPECT/CT ter odštevni scintigrafiji pri bolnikih z biokemično dokazanim primarnim hiperparatiroidizmom (PHP)ugotoviti če velikost PO, serumski parathormon (PTH), kalcij (Ca) in fosfor (P) korelira z uspešno lokalizacijooceniti izpostavljenost sevanju bolnikov pri katerih opravimo zgodni in kasni SPECT/CT ter odštevno scintigrafijo. V raziskavi je sodelovalo 41 bolnikov, pri katerih smo opravili zgodnji in kasni SPECT/CT ter odštevno scintigrafijo. Za vse scintigrafske metode smo izračunali občutljivost, specifičnost, pozitivno in negativno napovedno vrednost ter točnost. ROC analiza je bila uporabljena za oceno odnosa med rezultati scintigrafskih metod in velikostjo PO, serumskih vrednosti Ca, P in PTH. Za izračun sevalne obremenitve bolnikov smo uporabili ImPACT CT kalkulator za dozimetrijo in utežne faktorje za radiofarmake (MIBI & pertehnetat). Občutljivost in specifičnost sta bili 51.1% in 98.3 za odštevno scintigrafijo, 65.1% in 97.5% za zgodnji SPECT/CT in 65.1% in 95.5% za kasni SPECT/CT. Pri kombiniranem zgodnjem in kasnem SPECT/CT sta bili občutljivost in specifičnost 74.4% in 95.1%. Samo velikost PO je korelirala z uspešnostjo lokalizacije v naši raziskavi (AUC 0.791-0.810). Najvišja povprečna efektivna doza na pacienta je bila pri odštevni scintigrafiji (7.37±0.40 mSv), kar je bilo statistično signifikantno višje kot pri kombiniranem zgodnjem in kasnem SPECT/CT (6.81±0.44 mSv). Najbolj občutljiva in najbolj točna metoda predoperativne lokalizacije PO pri bolnikih s PHP je kombinirani zgodnji in kasni SPECT/CT. Samo velikost PO je povezana z uspešno lokalizacijo. Največja izpostavljenost sevanju je po odštevni scintigrafiji

Optimal scan time for evaluation of parathyroid adenoma with [18F]-fluorocholine PET/CT

Background. Parathyroid adenomas, the most common cause of primary hyperparathyroidism, are benign tumours which autonomously produce and secrete parathyroid hormone. [18F]-fluorocholine (FCH), PET marker of cellular proliferation, was recently demonstrated to accumulate in lesions representing enlarged parathyroid tissue; however, the optimal time to perform FCH PET/CT after FCH administration is not known. The aim of this study was to determine the optimal scan time of FCH PET/CT in patients with primary hyperparathyroidism

Best practice for the nuclear medicine technologist in CT-based attenuation correction and calcium score for nuclear cardiology

Abstract The use of hybrid systems is increasingly growing in Europe and this is progressively important for the final result of diagnostic tests. As an integral part of the hybrid imaging system, computed tomography (CT) plays a crucial role in myocardial perfusion imaging diagnostics. Throughout Europe, a variety of equipment is available and also different university curricula of the nuclear medicine technologist are observed. Hence, the Technologist Committee of the European Association of Nuclear Medicine proposes to identify, through a bibliographic review, the recommendations for best practice in computed tomography applied to attenuation correction and calcium score in myocardial perfusion imaging, which courses in the set of knowledge, skills, and competencies for nuclear medicine technologists. This document aims at providing recommendations for CT acquisition protocols and CT image optimization in nuclear cardiology

Optimal scan time for evaluation of parathyroid adenoma with [18F]-fluorocholine PET/CT

BACKGROUND: Parathyroid adenomas, the most common cause of primary hyperparathyroidism, are benign tumours which autonomously produce and secrete parathyroid hormone. [(18)F]-fluorocholine (FCH), PET marker of cellular proliferation, was recently demonstrated to accumulate in lesions representing enlarged parathyroid tissue; however, the optimal time to perform FCH PET/CT after FCH administration is not known. The aim of this study was to determine the optimal scan time of FCH PET/CT in patients with primary hyperparathyroidism. PATIENTS AND METHODS. 43 patients with primary hyperparathyroidism were enrolled in this study. A triple-phase PET/CT imaging was performed five minutes, one and two hours after the administration of FCH. Regions of interest (ROI) were placed in lesions representing enlarged parathyroid tissue and thyroid tissue. Standardized uptake value (SUV(mean)), retention index and lesion contrast for parathyroid and thyroid tissue were calculated. RESULTS: Accumulation of FCH was higher in lesions representing enlarged parathyroid tissue in comparison to the thyroid tissue with significantly higher SUV(mean) in the second and in the third phase (p < 0.0001). Average retention index decreased significantly between the first and the second phase and increased significantly between the second and the third phase in lesions representing enlarged parathyroid tissue and decreased significantly over all three phases in thyroid tissue (p< 0.0001). The lesion contrast of lesions representing enlarged parathyroid tissue and thyroid tissue was significantly better in the second and the third phase compared to the first phase (p < 0.05). CONCLUSIONS: According to the results the optimal scan time of FCH PET/CT for localization of lesions representing enlarged parathyroid tissue is one hour after administration of the FCH