A graphical user interface for calculating the arterial input function during dynamic positron emission tomography.

Purpose.Dynamic positron emission tomography (dPET) requires the acquisition of the arterial input function (AIF), conventionally obtained via invasive arterial blood sampling. To obtain the AIF non-invasively, our group developed and combined two novel solutions consisting of (1) a detector, placed on a patient's wrist during the PET scans to measure the radiation leaving the wrist and (2) a Geant4-based Monte Carlo simulation software. The simulations require patient-specific wrist geometry. The aim of this study was to develop a graphical user interface (GUI) allowing the user to import 2D ultrasound scans of a patient's wrist, and measure the wrist features needed to calculate the AIF.Methods.The GUI elements were implemented using Qt5 and VTK-8.2.0. The user imports a patient's wrist ultrasound scans, measures the radial artery and veins' surface and depth to model a wrist phantom, then specifies the radioactive source used during the dPET scan. The phantom, the source, and the number of decay events are imported into the Geant4-based Monte Carlo software to run a simulation. In this study, 100 million decays of18F and68Ga were simulated in a wrist phantom designed based on an ultrasound scan. The detector's efficiency was calculated and the results were analyzed using a clinical data processing algorithm developed in a previous study.Results.The detector's total efficiency decreased by 3.5% for18F and by 51.7% for68Ga when using a phantom based on ultrasound scans compared to a generic wrist phantom. Similarly, the data processing algorithm's accuracy decreased when using the patient-specific phantom, giving errors greater than 1.0% for both radioisotopes.Conclusions.This toolkit enables the user to run Geant4-based Monte Carlo simulations for dPET detector development applications using a patient-specific wrist phantom. Leading to a more precise simulation of the developed detector during dPET and the calculation of a personalized AIF.

Dosimetry of [18F]TRACK, the first PET tracer for imaging of TrkB/C receptors in humans.

BACKGROUND: Reduced expression or impaired signalling of tropomyosin receptor kinases (Trk receptors) are found in a vast spectrum of CNS disorders. [18F]TRACK is the first PET radioligand for TrkB/C with proven in vivo brain penetration and on-target specific signal. Here we report dosimetry data for [18F]TRACK in healthy humans. 6 healthy participants (age 22-61 y, 3 female) were scanned on a General Electric Discovery PET/CT 690 scanner. [18F]TRACK was synthesized with high molar activities (Am = 250 ± 75 GBq/µmol), and a dynamic series of 12 whole-body scans were acquired after injection of 129 to 147 MBq of the tracer. Images were reconstructed with standard corrections using the manufacturer's OSEM algorithm. Tracer concentration time-activity curves (TACs) were obtained using CT-derived volumes-of-interest. Organ-specific doses and the total effective dose were estimated using the Committee on Medical Internal Radiation Dose equation for adults and tabulated Source tissue values (S values). RESULTS: Average organ absorbed dose was highest for liver and gall bladder with 6.1E-2 (± 1.06E-2) mGy/MBq and 4.6 (± 1.18E-2) mGy/MBq, respectively. Total detriment weighted effective dose EDW was 1.63E-2 ± 1.68E-3 mSv/MBq. Organ-specific TACs indicated predominantly hepatic tracer elimination. CONCLUSION: Total and organ-specific effective doses for [18F]TRACK are low and the dosimetry profile is similar to other 18F-labelled radio tracers currently used in clinical settings.

3D reconstruction of the human trunk for designing personalized braces : Precision study.

The customized design of braces for adolescent idiopathic scoliosis (AIS) treatment requires the acquisition of the 3D external geometry of the patients' trunks. Three body scanning systems are available at CHU Sainte-Justine in Montreal: a fixed system of InSpeck Capturor II LF digitizers and two portable scanners, BodyScan and Structure Sensor. The aim of this study is to compare them by evaluating their accuracy and repeatability. To achieve this, we placed 46 surface markers on an anthropomorphic manikin and scanned it three times with each system. We also measured the 3D coordinates of the same markers using a coordinate measuring machine (CMM), serving as ground-truth. We evaluated the repeatability and accuracy of the three systems: the former, by measuring the bidirectional mean distance between the three surfaces acquired with a given modality; the latter, by calculating the residual normal distance separating each of the 3D surfaces and the CMM point cloud. We also compared texture mapping accuracy between InSpeck and Structure Sensor by examining the CMM point cloud versus the marker 3D coordinates selected on the trunk surface. The results show good accuracy and repeatability for all three systems, with slightly better geometric accuracy for BodyScan (p-value ≈ 10-6). In terms of texture mapping, InSpeck showed better accuracy than Structure Sensor (p-value = 0.0059).

Impact of restrictive versus obstructive pulmonary function patterns on mortality in patients undergoing transcatheter aortic valve implantation.

BACKGROUND: Pulmonary function tests to estimate force vital capacity (FVC) and forced expiratory volume in the first second (FEV1) have increasingly been used in patients evaluated for transcatheter aortic valve implantation (TAVI). The impact of obstructive versus restrictive lung disease on mortality remains unclear. The authors sought to identify differences in survival in patients with 2 distinct pulmonary function patterns (obstruction vs. restriction). METHODS: The authors retrospectively analyzed all patients with abnormal FEV1 (lower than 80% of predicted) detected on the pulmonary function tests prior to TAVI from May 2011 to November 2014. Patients were divided into a group with obstructive pattern (FEV1/FVC<70% of predicted) and a group with restrictive pattern (FEV1/FVC>70% of predicted). Cox proportional hazards regression was used to explore the impact of FEV1 on mortality. RESULTS: A total of 94 patients were included in this analysis. Forty-one percent (n=38) had obstructive pattern, and 59% (n=56) had restrictive pattern. FEV1 values were similar between both groups (43±19 vs. 42±26, p=0.89). Both groups had similar rates of in-hospital, 30-day, and 1-year mortality. FEV1 was not a correlate for 1-year mortality. Patients with pulmonary obstructive and restrictive patters had similar rates of mortality. Moreover, FEV1 value is not a correlate for 1-year mortality. CONCLUSION: In the current era, the pattern on pulmonary function tests and FEV1 values should not influence the decision on whom to offer a transcatheter option for their severe valvular disease.