Publications by authors named "Alex Frenkel"
Background: Research and dissemination of smartphone apps to deliver coaching and psychological driven intervention had seen a great surge in recent years. Notably, Acceptance Commitment Therapy (ACT) protocols were shown to be uniquely effective in treating symptoms for both depression and anxiety when delivered through smartphone apps. The aim of this study is to expand on that work and test the suitability of artificial intelligence-driven interventions delivered directly through popular texting apps.
View Article and Find Full Text PDFSpace-filling generally governs hard particle packing and the resulting phases and interparticle orientations. Contrastingly, hard-shaped nanoparticles with grafted soft-ligands pack differently since the energetically interacting soft-shell is amenable to nanoscale sculpturing. While the interplay between the shape and soft-shell can lead to unforeseen packing effects, little is known about the underlying physics.
View Article and Find Full Text PDFBackground: Data regarding cardiac cadmium-zinc-telluride (CZT)-specific augmented databases and their impact on CT-based attenuation correction (AC) perfusion scores in myocardial perfusion imaging (MPI) were obtained on a multiple-pinhole CZT SPECT/CT.
Methods And Results: Summed stress (SSS) and rest scores (SRS) were measured using automated software in three independent patient groups: group 1 (n = 80) underwent MPI on both CZT and conventional sodium iodide (NaI) devices, group 2 (n = 80) with low coronary artery disease likelihood and normal MPI provided reference CZT databases; and group 3 (n = 152) served to compare AC and non-AC (NAC) scores on CZT. Group 1 CZT and NaI scores gave a significant 1:1 linear correlation for CZT scores referenced to the custom database vs NaI scores referenced to the default database, but these were not concordant when CZT scores were referenced to the default database.
Background: The effective non-invasive identification of coronary artery disease (CAD) and its proper referral for invasive treatment are still unresolved issues. We evaluated our quantification of myocardium at risk (MAR) from our second generation 3D MPI/CTA fusion framework for the detection and localization of obstructive coronary disease.
Methods: Studies from 48 patients who had rest/stress MPI, CTA, and ICA were analyzed from 3 different institutions.
Purpose: Minimally invasive surgery for parathyroid adenomas (PTA) requires precise identification and localization of the diseased gland prior to exploration for optimal surgical planning. The Perrier classification allows for accurate, reproducible, and reliable description of PTA location and communication of clinically significant information to surgeons. The current study compares the Perrier localization of PTA on [Tc]methoxyisobutylisonitrile ([Tc]MIBI) single-photon emission computed tomography (SPECT)/X-ray computed tomography (CT) with the results of surgery.
View Article and Find Full Text PDFObjective: The superiority of sodium F-fluoride PET (F-PET)/computed tomography (CT) over planar and single field-of-view single-photon emission computed tomography (SPECT) bone scintigraphy with Tc-methylene diphosphonate in bone metastases detection has been established. The present study prospectively compares whole-body Tc-methylene diphosphonate SPECT (WB-SPECT) and F-PET performance indices for the detection of bone metastases in breast cancer.
Methods: A total of 41 pairs of studies in female breast cancer patients (average age 58 years, range 30-75) were included.
Objective: The aim of the study was to compare the detectability rate of bone metastases in breast cancer patients using whole-body single-photon emission computed tomography (WB-SPECT) performed with a half-time acquisition algorithm with that of planar ± selected field-of-view SPECT [standard bone scintigraphy (BS)].
Materials And Methods: Ninety-two consecutive breast cancer patients (age range 35-74 years) underwent planar BS followed by WB-SPECT (acquisition time 28 min). Clinical and imaging follow-up data from BS, 18F-FDG-PET/CT and CT were used as composite reference standards.
Unlabelled: CT-guided fine-needle aspiration (FNA) of lung lesions is subject to sampling errors. The current study assessed whether information provided by (18)F-FDG PET/CT will decrease the false-negative (FN) rate and thus improve the accuracy of CT-guided FNA.
Methods: Data from 311 consecutive patients with lung nodules who underwent (18)F-FDG PET/CT and CT-guided FNA within an interval of less than 30 d were retrospectively assessed.
Background: A solid-state cadmium zinc telluride (CZT) SPECT device provides ultrafast myocardial perfusion imaging (MPI) with a spherical field-of-view (FOV). This study aims at determining the spatial resolution and sensitivity throughout this FOV as a guide for patient positioning.
Methods And Results: For this CZT camera (Discovery 570c, GE Healthcare), the iteratively reconstructed spatial resolution along 3 Cartesian axes was compared (average resolution 6.
Unlabelled: This study aimed to assess the role of a quantitative dynamic PET model in pancreatic cancer as a potential index of tumor aggressiveness and predictor of survival.
Methods: Seventy-one patients with (18)F-FDG-avid adenocarcinoma of the pancreas before treatment were recruited, including 27 with localized tumors (11 underwent pancreatectomy, and 16 had localized nonresectable tumors) and 44 with metastatic disease. Dynamic (18)F-FDG PET images were acquired over a 60-min period, followed by a whole-body PET/CT study.
The aim of this study was to assess the effect of attenuation correction (AC) on left ventricular (LV) volumes and LV transient ischemic dilatation (TID) during dual-isotope single-photon emission computer tomographic (SPECT) myocardial perfusion imaging (MPI). Ninety-six patients (mean age 58 ± 11 years, 15% women, 38 patients completed exercise and 58 dipyridamole pharmacologic stress tests) assessed for known or suspected coronary artery disease underwent dual-isotope thallium-201 rest and technetium-99m sestamibi stress SPECT MPI with computed tomography-based AC. The TID ratio was calculated separately for non-AC and AC SPECT MPI studies as the ratio of the LV endocardial volume at stress divided by LV endocardial volume at rest.
View Article and Find Full Text PDFPurpose: Reduced SPECT acquisition time protocols have been recently developed based on collimator-detector response compensation reconstruction. The present study aims to evaluate the potential use of a short-time technetium-99m methoxyisobutylisonitrile (Tc99m-MIBI) SPECT algorithm in the investigation of parathyroid adenoma (PTA).
Procedures: Ninety patients (59 women; age range, 21-76 years) with biochemical evidence of hyperparathyroidism were referred for Tc99m-MIBI scintigraphy for diagnosis and localization of PTA.
Purpose: To assess the impact of respiration on myocardial perfusion imaging (MPI) SPECT processed with advanced algorithmic reconstructions.
Methods: SPECT studies obtained from a phantom simulation and 49 respiratory-gated,one-day 99mTc-sestamibi scans were corrected for respiratory-related cardiac movement. Three types of reconstruction algorithms: (a) filtered back projection (FBP), (b) ordered subset expectation maximization in which collimator detector response was incorporated (OSEMCDR), and (c) OSEM-CDR with additional attenuation and scatter corrections (OSEM-CDRACSC) were applied to the corrected and uncorrected sets and analyzed quantitatively and qualitatively.
Unlabelled: CT-based attenuation-corrected (AC) myocardial perfusion imaging (MPI) studies may show significant artifacts caused by misregistration between SPECT and CT data. The present study aimed at identifying the directions and magnitudes of misregistration with greatest impact on AC myocardial perfusion image quality.
Methods: The incidence, magnitude, and direction of misregistration were assessed in 248 consecutive stress-rest MPI studies in 124 patients.
Unlabelled: Recent converging evidence suggests that the brain may receive stimuli and possibly modulate tumor progression via the vagus nerve. The present study aimed to compare brain metabolism in patients with and without lung cancer and to assess if significant differences exist in regions associated with the vagus nerve.
Methods: Eighteen patients with lung malignancy and 19 controls underwent (18)F-FDG PET of the brain.
Unlabelled: (18)F-FDG uptake in the thymus, mainly related to hyperplasia after chemotherapy, has been described. Thymic uptake can challenge the accurate assessment of cancer patients by (18)F-FDG imaging. The present study defines the incidence, patterns, and intensity of thymic (18)F-FDG uptake in relationship to age and time after treatment in a large cohort of patients.
View Article and Find Full Text PDFUnlabelled: The purpose of this study is to define the relationship between SPECT and CTA measured parameters of left ventricular (LV) function and volumes obtained in a single session using SPECT/64-slice CT hybrid imaging device, and in addition, to assess the reproducibility of LV parameters measured using 64-slice CTA.
Materials And Methods: Seventy-six patients with suspected or known coronary artery disease underwent cardiac CTA and GSPECT in one session using a hybrid SPECT/CT device. LV end-diastolic volume (EDV), end-systolic volume (ESV) and ejection fraction (EF) were measured on each component of the hybrid device.
Objectives: This article assesses the effect of a new correction technique ("motion-frozen heart") which compensates for the previously described nonuniform blurring of myocardial perfusion imaging (MPI) due to respiration motion or cardiac contraction.
Methods: Respiratory and ECG-gated one-day (99m)Tc-MIBI MPI studies performed in 48 patients were evaluated. MPI scans were acquired on a gamma camera supporting list-mode functionality synchronized with an external respiratory strap and an ECG device.
Purpose: To provide PET/CT image fusion with an improved PET resolution and better contrast ratios than standard reconstructions.
Method: Using a super-resolution algorithm, several PET acquisitions were combined to improve the resolution. In addition, functional PET data was smoothed with a hybrid computed tomography algorithm (HCT), in which anatomical edge information taken from the CT was employed to retain sharper edges.
CT beam hardening artifacts near metal hip implants may erroneously enhance or diminish radiotracer uptake following CT attenuation correction (AC) of PET images. An artifact reduction algorithm (ARA) was developed to reduce metal artifacts in CT-based AC-PET. The algorithm employed a Bayes classifier to identify beam-hardening artifacts, followed by a partial correction of the attenuation map.
View Article and Find Full Text PDFUnlabelled: Several studies have described nonuniform blurring of myocardial perfusion imaging (MPI) due to respiration. This article describes a technique for correcting the respiration effect and assesses its effectiveness in clinical studies.
Methods: Simulated phantoms, physical phantoms, and patient scans were used in this study.
Objectives: The purpose of this study was to assess the physiologic significance of coronary artery lesions with an integrated single-photon emission computed tomography (SPECT) and computed tomography coronary angiography (CTCA) device.
Background: Myocardial perfusion imaging (MPI) with SPECT is of value for assessing the physiologic significance of coronary lesions. Computed tomography coronary angiography is a new technique to noninvasively detect coronary stenosis, with high sensitivity and negative predictive value (NPV) but lower specificity and positive predictive value (PPV).
Unlabelled: The effect of multiple patient-related factors on the degree of cardiac 18F-FDG uptake was assessed.
Methods: Five hundred four consecutive patients undergoing routine 18F-FDG PET/CT studies completed a clinical questionnaire. 18F-FDG uptake was measured as the mean standardized uptake value within the heart delineated on the CT component of the study.