Is the physical decay correction of the (18)F-FDG input function in dynamic PET imaging justified?

Unlabelled: In this theoretic note, the rationale for the physical decay correction of the (18)F-FDG input function in dynamic PET is investigated, using the Patlak equation as an example.

Methods: The Patlak equation conventionally obtained when correcting the (18)F-FDG input function and correcting the tissue activity measurement for (18)F physical decay can also be derived from a 2-compartment analysis that does not conceptually involve any physical decay correction of the (18)F-FDG input function but accounts only for the physical decay of the trapped tracer.

Results: We demonstrate that exactly the same equation can be derived from the 2 conceptual approaches, and hence each approach yields the correct uptake rate of the tracer.

Assessment of dual-time-point 18F-FDG-PET imaging for pulmonary lesions.

Objective: The objective of this study was to assess suitability of dual-time-point 18F-FDG [(18F)-fluoro-2-deoxyglucose]-PET imaging for differentiating between malignant and benign pulmonary lesions, whose size and maximal standardized uptake values (SUVs) are greater than 10 mm and 2.5, respectively.

Methods: A total of 38 patients, 27 with malignant lesions (n = 30), and 11 with benign lesions (n = 22), were investigated by performing two static acquisitions started at mean times t = 79 and t = 158 min after the tracer injection.

The effect of renal failure on 18F-FDG uptake: a theoretic assessment.

Unlabelled: This work addresses the issue of using (18)F-FDG PET in patients with renal failure.

Methods: A model analysis has been developed to compare tissue (18)F-FDG uptake in a patient who has normal renal function with uptake in a theoretic limiting case that assumes tracer plasma decay is tracer physical decay and is trapped irreversibly.

Results: This comparison has allowed us to propose, in the limiting case, that the usually injected activity be lowered by a factor of 3.

Systemic tuberculosis presenting as an epiglottic mass detected on F-18 FDG PET/CT.

A 32-year-old man presented with asthenia, weight loss, cough, and dysphagia following a recent stay in Morocco. Endoscopy showed a bulky mass of the epiglottis suspected of being a malignant tumor. The patient underwent jointly an F-18 FDG PET/CT and a biopsy of the tumor.

Feasibility of an SUV normalization to 1 hour after the 18F-FDG injection.

The aim of this work was to reduce the SUV variability related to the time delay between 18F-FDG injection and the static PET acquisition, by means of a normalization to a 1-h time delay. Two static PET acquisitions separated by approximately 1 h were performed on each of 14 cancer patients, with SUVs on 22 hypermetabolic lesions calculated for both scans. The pairs of SUVs were normalized to each other using the parameterized input function with one free parameter (alpha3).

Normalization in quantitative [18F]FDG PET imaging: the 'body surface area' may be a volume.

Non-invasive methods for quantifying [(18)F]FDG uptake in tumours often require normalization to either body weight or body surface area (BSA), as a surrogate for [(18)F]FDG distribution volume (DV). Whereas three dimensions are involved in DV and weight (assuming that weight is proportional to volume), only two dimensions are obviously involved in BSA. However, a fractal geometry interpretation, related to an allometric scaling, suggests that the so-called 'body surface area' may stand for DV.

Quantitative MRI comparison of pulmonary hemodynamics in mustard/senning-repaired patients suffering from transposition of the great arteries and healthy volunteers at rest.

In Mustard/Senning-repaired (MSR) patients, the right and left ventricles (RV, LV) act as the systemic and pulmonary ventricle, respectively. The purpose of the study was to compare non-invasively, at rest, pulmonary ventricle systolic function and hemodynamics in MSR patients with those of healthy volunteers. Velocity-encoded MR imaging was performed at the level of the main pulmonary artery (MPA) in ten male patients late after a Mustard/Senning correction performed early in infancy and in ten male volunteers.

131I in blood samples: a danger for professionals? A problem for immunoassays?

Objective: Our objective was to investigate the safety of radioactive blood samples from patients receiving 131I and whether the radioactivity affects the validity of assays.

Methods: First, the activity of samples from patients given 131I was measured by 3 methods and compared with the upper threshold. Then, pilot sera were spiked with 131I, and possible interference was investigated using 2 immunoradiometric assays.

A method to quantify at late imaging a release rate of 18F-FDG in tissues.

This theoretical work shows that the rate constant for the (18)F-FDG release in tissues can be assessed without needing any arterial blood sampling. The method requires that the clearance of (18)F-FDG from plasma has occurred, whereas (18)F-FDG is still present in the tissue. This condition can be met dating from 3 h after (18)F-FDG injection, when hydration and/or phlorizin injection are applied after the routine static acquisition.

Feasibility of aortic pulse pressure and pressure wave velocity MRI measurement in young adults.

Purpose: To investigate the feasibility of assessing, noninvasively, aortic pulse pressure (APP) and pulse wave velocity (PWV) in the ascending aorta of young adults by means of velocity-encoded magnetic resonance (MR) imaging.

Materials And Methods: In a series of 11 healthy volunteers, velocity-encoded MR imaging provided pairs of magnitude and phase-contrast images. Blood flow velocity and aortic cross-sectional area (CSA) were determined with a 30-msec temporal resolution.

A method to quantify the uptake rate of 2-[18F]fluoro-2-deoxy-D-glucose in tissues.

A two-compartment model is used to derive the tissue time-activity curve of 2-[18F]fluoro-2-deoxy-D-glucose (18F-FDG). At the later phase of the 18F-FDG activity in the tissue, the model leads to a method which allows the assessment of the 18F-FDG uptake rate constant. The proposed method is both compared with the standard uptake value (SUV) method and with Patlak's graphical analysis.

Quantitative MRI comparison of systemic hemodynamics in Mustard/Senning repaired patients and healthy volunteers at rest.

The purpose of the present study was to non-invasively compare ascending aortic blood flow and cross-sectional area (CSA) variations vs time in Mustard or Senning repaired (MSR) patients against those of healthy volunteers at rest. Velocity-encoded MR imaging was performed in 10 male patients (age range 18-24 years, median age 20.5 years) late after a Mustard or Senning correction, and in 10 male healthy volunteers (age range 21-25 years, median age 22.

MRI quantification of the role of the reflected pressure wave on coronary and ascending aortic blood flow.

The respective roles of the windkessel effect, which is related to the vessel compliance, and of the returning pressure wave, which is reflected off peripheral resistances, in generating the total diastolic blood flow in the ascending aorta (VT: coronary + flow through the upper part of the ascending aorta) were assessed under physiological conditions. In ten healthy young men (21-30 years), magnetic resonance phase mapping was used to assess non-invasively both blood flow and vessel cross-sectional area (CSA) at the upper part of the ascending aorta. Measurements of blood flow velocities and CSAs were carried out over complete cardiac cycles, with a 30 ms resolution time.

A computed method for noninvasive MRI assessment of pulmonary arterial hypertension.

The present method enables the noninvasive assessment of mean pulmonary arterial pressure from magnetic resonance phase mapping by computing both physical and biophysical parameters. The physical parameters include the mean blood flow velocity over the cross-sectional area of the main pulmonary artery (MPA) at the systolic peak and the maximal systolic MPA cross-sectional area value, whereas the biophysical parameters are related to each patient, such as height, weight, and heart rate. These parameters have been measured in a series of 31 patients undergoing right-side heart catheterization, and the computed mean pulmonary arterial pressure value (Ppa(Comp)) has been compared with the mean pressure value obtained from catheterization (Ppa(Cat)) in each patient.