Clinical application of autologous technetium-99m-labelled eosinophils to detect focal eosinophilic inflammation in the lung.

The detection of focal eosinophilic inflammation by non-invasive means may aid the diagnosis and follow-up of a variety of pulmonary pathologies. All current methods of detection involve invasive sampling, which may be contraindicated or too high-risk to be performed safely. The use of injected autologous technetium-99m (Tc-99m)-labelled eosinophils coupled to single-photon emission computed tomography (SPECT) has been demonstrated to localise eosinophilic inflammation in the lungs of a patient with antineutrophil cytoplasmic antibody-positive vasculitis. Here, we report on the utility of this technique to detect active eosinophilic inflammation in a patient with focal lung inflammation where a biopsy was contraindicated.

Experimental results from a prototype slit-slat collimator with mixed multiplexed and non-multiplexed data.

We have previously shown with simulations that a gain in signal-to-noise ratio (SNR) can be obtained by using mixed multiplexed (MX) and non-MX data in a slit-slat SPECT system as compared to using non-MX data only. We have now developed a prototype slit-slat collimator for a conventional gamma camera in order to validate these simulation results. The prototype collimator consists of seven slits and multiple parallel slats. Image reconstruction is performed using a modified OSEM algorithm, which takes into account geometric sensitivity variations and attenuation, but not scatter or resolution effects. Here, we first describe the calibration of the system and then we present the experimental validation with phantom experiments. SPECT acquisitions using different geometric and anthropomorphic phantoms were performed with and without multiplexing. The results show that reconstruction of the MX projections with the non-MX-projections eliminates artefacts caused by multiplexing. SNR gains obtained using the mixed MX and non-MX configurations were in the range of 26% to 51% for different phantoms. The results were in agreement with our previously published simulation work, proving that combining MX and non-MX data can result in artefact-free reconstructed images with improved SNR.

The potential for mixed multiplexed and non-multiplexed data to improve the reconstruction quality of a multi-slit-slat collimator SPECT system.

Multiplexing is a way of increasing the sensitivity in a multi-slit-slat SPECT system by allowing the overlap of projections from neighboring apertures. The fundamental objective of multiplexing is to increase the signal-to-noise ratio for a given system resolution. Multiplexing may therefore lead to an improved tradeoff between resolution and sensitivity. Overlapped projections, however, introduce ambiguities in the data which can lead to non-uniqueness of solution for the inverse problem, deterioration in the quality of reconstruction and ultimately loss of resolution. Therefore, it is not straightforward to evaluate the advantage of the extra sensitivity gained by multiplexing, without first devising a method to overcome the image artifacts caused due to this overlapping of projection data. In this paper we investigate the effect of multiplexing on the reconstructed image quality and we determine whether reconstruction of multiplexed data could be improved by the addition of non-multiplexed data. For this purpose we have done simulations based on three digital phantoms. We compared the reconstructed images both qualitatively and quantitatively for different degrees of multiplexing and different fractions of non-multiplexed data. Our results indicate that the recovery coefficient (and therefore spatial resolution) can be maintained with a high degree of multiplexing leading to a significant increase in the SNR (up to 25%) due to a reduced noise level. This gain in the SNR corresponds to a 75% increase in counts or sensitivity which can be utilized to reduce acquisition time, patient dose or/and improve image quality.

Vascular inflammation imaging with 18F-FDG PET/CT: when to image?

UNLABELLED: We prospectively investigated the ideal imaging time to measure vascular uptake after injection of (18)F-FDG. METHODS: A total of 17 patients with atherosclerotic abdominal aortic aneurysm underwent dynamic abdominal PET/CT using 2-min frames between 45 and 53, 57 and 65, 115 and 123, and 175 and 183 min after injection of (18)F-FDG. For each period of dynamic imaging, vessel wall and lumen uptake were measured using the maximum standardized uptake value (SUV(max)) and target-to-background ratio (TBR). RESULTS: No significant difference in TBR across all time points (repeated measures ANOVA, P = 0.206) was observed, despite a significant difference in aortic wall and lumen uptake with time (repeated measures ANOVA, P = 0.02 and P < 0.001, respectively). There was no significant difference between aortic wall uptake at 60 min (SUV(max), 2.15 +/- 0.11 SE) and 180 min (SUV(max), 1.99 +/- 0.18 SE) (paired t test, P = 0.367). There was a significant difference in lumen uptake at 60 min (SUV(max), 2.4 +/- 0.11 SE) and 180 min (SUV(max), 1.7 +/- 0.1 SE) (paired t test, P = 0.001). There was no significant difference in TBR between 60 min (0.91 +/- 0.03) and 180 min (1.01 +/- 0.06 SE) (paired t test, P = 0.131). With increasing delayed imaging, there was increasing variability (SE) in the SUV(max) for the aortic wall and TBRs. CONCLUSION: There was no significant advantage in imaging at 3 h over 1 h after (18)F-FDG injection.

Fusion of metabolic function and morphology: sequential [18F]fluorodeoxyglucose positron-emission tomography/computed tomography studies yield new insights into the natural history of bone metastases in breast cancer.

PURPOSE: By monitoring bone metastases with sequential [(18)F]fluorodeoxyglucose positron-emission tomography/computed tomography ([(18)F]FDG-PET/CT) imaging, this study investigates the clinical relevance of [(18)F]FDG uptake features of bone metastases with various radiographic appearances. PATIENTS AND METHODS: Bone metastases were found in 67 of 408 consecutive patients with known/suspected recurrent breast cancer on [(18)F]FDG-PET/CT, characterized by CT morphology changes and/or bony [(18)F]FDG uptake. Twenty-five of the patients had sequential [(18)F]FDG-PET/CT examinations (86 studies) over an average follow-up period of 23 months. The temporal changes in [(18)F]FDG uptake and corresponding CT morphology features of 146 bone lesions identified in these 25 patients were followed up and correlated with therapeutic outcome retrospectively. RESULTS: The 146 lesions were classified as osteolytic (77), osteoblastic (41), mixed-pattern (11), or no change/negative (17) on CT. The majority of the osteolytic (72; 93.5%) and mixed-pattern lesions (nine; 81.8%), but fewer of the osteoblastic lesions (25; 61%), showed increased [(18)F]FDG uptake. After treatment, 58 osteolytic lesions (80.5%) became [(18)F]FDG negative and osteoblastic on CT and only 14 relatively large lesions (19.5%) remained [(18)F]FDG avid. Of the 25 [(18)F]FDG-avid osteoblastic lesions, 13 (52%) became [(18)F]FDG negative, but 12 (48%) remained [(18)F]FDG avid and increased in size on CT. Five of the mixed-pattern lesions remained [(18)F]FDG avid after treatment. All 17 CT-negative lesions became [(18)F]FDG negative; however, nine of them became osteoblastic. None of the initially [(18)F]FDG-negative lesions showed [(18)F]FDG avidity during follow-up. CONCLUSION: [(18)F]FDG uptake reflects the immediate tumor activity of bone metastases, whereas the radiographic morphology changes vary greatly with time among patients.

How often do patients undergo repeat PET or PET/CT examinations? Experience from a UK institution.

BACKGROUND AND AIM: According to the report of the Intercollegiate Standing Committee on Nuclear Medicine, the UK requires 40-60 positron emission tomography (PET) machines in the next decade (Intercollegiate Standing Committee on Nuclear Medicine). Positron Emission Tomography: a Strategy for Provision in the UK. London: Royal College of Physicians of London; 2003, pp. 1-9). This figure is based mainly on patients receiving only one examination and restricting the clinical indication to three primary diagnoses. The aim of this study was to assess the appropriateness of this figure and the assumptions made in the Intercollegiate report on UK PET provision. METHODS: We examined retrospectively our institution's entire PET and PET/computed tomography (CT) database, which spans 4 years and 9 months. We recorded the number of patients who received repeat examinations. RESULTS: Reports were available for 3354 PET/CT or PET-only studies; 418 of 2268 patients (18.4%) received at least one repeat PET/CT examination. The three main indications for PET examination in the Intercollegiate report only accounted for approximately 60% of the examinations undertaken. CONCLUSION: Our records suggest that basing the UK's future PET provision on a single examination and on three clinical indications only is no longer realistic.

A bolus/infusion paradigm for the novel NMDA receptor SPET tracer [123I]CNS 1261.

We have previously performed quantitative kinetic modeling of [(123)I]CNS 1261, a new SPET ligand for the MK801 intrachannel site of the NMDA receptor. We now report a bolus-infusion protocol, which eliminates the need for arterial blood sampling. Dynamic SPET scanning and venous blood sampling were performed in 7 healthy volunteers. Good agreement was obtained between kinetic and equilibrium analysis. SPET scanning with a bolus-infusion protocol is a valid method to estimate the total volume of distribution for [(123)I]CNS 1261 in clinical populations.