Search

Purpose: Q.Clear is a block sequential regularized expectation maximization (BSREM) penalized-likelihood reconstruction algorithm for PET. It tries to improve image quality by controlling noise amplification during image reconstruction. In this study, the noise properties of this BSREM were compared to the ordered-subset expectation maximization (OSEM) algorithm for both phantom and patient data acquired on a state-of-the-art PET/CT. Methods: The NEMA IQ phantom and a whole-body patient study were acquired on a GE DMI 3-rings system in list mode and different datasets with varying noise levels were generated. Phantom data was evaluated using four different contrast ratios. These were reconstructed using BSREM with different β-factors of 300–3000 and with a clinical setting used for OSEM including point spread function (PSF) and time-of-flight (TOF) information. Contrast recovery (CR), background noise levels (coefficient of variation, COV), and contrast-to-noise ratio (CNR) were used to determine the performance in the phantom data. Findings based on the phantom data were compared with clinical data. For the patient study, the SUV ratio, metabolic active tumor volumes (MATVs), and the signal-to-noise ratio (SNR) were evaluated using the liver as the background region. Results: Based on the phantom data for the same count statistics, BSREM resulted in higher CR and CNR and lower COV than OSEM. The CR of OSEM matches to the CR of BSREM with β = 750 at high count statistics for 8:1. A similar trend was observed for the ratios 6:1 and 4:1. A dependence on sphere size, counting statistics, and contrast ratio was confirmed by the CNR of the ratio 2:1. BSREM with β = 750 for 2.5 and 1.0 min acquisition has comparable COV to the 10 and 5.0 min acquisitions using OSEM. This resulted in a noise reduction by a factor of 2–4 when using BSREM instead of OSEM. For the patient data, a similar trend was observed, and SNR was reduced by at least a factor of 2 while preserving contrast. Conclusion: The BSREM reconstruction algorithm allowed a noise reduction without a loss of contrast by a factor of 2–4 compared to OSEM reconstructions for all data evaluated. This reduction can be used to lower the injected dose or shorten the acquisition time. [ABSTRACT FROM AUTHOR]

BACKGROUND: Hospitalized patients on clozapine are at risk for dysregulation of their clozapine blood concentration due to smoking cessation, (pre-existing) infections and the use of drugs which influence the metabolism of clozapine. In July 2017 a therapeutic guideline was implemented in the Haga Teaching Hospital and Haaglanden Medical Centre to monitor patients during hospital admission to prevent clozapine toxicity. OBJECTIVE Primary objective was to study the effect of the guideline by comparing the percentage of hospitalized patients with one or more serum clozapine levels > 0,80 mg/L and/or > 50% increase of their serum clozapine level during admission, before and after implementation of the guideline. DESIGN We conducted a non interventional retrospective study. METHODS In a period of ten months before and after the implementation of the guideline, data from all hospitalized patients ≥ 18 years using clozapine for schizophrenia were collected from electronic patient files. RESULTS In 90% of all patients an intervention was necessary according to the guideline. There was no significant difference between the percentage of patients with supratherapeutic clozapine levels before and after the implementation of the guideline (P = 0,695). The involvement of the hospital pharmacist improved significantly after implementation of the therapeutic guideline (number of interventions; P < 0,001). The hospital pharmacist recommended the involvement/consultation of the psychiatrist in 39% of the admissions after implementation of the guideline. CONCLUSION The therapeutic guideline did not reduce the number of patients with supratherapeutic clozapine levels. However, the involvement of the hospital pharmacist resulted in earlier involvement of the psychiatrist. According to the guideline an intervention was necessary in most patients (90%). All patients with supratherapeutic clozapine levels (n = 28) had an infection and/or an elevated CRP which suggests early dose reductions are required. [ABSTRACT FROM AUTHOR]

Purpose: Mobile health (mHealth) could improve the outcome of grown-up patients with congenital heart disease (GUCH) and reduce their emergency care utilisation. Inappropriate use of mHealth, however, can lead to data overload for professionals and unnecessary data collection for patients, increasing the burden for both. We aimed to determine the clinical characteristics of patients with high emergency care utilisation and to test whether these patients were willing to start using mHealth.Methods: Clinical characteristics and emergency care utilisation of consecutive GUCH patients who visited one of the two participating cardiologists at the outpatient clinic of the Academic Medical Centre in Amsterdam were studied retrospectively. All patients were approached to fill in an mHealth questionnaire. A frequency of three or more emergency visits in 5 years was defined as high emergency care utilisation.Results: In total, 202 consecutive GUCH patients who visited one of the two participating cardiologists were studied. Median age was 41 years, 47% were male, and 51% were symptomatic. In the previous 5 years, 134 emergency visits were identified. Of all patients, 8% had high emergency care utilisation. High emergency care utilisation was associated with patients being symptomatic, using antiarrhythmic drugs or diuretics. In total, 75% of all patients with high emergency care utilisation were willing to start using mHealth.Conclusion: GUCH patients who are symptomatic, those on antiarrhythmic drug therapy and those on diuretics are suitable candidates for enrolment in future mHealth initiatives because of both high care utilisation and high motivation to start using mHealth. [ABSTRACT FROM AUTHOR]

Background: Arrhythmias and heart failure are common and invalidating sequelae in adult patients with congenital heart disease (CHD). Mobile health (m-Health) enables daily monitoring and a timely response that might prevent deterioration. We present an observational prospective registry to evaluate feasibility of an m‑Health telemonitoring program for managing arrhythmia, heart failure and blood pressure in symptomatic adults with CHD.Methods: Symptomatic adult patients with CHD are enrolled in an m‑Health telemonitoring program, which evaluates single-lead ECG, blood pressure and weight measurements. In case of symptoms extra measurements could be performed. Data are collected by mobile apps, matched with individualised thresholds. Patients are contacted if thresholds were exceeded or if arrhythmias were found, for treatment adjustments or reassurance. Data on emergency care utilisation, hospitalisation and patient-reported outcome measures are used to assess quality of life and self-management.Results: 129 symptomatic CHD patients were invited to participate, 55 participated. Reasons for refusing consent included too time consuming to participate in research (30) and to monitor vital signs (14). At baseline 22 patients were in New York Heart Association class ≥ II heart failure, 43 patients had palpitations or documented arrhythmias, and 8 had hypertension. Mean follow-up was 3.0 months, one patient dropped out, and adherence was 97%.Conclusion: The first results indicate that this program is feasible with high adherence. [ABSTRACT FROM AUTHOR]

Objectives: To compare the diagnostic accuracy of (111)In-pentetreotide-scintigraphy with (68)Ga-DOTATOC-positron emission tomography (PET)/computed tomography (CT) in patients with metastatic-neuroendocrine tumour (NET) scheduled for peptide receptor radionuclide therapy (PRRT). Incremental lesions (ILs) were defined as lesions observed on only one modality.Methods: Fifty-three metastatic-NET-patients underwent (111)In-pentetreotide-scintigraphy (24 h post-injection; planar+single-photon emission CT (SPECT) abdomen) and whole-body (68)Ga-DOTATOC-PET/CT. SPECT and PET were compared in a lesion-by-lesion and organ-by-organ analysis, determining the total lesions and ILs for both modalities.Results: Significantly more lesions were detected on (68)Ga-DOTATOC-PET/CT versus (111)In-pentetreotide-scintigraphy. More specifically, we observed 1,098 lesions on PET/CT (range: 1-105; median: 15) versus 660 on SPECT (range: 0-73, median: 9) (p<0.0001), with 439 PET-ILs (42/53 patients) and one SPECT-IL (1/53 patients). The sensitivity for PET/CT was 99.9 % (95 % CI, 99.3-100.0), for SPECT 60.0 % (95 % CI, 48.5-70.2). The organ-by-organ analysis showed that the PET-ILs were most frequently visualized in liver and skeleton.Conclusion: Ga-DOTATOC-PET/CT is superior for the detection of NET-metastases compared to (111)In-pentetreotide SPECT.Key Points: Somatostatin receptor PET is superior to SPECT in detecting NET metastases. PET is the scintigraphic method for accurate depiction of NET tumour burden. The sensitivity of PET is twofold higher than the sensitivity of SPECT. [ABSTRACT FROM AUTHOR]

Background and Purpose: The aim of this work was to determine whether 11C-choline positron emission tomography (PET)-computed tomography (CT) makes a positive contribution to multiparametric magnetic resonance imaging (MRI) for localisation of intraprostatic tumour nodules.Patients and Methods: A total of 73 patients with biopsy-proven intermediate- and high-risk prostate cancer were enrolled in a prospective imaging study consisting of T2-weighted (T2w), dynamic contrast-enhanced (DCE) and diffusion-weighted (DW) MRI and 11C-choline PET-CT before radical prostatectomy. Cancerous regions were delineated on the whole-mount prostatectomy sections and on the different MRI modalities and analysed in 24 segments per patient (3 sections, 8 segments each). To analyse PET-CT images, standardized uptake values (SUV) were calculated per segment.Results: In total, 1,752 segments were analyzed of which 708 (40.4%) were found to be malignant. A high specificity (94.7, 93.6 and 92.2%) but relatively low sensitivity (31.2, 24.9 and 44.1%) for tumour localisation was obtained with T2w, DCE and DW MRI, respectively. Sensitivity values significantly increased when combining all MRI modalities (57.2%). For PET-CT, mean SUVmax of malignant octants was significantly higher than mean SUVmax of benign octants (3.68±1.30 vs. 3.12±1.02, p<0.0001). In terms of accuracy, the benefit of adding PET-CT to (multiparametric) MRI was less than 1%.Conclusion: The additional value of 11C-choline PET-CT to MRI in localising intraprostatic tumour nodules is limited, especially when multiparametric MRI is used. [ABSTRACT FROM AUTHOR]

Copyright of Strahlentherapie und Onkologie is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The type 1 neurokinin receptor (NK1R) antagonist aprepitant and its i.v. prodrug fosaprepitant have been approved for prevention of acute and delayed nausea and vomiting associated with chemotherapy. This study evaluated the magnitude and duration of brain NK1R occupancy over a period of 5 days after single-dose i.v. infusion of 150-mg fosaprepitant and single-dose oral administration of 165-mg aprepitant, using serial [18F]MK-0999 positron emission tomography (PET) in 16 healthy subjects. Each subject underwent three scans. Brain NK1R occupancy rates after i.v. fosaprepitant at time to peak concentration (Tmax; ~30 min), 24, 48, and 120 h after the dose were 100, 100, ≥97, and 41-75%, respectively. After aprepitant, NK1R occupancy rates at these time points (Tmax ~4 h) were ≥99, ≥99, ≥97, and 37-76%, respectively. Aprepitant plasma concentration profiles were comparable for the two dosage forms. The study illustrates the utility of PET imaging in determining central bioequivalence in a limited number of subjects. [ABSTRACT FROM AUTHOR]

Purpose. The aim of the study was to determine the accuracy of non-rigid nine-parameter image registrations based on 153Gd transmission computed tomography (TCT) images as compared with those based on 99mTc-ethyl cysteinate dimer (ECI)) images and to assess whether normalised mutual information (NMI) or count difference (CD) should he used. Methods. TCT and ECD data were acquired in 25 randomly selected patients. Emission images were registered to an ECD template with a CD cost function. The same registration parameters were applied to the transmission images to create a TCT template. All TCT images were registered to the TCT template and the same registration parameters were applied to the ECD images. The procedure was repeated with NMI as cost function. Accuracy of both ECD-based and TCT-based registrations was assessed by comparing the normalisation parameter values and regional activities in the spatially normalised ECD images, using a mixed-model analysis of variance (ANOVA). Scheffé post hoc tests were performed. Results. No significant differences were found between ECD/CD, ECD/NMI and TCT/CD, suggesting that ECD registration can he done with either CD or NMI, and that TCT registration using CD is equally as accurate as ECD registration. The accuracy of TCT registration with NMI was lower, with discrepancies occurring in the frontal inferior region and the cerebellum. The analysis of normalisation parameters indicated that z-scaling is underestimated and yz-rotation overestimated with TCT/NMI registration. Conclusion. We conclude that ECD registrations with CD or NMI are as accurate as TCT registrations with CD and that TCT registrations with NMI should he avoided. [ABSTRACT FROM AUTHOR]

Provides information on a study which presented a method for calculating the three-dimensional geometric sensitivity profiles for any triple-headed gamma camera configuration and for coincidence imaging with any number of planar detector heads. How the study was conducted; Results; Discussion of the results; Conclusion.

Presents abstracts of several studies on medical instruments and imaging. Exploration on the use of image texture analysis for the automated identification of tissue abnormalities in low-power scans of prostate histology; Details of a proposed projection operator that can be changed easily according to the system specified; Development of an algorithm customized to badly defined objects detected in hippocampus atrophy.

Aims: To evaluate the impact of second harmonic (SH) imaging compared to fundamental mode (FM) on the echocardiographic determination of ejection fraction (EF) and wall motion score index (WMSI), using MIBI gated SPECT as an independent reference.Methods: Sixty-two consecutive patients underwent an echocardiography study and a MIBI gated SPECT over 24 hours. EF was estimated visually (estimated-E) and was calculated with the Simpson biplane method (Tracing-T), for both FM and SH. WMSI was determined by two independent echo-readers blinded to the nuclear imaging results. The same segmentation and scoring system was used for WMSI determined by MIBI gated SPECT.Results: The percentages of unscored segments because of suboptimal endocardial border detection were 19·5% (FM) and 9·0% (SH). The correlation coefficients (r) between SPECT-EF and echo-EF were: FM (E)=0·705, FM (T)=0·546, SH (E)=0·771, SH (T)=0·743. Agreement between SPECT-EF and echo-EF was acceptable for both imaging modalities (mean of the difference±2 S.D.): −2·8±18·5 (FM) and −3·5±16·4 (SH). Correlation coefficients (r) between WMSI calculated by SPECT and by echo were 0·715 (FM) and 0·789 (SH). Agreement between SPECT-WMSI and echo-WMSI was good for all imaging modes but better with SH compared to FM: 0·12±0·91 (FM), 0·10±0·77 (SH). The interobserver correlation coefficients (r) for the WMSI were 0·939 (FM) and 0·996 (SH). The agreement between the two observers was better for SH compared to FM. The systematic differences (mean differences) were 0·21 (FM) and −0·01 (SH), and the random differences between both observers (2 S.D.) decreased from 1·55 (FM) to 0·29 (SH).Conclusions: The use of SH echocardiography decreases the number of unscored segments. This results in an important gain in correlation and agreement for EF determination between echo and SPECT, and in a considerable decline of the interobserver variability for the echo-determined WMSI. WMSI determined by MIBI gated SPECT correlated closely with the SH WMSI, and agreement between both methods was excellent. [ABSTRACT FROM AUTHOR]

Aims To investigate the importance of venous pooling and variation in venous tone during nitrate-stimulated tilt testing in patients. Methods Ten patients with a history of vasovagal syncope underwent an upright tilt test after an injection of99mTc-labelled albumin. A gamma camera was positioned at the level of the lower legs. The patients were tilted to 90° for 30 min or until symptoms developed. In those subjects who did not show any symptoms before the end of the 30-min period, isosorbide dinitrate (ISDN) 5 mg was given sublingually and the test was prolonged for a maximum of 15 min. Results Nine of 10 patients needed nitrate stimulation to develop symptoms, and one patient remained symptom free following ISDN administration. Measurement of radioactivity revealed no significant increase in calf volume after nitrate stimulation (the mean volume increase was 77% before ISDN stimulation and a further 0·9% afterwards). Conclusions The higher sensitivity for vasovagal syncope during upright tilt testing after administration of sublingual ISDN is not due to an increase in venous pooling in the lower extremities. [ABSTRACT FROM PUBLISHER]

Background: Fully integrated PET/MR systems are being used frequently in clinical research and routine. National Electrical Manufacturers Association (NEMA) characterization of these systems is generally done with 18F which is clinically the most relevant PET isotope. However, other PET isotopes, such as 68Ga and 90Y, are gaining clinical importance as they are of specific interest for oncological applications and for follow-up of 90Y-based radionuclide therapy. These isotopes have a complex decay scheme with a variety of prompt gammas in coincidence. 68Ga and 90Y have higher positron energy and, because of the larger positron range, there may be interference with the magnetic field of the MR compared to 18F. Therefore, it is relevant to determine the performance of PET/MR for these clinically relevant and commercially available isotopes. Methods: NEMA NU 2–2007 performance measurements were performed for characterizing the spatial resolution, sensitivity, image quality, and the accuracy of attenuation and scatter corrections for 18F, 68Ga, and 90Y. Scatter fraction and noise equivalent count rate (NECR) tests were performed using 18F and 68Ga. All phantom data were acquired on the GE Signa integrated PET/MR system, installed in UZ Leuven, Belgium. Results: 18F, 68Ga, and 90Y NEMA performance tests resulted in substantially different system characteristics. In comparison with 18F, the spatial resolution is about 1 mm larger in the axial direction for 68Ga and no significative effect was found for 90Y. The impact of this lower resolution is also visible in the recovery coefficients of the smallest spheres of 68Ga in image quality measurements, where clearly lower values are obtained. For 90Y, the low number of counts leads to a large variability in the image quality measurements. The primary factor for the sensitivity change is the scale factor related to the positron emission fraction. There is also an impact on the peak NECR, which is lower for 68Ga than for 18F and appears at higher activities. Conclusions: The system performance of GE Signa integrated PET/MR was substantially different, in terms of NEMA spatial resolution, image quality, and NECR for 68Ga and 90Y compared to 18F. But these differences are compensated by the PET/MR scanner technologies and reconstructions methods. [ABSTRACT FROM AUTHOR]