13 research outputs found
Myocardial perfusion scintigraphy dosimetry: optimal use of SPECT and SPECT/CT technologies in stress-first imaging protocol
No full textPurpose: Over the past decade, nuclear medicine experts have been seeking to minimize patient exposure to radiation in myocardial perfusion scintigraphy (MPS). This review describes the latest technological innovations in MPS, particularly with regard to dose reduction. Methods: We searched in PubMed for original clinical papers in English, published after 2008, using the following research criteria: (dose) and ((reduction) or (reducing)) and ((myocardial) or (cardiac) or (heart)) and ((nuclear medicine) or (nuclear imaging) or (radionuclide) or (scintigraphy) or (SPET) or (SPECT)). Thereafter, recent reviews on the topic were considered and other relevant clinical papers were added to the results. Results: Of 202 non-duplicate articles, 17 were included. To these, another eight papers cited in recent reviews were added. By optimizing the features of software, i.e., through algorithms for iterative reconstruction with resolution recovery (IRRs), and hardware, i.e., scanners and collimators, and by preferring, unless otherwise indicated, the use of stress-first imaging protocols, it has become possible to reduce the effective dose by at least 50% in stress/rest protocols, and by up to 89% in patients undergoing a diagnostic stress-only study with new technology. With today’s SPECT/CT systems, the use of a stress-first protocol can conveniently be performed, resulting in an overall dose reduction of about 35% if two-thirds of stress-first examinations were considered definitively normal. Conclusion: Using innovative gamma cameras, collimators and software, as well as, unless otherwise indicated, stress-first imaging protocols, it has become possible to reduce significantly the effective dose in a high percentage of patients, even when X-ray CT scanning is performed for attenuation correction
Comparative analysis of iterative reconstruction algorithms with resolution recovery and time of flight modeling for (18)F-FDG cardiac PET: A multi-center phantom study
No full textBACKGROUND The purpose of this study was to evaluate the image quality in cardiac (18)F-FDG PET using the time of flight (TOF) and/or point spread function (PSF) modeling in the iterative reconstruction (IR). METHODS Three scanners and an anthropomorphic cardiac phantom with an insert simulating a transmural defect (TD) were used. Two sets of scans (with/without TD) were acquired, and four reconstruction schemes were considered: (1) IR; (2) IR + PSF, (3) IR + TOF, and (4) IR + TOF + PSF. LV wall thickness (FWHM), contrast between LV wall and inner chamber (C IC), and TD contrast in LV wall (C TD) were evaluated. RESULTS Tests of the reconstruction protocols showed a decrease in FWHM from IR (13 mm) to IR + PSF (11 mm); an increase in the C IC from IR (65%) to IR + PSF (71%) and from IR + TOF (72%) to IR + TOF + PSF (77%); and an increase in the C TD from IR + PSF (72%) to IR + TOF (75%) and to IR + TOF + PSF (77%). Tests of the scanner/software combinations showed a decrease in FWHM from Gemini_TF (13 mm) to Biograph_mCT (12 mm) and to Discovery_690 (11 mm); an increase in the C IC from Gemini_TF (65%) to Biograph_mCT (73%) and to Discovery_690 (75%); and an increase in the C TD from Gemini_TF/Biograph_mCT (72%) to Discovery_690 (77%). CONCLUSION The introduction of TOF and PSF increases image quality in cardiac (18)F-FDG PET. The scanner/software combinations exhibit different performances, which should be taken into consideration when making cross comparisons
Impact of low-dose SPECT imaging on normal databases and myocardial perfusion scores
No full textPurpose: We have recently demonstrated that iterative reconstruction algorithms with resolution recovery require the adoption of specific normal databases (NDBs) for perfusion SPECT quantification. This work was aimed at investigating the impact of patient low-dose imaging on NDBs and percent summed rest (SR%) and stress (SS%) scores. Methods: Assuming that count statistics of shorter acquisition time may simulate that of lower patient dose, three simultaneous scans were acquired (BrightView, Philips) with different acquisition-time/projection: 30, 15 and 8 s (from 100% to 25% of the reference). Fifty-two normal patients with low likelihood of coronary artery disease were enrolled and three homemade NDBs were then generated and compared (AstonishTM algorithm with default parameters): 100%-HM-NDBs, 50%-HM-NDBs and 25%-HM-NDBs. SR% and SS% were subsequently calculated for another group of 38 patients (normal/abnormal = 5/33). SR% and SS% values of 100%-HM-NDBs were compared with those obtained with the NDBs available on the workstation. Moreover, the impact of the study count statistics on perfusion scores was evaluated using the count-specific NDBs. Results: Significantly higher standard-deviation values were found for 25%-HM-NDBs compared to the other HM-NDBs (p < 0.02). Significantly higher SS% were also found for the 100%-HM-NDBs compared to the workstation NDBs (95%CI: 0.15–2.11%). Moreover, a post-hoc test showed significantly lower SR% and SS% for 25%-count statistics compared to 100%-HM-NDBs (p < 0.03). Conclusions: NDBs and perfusion scores depend significantly on study count-statistics. A 50% reduction in patient dose is ultimately the limit for AstonishTM (with the default parameters) in order to prevent a significant variation in myocardial perfusion quantification
Impact of non-specific normal databases on perfusion quantification of low-dose myocardial SPECT studies
No full textAim: To evaluate the impact of non-specific normal databases on the percent summed rest score (SR%) and stress score (SS%) from simulated low-dose SPECT studies by shortening the acquisition time/projection. Methods: Forty normal-weight and 40 overweight/obese patients underwent myocardial studies with a conventional gamma-camera (BrightView, Philips) using three different acquisition times/projection: 30, 15, and 8 s (100%-counts, 50%-counts, and 25%-counts scan, respectively) and reconstructed using the iterative algorithm with resolution recovery (IRR) AstonishTM (Philips). Three sets of normal databases were used: (1) full-counts IRR; (2) half-counts IRR; and (3) full-counts traditional reconstruction algorithm database (TRAD). The impact of these databases and the acquired count statistics on the SR% and SS% was assessed by ANOVA analysis and Tukey test (P < 0.05). Results: Significantly higher SR% and SS% values (> 40%) were found for the full-counts TRAD databases respect to the IRR databases. For overweight/obese patients, significantly higher SS% values for 25%-counts scans (+19%) are confirmed compared to those of 50%-counts scan, independently of using the half-counts or the full-counts IRR databases. Conclusions: AstonishTM requires the adoption of the own specific normal databases in order to prevent very high overestimation of both stress and rest perfusion scores. Conversely, the count statistics of the normal databases seems not to influence the quantification scores
Differences in polar-map patterns using the novel technologies for myocardial perfusion imaging
No full textBackground: New technologies are available in MPI. Our aim was to evaluate their impact on the uniformity of normal myocardial uptake in the polar-map representation, over different count statistics, with and without the attenuation (AC) and scatter corrections (SC). Methods: A phantom study was performed using 5 Anger gamma cameras with filtered back projection or iterative reconstruction with resolution recovery (IRR), with or without SCAC; a D530c, with or without AC; and a D-SPECT. Count statistics ranged up to a quarter of the reference for the conventional gamma cameras and up to one half for the advanced scanners. Using polar maps, the segmental uptakes and their uncertainties, the ‘global uniformity’ of polar maps expressed as the coefficient of variation (COV) among the segmental uptakes and the anterior/inferior (ANT/INF) ratio were calculated. Results: Both segmental uptakes and their uncertainties did not depend on the count statistics in the range studied. An increase in the segmental uptakes was found from IRR to IRR + SCAC (78.0% ± 13.5% vs 86.1% ± 9.4%; P < .0001). COV was lower for D-SPECT (10.1% ± 0.5%) and after SCAC for both conventional (9.9% ± 3.0%) and advanced systems (8.9% ± 1.7%). The ANT/INF ratio was above 1 for IRR (1.12 ± 0.07) and fell slightly below 1 for IRR + SCAC (0.97 ± 0.05). Conclusions: To compare data from the analysis of polar maps across different systems will require the adoption of specific normality databases, developed for each system and reconstruction method employed
Erratum to: Comparative analysis of iterative reconstruction algorithms with resolution recovery and time of flight modeling for 18F-FDG cardiac PET: A multicenter phantom study
No full textComparative analysis of cadmium-zincum-telluride cameras dedicated to myocardial perfusion SPECT : a phantom study
No full textBackground: This investigation used image data generated by an anthropomorphic phantom with a cardiac insert for a comparison between two solid state cameras: D-SPECT and D530c. Methods: For each camera, two sets (with and without a simulated transmural defect (TD)) of scans were acquired starting from the in vivo standard count statistics in the left ventricle (LV). Other two acquisitions corresponding to 150% and 50% of the reference count statistics were acquired. Five performance indices related to spatial resolution, contrast, and contrast-to-noise ratio (CNR) were analyzed. Results: D-SPECT showed a lower LV wall thickness and an inferior sharpness than D530c. No significant differences were found in terms of contrast between LV wall and the inner cavity, TD contrast or CNR. No significant differences were observed in CNR when moving from the reference level of count statistics down to 50% or up to 150% of the counts acquired on the LV. Conclusions: Our results show that D-SPECT and D530c have different performances. The lack of differences in the image performance indices along the range of count statistics explored, indicates that there is the possibility for a further reduction in the injected activity and/or the acquisition time, for both systems
Comparative analysis of iterative reconstruction algorithms with resolution recovery for cardiac SPECT studies : a multi-center phantom study
No full textBackground
This investigation used image data generated by a physical phantom over a wide range of count statistics to evaluate the effectiveness of several of the newer commercially available SPECT reconstruction iterative algorithms (IRR) in improving perfusion defect contrast and spatial resolution, while controlling image noise.
Methods
A cardiac phantom was imaged using four different gamma cameras over a wide range of counts statistics (from 6 to 0.8 Mcounts). Images were reconstructed with FBP, OSEM, and the IRR available on site. IRR were applied without corrections (IRR NC), with attenuation correction (IRR AC), scatter correction (IRR SC), and attenuation + scatter corrections (IRR SCAC). Four image performance indices related to spatial resolution, contrast, and image noise were analyzed.
Results
IRR NC always determined significant improvements in all indices in comparison to FBP or OSEM. Improvements were emphasized with IRR SC and IRR SCAC. Count reduction from 6 to 1.5 Mcounts did not impair the performances of any of the considered indices.
Conclusions
This is the first study comparing the relative performance of different, commercially available, IRR software, over a wide range of count statistics; the additional effect of scatter and attenuation corrections, alone or in combination, was also evaluated. Our results confirm that IRR algorithms produce substantial benefits with respect to conventional FBP or OSEM reconstruction methods, as assessed through different figures of merit, in particular when SC and/or SCAC are also included
A multi-element psychosocial intervention for early psychosis (GET UP PIANO TRIAL) conducted in a catchment area of 10 million inhabitants: study protocol for a pragmatic cluster randomized controlled trial
No full textBackground
Multi-element interventions for first-episode psychosis (FEP) are promising, but have mostly been conducted in non-epidemiologically representative samples, thereby raising the risk of underestimating the complexities involved in treating FEP in ‘real-world’ services.
Methods/Design
The Psychosis early Intervention and Assessment of Needs and Outcome (PIANO) trial is part of a larger research program (Genetics, Endophenotypes and Treatment: Understanding early Psychosis - GET UP) which aims to compare, at 9months, the effectiveness of a multi-component psychosocial intervention versus treatment as usual (TAU) in a large epidemiologically based cohort of patients with FEP and their family members recruited from all public community mental health centers (CMHCs) located in two entire regions of Italy (Veneto and Emilia Romagna), and in the cities of Florence, Milan and Bolzano. The GET UP PIANO trial has a pragmatic cluster randomized controlled design. The randomized units (clusters) are the CMHCs, and the units of observation are the centers’ patients and their family members. Patients in the experimental group will receive TAU plus: 1) cognitive behavioral therapy sessions, 2) psycho-educational sessions for family members, and 3) case management. Patient enrolment will take place over a 1-year period. Several psychopathological, psychological, functioning, and service use variables will be assessed at baseline and follow-up. The primary outcomes are: 1) change from baseline to follow-up in positive and negative symptoms’ severity and subjective appraisal; 2) relapse occurrences between baseline and follow-up, that is, episodes resulting in admission and/or any case-note records of re-emergence of positive psychotic symptoms. The expected number of recruited patients is about 400, and that of relatives about 300. Owing to the implementation of the intervention at the CMHC level, the blinding of patients, clinicians, and raters is not possible, but every effort will be made to preserve the independency of the raters. We expect that this study will generate evidence on the best treatments for FEP, and will identify barriers that may hinder its feasibility in ‘real-world’ clinical settings, patient/family conditions that may render this intervention ineffective or inappropriate, and clinical, psychological, environmental, and service organization predictors of treatment effectiveness, compliance, and service satisfaction
Language production impairments in patients with a first episode of psychosis
No full textLanguage production has often been described as impaired in psychiatric diseases such as in psychosis. Nevertheless, little is known about the characteristics of linguistic difficulties and their relation with other cognitive domains in patients with a first episode of psychosis (FEP), either affective or non-affective. To deepen our comprehension of linguistic profile in FEP, 133 patients with FEP (95 non-affective, FEP-NA; 38 affective, FEP-A) and 133 healthy controls (HC) were assessed with a narrative discourse task. Speech samples were systematically analyzed with a well-established multilevel procedure investigating both micro- (lexicon, morphology, syntax) and macro-linguistic (discourse coherence, pragmatics) levels of linguistic processing. Executive functioning and IQ were also evaluated. Both linguistic and neuropsychological measures were secondarily implemented with a machine learning approach in order to explore their predictive accuracy in classifying participants as FEP or HC. Compared to HC, FEP patients showed language production difficulty at both micro- and macro-linguistic levels. As for the former, FEP produced shorter and simpler sentences and fewer words per minute, along with a reduced number of lexical fillers, compared to HC. At the macro-linguistic level, FEP performance was impaired in local coherence, which was paired with a higher percentage of utterances with semantic errors. Linguistic measures were not correlated with any neuropsychological variables. No significant differences emerged between FEP-NA and FEP-A (p≥0.02, after Bonferroni correction). Machine learning analysis showed an accuracy of group prediction of 76.36% using language features only, with semantic variables being the most impactful. Such a percentage was enhanced when paired with clinical and neuropsychological variables. Results confirm the presence of language production deficits already at the first episode of the illness, being such impairment not related to other cognitive domains. The high accuracy obtained by the linguistic set of features in classifying groups support the use of machine learning methods in neuroscience investigations
