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We describe the case of a 54-year-old woman admitted to the cardiology ward for the correction of radiation-induced aortic stenosis and coronary artery disease. After careful workup, she underwent surgical aortic valve replacement and aortocoronary bypass with venous grafts. This case demonstrates the late cardiovascular complications that can develop after radiation therapy for cancer, and the surgical complexity of these patients. Thorough workup is needed for the treatment of radiation-induced valvulopathy and coronary artery disease, as these patients are often poor surgical candidates with hostile chests. Multidisciplinary heart-team assessment is paramount, and consideration should be given to catheter-based approaches.

Background Immune checkpoint inhibitor (ICI)-associated myocarditis is associated with a markedly increased risk of morbidity and mortality. The occurrence of ventricular arrhythmias (VA) in patients with ICI-associated myocarditis has not been well characterized. Purpose The aim of this study was to determine the characteristics and risk factors for severe VA in patients with ICI myocarditis. Methods The cohort consisted of 202 patients with ICI myocarditis. Ventricular arrhythmias were defined as a composite of sustained ventricular tachycardia and ventricular fibrillation. We used a multivariable logistic regression model to test the association between clinical variables and the development of VA. Results From a cohort of 202 patients with ICI myocarditis (67±13 years, 35% female, 60% hypertension, 23% diabetes mellitus), 41 (20.3%) developed VA, of which, 33 had VT and 8 had VF. The median time from admission to VF was 144 hours and to VT was 72 hours. A VA occurred in 17.5% of patients with a normal LVEF, and 25% of patients with reduced LVEF. On univariate analysis, a QRS duration >110ms (OR 2.88, 95% CI 1.40 to 6.16, P=0.005) and a QTc duration >470ms were associated with an increased probability of VA (OR 2.58, 95% CI 1.23, 5.41, P=0.012). The association remained significant after adjustment for age and gender. Additionally, a longer time from admission to initiation of corticosteroids was associated with a higher probability of VA (OR 1.06, 95% CI 1.01 to 1.13, P=0.027). The association between the time from admission to administration of corticosteroids and probability of VA remained significant after adjustment for age, gender, and LVEF on admission (OR, 1.06, 95% CI 1.00, 1.13, P=0.037) where each 6-hour delay in the initiation of corticosteroids was associated with a 4% increase in the risk for VA. Conclusions Ventricular arrhythmias are common in the setting of ICI myocarditis and are observed in patients presenting with both a preserved and a reduced LVEF. Wider QRS and longer QT at presentation and longer time from admission to initiation of corticosteroids were associated with an increased risk of VA. Funding Acknowledgement Type of funding sources: None.

Visual Abstract, Highlights • The impact of breastfeeding on prolactin, cellular immune activation, and myocardial recovery was analyzed in 100 women with peripartum cardiomyopathy • Cardiac function was assessed by echocardiography at presentation and at serial intervals over the first year postpartum • The levels of circulating prolactin were assessed by ELISA, and cellular immunophenotyping by flow cytometry, and compared between breastfeeding and nonbreastfeeding women • Prolactin levels were higher in breastfeeding women and correlated with significant increases in CD8+ T cells • Despite significantly higher prolactin levels and increased CD8+ cells, myocardial recovery was similar in breastfeeding and nonbreastfeeding women, Summary The etiology of peripartum cardiomyopathy remains unknown. One hypothesis is that an increase in the 16-kDa form of prolactin is pathogenic and suggests that breastfeeding may worsen peripartum cardiomyopathy by increasing prolactin, while bromocriptine, which blocks prolactin release, may be therapeutic. An autoimmune etiology has also been proposed. The authors investigated the impact of breastfeeding on cellular immunity and myocardial recovery for women with peripartum cardiomyopathy in the IPAC (Investigations in Pregnancy Associated Cardiomyopathy) study. Women who breastfed had elevated prolactin, and prolactin levels correlated with elevations in CD8+ T cells. However, despite elevated prolactin and cytotoxic T cell subsets, myocardial recovery was not impaired in breastfeeding women.

International audience; BACKGROUND Myocarditis is a potentially fatal complication of immune checkpoint inhibitor (ICI) therapy. Data on the utility of cardiovascular magnetic resonance (CMR) T1 and T2 mapping in ICI myocarditis are limited.OBJECTIVES This study sought to assess the value of CMR T1 and T2 mapping in patients with ICI myocarditis.METHODS In this retrospective study from an international registry of patients with ICI myocarditis, clinical and CMR findings (including T1 and T2 maps) were collected. Abnormal T1 and T2 were defined as 2 SD above site (vendor/field strength specific) reference values and a z-score was calculated for each patient. Major adverse cardiovascular events (MACE) were a composite of cardiovascular death, cardiogenic shock, cardiac arrest, and complete heart block.RESULTS Of 136 patients with ICI myocarditis with a CMR, 86 (63%) had T1 maps and 79 (58%) also had T2 maps. Among the 86 patients (66.3 +/- 13.1 years of age), 36 (41.9%) had a left ventricular ejection fraction

Mitral valve prolapse is a common finding in Graves’ disease. However, severe mitral regurgitation (MR) is a relatively uncommon manifestation of Graves’ disease. We report a case of a 32-year-old woman with toxic Graves’ disease and MR. The echocardiogram was suggestive of severe MR with biventricular failure, severe enough to be considered for mitral valve replacement. With medical control of the thyrotoxic state, a repeat echocardiogram revealed only trace MR, with normal left ventricular function. The timely management of the thyrotoxic state in this patient with Graves’ disease and moderate to severe MR possibly related to myxomatous degeneration, averted the need for mitral valve replacement.

Several echocardiographic measures have prognostic value in heart failure (HF). However, no definitive data exist on how changes in these parameters with treatment affect survival in this patient population. We hypothesized that early improvement on echocardiography could predict long-term survival.We conducted a retrospective review of 404 patients seen in the HF clinic from 2002 to 2008 (6.5 years). Patients had one echocardiogram ≤1 year before and another ≥1 month (10 ± 7 months) after treatment onset. We studied changes in standard echocardiographic parameters, including left (LV) and right (RV) ventricular size and/or function (systolic and/or diastolic), valvular (mitral and tricuspid) function, and pulmonary artery pressure. Survival curves and hazard ratios were generated for patients showing improvement on the 2nd echocardiogram versus those who did not. Multivariable analyses were performed adjusting for age, sex, ischemic etiology, and significant baseline echocardiographic parameters. Average follow-up was 2.9 ± 1.5 years. Improvement in LV end-systolic dimension, RV function, and mitral regurgitation were independent predictors of 5-year survival (P.05) and, importantly, more predictive than baseline values of these parameters alone (higher hazard ratios).Early echocardiographic improvement is strongly associated with 5-year survival in patients with HF. Serial echocardiography may aid in stratifying patient care.

OBJECTIVE: The aim of this work was to evaluate the hypothesis that the distribution of circulating immune cell subsets, or their activation state, is significantly different between peripartum cardiomyopathy (PPCM) and healthy postpartum (HP) women. BACKGROUND: PPCM is a major cause of maternal morbidity and mortality, and an immune-mediated etiology has been hypothesized. Cellular immunity, altered in pregnancy and the peripartum period, has been proposed to play a role in PPCM pathogenesis. METHODS: The Investigation of Pregnancy-Associated Cardiomyopathy (IPAC) study enrolled 100 women presenting with a left ventricular ejection fraction of

Background The Canadian Cardiology Society recommends that patients should be seen within 2 weeks after an emergency department (ED) visit for heart failure (HF). We sought to investigate whether patients who had an ED visit for HF subsequently consult a physician within the current established benchmark, to explore factors related to physician consultation, and to examine whether delay in consultation is associated with adverse events (AEs) (death, hospitalization, or repeat ED visit). Methods Patients were recruited by nurses at 8 hospital EDs in Quebec, Canada, and interviewed by telephone within 6 weeks of discharge and subsequently at 3 and 6 months. Clinical variables were extracted from medical charts by nurses. We used Cox regression in the analysis. Results We enrolled 410 patients (mean age 74.9 ± 11.1 years, 53% males) with a confirmed primary diagnosis of HF. Only 30% consulted with a physician within 2 weeks post-ED visit. By 4 weeks, 51% consulted a physician. Over the 6-month follow-up, 26% returned to the ED, 25% were hospitalized, and 9% died. Patients who were followed up within 4 weeks were more likely to be older and have higher education and a worse quality of life. Patients who consulted a physician within 4 weeks of ED discharge had a lower risk of AEs (hazard ratio 0.59, 95% CI 0.35-0.99). Conclusion Prompt follow-up post-ED visit for HF is associated with lower risk for major AEs. Therefore, adherence to current HF guideline benchmarks for timely follow-up post-ED visit is crucial.

Background: Although prevalence of heart failure (HF) is similar in women and men, more men are admitted to specialized HF clinics, possibly owing to a perception that men benefit more. Our aim was to describe 1-year outcomes in men and women attending specialized HF clinics. Methods and Results: We enrolled 531 newly referred patients (mean age 66 years, 26% women) to 1 of 6 HF multidisciplinary clinics in Quebec. Data were collected at time of entry to the clinic and 6 and 12 months later. The 3 main outcomes, mortality, disease evolution (New York Heart Association functional class, quality of life, 6-minute walk), and number of hospital admissions/emergency department visits were analyzed separately. Survival was higher in women than in men (adjusted hazard ratio 2.53, 95% confidence interval 1.10e5.80). Both women and men improved over the 12-month period in terms of quality of life, 6-minute walk, and lower use of hospital and emergency department. Persons who at entry to the clinic had more severe disease showed more improvement. Deterioration over the year was associated with higher number of comorbidities, but not with age or gender. Conclusions: Both men and women with HF who attend specialized HF clinics improved, including those with more severe disease. (J Cardiac Fail 2011;17:540e546)

Background We compared severity of heart failure (HF) between men and women at entry to the multidisciplinary HF clinic based on 3 measures: New York Heart Association functional class, norm-referenced 6-minute walk distance, and health-related quality of life. Methods Newly admitted patients to 1 of 6 HF clinics were enrolled. Data were collected from a clinical database, questionnaires were administered to patients, and tests were administered by clinic nurses. We compared men and women with respect to the 3 severity indicators at entry to the clinic. Results In adjusted analyses, women had a lower health-related quality of life ( P = 0.04) but did not have lower norm-referenced 6-minute walk distance or lower New York Heart Association functional class on entry to the clinic. Having more comorbid conditions, being on medication, and having visited the emergency department or been admitted to hospital in the past 6 months were associated with higher severity at entry according to all 3 indicators. Conclusions Women report a lower health-related quality of life at entry to the clinic, although functional capacity does not seem to differ between women and men. Reasons for these discrepancies will need to be elucidated to better address women's health needs.

Background Congestive heart failure (CHF) is a common cause of hospitalization and has a poor prognosis. Specialized multidisciplinary clinics are effective in the management of CHF. Objectives To measure time of admission to the specialized clinics and explore factors related to the time of admission to these clinics. Methods Patients who were newly admitted to one of six CHF multidisciplinary clinics in the province of Quebec were enrolled in the study. Data were collected from the common clinical database used at these clinics as well as from questionnaires administered to the patients. Results A total of 531 patients with a mean age of 65.9 years were enrolled. Only 26% were women. The median duration of disease before admission to the CHF clinic was 1.2 years. The majority of patients (62%) were referred by a cardiologist or an internist, while 24% were referred by other specialists, and 14% by general practitioners. One-fifth of patients did not have regular follow-up for their CHF before being admitted to the clinic. Factors associated with shorter disease duration at admission to the clinic were referral by a specialist, not having regular medical follow-up for CHF, having a higher income and having visited the emergency room for CHF. Conclusion There may be a need to improve dissemination of information regarding availability and benefits of CHF clinics and criteria for referral.

Background The 6-minute walk test (6MWT) is a widely used measure of functional capacity in patients with chronic heart failure (CHF). Norm-referenced equations that predict the 6-minute walk distance (6MWD) according to age, height, weight, and gender have been proposed for healthy patients. We explored whether these equations apply to CHF patients. Methods and Results The sample consisted of 213 patients newly admitted to specialized CHF clinics in Montreal, Canada. Percent predicted value (PPV) for 6MWD was calculated using norm-referenced equations. We explored correlations between different measures: PPV, 6MWD, Minnesota Living with Heart Failure Quality of Life score (MLHF-QOL). We compared severity among different age, gender, and BMI (body mass index) subgroups and assessed consistency using different measures of severity. Mean age was 65.5 years and 77.5% were men. Compared with the 6MWD, PPV had a slightly better correlation with MLHF-QOL score (−0.26 versus −0.20), and slightly more predictive power in linear regressions (adjusted r2 = 6.5% versus 4.2%). When PPV was used to differentiate severity between different age, gender, and BMI subgroups, it consistently led to similar conclusions as the MLHF-QOL score, unlike 6MWD. Conclusion The 6MWD in meters may give misleading results when used as an indicator of severity of CHF condition to compare groups with different sex, age, and BMI distributions. It may be necessary to standardize it using norm-referenced equations.

Clinical outcomes and echocardiographic parameters associated with aortic valve replacement (AVR) for bicuspid aortic valve are scarce.We conducted retrospective analysis of 208 adults with bicuspid aortic valve referred for transthoracic echocardiograms.The Kaplan-Meier survival free of death or need for cardiac surgery was 72% at 5 years. Cardiac surgery was performed in 19%, the majority (68%) for symptomatic aortic stenosis. Peak gradient 80 mm Hg or greater (hazard ratio 11.8, 95% confidence interval 3.7-37.8, P.0001) and aortic valve area less than or equal to 0.75 cm(2) (hazard ratio 2.9, 95% confidence interval 1.0-8.5, P = .05) predicted the need for AVR. Patients with a large (54%) versus normal left ventricular outflow tract dimension underwent AVR for symptomatic aortic stenosis at a larger calculated aortic valve area (1.07 +/- 0.21 vs 0.75 +/- 0.18 cm(2), P.0001) but at a similar peak gradient and velocity ratio (76 +/- 19 vs 76 +/- 22 mm Hg, P = not significant; 0.23 +/- 0.06 vs 0.26 +/- 0.12, P = not significant, respectively).Clinical events are common among patients with bicuspid aortic valve. Peak gradient 80 mm Hg or more and aortic valve area less than or equal to 0.75 cm(2) predicts the need for AVR. Gradients and velocity ratio better reflect the hemodynamic burden of aortic stenosis in patients with a large left ventricular outflow tract.

One out of two patients with advanced cardiovascular disease exhibits signs of frailty or cognitive impairment. Identification of frailty or cognitive impairment, when objectified with a validated instrument, confers a negative effect on prognosis and may be an important clue that the patient with advanced cardiovascular disease is entering the end-of-life phase. These patients have special needs that are best addressed in conjunction with a multidisciplinary palliative care team. Challenges include recognizing and managing pain and other symptoms, assessing competence to make medical decisions, maintaining informed communication with the patients and their families, and differentiating potentially treatable etiologies such as: low cardiac output with hypoperfusion, sleep-disordered breathing, metabolic disturbances, delirium, and depression. Advanced care planning should be encouraged, with the foreseeable outcomes framed around the patient’s cardiovascular disease status but also around their resiliency and homeostatic reserve. Ultimately, an approach of shared decision-making is central to the care of frail and cognitively impaired patients at the end-of-life.

Quantitative estimation of brain glucose metabolism (rCMRGlc) with positron emission tomography and fluorodeoxyglucose involves arterial blood sampling to estimate the delivery of radioactivity to the brain. Usually, for an intravenous injection of 30 s duration, an accurate input curve requires a frequency of one sample every 5 s or less to determine the peak activity in arterial plasma during the first 2 min after injection. In this work, 13 standardized sampling times were shown to be sufficient to accurately define the input curve. This standardized input curve was subsequently fitted by a polynomial function for its rising part and by spectral analysis for its decreasing part. Using the measured, the standardized, and the fitted input curves, rCMRGlc was estimated in 32 cerebral regions of interest in 20 normal volunteers. Comparison of rCMRGlc values obtained with the measured and the fitted input curves showed that both procedures gave consistent results, with a maximal relative error in mean rCMRGlc of 1% when using the autoradiographic method and 2% using kinetic analysis of dynamic data. This input-curve-fitting technique, which is not dependent on the peak time occurrence, allows an accurate determination of the input-curve shape from reduced sampling schemes.

The high computational cost of data processing in volume PET imaging is still hindering the routine application of this successful technique, especially in the case of dynamic studies. This paper describes two new algorithms based on an exact rebinning equation, which can be applied to accelerate the processing of three-dimensional (3-D) PET data. The first algorithm, FOREPROJ, is a fast-forward projection algorithm that allows calculation of the 3-D attenuation correction factors (ACF's) directly from a two-dimensional (2-D) transmission scan, without first reconstructing the attenuation map and then performing a 3-D forward projection. The use of FOREPROJ speeds up the estimation of the 3-D ACF's by more than a factor five. The second algorithm, FOREX, is a rebinning algorithm that is also more than five times faster, compared to the standard reprojection algorithm (3DRP) and does not suffer from the image distortions generated by the even faster approximate Fourier rebinning (FORE) method at large axial apertures. However, FOREX is probably not required by most existing scanners, as the axial apertures are not large enough to show improvements over FORE with clinical data. Both algorithms have been implemented and applied to data simulated for a scanner with a large axial aperture (30 degrees), and also to data acquired with the ECAT HR and the ECAT HR+ scanners. Results demonstrate the excellent accuracy achieved by these algorithms and the important speedup when the sinogram sizes are powers of two.

The Seattle Heart Failure Model (SHFM) is 1 of the most widely used tools to predict survival in patients with heart failure. However, it does not accommodate very elderly patients. We decided to assess the applicability of the SHFM in patients >80 years old enrolled in a tertiary care heart failure clinic. We evaluated the difference between observed survival and mean life expectancy as predicted by the SHFM on 261 patients >80 years old enrolled in a heart failure clinic at the Jewish General Hospital, Montreal, Quebec, Canada from January 2002 through March 2010. Average age of the patient population was 85 ± 4 years (range 80 to 105). Sixty-two percent of the population consisted of men, 63% had ischemic cardiomyopathy (ICM), and average ejection fraction was 36 ± 18%. Median observed survival was 1.91 years (interquartile range 0.68 to 5.53) for the total population (n = 261). The SHFM (predicted median survival 6.7 years, interquartile range 3.8 to 11.2) overestimated life expectancy by an average of 4.79 years. For patients with ICM (n = 164) versus non-ICM (n = 97), the score overestimated survival by 4.29 versus 5.69 years, respectively. In conclusion, the SHFM overestimates life expectancy in elderly patients followed in a tertiary care heart failure clinic. Further studies are needed to more accurately estimate prognosis in this patient population.

Quality of life (QoL) is an important end point in heart failure (HF) studies. The Minnesota Living with Heart Failure questionnaire (MLHFQ) is the instrument most widely used to evaluate QoL in Heart Failure (HF) patients. It is a questionnaire containing 21 questions with scores ranging from 0 to 105. A best cut-off value for MLHFQ scores to identify those patients with good, moderate or poor QoL has not been determined.To determine a cut-off score for the MLHFQ based on the neural network (NN) approach. These cut-off scores will help discriminate between HF patients having good, moderate or poor QoL.This research was carried out in the context of a longitudinal cohort study of new patients attending specialized HF clinics in six participating centers in Quebec, Canada. Patients completed a questionnaire that included the MLHFQ. In addition to this scale, self-perceived health status and clinical information related to the severity of HF were obtained including: the New York Heart Association (NYHA) functional class, 6 minute walk test and survival status. We analyzed the database using NN and conventional statistical tools. The NN is a statistical program that recognizes clusters of MLHFQ and relates similar QoL measures to one another. Among the 531 eligible patients, 447 patients with complete questionnaires were used to build randomly two sets for training (learning set) and for testing (validation set) the NN.Participants had a mean age of 65 years and 24% were women. The median MLHFQ score was 45 (inter-quartile range: 27 to 64). NN identified 3 distinct clusters of MLHFQ that represent the full spectrum of possible scores on the MLHFQ. We estimated that a score of24 on the MLHFQ represents a good QoL, a score between 24 and 45 represents a moderate QoL, and a score45 represents a poor QoL. Validation with the different severity measures confirmed these categories. These cut-offs allowed us to reach a good total accuracy (91%). These cutoffs were strongly correlated with survival status (p = 0.004), self-perceived health status (p = 0.0032), NYHA functional class (p0.0001) and standardized 6 minutes walk test (p = 0.05)The identification of three levels of MLHFQ should be useful in clinical decision making.

Continuous whole-body PET scanning, continuous bed motion (CBM) acquisition has a number of advantages over the traditional step-and-shoot (SS) mode. Strengths of CBM include a uniform axial signal-to-noise ratio, continuous sampling in the axial direction that reduces resolution artifacts, reduction of noise from detector normalization, and reduction of sensitivity to small patient movements. This work highlights the acquisition and data handling methodology that was implemented for a series of phantoms and over 40 patient studies acquired on a high resolution, 16-slice LSO combined PET/CT scanner (CPS Innovations, Knoxville, TN). CBM data were acquired in 32-bit listmode with the bed moving at a constant speed of typically 0.6 mm/s to match the acquisition time per plane of the SS mode. CBM data were processed using the novel, virtual scanner concept that can be applied to a scanner of any axial length. For the high resolution scanner, the LSO PET detectors are arranged in a truncated spherical geometry and therefore normalization and geometrical corrections are applied on an event-by-event basis during histogramming of the 32-bit listmode data. Scatter correction is calculated on the entire image volume, in contrast to the SS mode where scatter is estimated for each bed position. The final 3D data set was reconstructed using ordinary Poisson OSEM3D. This paper will present results from phantom studies and compare clinical patient scans acquired in both SS and CBM modes

Four generations of PET scanners have emerged since the first clinical PET system. In this paper we predict the achievable performance of a fifth generation PET scanner, defined as a fully 3D system with no septa, an axial FOV approaching 30 cm with a spatial resolution mainly dictated by the positron physics. The predictions are based on the HIREZ (CPS/Siemens) performance plus current insights in detector technology, electronics and image reconstruction. The HIREZ system uses LSO scintillators, providing fast timing, good energy resolution, high spatial resolution and high system live time. LSO is an excellent candidate for a TOF detector with a proven 400 ps time resolution for detector blocks in coincidence. We have considered and integrated improvements that can be made to the key components necessary to the design of a fifth generation PET scanner. The spatial resolution can be improved by using a finer detector grid. The time window can be reduced. Packing fraction can be increased. The axial extension can be increased, giving more solid angle coverage and therefore better NEC. Based on the predicted gains in reduced randoms, dead time and TOF advantages, we have made initial simulations of the NEC for different axial field of views. An axial extension of /spl sim/32 cm with ECAT EXACT ring geometry gives at least four times higher NEC count rate than for a 16 cm axial FOV system. This will be combined with the improved image quality due to higher spatial sampling and TOF.

High spatial resolution dynamic brain PET imaging with the ECAT HRRT scanner with short frame durations is characterized by very few counts per sinogram bin due to the small size of the crystal surface. The use of various weighting schemes for OSEM-3D can result in significantly different results. In particular, the correction for random and scattered coincidences prior to the reconstruction can lead to a systematic positive bias in the reconstructed image. We show that the use of Ordinary Poisson OSEM-3D, where all corrections are applied during the iterative steps, allows to avoid this bias without compromising spatial resolution, at a price of a lower convergence rate.

One distinctive feature of processing faces, as compared to other categories, is thought to be the large dependence on configural cues such as the metric relations among features. To test the role of low spatial frequencies (LSFs) and high spatial frequencies (HSFs) in configural and featural processing, subjects were presented with triplets of faces that were filtered to preserve either LSFs (below 8 cycles per face width), HSFs (above 32 cycles per face width), or the full frequency spectrum. They were asked to match one of two probe faces to a target face. The distractor probe face differed from the target either configurally, featurally, or both featurally and configurally. When the difference was at the configural level, performance was better with LSF faces than with HSF faces. In contrast, with a featural difference, a strong performance advantage was found for HSF faces as compared to LSF faces. These results support the dominant role that LSFs play in the configural processing of faces, whereas featural processing is largely dependent on HSFs.

We present a method of performing fully 3D OSEM reconstruction using projectors based on data acquired by planar detector arrays. By using a special choice of parameters to index a line of response (LOR) for a pair of planar detectors, rather than the conventional parameters used for a circular tomograph, all the LORs passing through a point in the field of view (FOV) lie on a 2D plane in the 4D data space. This approach, the 'planogram method' is a 3D extension of the 2D-linogram technique of Edholm. The key point is where the integration along a sinusoid in the standard approach becomes integration along a line in the planogram data sets resulting in fast and accurate reconstruction operators. We used matched back-projection and forward-projection operators based on a voxel-driven approach to implement fully 3D OSEM. Analytical simulations of noiseless and noisy data sets were used to validate the 3D algorithm. The test object is a 320 mm diameter sphere filled with 40 mm diameter hot and cold lesions. The contrast between the hot lesion and the surrounding background was 2:1. The reconstructed image of noiseless data presents no significant artifacts. We show that the convergence of the algorithm for hot lesions is faster than for the cold lesions and reach a plateau after 30 equivalent EM-ML iterations. The computing time for each iteration on a 1Gh PC based platform is less than 15 minutes.

Previous publications introduced an array of collimated coincidence point sources for transmission imaging in PET. The design of the point source array matches transmission lines-of- response with emission ones in direct planes. The attenuation map is reconstructed front transmission projection data collected with single slice rebinning and nearest neighbor approximation imposed by the matching with emission acquisition geometry. Since transmission measurements are performed with an axially focused converging geometry, the goal of this work is to investigate potential improvements in attenuation map reconstruction by using an iterative cone beam reconstruction whose parameters depend on number of sources, source position and collimator design. By using Defrise's and anthropomorphic phantoms we demonstrated that iterative cone beam reconstruction improves axial resolution in the region between point sources when compared with present data processing.

This paper describes design strategies and algorithms which have been developed for visualization. registration, Volume of Interest (VoI) definition and measurements on multimodality single subject head and neck CT, MR, PET and surgical tumor specimen images. This work was part of a project that measured the usefulness of MR and PET images in three-dimensional radiotherapy treatment planning which was originally based only on CT images. The VoIs. which could be defined on any of the registered volume. were exported with the CT images to the treatment planning system, using DICOM. The major problem was the handling of large datasets with big differences in FOV and voxel sizes. We used object-oriented design and C++ programming language to develop object classes and methods for efficient data management. We used the eXtensible Markup Language (XMEL) standard to save the registration transformers and the VoIs. The registered volumes were resliced on the fly for visualization or VoI statistical information computing. Therefore, we avoided creation of large resliced dataset files. We used the new classes to extend two existing applications: interactive registration and RoI drawing. The paper describes: (i) the data handling problems.. (ii) the developed objects relationship and methods and (iii) the two applications.

A dedicated whole human brain positron emission tomograph (PET), the High Resolution Research Tomograph (ECAT HRRT) is utilized to evaluate attenuation correction using single photon based transmission scanning. The patented transmission procedure uses a 740 MBq Cs-137 point source, which is extended into the FOV and collimated to flood the opposing detectors only. An attenuation map is then calculated iteratively using a blank and transmission scan, scaled to 511 keV, and re-projected using inverse Fourier rebinning to estimate the 3D attenuation correction. We have evaluated the accuracy of the single-based transmission procedure and attenuation correction process. In particular, we compare variance weighted OSEM and a dedicated TR algorithm with regularization (MAP-TR) for the reconstruction of the /spl mu/-image. Contamination from emission is estimated from a mock scan without moving the source. Results of a measurement of the patient dose during HRRT transmission scans show a 4 times lower dose compared to patient transmission scans on the ECAT HR.

Registration of three-dimensional medical image modalities (PET and MRI) of the human brain is performed by a multi-scale morphological shape description combined with 3D Chamfer matching. Objects of Interest are first segmented. For MR images of the head, a Directional Watershed algorithm is used to obtain an accurate segmentation of the brain. PET images are segmented by thresholding combined with region growing. The shape description is then performed by generalized morphological skeletons, introduced in this article, providing a multi-scale representation of the object shape. Registration is finally operated by Chamfer matching, using a rigid transform for PET-MRI registration. Non-rigid registration is also evoked.

A method of scatter correction using dual energy window acquisition was studied on a Siemens/CTI 953B brain scanner operated without septa. The basis of the method is to determine the scatter component by direct measurement using improved block detector spectroscopy. Unscattered events are derived from a knowledge of the ratios, between the two windows, of scattered events (R/sub sc/) and unscattered events (R/sub unsc/) The upper (photopeak) window was set at 380-850 keV and the lower window accepted coincidences where one or both photons deposited energy between 200 and 380 keV. The choice of windows is a compromise between maximizing counting statistics and minimizing the spatial variation of R/sub unsc/. Transaxially R/sub sc/ does not vary significantly over the central 10 cm of a 20-cm cylinder either for a central line source or uniformly distributed activity. The variation is similar for a 15-cm cylinder with the absolute level about 10% lower. R/sub unsc/ is practically flat over the 40-cm transaxial FOV (field of view). There is a systematic axial variation in R and R/sub unsc/ which follows the block detector structure but which can be allowed for by interplane normalization. In phantoms with asymmetric and uniform activity distributions this method of correction shows good improvement in contrast. >

PET images suffer from statistical fluctuations where pixels representing the same tissue present different amplitudes, especially in short frames acquired in dynamic studies. Another difficulty is the time consuming in fitting images pixel by pixel in order to obtain parametric images. In the present work, a flexible method based on spatial and temporal pixel variance to compute parametric images is reported. For fluorodeoxyglucose and [/sup 15/O]-labeled water brain studies, a template image is obtained using: (1) summed frames, (2) thresholds to exclude background, (3) segmentation based on coefficients of variation and correlation coefficients of neighboring pixels, and (4) parameter estimation by dynamic fitting (DYN) or autoradiographic (ARG) method. Visually better images and images of parameters other than regional cerebral metabolic rates for glucose (rCMRGlc) or regional cerebral blood flow (rCBF) are obtained. For comparison, rCMRGlc and rCBF in both DYN and ARG methods estimated from segmented and usual images are compared. The maximal relative error is found to be 4% for ARG rCMRGlc, 10% for DYN rCMRGlc, and 17% for DYN rCBF, while the F-test shows no difference between values estimated from segmented and usual images. This technique allows more accurate parameter estimation in a reduced computation time.

In order to characterize physiological cerebral activation or tissue response to a treatment, at least two FDG-PET studies are mandatory. In this work, a study of one hour duration with two injections at 30 min apart is reported. The separation of the two input curves (IC) consisted of fitting the blood curve corresponding to the first injection using spectral analysis, then estimating the second blood curve by removing the remnant of the first. Tissue time activity curves (tTAC) were fitted for the first 30 min using the first IC and were extrapolated till 60 min. This extrapolated part was removed from the tissue response to the second injection before being fitted using the second IC. Other data were obtained for simple injection from which regional cerebral metabolic rates for glucose (rCMRGlu) estimated from 0-30 min were compared to those obtained from 0-60 min. Maximal rCMRGlu differences in double injection with activation were found to be on the average four times higher than those from 0-30 and 0-60 min baseline simple injection. The method is expected to be more accurate to observe drug uptake or tumor response to a treatment.

Quantitative measurement of brain glucose metabolism with positron emission tomography (PET) and fluorodeoxyglucose (FDG) involves arterial blood sampling to estimate the delivery of radioactivity to the brain. Usually, for an intra-venous bolus injection of 30 sec duration, an optimal manual sampling requires more than 25 blood samples since a frequency of 1 sample every 5 sec or less is necessary to determine the peak activity in arterial plasma during the first 2 minutes after injection. In the present work, 13 standardized sampling times were shown to be sufficient to accurately define the input curve. This standardized input curve was subsequently fitted by a polynomial function for its rising part and by spectral analysis for its decreasing part. Using the measured, the standardized as well as the fitted input curves, the regional cerebral metabolic rate for glucose (rCMRGlc) was estimated in 32 cerebral regions of interest (ROIs) in 20 normal volunteers. Metabolic values were obtained by both the autoradiographic method (ARG) and the kinetic analysis of dynamic data (DYN). Comparison of rCMRGlc values obtained with the measured and the fitted input curves showed that both procedures gave consistent results, with a maximal relative error in mean rCMRGlc of about 1% in ARG and 2% in DYN studies. This input curve fitting technique which was not dependent on the peak time occurrence, allowed an accurate determination of the input curve shape from reduced sampling schemes.

A new algorithm for automatic and accurate segmentation of 3-D magnetic resonance images (MRI) is presented. It improves the classical watershed transformation (WST) whose results are inaccurate when applied on 3-D noisy data. It uses directional information and is less sensitive to noise since it does not require the gradient image. Initial results are presented.

A set of software tools has been developed to assist the neuro(physio)logist in the analysis of a series of cerebral images from single subjects by fusing sulci manually delineated on MRI brain surface into PET functional data. The procedure requires coregistered datasets and involves 4 steps: (i) segmentation of anatomical MRI data in order to extract the brain surface, (ii) generate the brain surface views by parallel ray casting, (iii) manual delineation of the relevant sulci from the surface views and (iv) fusion of the landmarks into any coregistered dataset from the same subject. The brain surface is segmented automatically from 3D MRI data using a new "Directional Watershed Transform" algorithm. From the segmented brain surface, 8 orthogonal surface views are calculated as visual support for interactive stereo definition of the major brain sulci. Each sulcus is built as a 3D trace line using a few vertices which are manually defined on one or several surface views. This technique allows one to follow the brain surface curvature rather independently of the number and the position of the vertices. The sulci are saved in an individual file for further use. The brain surface viewer is linked (via the 3D cursor position) to an independent volume viewer containing a coregistered (anatomical or functional) volume. Sulcal landmarks are finally projected onto this volume allowing further volume of interest definition. The use of the tool set is illustrated by a single subject brain activation study after /sup 15/O water injection.

The Fourier rebinning algorithm has been implemented to reconstruct 3D PET data from the 24 ring scanner ECAT EXACT HR. The performance of the algorithm is studied using measurements of line sources, of uniform cylinders and of an FDG brain scan. Both the resolution and the signal-to-noise ratio are as good as those obtained with the standard reprojection algorithm (3DRP) algorithm, and the noise structure is also very similar. Low level ring artefacts are observed in the difference image between the FORE and the 3DRP reconstructions.

With the advantages of the increased sensitivity of 3D PET imaging for wholebody imaging come the challenges of more complicated quantitative corrections, and in particular an increase in the random coincidence field of view (FOV) relative to the true coincidence FOV. The most common method of correcting for random coincidences is the on-line subtraction of a delayed coincidence channel, which does not add bias but increases noise. An alternative approach is the post-acquisition subtraction of a low noise random coincidence estimate, which can be from a smoothed delayed coincidence channel, a calibration scan, or directly estimated. Each method makes different tradeoffs between noise amplification, bias, and data processing requirements. These tradeoffs are dependent on activity injected, the local imaging environment (e.g. near the bladder), and the reconstruction algorithm. Using 3D wholebody simulations and phantom studies, we show that the gains in sinogram NEC by using a noiseless random coincidence estimation method are translated to improvements in image SNR. The image SNR, however, depends on the image reconstruction method and the local imaging environment. For 3D wholebody imaging, a low noise estimate of random coincidences based on the single photon rates improves sinogram and image SNRs by approximately 15% compared to on-line subtraction of delayed coincidences, and performs only slightly worse than using a 3D extension of the Casey-Hoffman smoothing of a separately acquired delayed coincidence sinogram.

Various strategies were investigated to reconstruct 3D data from the HRRT, the LSO brain PET installed at the MPI. In this octagonal geometry, the sampling is not complete due to the gaps between flat panel detectors. The standard reconstruction scheme uses a gap-filling step followed by Fourier rebinning (FORE) and attenuation-weighted (AW) OSEM. Scatter correction is performed the single scatter simulation (SSS) approximation. The authors propose the use of 3D weighted OSEM schemes which do not require gap-filling or FORE and which are not sensitive to noise and bias due to those approximations. When list mode data were sorted as true coincidences, the attenuation and normalization OSEM scheme was used. The image from the first iteration was corrected for scatter using the SSS algorithm. The scatter image was used at subsequent iterations to estimate a scatter sinogram. The use of a shifted Poison scheme was precluded since information from singles was missing. When list mode data were sorted as prompt and separate delayed coincidences, an ordinary Poisson scheme was implemented. Images obtained with OSEM 3D were better than those obtained with the standard scheme and were reconstructed at high spatial resolution with 3 iterations and 16 subsets in about 13 hours on a Compaq XP1000 (EV67) workstation.

Iterative reconstruction techniques are usually too time consuming on most single processor machines that are affordable. This is especially true for the HRRT (High Resolution Research Tomograph) which produces huge sinogram data in order to take full advantage of its enhanced resolution. The use of Fourier Rebinning (FORE) in a preprocessing step is the basis for a simple cluster computing approach. The authors were able to scale down the reconstruction time with implementations utilizing RPC and Syngo mechanics, resp. on Windows NT networks.

Presents a 3D whole-body PET simulator that generates multiple, yet statistically accurate, realizations of projection data within a computation time that is short enough to enable the measurement of the task performance of image reconstruction algorithms. The whole-body simulator takes into account the following effects: the separate amounts of statistical noise contributed by true, scattered, and random coincidences, activity outside the field of view, activity decay between bed positions, detector efficiencies and resolution, and noise arising from the transmission scan. The principle of the simulation is to analytically calculate projections based on the geometrical specification of the emission and attenuation objects that comprise the MCAT phantom. A pre-determined level of statistical noise is then added to the projection data, which is then inputted to the same data correction and image reconstruction procedures used in practice. The authors compare the results of multiple realizations of simulated and measured phantom studies at statistical noise levels similar to those encountered in 3D whole-body PET scanning. They obtain comparable statistical noise properties for the fully corrected emission sinograms, and also show that a simple model accurately predicts the statistical noise added by random and scattered coincidences generated by activity outside the field of view.

For count-limited PET imaging protocols, two different approaches to reducing statistical noise are volume, or 3D, imaging to increase sensitivity, and statistical reconstruction methods to reduce noise propagation. These two approaches have largely been developed independently, likely due to the perception of the large computational demands of iterative 3D reconstruction methods. The authors present results of combining the sensitivity of 3D PET imaging with the noise reduction and reconstruction speed of 2D iterative image reconstruction methods. This combination is made possible by using the recently-developed Fourier rebinning technique (FORE), which accurately and noiselessly rebins 3D PET data into a 2D data set. The resulting 2D sinograms are then reconstructed independently by the ordered-subset EM (OSEM) iterative reconstruction method, although any other 2D reconstruction algorithm could be used. The authors demonstrate significant improvements in image quality for whole-body 3D PET scans by using the FORE+OSEM approach compared with the standard 3D Reprojection (3DRP) algorithm. In addition, the FORE+OSEM approach involves only 2D reconstruction and it therefore requires considerably less reconstruction time than the 3DRP algorithm, or any fully 3D statistical reconstruction algorithm.

When this journal appeared as the Journal of Chronic Diseases, major reviews were published from time to time that summarized the state of science about a particular topic or a current issue. Although the editorial policy then and now has given reports of original research the highest priority, our readers have always appreciated the value and convenience of summary, synthesis and interpretation afforded by papers such as this Commentary by Sniderman and his colleagues. As usual, letters and other comments will be welcome. W.O.S.

A method is presented for the measurement of cerebral blood flow (CBF) with a bolus of water labelled with oxygen 15. The method, which has been evaluated in normal volunteers, is based on Kety's model, with two additional parameters to account for the difference in the time of tracer arrival in the radial and carotid arteries ("delay") and for dispersion of the tracer in the body and/or blood counting systems. It combines the advantages of: (i) dynamic data collection for estimation of delay and dispersion; (ii) robustness and linearity of CBF estimates with an integral method; and (iii) simplicity of continuous external monitoring of arterial blood radioactivity, particularly with repeated measurements. An optimized protocol is proposed for routine applications in neurological and neurophysiological studies.