Myocardial work analysis for early detection of type 1 CTRCD and patient risk stratification

Aim

This prospective longitudinal study analyses the potential role of Myocardial Work in early detection of cardiotoxicity during chemotherapy and its added value for prognosis and patients' risk stratification.

Methods

We enrolled 47 consecutive female patients with HER2-positive breast cancer referred for anti-cancer therapy based on anthracycline and taxane. Patients with depressed LV function at baseline were excluded. Medical therapy, clinical parameters and echocardiographic data were recorded at baseline and at 3, 6, 12 months follow-up. Additionally, cuff blood pressure was measured at the time of 2D-TTE examination and adequate echocardiographic images were stored for off-line analysis.

Results

CTRCD was detected in 17 patients (36%) while 30 patients remained free of CTRCD (64%). There were no intergroup differences for age, body mass index, resting heart rate and brachial arterial pressure. Both groups presented unaltered LV systolic function after 3 months follow-up yet overt cardiac dysfunction showed up in the CTRCD group at 6 months with significant decline in LVEF, GLS, MWI, MWE and CW from baseline values (LVEF, %: 56.0±4.1 vs 52.2±6.5; GLS, %: −20.9±1.9 vs −17.6±3.2; MWI, mmHg%: 2125±348 vs 1704±620; MWE, %: 95±2.6 vs 93±3.9 and CW, mmHg%: 2562±3567 vs 2212±455, p<0.05). Additionally, GLS, MWI and MWE at 6 months were significantly worse in the CTRCD group vs non-CTRCD group (GLS, %: −17.6±3.2 vs −20.6±1.8; MWI, mmHg%: 1704±620 vs 2087±347; MWE, %: 93±3.9 vs 96±1.5, p<0.05). Depressed LV systolic function persisted after 1 year follow-up (Figure 1). After 3 months, only de relative change in GLS and WW from baseline were significantly worse in CTRCD vs non-CTRCD (ΔGLS: +3.7±11 vs −3.9±10, ΔWW: +46.1±83 vs +2.2±45). Whereas no correlation was found, the combination of both ΔGLS and ΔWW at 3 months showed stronger prognostic value for CTRCD than each parameter alone, AUC of 0.72 (Figure 2).

Conclusion

These findings point the superiority of Myocardial Work for early type 1 CTRCD detection in comparison to the current diagnostic tools. Additionally, we suggest the add-on value of ΔWW on top of ΔGLS quantification for better patient risk stratification. These are promising results for better clinical surveillance of cardiac function during cancer treatment.

Funding Acknowledgement

Type of funding sources: None.

Global longitudinal strain and NT-proBNP as predictors for LV function recovery after TAVR

Introduction

Abnormal GLS values as well as high plasma levels of NT-proBNP previous to TAVR are independent predictors for higher peri-procedural mortality. Moreover, in a subgroup of TAVR patients LV function does not recover following the procedure. Until today, it is still unclear how to predict impaired post-procedural LV function for optimal clinical patient's management.

Purpose

This study was set up to assess the predictive value of baseline GLS and NT-proBNP levels on LV function recovery (LVfr) in a cohort of patients with severe AS referred for TAVR.

Methods

A total of 25 patients (9 male, 84±5 yo, EF 50±11%) with severe AS (AVA 0.6±0.3 cm2, MPG 49±16 mmHg) referred for TAVR were included. Blood analysis and TTE were performed before intervention (baseline, bl) and at follow-up (fu). Myocardial work was analysed offline integrating the longitudinal strain and afterload pressure (SBP + AVPmean). LVfr was defined as GLS <−19% at fu. The median values at bl of NT-proBNP (1781 ng/L) and GLS (−15%) were taken as cut-off to categorize patients in 4 groups: NT-proBNPhighGLShigh, NT-proBNPlowGLShigh, NT-proBNPhighGLSlow and NT-proBNPlowGLSlow. The ROC curve analysis for prediction of LVfr after TAVR were performed.

Results

LV function recovered in 13 patients (52%). Despite similar EF and global MWI after TAVR, the LV contraction became more efficient as evidenced by a significant improvement (bl vs fu, p<0.05) in GLS (−14±4.5 vs −18±4.2%), MWW (400±510 vs 157±107 mmHg%) MWE (88±6 vs 92±6%) together with a reduction in afterload pressure (203±38 vs 156±22 mmHg, p<0.05). In the NT-proBNPlow groups, GLS (−15±4 vs −20±3%, p<0.05) and MCW (2166±874 vs 2978±634 mmHg%, p<0.05) at fu were significantly better when compared to the NT-proBNPhigh groups. Likewise, the GLSlow groups showed higher EF (47±10 vs 54±6%, p<0.05) and MCW (2181±832 vs 2961±715 mmHg%, p<0.05) than the GLShigh groups at fu. Interestingly, the GLSlow groups had lower LVESV (57±38 vs 29±10 ml, p<0.05) and LVEDV (113±49 vs 80±20 ml, p<0.05) post-TAVR than the GLShigh groups which suggests a positive remodelling following afterload reduction. At the ROC curve analysis, combined GLS and NT-proBNP at bl were better predictors for LVfr than each parameter alone, AUC 0.86 (Fig. 1). Additionally, only 20% LVfr was seen in the NT-proBNPhighGLShigh group in contrast to 67–75% in the other groups.

Conclusion

Elevated afterload in severe AS leads to a physiological reduction of GLS. Although the decrease in afterload after TAVR beneficially affects GLS and may lead to LVfr, this was not observed in a subgroup of patients with high NT-proBNP levels in whom GLS remained impaired at follow-up. We speculate that myocardial tissue damage and fibrosis due to long lasting high pressure exposure may partly be responsible for this observation. The combination of pre-procedural NT-proBNP levels and GLS shows strong predictive potential for LVfr after TAVR and larger studies are warranted for further evaluation and cut-off values determination.

Funding Acknowledgement

Type of funding sources: Foundation. Main funding source(s): Cardiovascular Research Center Aalst (npo)

Deep learning for mortality prediction in patients with a de-novo or worsened heart failure

Background

Heart failure (HF) is a heterogenous syndrome with complex pathophysiology. Biomarkers and clinical risk scores often fail to provide optimal patient-level precision in the prognostic stratification. As utilizing single observational timepoint, they do not capture the entire care pathway with variations in individual patient management. Electronic patient records provide an opportunity to develop new artificial intelligence (AI) strategies for comprehensive prognostic re-stratification reflecting diagnostic and therapeutic management.

Purpose

We sought to use deep artificial intelligence (AI) and develop an unbiased predictive algorithm for all-cause mortality in a cohort of patients hospitalized with a de novo or worsened HF.

Methods

In a cohort of 2449 HF patients hospitalized between 2011–2017, we utilized 151 451 patient exams from 422 parameters. They included clinical phenotyping, medication, ECG, laboratory, echocardiography, catheterization data or percutaneous and surgical interventions gathered on a routine clinical basis reflecting standard of care as captured in individual electronic records. The AI model development consisted of 101 iterations of repeated random subsampling splits into balanced training and validation sets.

Results

AI models yielded performance ranging from 0.83 to 0.89 AUC on the outcome-balanced validation set in predicting all-cause mortality at 30-, 90-, 180-, 360- and 720-day time-limits (Figure 1). The primary endpoint, 1-year mortality prediction model, recorded an 0.85 AUC accuracy. We observed stable model performance across all HF phenotypes: HFpEF 0.83 AUC, HFmrEF 0.85 AUC and HFrEF 0.86 AUC, respectively).

Conclusion

Our findings present a novel, patient-level, AI-based risk prediction of all-cause mortality in heart failure with a robust accuracy across its phenotypes. This suggests the potential of AI based predictive models in a point-of-care approach to guide clinical risk stratification.

Funding Acknowledgement

Type of funding sources: Foundation. Main funding source(s): VZW Cardiovascular Research Center Aalst

Role of myocardial work index in early detection of cardiotoxicity in breast cancer patient

Introduction

Breast cancer patients receiving anthracyclines are particularly prone to develop cancer therapeutics-related cardiac dysfunction. Early detection of cardiotoxicity onset is required for optimal timing of cardio protection treatment. The latest guidelines consider a relative reduction of 15% in global longitudinal strain (GLS) from baseline as risk for cardiotoxicity. Nevertheless, the more recent Myocardial Work Index (MWI) offers a load-independent tool for detection of subclinical heart failure (HF). However, data in cancer patients are still scarce.

Purpose

This study analyses the predictive value of MWI for cardiotoxicity diagnosis after 6 months chemotherapy.

Methods

The study population consists of breast cancer patients referred for chemotherapy with anthracyclines and taxanes. Patients with a history of HF previous to chemotherapy or depressed LV function at baseline were excluded. Echocardiography was performed before onset of the chemotherapy (baseline) and after 6 months follow-up. LVEF, GLS and MWI were assessed offline using EchoPAC software. The values at baseline and 6 months follow-up were pairwise compared to detect subclinical cardiac dysfunction. LVEF, GLS and MWI means at baseline were taken as cut-off to compare the predictive value of each parameter. Moreover, patients were categorized in one group with GLS reduction >15% (Group 1) and one group with GLS reduction <15% (Group 2).

Results

From April 2016 to July 2020, 28 women with breast cancer were included (age 54±11 years, LVEF 58±4%, GLS −21±2%, MWI 2160±308 mmHg). All patients underwent the same standard chemotherapy protocol (4xEC, 12xTaxol). No difference in baseline characteristics between group 1 (n=13) and group 2 (n=15) was observed. At 6 months follow up a significant decrease in LVEF (53±8%, p=0.003), GLS (−19±3%, p=0.002) and MWI (1920±391 mmHg, p=0.005) was shown without any change in blood pressure. However, while mean LVEF and GLS at baseline did not predict any significant change, patients with MWI under the mean value at baseline (n=15) presented significant lower LVEF (50±8 vs 57±6% p=0.006), GLS (−17±3 vs −20±2%, p=0.01), MWI (1733±320 vs 2136±362 mmHg, p=0.005) after 6 months. Additionally, both groups had similar MWI at baseline (2148±335 mmHg vs 2170±294 mmHg, p=0.85), whereas those patients with GLS reduction >15% showed significant lower MWI after 6 months (1694±332 mmHg vs 2116±334 mmHg, p=0.003, Figure 1).

Conclusions

At 6 months follow up, a decline of the LV systolic function as side effect of chemotherapy can be seen. MWI at baseline shows the best predictive value for development of cardiotoxicity, in comparison to LVEF and GLS. Further studies are warranted to better understand the role of MWI for early detection of cardiotoxicity and its clinical relevance.

Funding Acknowledgement

Type of funding sources: Private hospital(s). Main funding source(s): Onze-Lieve-Vrouw hospital in Aalst (Belgium)

Myocardial work index: a novel tool for detection of early cardiotoxicity in breast cancer patient

Funding Acknowledgements

Type of funding sources: Foundation. Main funding source(s): Cardiovascular Research Center Aalst, (Aalst, Belgium)

Introduction

Breast cancer patients receiving anthracyclines are particularly prone to develop cancer therapeutics-related cardiac dysfunction (CTRCD). Early detection of cardiotoxicity onset is required for optimal timing of cardio protection treatment. The latest guidelines consider a relative reduction of 15% in global longitudinal strain (GLS) from baseline as risk for cardiotoxicity. Nevertheless, the more recent Myocardial Work Index (MWI) offers a load-independent tool for detection of subclinical heart failure (HF). Data in cancer patients are still scarce. 

Purpose

This study analyses the predictive value of MWI for cardiotoxicity diagnosis after 6 months chemotherapy.

Methods

The study population consists of breast cancer patients referred for chemotherapy with anthracyclines and taxanes. Patients with a history of HF previous to chemotherapy or depressed LV function at baseline were excluded. Echocardiography was performed before onset of the chemotherapy (baseline) and after 6 months follow-up. LVEF, GLS and MWI were assessed offline using EchoPAC software. The values at baseline and 6 months follow-up were pairwise compared to detect subclinical cardiac dysfunction. Mean LVEF, GLS and MWI at baseline were taken as cut-off value to compare the predictive value of each parameter. Moreover, patients were categorized in one group with GLS reduction >15% (Group 1) and one group with GLS reduction <15% (Group 2).  

Results

From April 2016 to January 2020, 24 women with breast cancer were included (age 54 ± 11 years, LVEF 58 ± 4%, GLS -21 ± 2%, MWI 2181 ± 325 mmHg). All patients underwent the same standard chemotherapy protocol (4xEC, 12xTaxol). No difference in baseline characteristics between group 1 (n = 9) and group 2 (n = 15) was observed. At 6 months follow up a significant decrease in LVEF (53 ± 8%, p = 0.003), GLS (-19 ± 3%, p = 0.002) and MWI (1933 ± 410 mmHg, p = 0.005) was shown without any change in blood systolic pressure. However, while mean LVEF and GLS at baseline did not predict any significant change, patients with MWI under the mean value at baseline (n = 13) presented significant lower LVEF (49 ± 8%, p = 0.006), GLS (-18 ± 4%, p = 0.045), MWI (1753 ± 341 mmHg, p = 0.018) after 6 months. Additionally, both groups had similar MWI at baseline (2199 ± 390 mmHg vs 2170 ± 294 mmHg, p = 0.85), whereas those patients with GLS reduction >15% showed significant lower MWI after 6 months (1626 ± 344 mmHg vs 2116 ± 334 mmHg, p = 0.003, Figure 1).

Conclusions

At 6 months follow up, a decline of the LV systolic function as side effect of chemotherapy can be seen. In comparison to LVEF and GLS, MWI shows the best predictive value for development of early cardiotoxicity. Further studies are warranted to better understand the role of MWI in predicting CTRCD and its clinical relevance.

Abstract Figure. Change in MWI

P6316Hemodynamic response to rapid saline loading in heart transplant recipients

Introduction

A pulmonary capillary wedge pressure (PCWP) ≥25 mm Hg following volume load or exercise has been proposed as a partition value for detection of HfpEF. However, the hemodynamic response to volume challenge in heart transplant (Tx) recipients has never been studied.

Methods

24 heart Tx recipients (age: 65 years) with normal LV function (55±7%) and without rejection and graft vasculopathy underwent right heart catheterization to measure hemodynamic response to volume loading before and after a rapid saline infusion of 7mL/kg over 10 min. PCWP, right atrial pressure (RAP), mean pulmonary artery pressure (AP) were obtained and the PCWP and indexed (i) stroke volume (SV) data were used to construct Starling (SVindex/PCWP) curves. Pts were categorized in those with elevated filling pressures (Group A, n=13 pts) defined by a PCWP ≥15 mm Hg at rest or ≥25 mm Hg following volume loading vs those without (Group B, n=11 pts).

Results

No difference in age of donor and transplant heart, baseline hemodynamics and EF was noted between both groups. Saline infusion significantly increased PCWP and mean AP in both Groups (table 1) without any significant change in BP and heart rate. Interestingly saline infusion was associated with a significant rise in SV and SVi in Group B not in Group A pts. Moreover, in Group B pts the Starling curves revealed a larger SVi at any give PCWP compared to Group A pts (Fig.1).

Table 1 All (n=24) Group A (n=13) Group B (n=11) Baseline Volume Loading Baseline Volume Loading Baseline Volume Loading RAP (mm Hg) 5.3±4.1 9.2±4.8* 7.6±4.8 11.4±5.2* 3.8±2.5 7.3±1.9* Mean AP 18.4±5.4 24.1±5.9* 21.7±5.1 26.8±6.5** 14.9±2.4 20.8±2.6* PCWP 12.1±4.9 16.8±6.7* 15.0±4.9 19.8±6.5** 8.4±1.9 14.6±3.7* SV 71.4±19.6 72.5±23.6 73.2±6.2 72.4±6.2 69.2±14.6 79.2±3.9 SViml/m2) 37.4±9.2 37.9±11.2 36.7±7.1 38.7±9.9 35.3±6.0 40.5±5.2* *p<0.01 compared to baseline; **p<0.05 compared to baseline.

Figure 1

Conclusions

In the transplanted heart volume loading increases filling pressures and is able to unmask left ventricular diastolic dysfunction. Interestingly, those with HFpEF are characterized by a blunted Frank Starling response as evidenced by higher PCWP and failure to increase SV for any given PCWP. Further prospective studies are warranted to unravel the underlying mechanisms.

Transfer of normal 99mTc-ECD brain SPET databases between different gamma cameras

A stereotactic, normal perfusion database is imperative for optimal clinical brain single-photon emission tomography (SPET). However, interdepartmental use of normal data necessitates accurate transferability of these data sets. The aim of this study was to investigate transfer of three normal perfusion databases obtained in the same large population of healthy volunteers who underwent sequential scanning using multihead gamma cameras with different resolution. Eighty-nine healthy adults (46 females, 43 males; aged 20-81 years) were thoroughly screened by history, biochemistry, physical and full neurological examination, neuropsychological testing and magnetic resonance imaging. After injection of 925 MBq technetium-99m labelled ethyl cysteinate dimer (ECD) under standard conditions, 101 scans were acquired from all subjects (12 repeat studies) on a triple-head Toshiba GCA-9300A (measured average FWHM 8.1 mm). Ninety-one sequential scans were performed on a dual-head Elscint Helix camera (FWHM 9.6 mm) and 22 subjects also underwent imaging on a triple-head Prism 3000 (FWHM 9.6 mm). Images were transferred to the same processing platform and reconstructed by filtered back-projection with the same Butterworth filter (order 8, cut-off 0.9 cycles/cm) and uniform Sorensen attenuation correction (mu = 0.09). After automated rigid intrasubject registration, all subjects were automatically reoriented to a stereotactic template by a nine-parameter affine transformation. The databases were analysed using 35 predefined volumes of interest (VOIs) with normalisation on total VOI counts. For comparison, the high-resolution data were smoothed with a 3D Gaussian kernel to achieve more similar spatial resolution. Hoffman phantom measurements were conducted on all cameras. Partial volume effects after smoothing varied between -6.5% and 10%, depending on VOI size. Between-camera reproducibility was 2.5% and 2.7% for the Toshiba camera versus the Helix and the Prism database, respectively. The highest reduction in between-camera variability was achieved by resolution adjustment in combination with linear washout correction and a Hoffman phantom-based correction. In conclusion, transfer of normal perfusion data between multihead gamma cameras can be accurately achieved, thereby enabling widespread interdepartmental use, which is likely to have a positive impact on the diagnostic capabilities of clinical brain perfusion SPET.

Carbon-11 labeled tracers for in vivo imaging P-glycoprotein function: kinetics, advantages and disadvantages

P-glycoprotein (P-gp) is a drug efflux transporter with broad substrate specificity localized in the blood-brain barrier and in several peripheral organs. In order to understand the role of P-gp in physiological and patho-physiological conditions, several carbon-11 labelled P-gp tracers have been developed and validated. This review provides an overview of the spectrum of radiopharmaceuticals that is available for this purpose. A short overview of the physiology of the blood-brain barrier in health and disease is also provided. Tracer kinetic modelling for quantitative analysis of P-gp function and expression is highlighted, and the advantages and disadvantages of the various tracers are discussed.

FDG PET for monitoring response to local and locoregional therapy in HCC and liver metastases

Local ablative therapies and loco-regional therapies are being increasingly used for the purpose of providing local control of primary liver tumors and liver metastases while sparing normal liver tissue. In this manuscript, literature on the use of fluorodeoxyglucose positron emission tomography (FDG PET) to monitor local and loco-regional treatment for hepatocellular carcinoma (HCC) and liver metastases, mainly limited to radiofrequency ablation (RFA) and selective internal radiation therapy (SIRT) is reviewed. Available data obtained primarily in secondary liver tumors and to a lesser extent in HCC support the notion that FDG PET performed early after RFA provides additional information about the efficacy of local tumor ablation by differentiating post-treatment changes from residual or recurrent malignant tumor. In addition, FDG PET was shown to have an added value for the detection of tumor recurrence. Thus, FDG PET imaging may not only improve treatment evaluation but also provide an opportunity for early re-intervention following RFA. Potential problems that might occur when using FDG PET for the purpose of evaluation of RFA are false negative results due to partial volume effect when dealing with small lesions (<1 cm) or due to diabetes and false positive results due to abscess formation. Larger studies are warranted to confirm these promising

RESULTS

With regard to SIRT, several studies, almost exclusively performed in patients suffering from liver metastases, have addressed the feasibility of using FDG PET for the assessment and quantification of metabolic response of SIRT with (90)Y-microspheres. These studies consistently show that traditional morphological imaging, computed tomography/magnetic resonance imaging, is insensitive in monitoring response, owing to the presence of necrosis, edema, hemorrhage and cystic changes, when compared to metabolic imaging. Thus, in view of the lack of reliability of tumor markers and/or the potential for delineating the presence of extra-hepatic metastatic cancers in these patients, when confirmed by additional studies, FDG PET may prove to be an excellent adjunct for assessing response following SIRT of liver metastases.

Synthesis and evaluation of a 99mTechnetium labeled chitin-binding protein as potential specific radioligand for the detection of fungal infections in mice

AIM

Radiopharmaceuticals can be used to exploit differences between microorganisms in order to distinguish fungal from bacterial infection. Chitin, abundant in the cell wall of fungi, is not present in mammalian or bacterial cells and therefore represents a highly specific target to localize fungal infection. In this study, we have examined the potential of chitin-binding protein (CBP21) from Serratia marcescens as a specific radiotracer for the detection of invasive fungal infections.

METHODS

CBP21 was labeled with 99mTc via hydrazinonicotinamide (HYNIC) and its characteristics were analyzed. In vitro binding studies with polymorphic chitin forms and microorganisms (fungi as well as bacteria) were performed. In vivo biodistribution of the compound was studied in immunocompromised mice with bacterial and fungal infections in the left and right thigh muscle, respectively, using 99mTc-HYNIC-myoglobin as size-matched control and 67Ga-citrate as positive control. Scintigraphic images were acquired at 1 and 7 h postinjection of the tracer.

RESULTS

99mTc-HYNIC-CBP21 was labeled with a radiochemical yield of 61% and a specific activity of 22.3 MBq/nmol. Highest in vitro binding percentages were found with beta-chitin (86.8+/-2.4%). Binding interactions to fungi were higher than to bacteria (P<0.05). In vivo, best ratios of fungal infection versus bacterial infection were seen at 5 and 7 h (3.6+/-1.2 and 2.9+/-1.4, respectively) postinjection of the tracer. Maximum uptake of the tracer in fungal infections (0.63+/-0.11%ID/g) at 7 h was significantly (P<0.05) higher than uptake seen in bacterial infections (0.34+/-0.11%ID/g) or the uptake of 99mTc-HYNIC-myoglobin (P<0.05) in the same infections (0.35+/-0.11%ID/g, respectively, 0.3+/-0.01%ID/g).

CONCLUSIONS

This study shows that 99mTc-HYNIC-CBP21 is able to specifically interact with chitin in vitro. Scintigraphy and postmortem in vivo data indicate that 99mTc-HYNIC-CBP21 is able to distinguish fungal infection from bacterial infection probably due to a specific interaction of the protein with the chitin in the fungal cell wall.

The effect of citalopram hydrobromide on 5-HT2A receptors in the impulsive-aggressive dog, as measured with 123I-5-I-R91150 SPECT

PURPOSE

Involvement of the serotonergic system in impulsive aggression has been demonstrated in both human and animal studies. The purpose of the present study was to investigate the effect of citalopram hydrobromide (a selective serotonin re-uptake inhibitor) on the 5-HT(2A) receptor and brain perfusion in impulsive-aggressive dogs by means of single-photon emission computed tomography.

METHODS

The binding index of the radioligand (123)I-5-I-R91150 was measured before and after treatment with citalopram hydrobromide in nine impulsive-aggressive dogs. Regional perfusion was measured with (99m)Tc-ethyl cysteinate dimer (ECD). Behaviour was assessed before treatment and again after 6 weeks of treatment.

RESULTS

A correlation was found between decreased binding and behavioural improvement in eight out of nine dogs. The 5-HT(2A) receptor binding index was significantly reduced after citalopram hydrobromide treatment in all cortical regions but not in the subcortical area. None of the dogs displayed alterations in perfusion on the post-treatment scans.

CONCLUSION

This study supports previous findings regarding the involvement of the serotonergic system in impulsive aggression in dogs in general. More specifically, the effect of treatment on the 5-HT(2A) receptor binding index could be demonstrated and the decreased binding index correlated with behavioural improvement.

Compression and reconstruction of sorted PET listmode data

BACKGROUND

In nuclear medicine data can be stored in histogram or listmode format. The most popular histogram format is the planar projection format. Due to the increase in detector blocks, the improved energy resolution and the trends towards time of flight, dynamic and gated imaging, it can be more appropriate to store the data in listmode format. The size of the storage in this format increases linearly with the number of properties (positions, energy, time info) while the histogram format increases exponentially. However, the datasize of listmode data also increases linearly with the number of coincidences. Due to the high number of counts in 3D PET this will lead to very large datasets. Therefore a good compression algorithm for listmode data is very important.

METHODS

A sorting and compression method is proposed to reduce the amount of space needed to store the listmode dataset. One event is represented by one number without any information loss compared to the original listmode file. The next step is to sort all events into an array of increasing numbers. These data are compressed by the gzip routine. One of the advantages of 3D PET listmode reconstructions is that they result in a more uniform resolution across the field of view (FOV), which is not always true for other reconstruction algorithms. This improved resolution is shown for the listmode data of a gamma camera operating in PET mode.

RESULTS

First the effect of positional accuracy in the listmode dataset is evaluated by comparing resolution in the reconstructions. It is shown that the highest accuracy is not necessary and a significant reduction in the size of the dataset can be obtained prior to lossless compression. A further reduction can be obtained by using the proposed sorting and compression techniques. It is shown that the storage space decreases linearly with the logarithm of the number of coincidences. The compression obtained by different acquisition matrices was compared. Finally it is shown that the 3D listmode reconstruction of sorted listmode data is faster because of improved cache behaviour. The method can be applied to any kind of listmode data. The compression factors will improve when the ratio of measured events to possible events increases.

Registration accuracy of 153Gd transmission images of the brain

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 (ECD) images and to assess whether normalised mutual information (NMI) or count difference (CD) should be 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). Scheffe post hoc tests were performed.

RESULTS

No significant differences were found between ECD/CD, ECD/NMI and TCT/CD, suggesting that ECD registration can be 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 be avoided.

Regional cerebral blood flow and episodic memory in Parkinson's disease: a single photon emission tomography study

In this paper we examined 46 nondemented Parkinson's disease (PD) patients by means of perfusion single photon emission computed tomography (SPECT) and neuropsychological testing. The aim was to detect correlations of regional cerebral blood flow with episodic memory performance, using an operator-independent technique for the analysis of SPECT data. A significant positive correlation was found between prefrontal blood flow and episodic memory performances. However, age was the most important determinant of memory scores. Age also correlated significantly negatively with prefrontal perfusion. Our methodology also allowed detection of an inverse correlation of left medial temporal lobe perfusion with the memory score. This had not been found in previous studies and might indicate compensatory mechanisms in the brain of PD patients. It is concluded that episodic memory in nondemented PD patients is most dependent on the effects of aging and that the aging effects on cerebral perfusion in the PD brain parallel to a large extent the findings in normal controls.

Regional binding index of the radiolabeled selective 5-HT2A antagonist 123I-5-I-R91150 in the normal canine brain imaged with single photon emission computed tomography

The pattern of the specific 5-HT2A (5-hydroxytryptamine 2A receptor) antagonist 123I-5-I-R91150 was measured in 10 healthy dogs without neurologic and behavior abnormalities. Eight cortical regions (left and right fronto-, temporo-, parieto-, and occipitocortical area), one global subcortical region (including the thalamic system) were compared with a reference region lacking receptors; that is, the cerebellum. The 123I labeled radioligand was injected intravenously 100-200 minutes before acquisition. Both transmission and emission data were obtained with a triple head gamma camera equipped with high-resolution fanbeam collimators. The emission data were corrected for scatter and attenuation. To delineate different cerebral regions more accurately, the regions of interest (ROI) defined in a former study on brain perfusion measured with 99mTc-ethyl cysteinate dimer (ECD) in the same dogs were used. The co-registration of the 99mTc-ECD and the 123I-5-I-R91150, obtained from each dog, was realized with the help of corresponding transmission maps. By normalizing each regional cerebral activity to the activity observed in the cerebellum, the regional radioactivity (binding index) could be relatively quantified. Highest brain uptake was noted in the frontocortical brain areas (right: 1.85, left: 1.89), followed by the temporocortical region (right: 1.58, left: 1.56). Least uptake was noted in the more caudal and middle brain regions [occipito- (right: 1.46, left: 1.41), parietocortical (right: 1.30, left: 1.26), and striatal region (1.19)]. No gender nor age influence was noted in this series. The 123I labeled serotonin-2A receptor ligand seems to have similar cortical binding in the normal canine brain, as shown in humans and other animal species. A frontocortical to occipitocortical (rostrocaudal) binding index gradient was identified within the dog, which has not been seen in imaging studies from humans and other animal species. The significance of these results will need further investigation. This normative data can be used to compare regional brain uptake of the 123I-radioligand to dogs with behavioral disorders related to the serotonergic system, in future studies.

Biodistribution and displacement studies of the selective 5-HT2A receptor antagonist 123I-5-I-R91150 in the normal dog

There is increasing interest in mapping receptors in vivo by using functional imaging modalities such as single photon emission tomography (SPET) and positron emission tomography (PET). Since SPET is a more accessible functional imaging modality than PET and, overall, it is more economical, radioligands suitable for this technique are in greater demand. Recently, 123I-5-I-R91150, a radioligand with high selectivity and affinity for 5-HT(2A) receptors in the brain, was introduced for SPET. This study reports on the whole-body distribution and brain uptake of the selective 123I-5-I-R91150 ligand in four normal dogs. The frontal to cerebellar ratio of uptake in time was determined in three dogs. Time-activity curve of venous blood was determined in one dog. Maximal global brain uptake was found at 10-60 min post-injection. Higher brain uptake was noted in the frontal cortical areas compared to the cerebellum. The frontal-cerebellar ratio reached the highest values at 90-180 min. Reversibility and pharmacological selectivity of ligand binding was demonstrated through displacement and blocking studies with the 5-HT(2A) receptor antagonist ketanserin. This study demonstrates that the specific 5-HT(2A) iodinated ligand can be used for imaging and semi-quantification of the 5-HT(2A) receptors in the canine brain in vivo by using SPET.

SPECT neuropsychological activation procedure with the Verbal Fluency Test in attempted suicide patients

Performance on the Verbal Fluency Test, as a measure of the ability of initiating processes, is reduced in depressed suicidal patients. The hampered results in this prefrontal executive task parallel the reduction in prefrontal blood perfusion and metabolism in depressed subjects. A neuropsychological activation study with the verbal fluency paradigm could evaluate a possible blunted increase in perfusion in the prefrontal cortex in depressed suicidal patients. Twenty clinically depressed patients who had recently attempted suicide and 20 healthy volunteers were included in a single photon emission computed tomography (SPECT) split-dose activation study following a verbal fluency paradigm. Statistical parametric mapping was used to determine voxelwise significant changes. Differences in regional cortical activation between the letter fluency and category fluency tasks in attempted suicide patients were found. These patients showed a blunted increase in perfusion in the prefrontal cortex. Methodological restrictions concerning group uniformity, medication bias and subjective effort of the participants are discussed. Our findings indicate a blunted increase in prefrontal blood perfusion as a possible biological reason for reduced drive and loss of initiative in attempted suicide patients.

The clinical value of nuclear medicine in the assessment of irradiation-induced and anthracycline-associated cardiac damage

Two groups of patients, those treated for Hodgkin's disease and breast cancer, are particularly at risk of developing late myocardial damage, since radiotherapy (RT) techniques for both patient groups may include (large) parts of the heart, and adjuvant systemic therapy is frequently administered to these patients, in particular anthracycline-containing chemotherapy. Available literature on the monitoring and prediction of RT-induced and anthracycline-associated cardiac damage using nuclear medicine techniques is presented. Based on relevant studies, the risk of overall cardiac disease post-RT and overt congestive heart failure during anthracycline-containing chemotherapy is probably low. Conventional nuclear medicine imaging, i.e. myocardial perfusion scintigraphy, may be of complementary use to echocardiographical evaluation for routine follow-up after RT with modern techniques, in a subgroup of patients with known cardiovascular risk factors. Left ventricle ejection fraction (LVEF) measurements, as assessed by radionuclide angiography for the monitoring of anthracycline-associated cardiac injury, are not very sensitive and early detection will probably be enhanced by combining LVEF measurements with other cardiac function parameters. Also, it may be expected that nuclear medicine techniques using molecular radioligands will constitute an essential future step in the evaluation of subclinical cardiac injury afforded by the combined effect of RT and cardiotoxic chemotherapy.

An infected hip prosthesis in a dog diagnosed with a 99mTc-ciprofloxacin (infecton) scan

This case report describes the use of the 99mTc-labeled radiopharmaceutical ciprofloxacin (Infecton) in a case of hip prosthesis loosening in a dog. Serial planar radiographs were not conclusive, and culture of the synovial fluid was negative. Antibiotic treatment did not result in improvement of the lameness. Scintigraphy was performed with 99-Tc-Infecton, a tracer claimed to be specific for infection. Antibiotic treatment was interrupted 6 weeks prior to the examination. Planar and tomographic images at 3 h and at 24 h postinjection showed increased activity along the acetabulum and the proximal femoral bone surrounding the femoral prosthesis, indicating focal infection. Bacteriology performed after removal of the implant revealed Pseudomonas aeruginosa.

Regional brain perfusion in 10 normal dogs measured using Technetium-99m ethyl cysteinate dimer spect

Single photon emission computed tomography (SPECT) of the brain using perfusion tracers allows estimation of regional brain perfusion. This allows in vivo examination of brain function in the setting of neuropsychologic and pathophysiologic changes. However functional imaging data on brain perfusion in dogs are limited. Hence, the aim of this study was to determine the scintigraphic regional perfusion pattern of the normal canine brain. Ten healthy shepherd type dogs were injected with 925 MBq Technetium-99m ethyl cysteinate (ECD) 20 minutes before the examination. Acquisition was performed using a triple head gamma camera equipped with fanbeam collimators. Uniform attenuation correction and triple energy window correction were applied. Computed tomographic images were obtained from the same dogs, reoriented along the orbito-meatal axis and SPECT perfusion data were coregistered to the CT-volume data. Based on morphological and suggested brain divisions, regions-of-interest (ROIs) were defined for the bilateral frontocerebral, temporocerebral, parietocerebral, occipitocerebral, cerebellar, thalamic, and striatal area. Regional count density was normalized on total counts. All dogs had the highest uptake in the thalamic/striatal area compared to a rather homogeneous cerebral uptake. No significant left/right count differences were found, but a rostro-caudal gradient (+12-13%) was present. In this group, age and gender did not influence the perfusion pattern.

The stopping of deuterons in lithium

The interaction of 52 MeV deuterons with lithium was investigated, in view of the optimization of a lithium target for an intense neutron source based on the d-Li stripping reaction. The experimental results are compared with theoretical calculations obtained from an updated version of the Bragg code. This code describes in detail the interaction of charged particles with matter. Within the experimental uncertainties the theoretical results are well reproduced by the experiments.

Non-invasive methods for absolute cerebral blood flow measurement using 99mTc-ECD: a study in healthy volunteers

Radionuclide angiography with technetium-99m ethyl cysteinate dimer (ECD) allows non-invasive estimation of absolute cerebral blood flow (CBF), either by graphical Patlak-Gjedde analysis (PGA) or by spectral analysis (SA). Other methods estimate CBF by means of single-point arterial or venous sampling. The aim of this study was to evaluate radionuclide scanning and single-point venous sampling as potential clinical non- to minimally invasive methods for CBF determination in a large set of carefully screened healthy volunteers over the adult age range. Eighty-three carefully screened healthy volunteers (20-81 years, 43 males, 40 females) underwent planar radionuclide angiography with 925 MBq 99mTc-ECD. After correction for camera dead-time loss, hemispheric CBF was calculated from brain perfusion indices (BPI): BPI(G) for PGA and BPI(S) for SA. Of the volunteers, 49 also underwent venous sampling 6 min post injection, from which the lipophilic octanol extraction fraction and hemispheric brain fractionation index (BFI) were determined. All datasets were correlated and evaluated as a function of age and gender. Intrasubject variability for the BPI measurements was assessed in 11 volunteers by repeat study within 2 weeks of the first acquisition. Graphical and spectral analysis BPIs were strongly correlated (R=0.846, P<0.00001). This correlation coefficient increased to R=0.903 for the 74 cases in which graphical analysis was not hampered by temporal tracer retention in cervicobrachial venous valves. The BFI was weakly correlated to both BPI indices (BPI(G): R=0.34, P=0.02; BPI(S): R=0.31, P=0.04). The right hemisphere showed significant asymmetry for BPI(S) (AI=2.7%+/-4.3%, P<0.001), in correspondence with previous 99mTc-ECD data. BPI(G), BPI(S) and BFI were all inversely related to age, with an increased gradient after the age of 55 years, while there was no significant gender difference. The ratio of BPI(G) to BIP(S), which is a measure of the cerebral extraction fraction for 99mTc-ECD, was not dependent on age. Intersubject variability was 15.5% for both radionuclide scanning-based methods and 18.2% for venous sampling, and in all cases was independent of age. A much lower intrasubject variability was observed for BPI(S) (7.2%) than for BPI(G) (12.6%). This study provides reference values for normal perfusion indices assessed by graphical and spectral analysis. The results also indicate that spectral analysis allows the most reproducible estimate of hemispheric perfusion by means of an operator-independent and objective approach. Whereas accurate calibration of normal BPI(S) values to hemispheric CBF with established methods needs to be performed, non-invasive calculation of regional absolute CBF using 99mTc-ECD is possible by application of a linearisation algorithm.

99mTc-ECD brain perfusion SPET: variability, asymmetry and effects of age and gender in healthy adults

Reliable and high-resolution reference data for regional cerebral blood flow measured with single-photon emission tomography (SPET) are necessary for optimal clinical and research use. Therefore, a large dataset of normal technetium-99m labelled ethylene cysteine dimer (ECD) perfusion SPET in carefully screened healthy volunteers with an age range spanning six decades was created, with correction for non-uniform attenuation and scatter and based on an anatomically standardised analysis. Eighty-nine healthy volunteers, stratified for gender (46 females, 43 males; age 20-81 years), were included. Twelve volunteers underwent repeated 99mTc-ECD SPET after 2.5+/-2.3 weeks. An automated whole-brain volume of interest analysis with MANOVA as well as voxelwise analysis using SPM99 was conducted. Average intersubject variability was 4.8% while intrasubject reproducibility was 3.0%. An age-related decline in tracer uptake was found in the anterior cingulate gyrus, bilateral basal ganglia, left prefrontal, left lateral frontal and left superior temporal and insular cortex (all P=0.001-0.02). There was an overall increase in right/left asymmetry with age, which was most pronounced in the frontal and temporal neocortex. The most significant correlations between AI and age decade were found in the prefrontal (R=0.35, P=0.001) and superior temporal neocortex (R=0.43, P<0.001). Women had significantly higher uptake in the right parietal cortex (P<0.001), while men showed higher uptake in the cerebellum and the left anterior temporal and orbitofrontal cortex (all P<0.01). This normative dataset allows age- and gender-specific patient and group assessment of 99mTc-ECD perfusion SPET under a wide variety of clinical circumstances in relation to normal variations and highlights the importance of both age- and gender-specific normal datasets for optimal analysis sensitivity.

Fibrinogen and C-reactive protein on admission as markers of final infarct size after primary angioplasty for acute myocardial infarction

BACKGROUND

In acute myocardial infarction (AMI) treated conservatively or with thrombolysis, marked increases of C-reactive protein (CRP) and fibrinogen have been observed. No data are however available concerning a possible relation between CRP and fibrinogen levels on admission and markers of infarct size after obtaining thrombolysis in myocardial infarction (TIMI) flow III by primary angioplasty.

METHODS

We studied 34 patients with a first AMI (29 men, mean age 54+/-11 years) who were treated with primary angioplasty (TIMI flow III in all patients, no concomitant treatment with glycoprotein IIb-IIIa antagonists) within 6 h of onset of pain. CRP and fibrinogen levels on admission were determined and related to the following markers of infarct size: peak creatine kinase MB (CKMB) levels, radionuclide left ventricular ejection fraction (LVEF) at discharge and thallium-201 single-photon emission computed tomography (SPECT) infarct size at 1 month.

RESULTS

Median CRP levels were 0.4 mg/dl (range 0.09-3 mg/dl), median fibrinogen levels 412 mg/dl (range 198-679 mg/dl), mean CKMB was 178+/-151 U/l, mean LVEF 52+/-8% and mean thallium-201 infarct size 7+/-6%. Although CRP levels were related to fibrinogen levels on admission (r=0.56, P=0.002), only fibrinogen levels were related to markers of infarct size (r=0.58, P=0.001 for CKMB, r=-0.44, P=0.01 for LVEF and r=0.64, P=0.001 for thallium-201 infarct size). No relation was found between CRP or fibrinogen levels on admission and the extent of coronary artery disease or the myocardial area at risk. In multiple regression analysis, the relation between fibrinogen and markers of infarct size was independent of CRP levels and the duration of pain on admission.

CONCLUSIONS

These findings indicate a relation between fibrinogen levels on admission and myocardial infarct size in patients treated with primary angioplasty for AMI. This relation seems to be independent of CRP levels and the duration of pain on admission. If confirmed in larger patient populations, fibrinogen levels on admission could have an important value for risk stratification and more aggressive reduction of infarct size in patients who are treated with primary angioplasty.

Differential regional cerebral uptake of (18)F-fluoro-2-deoxy-D-glucose in Alzheimer's disease and frontotemporal dementia at initial diagnosis

In this paper, the cerebral uptake of (18)F-fluoro-2-deoxy-D-glucose (FDG) was studied in a relatively small group of patients suffering from either clinically diagnosed Alzheimer's disease (AD) or frontotemporal dementia during the initial differential diagnostic workup. The image analysis was done visually and semiquantitatively using three different reference regions. Visual analysis confirmed earlier literature findings on the distribution of decreased FDG uptake and demonstrated prevalent asymmetric patterns in both groups. Only semiquantitative analysis using the sensorimotor cortex as a reference region confirmed the visual findings. Moreover, there were no differences in medial temporal lobe activities between both groups, and there was no correlation of medial temporal lobe activity with dementia severity. In the AD group, a correlation of parietal FDG uptake with MMSE scores was found.

Image filtering in single-photon emission computed tomography: principles and applications

Among the factors contributing to optimal image quality in single-photon emission computed tomography (SPECT), image filtering is an important, though mostly subjectively applied, image-processing parameter. We have aimed at giving an overview of current available SPECT filtering options. Current SPECT applications are discussed and practical guidelines to choose optimal filter parameters for a given situation are provided. It is shown that Hann and Butterworth filters allow accurate approximations to most filter types. The authors support the use of limited filter types in an attempt to standardise image-processing approaches, which may lead to better diagnostic compatibility and interpretation of interdepartmental results.

Coincidence camera FDG imaging for the diagnosis of chronic orthopedic infections: a feasibility study

PURPOSE

Results of dedicated [(18)F]fluoro-2-deoxy-d-glucose (FDG) PET imaging in patients with suspected orthopedic infections are promising. This study evaluates the feasibility of dual-head gamma-camera coincidence (DHC) imaging in this population.

METHOD

Twenty-four patients, referred for the confirmation or exclusion of orthopedic infection, were prospectively studied with consecutive FDG-dedicated PET and FDG DHC imaging. Images were read by two blinded readers experienced with FDG PET and compared with the final diagnosis, obtained by microbiologic proof in 11 patients and clinical follow-up of at least 9 months in 13 patients.

RESULTS

Nine patients had osseous infection on final diagnosis. Sensitivity, specificity, and accuracy in this limited series were (Reader 1/Reader 2), respectively, 100/100, 86/86, and 92/92% for FDG-dedicated PET and 89/89, 100/93, and 96/92% for FDG DHC imaging.

CONCLUSION

Despite lower image quality for FDG DHC imaging, results in this limited series were comparable with the results of FDG-dedicated PET. Further studies are needed to confirm the utility of FDG DHC imaging in suspected chronic orthopedic infections in larger patient groups.

Automated stereotactic standardization of brain SPECT receptor data using single-photon transmission images

Intra- or intersubject registration of anatomically poorly defined SPECT data, such as in neuroreceptor imaging, is important for longitudinal or group analysis. However, accurate registration is difficult with only emission CT (ECT) data. We investigated fully automated registration using transmission CT (TCT) data as an intermediary image set.

METHODS

The accuracy of TCT registration was compared to that of ECT registration for four types of data: gray-matter distribution (with [99mTc]ethylcysteinate dimer (ECD)), neocortical distribution (with [123I]R91150, a highly specific 5-HT2a receptor ligand), and striatal distribution of the D2-receptor ligand (with [123I]iodobenzamide (IBZM)) and the dopamine transporter ligand (with [123I]2beta-carbomethoxy-3beta-(4-fluorophenyl)tropane (CIT)). In total, 10 datasets of the various study types were used, all collected on a Toshiba GCA9300 gamma camera with super-high-resolution fanbeam collimators and 3 x 370 MBq of 153Gd transmission sources (4-min sequential TCT scanning for receptor studies and 20-min simultaneous scanning for [99mTc]ECD studies). Per dataset, 15 random misalignments of 9 rigid-body parameters (translation, rotation, and anisotropic scaling) were conducted. All coregistrations were done twice, both to the subject's original scan and to a study-specific template. This was done manually by two independent experienced observers and with three automated voxel similarity algorithms: mutual information (M.I.), count difference (C.D.), and uniformity index (U.I.). As an outcome measure, the impact of misregistration on semiquantification for the various study types was established.

RESULTS

TCT matching allowed registration within 3.3 mm, 2.4 degrees, and 1.2% scaling (mean squared values for all directions) with an overall accuracy decrease in the following order: C.D. > M.I. > manual > U.I. For [99mTc]ECD and [123I]IBZM, TCT registration was as accurate as ECT registration, while it was far superior for the other receptor data types, especially for abnormal studies. The automated TCT registration accuracy corresponded to average quantification errors of 2.9% ([99mTc]ECD), 4.2% ([123I]BZM), 5.7% ([123I]R91150), and 6.1% ([123I]beta-CIT).

CONCLUSION

Fully automated registration through intermediary TCT images is clinically feasible, fast, and accurate. In addition to nonuniform attenuation correction, TCT scanning therefore allows coregistration for group comparisons of SPECT receptor data on a standardized or pixel-by-pixel basis.

Non-uniform versus uniform attenuation correction in brain perfusion SPET of healthy volunteers

Although non-uniform attenuation correction (NUAC) can supply more accurate absolute quantification, it is not entirely clear whether NUAC provides clear-cut benefits in the routine clinical practice of brain SPET imaging. The aim of this study was to compare the effect of NUAC versus uniform attenuation correction (UAC) on volume of interest (VOI)-based semi-quantification of a large age- and gender-stratified brain perfusion normal database. Eighty-nine healthy volunteers (46 females and 43 males, aged 20-81 years) underwent standardised high-resolution single-photon emission tomography (SPET) with 925 MBq 99mTc-ethyl cysteinate dimer (ECD) on a Toshiba GCA-9300A camera with 153Gd or 99mTc transmission CT scanning. Emission images were reconstructed by filtered back-projection and scatter corrected using the triple-energy window correction method. Both non-uniform Chang attenuation correction (one iteration) and uniform Sorenson correction (attenuation coefficient 0.09 cm(-1)) were applied. Images were automatically reoriented to a stereotactic template on which 35 predefined VOIs were defined for semi-quantification (normalisation on total VOI counts). Small but significant differences between relative VOI uptake values for NUAC versus UAC in the infratentorial region were found. VOI standard deviations were significantly smaller for UAC, 4.5% (range 2.6-7.5), than for NUAC, 5.0% (2.3-9.0) (P<0.01). Higher filter roll-off values of the transmission reconstruction filter increased noise in the emission images and altered estimated cortical attenuation coefficients as well as uptake values. In conclusion, semi-quantification based upon reconstruction with UAC results in very similar 99mTc-ECD uptake values in healthy volunteers to those obtained with NUAC, although values for the infratentorial region are slightly lower. NUAC produces a slight increase in inter-subject variability. Further study is necessary in various patient populations to establish the full clinical impact of NUAC in brain perfusion SPET.

Verbal fluency as a prefrontal activation probe: a validation study using 99mTc-ECD brain SPET

This study aimed to investigate the feasibility of brain single-photon emission tomography (SPET) in the letter and category fluency paradigm of the Controlled Oral Word Association (COWA) test in healthy volunteers. Two groups each comprising ten right-handed healthy volunteers were injected twice with 370 MBq technetium-99m ethyl cysteinate dimer following a split-dose paradigm (resting and activation condition). Statistical parametric mapping (SPM96) was used to determine voxelwise significant changes. The letter fluency and the category fluency activation paradigm had a differential brain activation pattern. The posterior part of the left inferior prefrontal cortex (LIPC) was activated in both paradigms, with the category fluency task having an extra activation in the anterior LIPC. In the category fluency task, but not the letter fluency task, an activation in the right inferior prefrontal cortex was found. These findings confirm to a large extent the results of previous functional magnetic resonance imaging and positron emission tomography studies in semantic and phonological activation paradigms. The choice and validity of various methodological characteristics of the experimental design leading to these results are critically discussed. It is concluded that brain SPET activation with the letter fluency and category fluency paradigm under standard neuropsychological conditions in healthy volunteers is both technically and practically feasible.

99Tc(m)-ECD SPET perfusion changes by internal pallidum stimulation in Parkinson's disease

High-frequency stimulation of the internal pallidum is an effective surgical approach for patients with advanced Parkinson's disease suffering from motor fluctuations and L-dopa induced dyskinesia. To study the acute effects of internal pallidum stimulation, changes in cerebral blood flow were measured by means of a single-day split-dose protocol using 99Tc(m)-ECD SPET. Nine patients with advanced Parkinson's disease and with a clinical picture predominated by tremor and drug-induced dyskinesia, were imaged before and immediately after electrostimulation. Brain perfusion data were mirrored to the same electrode side (five left and four right implants), co-registered and analysed statistically on a voxel-by-voxel basis (Statistical Parametric Mapping) and by an automated volume-of-interest approach. Acute stimulation of the internal pallidum induced a significantly decreased perfusion in the ipsilateral thalamus and striatum, as well as in the right parietal cortex. For the subgroup of seven patients with effective motor score improvements, a significant correlation between thalamic and striatal perfusion changes and UPDRS III motor score was present (P = 0.04). These results suggest that effective stimulation of the internal globus pallidus may produce symptom relief through decreased activity in pallido-thalamo-cortical circuits.

Automatic quantification of defect size using normal templates: a comparative clinical study of three commercially available algorithms

Infarct size assessed by myocardial single-photon emission tomography (SPET) imaging is an important prognostic parameter after myocardial infarction (MI). We compared three commercially available automatic quantification algorithms that make use of normal templates for the evaluation of infarct extent and severity in a large population of patients with remote MI. We studied 100 consecutive patients (80 men, mean age 63 +/- 11 years, mean LVEF 47% +/- 15%) with a remote MI who underwent resting technetium-99m tetrofosmin gated SPET study for infarct extent and severity quantification. The quantification algorithms used for comparison were a short-axis algorithm (Cedars-Emory quantitative analysis software, CEqual), a vertical long-axis algorithm (VLAX) and a three-dimensional fitting algorithm (Perfit). Semiquantitative visual infarct extent and severity assessment using a 20-segment model with a 5-point score and the relation of infarct extent and severity with rest LVEF determined by quantitative gated SPET (QGS) were used as standards to compare the different algorithms. Mean infarct extent was similar for visual analysis (30% +/- 21%) and the VLAX algorithm (25% +/- 17%), but CEqual (15% +/- 11%) and Perfit (5% +/- 6%) mean infarct extents were significantly lower compared with visual analysis and the VLAX algorithm. Moreover, infarct extent determined by Perfit was significantly lower than infarct extent determined by CEqual. Correlations between automatic and visual infarct extent and severity evaluations were moderate (r = 0.47, P < 0.0001 to r = 0.62, P < 0.0001) but comparable for all three algorithms. Correlations between LVEF and visual evaluation of infarct extent (r = -0.80, P < 0.0001) and severity (r = -0.82, P < 0.0001) were good but correlations were significantly lower for all three algorithms (r = -0.48, P < 0.0001 to r = -0.65, P < 0.0001). Systematically lower correlations were found in non-anterior infarctions (n = 69) and obese patients (BMI > or = 30 kg/m2, n = 32) compared with anterior infarctions and non-obese patients for all three algorithms. In this large series of post-MI patients, results of infarct extent and severity determination by automatic quantification algorithms that make use of normal templates were not interchangeable and correlated only moderately with semiquantitative visual analysis and LVEF.