Initial performance evaluation of a preclinical PET scanner available as a clip-on assembly in a sequential PET/MRI system

We evaluated the performance characteristics of a prototype preclinical PET scanner available as an easy clippable assembly that can dock to an MRI system. The single ring version of the PET system consists of eight detectors, each of which comprises a 12  ×  12 silicon photomultipliers (SiPMs) array coupled with a dual layer of offset scintillation crystals to measure depth of interaction. The crystal arrays have 29  ×  29 (30  ×  30 for the outer layer) 4 mm long LYSO crystals (6 mm for the outer layer). The ring diameter is 119.2 mm and the axial field of view is 50.4 mm. The NEMA NU 4-2008 protocol was followed for studying the PET performance. Temperature stability of SiPMs was also investigated. The peak system absolute sensitivity was 4.70% with an energy window of 250-750 keV. The spatial resolution was 1.28/1.88/1.85 mm FWHM (radial/tangential/axial) at a distance of 5 mm from the center. Peak noise equivalent counting rate and scatter fraction for mouse phantom were 61.9 kcps at 14.9 MBq and 21.0%, respectively. The uniformity was 6.3% and the spill-over ratios in the images of the water-and air-filled chambers were 0.07 and 0.17, respectively. Recovery coefficients ranged from 0.13 to 0.96. Change in sensitivity as a function of ambient temperature was 0.3%/°C. These first results indicate excellent spatial resolution performance for use with animal studies. Moreover, the clippable assembly can be upgraded to accept a second ring of SiPMs modules, leading to improved sensitivity and axial coverage.

Radiolabeled F(ab')2-cetuximab for theranostic purposes in colorectal and skin tumor-bearing mice models

PURPOSE

This study aimed to investigate theranostic strategies in colorectal and skin cancer based on fragments of cetuximab, an anti-EGFR mAb, labeled with radionuclide with imaging and therapeutic properties, ¹¹¹In and ¹⁷⁷Lu, respectively.

METHODS

We designed F(ab')₂-fragments of cetuximab radiolabeled with ¹¹¹In and ¹⁷⁷Lu. ¹¹¹In-F(ab')₂-cetuximab tumor targeting and biodistribution were evaluated by SPECT in BalbC nude mice bearing primary colorectal tumors. The efficacy of ¹¹¹In-F(ab')₂-cetuximab to assess therapy efficacy was performed on BalbC nude mice bearing colorectal tumors receiving 17-DMAG, an HSP90 inhibitor. Therapeutic efficacy of the radioimmunotherapy based on ¹⁷⁷Lu-F(ab')₂-cetuximab was evaluated in SWISS nude mice bearing A431 tumors.

RESULTS

Radiolabeling procedure did not change F(ab')₂-cetuximab and cetuximab immunoreactivity nor affinity for HER1 in vitro. ¹¹¹In-DOTAGA-F(ab')₂-cetuximab exhibited a peak tumor uptake at 24 h post-injection and showed a high tumor specificity determined by a significant decrease in tumor uptake after the addition of an excess of unlabeled-DOTAGA-F(ab')₂-cetuximab. SPECT imaging of ¹¹¹In-DOTAGA-F(ab')₂-cetuximab allowed an accurate evaluation of tumor growth and successfully predicted the decrease in tumor growth induced by 17-DMAG. Finally, ¹⁷⁷Lu-DOTAGA-F(ab')₂-cetuximab radioimmunotherapy showed a significant reduction of tumor growth at 4 and 8 MBq doses.

CONCLUSIONS

¹¹¹In-DOTAGA-F(ab')₂-cetuximab is a reliable and stable tool for specific in vivo tumor targeting and is suitable for therapy efficacy assessment. ¹⁷⁷Lu-DOTAGA-F(ab')₂-cetuximab is an interesting theranostic tool allowing therapy and imaging.

Abstract P5-01-03: HER2 imaging by SPECT-CT using 111In radiolabeled pertuzumab-fab DOTAGA-conjugate: A proof of concept study in a preclinical model of breast cancer

Introduction: HER2 is positive in approximately 20-30% of all breast cancer and is associated with poor prognosis, higher mortality and higher metastatic incidence. Current diagnosis of HER2 expression relies on invasive methods requiring tissue biopsy which can lead to variable results due to inter/intra-metastatic and intratumoral heterogeneity in breast cancers. It has been recently demonstrated that HER2 molecular imaging based on pertuzumab, an antibody targeting HER2, could represent a more accurate non-invasive method to assess HER2 expression and evaluate its spatial and temporal heterogeneity. Aim: In the present study, we aimed at developing radiolabeled pertuzumab Fab fragments for HER2 imaging. Tumor uptake of radiolabeled Fab was evaluated in an animal model of HER2 breast cancer by SPECT-CT, and the impact of trastuzumab on HER2 imaging was assessed. The objective of this study was to validate the feasibility of HER2 imaging with a pertuzumab-derived probe and to evaluate the possible translation of such a probe for clinical use in patients treated or not with anti-HER2 therapy. Methods: Fab fragments of pertuzumab have been generated by papain digestion and bioconjugated with the bifunctional chelating agent DOTAGA for incorporation of Indium 111 to generate an HER2-specific probe for SPECT (111In-DOTAGA-pertuzumab-Fab). The functionality of both radiolabeled Fab and whole pertuzumab was evaluated by in vitro assays using HER2-overexpressing human breast cancer cell line (HCC1954). Tumor uptake of pertuzumab-Fab and whole pertuzumab (111In-DOTAGA-Pertuzumab) has been evaluated in Balb/c nude mice bearing BT-474 tumors with or without pre-treatment with trastuzumab for 24h. Results: In the current study we demonstrate that Fab fragments of pertuzumab keep similar HER2 binding properties than whole pertuzumab and can therefore be a suitable HER2-targeted probe. In vivo, 111In-DOTAGA-pertuzumab-Fab showed better pharmacokinetics than whole pertuzumab with faster tumor uptake and blood clearance allowing faster imaging with better tumor/blood ratio. In addition, tumor uptake of 111In-DOTAGA-pertuzumab-Fab is not modified by pre-treatment with trastuzumab. Conclusion: We assume that radiolabeled pertuzumab-Fab should be of great interest if the intention to treat is based on anti-HER2 monoclonal antibodies-based therapies rather than small molecules (e.g. lapatinib). Interestingly, pertuzumab has been shown to be also beneficial in combination with trastuzumab and chemotherapy in non-metastatic patients through its approval for the neoadjuvant treatment and very recently in the APHINITY clinical trial aiming for an approval in the adjuvant treatment of early breast cancer. These data suggest that pertuzumab will be extensively used in various HER-2 positive breast cancers underlining the interest to perform molecular imaging of HER2 expression as a predictive biomarker of efficacy.

Citation Format: Oudot A, Bellaye P-S, Vrigneaud J-M, Raguin O, Bernhard C, Dumont L, Brunotte F, Savina A, Bouquet F, Fumoleau P, Collin B. HER2 imaging by SPECT-CT using 111In radiolabeled pertuzumab-fab DOTAGA-conjugate: A proof of concept study in a preclinical model of breast cancer [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P5-01-03.

Quantifying Stenosis in Renal Arteriograms: A Fuzzy Syntactic Analysis

The introduction of fuzzy logic improves a system for the automatic quantification of renal artery lesions seen in digital subtraction angiograms. A two-step approach has been followed. An earlier system based on non-fuzzy syntactic analysis provided a clear symbolic description of the stenotic lesions. Although this system worked correctly, it did not take into account the variability and uncertainty inherent to image processing and to knowledge on the reference diameter. This system has been improved by the introduction of fuzzy logic in the representation of the reference diameter. It provides a description of the stenosis in terms of fuzzy quantities. To illustrate the benefits of the fuzzy approach, the results of the two systems have been compared by plotting the differences of an index of variability. It appears that the differences are statistically different when using a two-tailed paired t-test (t = 2.37; p = 0.025). The result shows that the fuzzy approach is better than a non-fuzzy approach in the sense that the index of variability is reduced significantly.

Ionic Competition and 67Ga in Vivo Accumulation

Es wurde die Wirkung verschiedener Zitrate trivalenter Kationen auf die 67Ga-Zitrat-Speicherung von Tumortieren untersucht. Eine Beziehung zwischen der Ionengröße des gleichzeitig injizierten Kations und der Hemmung der 67Ga-Speicherung weist darauf hin, daß die Eigenschaften des Kations (Ionenradius und elektrische Ladung) die wichtigste Rolle in der Speicherung der Radioaktivität spielen. Die offenbare Übereinstimmung dieses Phänomens mit der Hypothese des isomorphen Ersatzes wird diskutiert.

MANOTA: a promising bifunctional chelating agent for copper-64 immunoPET

A comparison of four bifunctional chelating agents showed superior behaviour of a new NOTA derivative for ⁶⁴Cu labelling of antibody fragments.

Minor changes in the macrocyclic ligands but major consequences on the efficiency of gold nanoparticles designed for radiosensitization

Many studies have been devoted to adapting the design of gold nanoparticles to efficiently exploit their promising capability to enhance the effects of radiotherapy. In particular, the addition of magnetic resonance imaging modality constitutes an attractive strategy for enhancing the selectivity of radiotherapy since it allows the determination of the most suited delay between the injection of nanoparticles and irradiation. This requires the functionalization of the gold core by an organic shell composed of thiolated gadolinium chelates. The risk of nephrogenic systemic fibrosis induced by the release of gadolinium ions should encourage the use of macrocyclic chelators which form highly stable and inert complexes with gadolinium ions. In this context, three types of gold nanoparticles (Au@DTDOTA, Au@TADOTA and Au@TADOTAGA) combining MRI, nuclear imaging and radiosensitization have been developed with different macrocyclic ligands anchored onto the gold cores. Despite similarities in size and organic shell composition, the distribution of gadolinium chelate-coated gold nanoparticles (Au@TADOTA-Gd and Au@TADOTAGA-Gd) in the tumor zone is clearly different. As a result, the intravenous injection of Au@TADOTAGA-Gd prior to the irradiation of 9L gliosarcoma bearing rats leads to the highest increase in lifespan whereas the radiophysical effects of Au@TADOTAGA-Gd and Au@TADOTA-Gd are very similar.

Abstract P4-02-06: Molecular imaging with trastuzumab and pertuzumab of HER2-positive breast cancer in mice: a step towards personalized medicine

Introduction: The accurate and reliable assessment of HER2 status is an essential step in the diagnostic workup and selection of targeted treatment strategy in breast cancer patients. However, current ex vivo methods do not evaluate HER2 status possible discordance between primary tumor and distant metastases, nor immediate response to therapeutic intervention. Non-invasive imaging of HER2 expression could be a relevant alternative with additional benefits such as a better selection of patients for HER2-targeted therapies and the possible optimization of treatment strategies. Recent clinical trials suggest a better efficacy of trastuzumab/pertuzumab doublet but a lower activity of pertuzumab monotherapy over trastuzumab alone.

Aim: The aim of our study was therefore to evaluate preclinically the use of radiolabeled DOTAGA (2, 2′, 2″-(10-(2,6-dioxotetrahydro-2H-pyran-3-yl)-1,4,7,10-tetraazacyclododecane-1,4,7-triyl)triacetic acid) conjugated trastuzumab and pertuzumab for SPECT/CT (Single Photon Emission Computed Tomography/Computed Tomography) HER2 imaging purposes.

Methods: Trastuzumab and pertuzumab were conjugated to a new bifunctional chelating agent: DOTAGA anhydride (DOTA analog) and subsequently radiolabeled with the gamma-emitter Indium 111. The functionality of [111In]-DOTAGA-antibodies analogs was evaluated by in vitro saturation assays using HER2-overexpressing human breast cancer cell line (HCC1954). In vivo biodistribution was studied by SPECT/CT imaging at 24h, 48h and 72h after intravenous injection of [111In]-DOTAGA-antibodies in subcutaneous BT474 tumor-bearing rodents.

Results: [111In]-DOTAGA-trastuzumab and [111In]-DOTAGA-pertuzumab showed respectively 2.6 and 2.7 DOTAGA/antibody. Both [111In]-DOTAGA-trastuzumab and [111In]-DOTAGA-pertuzumab achieved a radiochemical purity > 95%. Biological activity of [111In]-DOTAGA-trastuzumab and [111In]-DOTAGA-pertuzumab was maintained: the affinity determined on HER2 expressing HCC1954 cell lines, was 5.5 and 5.6 nM. SPECT/CT imaging experiments in tumor-bearing rodents and gamma-counting of organs both showed that at 72h post-injection, more than 60 % of the activity was localized in the tumor (66.9±0.9 %ID/g for [111In]-DOTAGA-trastuzumab and 63.8±6.3 %ID/g for [111In]-DOTAGA-pertuzumab) and that an excess of non-radiolabeled corresponding antibody significantly shifted down tumor-targeting (to 17.6±2.4 %ID/g for [111In]-DOTAGA-trastuzumab and 8.7±0.8 %ID/g for [111In]-DOTAGA-pertuzumab.

Conclusions: Our results demonstrate a similar HER2 binding of trastuzumab and pertuzumab. Both radiolabeled [111In]-DOTAGA-trastuzumab and [111In]-DOTAGA-pertuzumab should be considered and might be promising tools for molecular imaging diagnosis of HER2 overexpression in breast cancer.

Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr P4-02-06.

Predictors of post-stress LVEF drop 6 months after reperfused myocardial infarction: a gated myocardial perfusion SPECT study

OBJECTIVE

To identify the predictive factors of myocardial stunning as assessed by the drop in post-stress Left Ventricular Ejection Fraction (LVEF) in patients with a recent history of myocardial infarction (MI).

METHODS

We prospectively included 215 consecutive patients admitted for acute MI who underwent percutaneous coronary intervention with a greater than or equal to grade-3 TIMI flow in the culprit vessel. Six months after discharge, a post-stress/rest 99mTc-sestamibi gated SPECT was performed. The perfusion score was evaluated visually using a 17-segment model. The LVEF drop was considered significant if the post-stress LVEF was ≥ 5% below the rest LVEF (QGS® software).

RESULTS

A post-stress LVEF drop was observed in 51 (24%) patients. Patients with an LVEF drop were more likely than patients with a stable post-stress LVEF to have diabetes (22% vs. 10%, p = 0.048), significant ischemia (SDS > 2) (51% vs. 28% p = 0.003) and higher rest LVEF [62% (56-69) vs. 56% (49-63) p < 0.001]. In contrast, summed rest score, related to infarct size, did not differ between the groups. Multivariate logistic regression analysis identified SDS > 2 (OR 3.78, 95% CI 1.8-7.92, p < 0.001), diabetes (OR 3.35, 95% CI 1.33-8.49; p = 0.011) and rest LVEF (OR 1.08, 95% CI 1.04-1.12, p < 0.001) as independent explanatory variables of an LVEF drop.

CONCLUSION

In patients with recent MI and post-procedural grade-3 TIMI flow, ischemia and diabetes were independent predictive factors of myocardial stunning. The higher incidence of reversible perfusion abnormalities validates the model of myocardial stunning in the post-MI period, and excludes the potential involvement of myocardial necrosis.

Changes in 18F-FDG tumor metabolism after a first course of neoadjuvant chemotherapy in breast cancer: influence of tumor subtypes

BACKGROUND

The aim of this study is to evaluate the impact of the different breast cancer subtypes on the tumor (18)F-FDG uptake at baseline and on its changes after the first course of neoadjuvant chemotherapy (NAC).

PATIENTS AND METHODS

One hundred and fifteen women with newly diagnosed, large or locally advanced breast cancer undergoing NAC were included. Estrogen receptor (ER), progesterone receptor (PR) and HER2 status were used to define three major tumor subtypes: triple negative (TN) (ER-/PR-/HER2-), luminal (ER+ and/or PR+; HER2-) and HER2 positive (HER2+). Using Fluorine-18 fluorodeoxyglucose positron emission tomography, the tumoral standard uptake value (SUV) maximal index was measured at baseline and just before the second course of NAC.

RESULTS

TN tumors presented the highest baseline SUV (11.3 ± 8.5; P < 0.0001). The decrease of SUV after the first course of NAC (ΔSUV) was significantly higher in TN and HER2-positive subtypes (-45% ± 25% and -57% ± 30%, respectively) than in luminal one (-19% ± 35%; P < 0.0001). ΔSUV was a predictive factor of the pathological complete response only in HER2-positive tumors (cut-off = -75%; P < 0.03) with an accuracy of 76%.

CONCLUSION

The baseline (18)F-FDG tumoral uptake but also its early response to NAC is different according to the immunohistological subtypes of breast cancer.

Abstract P5-01-06: 18[F]-FDG Tumoral Uptake and Metabolic Response after 1 Cycle of Primary Chemotherapy According to Tumoral Phenotype of Breast Cancer

To compare the 18[F]-FDG-PET (PET) metabolic characteristics in triple-negative, luminal and positive HER2 breast cancer. Material and Methods: One hundred and forty-five patients with newly diagnosed locally advanced breast cancer were evaluated. Twenty one metastatic patients (discovered in baseline PET) were excluded and 9 patients were lost. One hundred and fifteen had undergone FDG PET before and after the first course of neoadjuvant chemotherapy. Breast cancer lesions were imaged at 80-90 minutes after administration of FDG. Maximum standardized uptake values (SUV) were measured at both time point (SUV1 and SUV 2). Metabolic response was measured by the relative decrease of SUV (ΔSUV). Using Immunohistochemistry as a surrogate for expression profiling, the tumours were classified as follows: triple negative defined by the lack of oestrogen receptors, progesterone receptors and human epidermal growth factor receptors 2 (HER2) expression, luminal (hormonal receptor positive, HER2 negative) and HER2 positive (overexpression of HER 2). Relationships between baseline [18F]-FDG uptake and clinical, histopathological and biological parameters were assessed by Mann-Whitney test. Relationships between SUV1, SUV2, ΔSUV and the tumoral phenotype were assessed by Kruskal-Wallis test.

Results: In the overall population the mean ±SD SUV1, SUV2 and ΔSUV values were 6.7± 5.9, 3.7± 3 and −36.7% ± 35.7%, respectively. Significant relationships were found between baseline FDG uptake and initial clinical and histopathological parameters : a high mitotic activity (p≥0.0001), a high nuclear pleomorphism (≥0.0002), a high tumour grading (p≥0.0001) and a negative oestrogen hormonal receptor status (p≥0.0001) were associated with a high baseline SUV. Patient age, lymph node involvement, architectural differentiation, progesterone hormonal receptor and HER2 status were not found to be related with SUV values.

Metabolic characteristics (mean ± SD) according to tumoral phenotype:

Conclusion: Our results show a significant positive relationship between the baseline FDG uptake and the proliferation markers, the tumour grading, the number of mitoses and the nuclear pleomorphism. A significant negative relationship was found between the baseline FDG uptake and the oestrogen hormonal receptor status. The triple negative phenotype was associated with higher baseline FDG uptake and higher residual FDG uptake after one course of chemotherapy commensurate with their aggressive biology. Luminal tumours showed a lower ΔSUV reflecting their lower chemosensibility.

Abstract P5-01-09: Evaluation of Tumor Blood Flow with Dynamic 18F-Fluorodeoxyglucose Positron Emission Tomography: Correlation with Microvessel Density

Background: Breast cancer is typically associated with an increase in tumor blood flow (due to angiogenesis) and tumor metabolism. Thus, these 2 key parameters are essential to characterize aggressiveness of breast tumors. Moreover, angiogenesis is a potential target for specific therapies. Positron Emission Tomography (PET) with 18F-Fluorodeoxyglucose (FDG) has become the gold standard for in vivo evaluation of tumor metabolism. A method for simultaneous measurement of blood flow and metabolism from a single injection of FDG may be an important addition for functional imaging of breast tumors. Unfortunately, there is no consensus on the validity of dynamic FDG acquisition for the evaluation of tumor blood flow.

Objective: to compare a new technique for simultaneous evaluation of tumor blood flow and metabolism, using a dynamic acquisition of FDG PET, with proliferation and endothelial cell markers. Material and methods: Twenty-eight patients with new diagnosed locally advanced breast cancer were included. In addition to diagnosis and tumor grading, biopsy samples of each tumor were used to assess the Ki-67 index of proliferation and the immuno-staining for CD31 (a panendothelial cell marker) and CD105 (a proliferation-related endothelial cell marker) (both expressed as number of labeled vessels counted on 10 consecutive high power fields, 400X magnification). All patients underwent FDG PET at least one week after sample biopsy and before any treatment. Dynamic 2 minutes acquisition was performed immediately after intravenous injection of 5 MBq/Kg of FDG; tumor Blood Flow (BF, in ml/min/g) was then calculated using a single compartiment kinetic model. Static acquisition was performed 60 minutes after injection for quantification of delayed FDG tumor uptake (“Standardized Uptake Value”, SUV), reflecting tumor metabolism.

Results: Pathologic and PET data were available for all patients. The SUV measured on delayed PET images was strongly positively correlated with the expression of Ki-67 (r=+0.693; P&lt;0.0001). In contrast, there was no significant correlation between SUV and endothelial markers (CD31 and CD105). Tumor BF was positively correlated with the expression of CD31 (r=+0.392; p=0.039) and CD105 (r=+0.470; p=0.016). In contrast, there was no significant correlation between BF and Ki-67. Patients were categorized according to low (inframedian) or high (supramedian) tumor BF. Patients with high tumor BF showed a higher mean CD31 expression (236±169 vs 124±47, p=0.025) and a higher mean CD105 expression (110±73 vs 51±14; p=0.006) when compared with low tumor BF. In contrast there was no significant difference concerning SUV and Ki-67.

Conclusion: Tumor BF quantified by dynamic FDG PET is related to tumor microvessel density evaluated by immunohistochemistry. Thus, dynamic FDG PET is a valuable tool to evaluate both tumor blood flow and metabolism. Further investigations are needed to confirm the respective role of these 2 key parameters for elaboration of therapeutic strategies and response assessment in locally advanced breast cancer.

Citation Information: Cancer Res 2010;70(24 Suppl):Abstract nr P5-01-09.

Abstract P5-01-05: Prognostic Value at 4 Years of FDG PET, after the First Course of Neoadjuvant Chemotherapy in Breast Cancer

FDG-PET may be a powerful examination to evaluate the effectiveness of neoadjuvant chemotherapy: it appears to be possible to predict the preoperative histological response after the first cycle of chemotherapy. The aim of this prospective study was to investigate the prognostic value of the early decrease of tumoral glucidic metabolism, evaluated with FDG-PET, after the first cycle of neoadjuvant chemotherapy in breast cancer. Material and methods: FDG-PET was performed before and after the first cycle of neoadjuvant chemotherapy in 92 patients with large or locally advanced, non inflammatory, breast cancer. The change of 18F-FDG tumoral uptake was calculated from the maximum Standard Uptake Value corrected for body surface and glycemia (ΔSUVmax). Disease free survival (DFS) was assessed, and the prognostic value of ΔSUVmax was first studied among all patients. Using immunohistochemistry as a surrogate for expression profiling, patients were then classified according to tumoral phenotypes as follow: triple negative (defined by the lack of estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor 2 (HER2) expression), luminal (ER positive or PR positive, HER2 negative) and HER2 positive.

Results: The median follow-up was 46.3 months (range: 37–52 months). Twenty one patients had recurrent disease, 9 of whom died. Using univariate Cox regression analysis with all patients, DFS showed significant correlation with initial tumor size measured with ultrasound scan (p=0.03), and ΔSUVmax after the first cycle of neoadjuvant chemotherapy (cut-off = -45%, p=0.01). Using multivariate cox regression analysis, only ΔSUVmax remained an independent prognostic factor of DFS at four years (p=0.028). According to tumoral phenotypes, ΔSUVmax was a prognostic factor of DFS for the 50 patients with a luminal cancer : the risk of relapse was 8.7 times higher in women whose SUVmax decreased less than 24% after the first course of chemotherapy (p=0,04). No significant correlation between

ΔSUVmax and DFS was shown in the 22 triple negative phenotypes. For the 31 patients overexpressing HER2, a tumoral SUVmax lower than 1,8 after one cycle of chemotherapy tended to be a favorable prognostic factor with a lower risk of relapse (p = 0,058) but ΔSUVmax had no significant prognostic value (p=0.08).

Conclusion: Using immunohistochemistry, the change of tumoral FDG uptake after the first cycle of neoadjuvant chemotherapy in operable breast cancer patients appears to be an early surrogate marker of disease free survival for luminal tumors in this study. For HER2 positive tumors, FDG-PET seems to provide prognostic information but, as for the triple negative tumors, it was not statistically significant. FDG-PET might be useful to guide the early therapeutic choice for breast cancer treated with neoadjuvant chemotherapy.

Citation Information: Cancer Res 2010;70(24 Suppl):Abstract nr P5-01-05.

MR-based biomarkers in the diagnosis and the evaluation of the therapeutic response to radiotherapy (ETRR) in prostatic carcinoma (PCa): Implementation of clinical and experimental approaches

e16136

Background: ETRR in PCa remains a challenging task. New biomarkers in the form of metabolites, detected with Proton Magnetic Resonance Spectroscopy (1H-MRS), and quantitative Apparent Diffusion Coefficient (ADC), determined with Diffusion-Weighted Magnetic Resonance Imaging, could be of value in the ETRR for PCa. Methods: Twenty-one men with biopsy proven localized PCa were examined before external radiotherapy. 3D-1H-MRS was performed at 3.0T without endorectal coils. The delivered radiotherapy dose was 78 Gy in 39 fractions with 6 MV photons. MR follow-up examinations up to 36 months post-radiotherapy were performed. For the pre-clinical study, healthy rat prostate was studied in 3 nude rats. PC3-MM2 and PAC-120 tumors were subcutaneously (SC) and orthotopically (OT) xenografted in 5 nude rats, respectively. Radiotherapy anti-tumor efficacy administered as HDR-brachytherapy (SC) or X6 external beam irradiation (OT) delivering 10 Gy/5 fractions was evaluated. 1H-MRS was performed at 4.7 T using SVS. Results: Twelve men received the 3-month examination, 8 patients are at 6-months, 4 are at 9 months and 1 has been followed for 1 year. At baseline, healthy prostate shows a low Choline (Cho)/Citrate ratio, whereas the presence of cancer considerably increases this ratio. At 3 months, we observed metabolic atrophy except for Cho. Although, higher ADC values are normally found in peripheral zone than in central gland, these differences disappear after radiotherapy. In healthy rat prostate high levels of Cho without citrate were noted. Cho and free lipids were detected in PC3-MM2 and PAC120 SC-grafted tumors, with a higher Cho content in PC3-MM2. Radiotherapy induced significant antitumor activity in PC3-MM2 (SC) (T/C% = 38%) and OT (ILS% = 58%) tumors, but was not efficient in PAC120 SC-grafted tumors (T/C% = 90%). Radiotherapy slightly modified Cho content 4 days after the end of treatment but no modification on overall metabolic profile was observed before, during and after radiotherapy. Conclusions: Combined ADC and Cho are powerful biomarkers for the detection of PCa in men and could be useful for ETRR.The use of Cho in ETRR for PCa in rats appears to be promising.

No significant financial relationships to disclose.

Comparison of epirubicin and doxorubicin cardiotoxicity induced by low doses: evolution of the diastolic and systolic parameters studied by radionuclide angiography

BACKGROUND

Previous studies have demonstrated that epirubicin (EPI) has a lower propensity to produce cardiotoxic effects than doxorubicin (DXR) at high doses.

HYPOTHESIS

The aim of the study was to compare the cardiotoxicity induced by low doses of EPI and DXR in patients before and 1 month after the end of chemotherapy.

METHOD

In a prospective study, 99 patients with a mean age of 51 +/- 12 years and without cardiac disease were studied before and 1 month after the end of chemotherapy. Group 1 included 38 patients receiving 246 +/- 96 mg/m2 of DXR and Group 2 included 61 patients receiving EPI with and equivalent dose of 219 +/- 92 mg/m2 of DXR. Ejection fraction (EF) of the left ventricle (LV), peak ejection rate (PER), and peak filling rate (PFR) [expressed in end-diastolic volume/s (EDV/s)] were evaluated by gated radionuclide angiography; PFR/PER were also calculated.

RESULTS

Moderate and similar alterations of left ventricular ejection fraction were shown for low doses of anthracyclines. The EF of the LV decreased from 57 +/- 6% to 54 +/- 6% for DXR group (Group 1) (p = 0.005), and from 58 +/- 5% to 55 +/- 5% for the EPI group (Group 2)(p = 0.001). The PER of the left ventricle fell from 3.08 +/- 0.46 EDV/s to 2.79 +/- 0.49 in Group 1 (p = 0.004) and from 2.98 +/- 0.50 to 2.73 +/- 0.34 EDV/s in Group 2 (p = 0.001). In contrast, no significant alteration of PFR appeared in Group 2 (from 2.72 +/- 0.51 to 2.62 +/- 0.41 EDV/s) for the equivalent dose of anthracycline, while PFR of the LV dropped from 2.82 +/- 0.76 (EDV/s) to 2.41 +/- 0.55 after doxorubicin (p = 0.004). No difference was found between 1 and 12 months after the end of the treatment in 25 patients in Group 1 and 28 patients in Group 2. These results confirm the advantage of EPI over DXR in terms of cardiotoxicity and help explain the relationship of cellular damage mechanisms with the functional parameters of nuclear investigation.

CONCLUSION

A possible explanation for specific alteration after DXR could be the increased production of semiquinone free radicals, which are known to induce membrane damage and, consequently, myocardial edema and diastolic alteration.

Predicative value of [18F]-FDG PET scan for pathological complete response to neoadjuvant chemotherapy in breast cancer

505

Background: To evaluate, in breast cancer patients treated by neoadjuvant chemotherapy, the early predictive value of the FDG uptake decrease for the assessment of the pathological complete response (pCR). Methods: Forty seven women with non metastatic with conventional imaging, non inflammatory, large or locally advanced breast cancer were included. Pathological tumour regression determined on surgical resection specimens served as the gold standard for the assessment of the neoadjuvant chemotherapy response. According to the Sataloff classification, patients were classified in two groups: patients with a pathological complete response (pCR) and patients with a pathological non complete response (non pCR). FDG uptake of breast lesions was evaluated before and after the first course of neoadjuvant chemotherapy, using Standard Uptake Value maximum (SUV) corrected by body surface area and glycaemia. Relations between baseline [18F]-FDG uptake and clinical, histopathological and biological parameters were assessed by Mann-Whitney test. Predictive value of the FDG decrease for the assessment of the pCR was studied with logistic regression analysis. Results: An elevated baseline SUV was found independently associated with a high mitotic activity (p<0.002), tumour grading (p<0.004), high score of nuclear pleomorphism (p= 0.03) and positive hormonal receptor status (p<0.005). After completion of chemotherapy, 11 (23%) of the 47 breast tumours examined at surgery showed a pCR while 36 (77%) showed a non pCR. The relative decrease (ΔSUV) after the first course of neoadjuvant chemotherapy was significantly greater in the pCR group than in the non pCR group (p< 10-4). A SUV decrease of 85.4% ± 21.9% in pCR patients versus 22.6% ± 36.6% in non pCR patients was found. ΔSUV<-60% predicted pCR with an accuracy of 87%. With multivariate logistic regression analyses, ΔSUV<-60% was the only predictive factor of the pCR Conclusions: In breast cancer patients treated by neoadjuvant chemotherapy, the FDG uptake decrease, after only one course of treatment, is an early and powerful predictor of the pCR.

No significant financial relationships to disclose.

Left ventricular ejection fraction calculation from automatically selected and processed diastolic and systolic frames in short-axis cine-MRI

The calculation of the left ventricular ejection fraction (LVEF) is dependent upon the accurate measurement of diastolic and systolic left ventricular volumes. Although breath-hold cine magnetic resonance imaging (MRI) allows coverage of the whole cardiac cycle with an excellent time resolution, many authors rely on the visual selection of diastolic and the systolic short-axis slices in order to reduce the postprocessing time. An automatic method was developed to detect the endocardial contour on each image, allowing an automatic selection of the systolic frame. The calculated ejection fraction was compared with radionuclide ventriculography (RNV). Sixty-five patients were examined using an electrocardiogram (ECG)-gated gradient echo sequence. Among these examinations, manual and automatic processing with MRI were compared when the time of the systolic frame concorded. Good correlations have been found between the automatic MRI approach and RNV, and between manual and automatic processing on MRI alone. The results show that the automatic determination of the ejection fraction is feasible, and should constitute an important step toward a larger acceptance of MRI as a routine tool in heart disease imaging. One major benefit of using automatic postprocessing is that it may eliminate the visual choice of the systolic frame, inaccurate in more than 50% of the studied patients.

Is NAA reduction in normal contralateral cerebral tissue in stroke patients dependent on underlying risk factors?

BACKGROUND AND PURPOSE

This retrospective study investigated the dependence of N-acetyl aspartate (NAA) ratios on risk factors for cerebral vasculopathy such as sex, age, hypertension, diabetes mellitus, carotid stenosis, and dyslipidaemia, which may have affected brain vessels and induced metabolic brain abnormalities prior to stroke. We hypothesise that in stroke patients metabolic alterations in the apparently normal contralateral brain are dependent on the presence or not of such risk factors.

METHODS

Fifty nine patients (31 male, 28 female: 58.8+/-16.1 years old) with cortical middle cerebral artery (MCA) territory infarction were included. Long echo time chemical shift imaging spectroscopy was carried out on a Siemens 1.5 T Magnetom Vision scanner using a multi-voxel PRESS technique. Metabolite ratios (NAA/choline, NAA/creatine, lactate/choline, etc) were studied using uni- and multivariate analyses with respect to common risk factors. The influence of age, stroke lesion size, and time since stroke was studied using a linear regression approach.

RESULTS

Age, sex, and hypertension all appeared to individually influence metabolite ratios, although only hypertension was significant after multivariate analysis. In both basal ganglia and periventricular white matter regions in apparently normal contralateral brain, the NAA/choline ratio was significantly lower in hypertensive (1.37+/-0.16 and 1.50+/-0.19, respectively) than in normotensive patients (1.72+/-0.19 and 1.85+/-0.15, respectively).

CONCLUSIONS

Regarding MCA infarction, contralateral tissue remote from the lesion behaves abnormally in the presence of hypertension, the NAA ratios in hypertensive patients being significantly lower. These data suggest that hypertension may compromise the use of contralateral tissue data as a reference for comparison with ischaemic tissue.

[Role of visual analysis of first-pass contrast-enhanced MRI in reperfused myocardial infarction]

The aim of this work is to evaluate the relationship between improvement of regional myocardial function and visual analysis of contrast-enhanced (CE) MRI in patients after acute myocardial infarction. MRI was performed on 19 patients 1 and 11 weeks after a reperfused acute myocardial infarction. Perfusion data (first-pass images [FPI] and delayed CE images) were acquired after an intravenous bolus of gadolinium-DTPA and visually analyzed using a 17 segment model. Each segment was then classified in 3 groups, according to the presence or absence of FPI and CE patterns at baseline study: group 0: normal-appearing segments; group 1: segments with delayed hyper-enhancement but no early hypo-enhancement; group 2: segments with early hypoenhancement. Relative Wall thickening (RWT) was analyzed in each segment and its improvement evaluated in each group. Between first MRI and follow-up study, a significant improvement of RWT occurred in group 1 (mean +/- SD) [from 43.43 +/- 26.59% to 76.71 +/- 47.38%; p = 0.001] but not in group 2 (from 32.73 +/- 25.58% to 39.57 +/- 30.57%; p = NS). In group 0, RWT despite normal value at baseline study exhibited a significant improvement at follow-up (from 65.23 +/- 46.52% to 79.73 +/- 48.46%; p = 0.0015). In conclusion, the combined analysis of early and delayed perfusion abnormalities in MRI in the week following myocardial infarction can predict myocardial viability and allows in the future an evaluation of the efficacy of perfusion therapy.

[Analysis of variation in delivered dose in diagnostic and therapeutic cerebral angiography]

OBJECTIVES

Analysis of dose-area product (DAP) in cerebral angiography, according to the type of pathology and technique used.

MATERIALS AND METHODS

Use of dosimetric and clinical data resulting from 84 diagnostic cerebral angiograms and 32 cerebral embolizations.

RESULTS

The diagnostic angiography data were divided into three categories: A/ When a secondarily embolized aneurysm was diagnosed: n=17. B/ When the final diagnosis was an arteriovenous malformation (AVM): n=10. C/ In the case where the diagnosis was neither AVM, nor aneurysm to embolize: n=57. The cerebral embolizations were classified in two sub-groups: K/ When the embolization immediately followed the diagnostic angiogram: n=15. L/ When the embolization of the aneurysm took place 24 to 48H after the angiography: n=17. The mean DAP of group B containing the AVM is higher than mean DAP values in groups A and C, because of the increased cinegraphic time. There is a strong correlation between the duration of the fluoroscopy and the DAP (n=116; r=0.931; p<0.0001). Addition of runs in the group L contributes to the augmentation of the exposure time (significant difference in time: p=0.0054) and thus with the fact that DAP L>DAPK.

CONCLUSION

Radiation dose during diagnostic cerebral angiography is increased in the presence of AVM. DAP of embolizations are higher when diagnostic and therapeutic phases are separated in time.

[Neuroradiologic emergencies in infectious pathology]

The main goal of urgent imaging evaluation of patients with suspected CNS infection is to differentiate infectious from tumoral or vascular lesions in order to provide appropriate management. MR imaging, including diffusion weighted imaging and spectroscopy, is superior to CT imaging to characterize lesion location and etiology. The CT and MRI features of the more frequent bacterial, viral and parasitic CNS infections will be described.

[Spontaneous hyperdense intracranial vessels seen on CT scan in polycythemia cases]

PURPOSE

A better understanding of the significance of diffuse hyperdensity affecting the circle of Willis and the dural sinuses on unenhanced CT.

MATERIALS AND METHODS

We performed a retrospective study of 19 patients with a neurological manifestation and a CT scan without contrast injection. Among these 19 patients, six had been included because of primary or secondary polycythemia. The analysis of cerebral CT scans was made qualitatively by visual inspection and quantitatively.

RESULTS

In patients with a hematocrit percentage exceeding 60%, both circle of Willis and dural sinuses were dense on unenhanced CT scans. A linear relation between the hemoglobin level and the contrast of the dural sinuses compared with the grey matter was observed with an excellent correlation (r = 0.934; n < 0.0001; p = 19).

CONCLUSION

Increased density of cerebral vessels on unenhanced CT is a sign of a high hemoglobin level.

[Magnetic resonance imaging early after acute myocardial infarction. A visual analysis of myocardial perfusion based on a 17 segment model]

Magnetic resonance imaging allows an accurate calculation of the left ventricular ejection fraction and left ventricular volumes. Additionally, it makes possible to assess myocardial perfusion after gadolinium chelate injection. Late after the injection, the presence of a myocardial hyper-enhancement can be visualized. The present study has used the 17 segment standardized nomenclature for tomographic imaging of the heart as recommended for all cardiac imaging modalities. Sixty nine patients were studied after a revascularised myocardial infarction. All patients had Timi grade 3 flow in the infarct-related artery after therapy. Regional and global function was studied using cine MR short axis slices. The gadolinium chelate first pass was scored using a 5 level scale reflecting the transmural extent of the segmental myocardial enhancement. The delayed enhancement due to gadolinium accumulation in the myocardium 10 min post injection was scored in the same manner. Left ventricular ejection fraction was 51 +/- 13%. Segmental thickening parameters (systolic thickness, absolute thickening and relative thickening) appeared statistically related to the hypoperfusion and delayed enhancement scores. Absolute myocardial thickening varied from 4.8 +/- 2.7 mm in the myocardial segments free of any delayed enhancement to 2.4 +/- 2.1 mm in segments presenting with a transmural extent of the delayed hyper-enhancement. Scores obtained after gadolinium injection were also well correlated with the global left ventricular function (r = 0.65, p < 0.01 for late enhancement). Magnetic resonance imaging of the heart allows a precise characterisation of revascularised myocardium which makes this technique very attractive for evaluating the treatments designed to improve myocardial microperfusion.

[Early study of myocardial perfusion with MRI in revascularized infarcts]

The aim of this work is to study the regional myocardial perfusion by MRI early after revascularised myocardial infarction and to compare it with regional function. This prospective work has included 15 patients with acute first myocardial infarction that was precociously revascularised. A myocardial MRI was performed between D2 and D10 after myocardial infarction. The regional myocardial thickening was evaluated from cine-MRI sequences. For the study of myocardial perfusion, the first pass of the contrast agent was analysed from curves of the signal evolution versus time. The signal enhancement on late images acquired 10 minutes after the perfusion of the contrast agent was also evaluated. Among 384 studied myocardial segments, those with a normal gadolinium first pass curve had a relative thickening of 46 +/- 38%. The segments with a severely reduced first pass kinetic have a markedly reduced relative thickening (14 +/- 20%) in relation with myocardial hypoperfusion. The myocardial enhancement is frequently seen in the infarct territory and appears related to a reduced regional contractility. The myocardium is enhanced on late images in 12% of the normally perfused segments. These segments have a mildly reduced wall thickening (3.36 +/- 2.84 mm vs 4.42 +/- 2.83 mm). The segmental contractility in a reperfused myocardial infarction appears to depend both on the myocardial perfusion which reflects the microvascularisation and on the myocardial enhancement which is linked to myocardial structural alterations. MRI appears to be an adequate method to evaluate these abnormalities and allows an easy assessment of the no-reflow phenomenon, if present.

Long-term prognostic value of 201Tl single-photon emission computed tomographic myocardial perfusion imaging after coronary stenting

BACKGROUND

The prognostic value of (201)Tl myocardial imaging has been demonstrated in several studies concerning patients with a known significant coronary artery disease. However, the evolution of a coronary stenosis after stenting is difficult to predict. This study was designed to assess the prognostic value of (201)Tl single-photon emission computed tomography (thallium SPECT) perfusion imaging in patients after intracoronary stenting.

METHODS

One hundred fifty-two patients were studied. They were followed up during 40 +/- 13 (mean +/- SD) months after thallium SPECT. Stent-related events were studied after thallium stress testing and included cardiovascular death, myocardial infarction, and revascularization. Stress thallium imaging was performed 5 +/- 2 months after stenting, and ischemia was considered to be present if at least 2 contiguous segments were showing reversible defects.

RESULTS

Only 3 (3%) among the 105 nonischemic patients had major cardiac events during the follow-up versus 13 (28%) of the 47 ischemic patients (P < .001) after thallium SPECT. The relative risk of major cardiac events for patients with significant ischemia was 10.5 compared with nonischemic patients (P < .001). Fourteen (30%) of the ischemic patients and 8 (8%) among the nonischemic patients underwent iterative revascularization (P < .001). Therefore, only 11 (10%) of the nonischemic patients had major cardiac events or revascularization compared with 24 (51%) of the ischemic patients (P < .001).

CONCLUSIONS

Absence of ischemia on thallium SPECT imaging at 5 months after coronary stenting indicates a low risk for cardiovascular events or interventional procedure. These results may have important clinical implications in patient treatment.

[Magnetic resonance imaging of dilatation of the ascending aorta after repair of coarctation of the aorta]

The authors studied the risk factors for dilatation of the ascending aorta in patients operated for coarctation of the aorta. A prospective study of the diameters of the ascending aorta by magnetic resonance imaging was undertaken in 46 patients with an average age of 30 months (range 6 days to 11 years) at surgery, and 10 years of age (6 months to 31 years) at the time of the investigation. The diameters were measured at the level of the sinus of Valsalva, at the sino-tubular junction, and compared with reference tables with respect to body surface area. Twenty six per cent of patients had dilatation of the ascending aorta. The predisposing factors were investigated. Age, type of surgery, postoperative hypertension. Doppler gradient in the isthmic region, anatomical appearances of the repair observed by MRI were not predictive of this complication. On the other hand, age of patients at MRI and bicuspid aortic valves (present in 66% of cases) (p < 0.05) were significant risk factors. These results indicate that regular follow-up by echocardiography or MRI of the diameter of the ascending aorta is necessary in patients operated for coarctation of the aorta and with bicuspid aortic valves.

Correlation between inter-ictal regional cerebral blood flow and sphenoidal electrodes--recorded inter-ictal spikes in mesial temporal lobe epilepsy

The objective of this study was to assess the reliability of the diagnosis of mesial temporal lobe epilepsy using EEG and sphenoidal electrodes. Inter-ictal 99 m Tc-HMPAO SPECT scans were registered in 21 patients with confirmed mesial temporal lobe epilepsy identified by scalp EEG and sphenoidal electrodes. Visual and quantitative SPECT analysis was performed blind to EEG data. An asymmetry index (AI) was measured from the ratio of two symmetrical regions of interest. A temporal lobe hypoperfusion was defined as an uptake reduced by 5% with respect to the contralateral region. Inter-ictal SPECT abnormalities were observed in 12 out of 21 patients (57%) from both visual and quantitative analysis (focal hypoperfusion in 11 cases, focal hyperperfusion in one case). In seven patients (33%) both visual and quantitative scintigraphy were normal. Abnormal AI was found in 11/15 patients with a high frequency of seizures and in 1/6 patients with a low frequency of seizures. The major data is that the probability to have an abnormal SPECT is statistically correlated to the frequency of the epileptic fits. The couple EEG recordings with sphenoidal electrodes and SPECT is sensitive and reliable in the diagnosis of mesial temporal lobe epilepsy.

Multi-variate analysis predicts clinical outcome 30 days after middle cerebral artery infarction

BACKGROUND AND PURPOSE

To evaluate the functional prognostic value of proton magnetic resonance spectroscopy performed within the 5 days of an infarction of the middle cerebral artery territory, compared with previously demonstrated prognostic factors.

METHODS

Proton magnetic resonance spectroscopy was performed on 77 consecutive non-comatosed patients during the acute stage of middle cerebral artery infarction. The functional status was determined for each patient via the Orgogozo score. Proton magnetic resonance spectroscopic data were acquired in the infarction and in contra-lateral normal tissue and the results were expressed as metabolite ratios. Correlations were evaluated between the Orgogozo score at day 1 and day 30, the age, the sex, the volume of the infarction, and the metabolic ratios.

RESULTS

In a monovariate analysis, the decrease of the NAA/choline ratio was correlated with a low Orgogozo score at days 1 and 30 (P<0.05) and with a large infarction (P<0.05). A stepwise analysis showed a significant relationship between the Orgogozo score at day 30 and the Orgogozo score at day 1, the sex, the volume of infarction, and the NAA/Cho ratio within the infarction.

CONCLUSIONS

Our work demonstrates that a good clinical outcome at day 30 depends on a good initial clinical score at day 1, a small volume of infarction, a small decrease of NAA/Cho, and being of the female gender.

[The best of non-invasive cardiac imaging in 1999]

The term non-invasive and non-echographic myocardial imaging is used to describe the advances in nuclear cardiology and magnetic resonance imaging underlying the most recent developments in investigating the myocardium. The value of new techniques such as rapid CT scan and cardiological applications of the synchroton are described. The main clinical applications of these techniques in the present and future are reviewed, especially with regards to ischaemic heart disease.

Muscle metabolism assessed by phosphorus-31 nuclear magnetic resonance spectroscopy after myocardial infarction in rehabilitated patients: a 1-year follow-up

BACKGROUND

The most common effect of postmyocardial infarction (post MI) rehabilitation is an increase of peak maximal oxygen consumption correlated with changes in calf muscle metabolism, but there are few data on follow-up after rehabilitation on skeletal muscle and maximal oxygen consumption. The purpose of this study was to investigate the respective modifications in skeletal muscle metabolism and peak oxygen consumption (VO2) occurring during a supervised rehabilitation program and 1 year after MI in patients free of heart failure.

METHODS

Fifteen outpatients were studied prospectively after the acute phase of the MI, at the end of the rehabilitation program (2 months after the MI), and 1 year after. The rehabilitation comprised 20 sessions with three sessions per week. The program consisted of exercise training with bicycle, arm ergometer, and treadmill. The program also included respiratory exercises, psychological support, and counseling for secondary prevention of cardiovascular diseases. At each visit, a stress test on a bicycle ergometer was performed and the peak VO2 was measured. Phosphorus magnetic resonance spectroscopy of the gastrocnemius muscle was performed at rest and during a plantar flexion-type exercise against an adjustable load. Data were analyzed using analysis of variance and post-hoc test when appropriate.

RESULTS

The mechanical power output measured during the bicycle exercise increased from 111 +/- 28 watts at the post MI test to 136 +/- 40 watts after rehabilitation (post rehab) and decreased to 125 +/- 36 watts at 1 year. The peak VO2 increased significantly (P < 0.05) from 22 +/- 7 ml/kg-1/min-1 (post MI) to 27 +/- 9 ml/kg-1/min-1 (post rehab), and decreased significantly to 24 +/- 8 ml/kg-1/min-1 (1 year). The mechanical power output measured in the magnet during the stress test increased from 2.22 +/- 0.13 watts (post MI) to 2.85 +/- 1.24 (post rehab), and stabilized at 2.78 +/- 1.10 watts at 1 year. At the highest workload attained in the three successive tests, the phosphocreatine/(phosphocreatine + inorganic phosphate) ratio rose significantly (P < 0.05) from 0.46 +/- 0.13 (post MI) to 0.51 +/- 0.13 (post rehab) and remained at 0.51 +/- 0.13 at 1 year.

CONCLUSION

The improvement of the peak VO2 after training post MI is not maintained 1 year later. This decline is not accompanied by muscular metabolic abnormalities. This suggests that the muscle metabolism after MI remains normal, and that the long-term decrease of the peak VO2 reflects a global deconditioning that should be avoided by maintaining a long-term phase III rehabilitation program.

MR imaging of the heart in patients after myocardial infarction: effect of increasing intersection gap on measurements of left ventricular volume, ejection fraction, and wall thickness

PURPOSE

To determine the extent to which the number of planes imaged at magnetic resonance (MR) imaging could be reduced without modifying the calculated volume and thickness of the left ventricle.

MATERIALS AND METHODS

Sixty-one patients were examined after a myocardial infarction. The whole left ventricle was imaged by using 5-mm contiguous breath-hold cine MR short-axis sections with no gap (SAng) (two-dimensional fast low-angle shot sequence, 9/4.8 [repetition time msec/echo time msec]). The effect of omitting one section in two (short-axis sections with 5-mm gap [SA5 mm]) or two sections in three (short-axis sections with 10-mm gap [SA10 mm]) was studied.

RESULTS

In the comparison of SA5 mm or SA10 mm with respect to the reference SAng, the standard error of the estimate (SEE) for the diastolic volume did not exceed the 6.1% interobserver SEE, and the SEE for the ejection fraction remained lower than the 3% interobserver SEE. The measured wall thickness was not affected. In addition, six simple geometric models were compared with SAng and yielded an SEE of 9.5%-28.1% for the diastolic volume and 3.8%-13.3% for the ejection fraction.

CONCLUSION

In the study of left ventricles with heterogeneous contractility, short-axis imaging is more accurate than geometric modeling and permits wall thickness measurements when an intersection gap of 5 or 10 mm is used.

The time course of haemodynamic, autonomic and skeletal muscle metabolic abnormalities following first extensive myocardial infarction in man

We investigated the time course of genesis of skeletal muscle dysfunction and sympatho-vagal imbalance after myocardial infarction. We studied 22 normal controls, 22 patients with >6 months stable chronic heart failure and 10 patients after a first massive myocardial infarction at 1-3 weeks (the "early" period), 6-8 weeks ("mid") and 6-9 months ("late") following their infarct. Four patients developed overt heart failure. Forearm muscle metabolism was studied using (31)P magnetic resonance spectroscopy (MRS). Sympatho-vagal balance was assessed by heart rate variability and radiolabelled norepinephrine kinetics. Increased norepinephrine spillover (0.55+/-0.02 v 0.27+/-0.04 mg/min/m(2); P<0.01) and decreased heart rate variability were confined to those post-myocardial infarction patients who subsequently developed heart failure. Resting cardiac output was normal in all the post-myocardial infarction patients, although the response of cardiac output to supine bicycle exercise at the "mid" study point was less in the group who subsequently developed heart failure (9+/-1 v 41+/-8 %; P<0.005). In the MRS studies, there were no detectable differences between those who did or did not develop heart failure. The initial rate of ATP turnover, calculated from initial-exercise changes in pH and phosphocreatine (PCr), was increased in established chronic heart failure, but in the post-myocardial infarction patients a numerically similar increase reached statistical significance only in the early group (19+/-3 v 11+/-1 mM/min; P<0.005). The apparent maximum rate of oxidative ATP synthesis, calculated from post-exercise PCr recovery kinetics, was lower than control in the late post-myocardial infarction and established chronic heart failure groups 34+/-5 v 55+/-4 mM/min; P<0.03 and 38+/-3 v 55+/-4 mM/min; P<0.003, respectively). Skeletal muscle metabolism and autonomic function become abnormal after an extensive myocardial infarction. While skeletal muscle abnormalities are relatively slow to develop and unrelated to the degree of failure, excessive neurohormonal activation and impaired cardiac output response to exercise seem from an early stage to characterize patients who subsequently develop chronic heart failure.

Cerebral metabolism after transient ischemic attack. A 1H MR spectroscopy study

Metabolic changes induced by cerebral infarction or by stenosis and occlusion of the internal carotid artery have been previously described in 1H Magnetic Resonance Spectroscopy (1H MRS). These changes are essentially characterized by decreased N-acetyl-aspartate (NAA) and increased lactate concentration. Little is known about the metabolic changes observed in the three days following a transient ischemic attack (TIA), in the absence of stenosis or occlusion of the internal carotid artery, and without visible infarction on Magnetic Resonance Imaging (MRI). We studied five patients with a TIA lasting between 30 min and 3 h, affecting the sensory and motor functions of the brachio-facial territory with or without aphasia. A Computerized Tomography Scan (CT-scan), an electro-encephalogram, cervical Doppler ultrasound and MRI with proton magnetic resonance spectroscopy were performed on the affected cerebral area and on the normal contralateral homologous cerebral area within three days of the onset of TIA. None of the five patients had stenosis or occlusion of the internal carotid artery on Doppler ultrasound, or cerebral infarction on MRI. From 1H MRS ratio measurements, we did not observe any significant changes in the NAA/Creatine ratio. However, a rise in Lactate/Creatine ratio was observed in the symptomatic non-infarcted area compared with the normal cerebral tissue. During the first three days following a transient ischemic attack, there is an increase in lactate production. This change may reflect transient local hypoperfusion which could be long enough to stimulate lactate production, but short enough not to induce infarction. This region could be at risk from infarction in the long term.

Quantifying stenosis in renal arteriograms: a fuzzy syntactic analysis

The introduction of fuzzy logic improves a system for the automatic quantification of renal artery lesions seen in digital subtraction angiograms. A two-step approach has been followed. An earlier system based on non-fuzzy syntactic analysis provided a clear symbolic description of the stenotic lesions. Although this system worked correctly, it did not take into account the variability and uncertainty inherent to image processing and to knowledge on the reference diameter. This system has been improved by the introduction of fuzzy logic in the representation of the reference diameter. It provides a description of the stenosis in terms of fuzzy quantities. To illustrate the benefits of the fuzzy approach, the results of the two systems have been compared by plotting the differences of an index of variability. It appears that the differences are statistically different when using a two-tailed paired t-test (t = 2.37; p = 0.025). The result shows that the fuzzy approach is better than a non-fuzzy approach in the sense that the index of variability is reduced significantly.