Luca Camoni

Sub-endocardial and sub-epicardial measurement of myocardial blood flow using 13NH3 PET in man

BackgroundThis study examined whether measuring myocardial blood flow (MBF) in the sub-endocardial (SEN) and sub-epicardial (SEP) layers of the left ventricular myocardium using 13NH3 positron emission tomography (PET) and an automated procedure gives reasonable results in patients with known or suspected coronary artery disease (CAD).MethodsResting and stress 13NH3 dynamic PET were performed in 70 patients. Using ≥ 70% diameter stenosis in invasive coronary angiography (ICA) to identify significant CAD, we examined the diagnostic value of SEN- and SEP-MBF, and coronary flow reserve (CFR) vs. the corresponding conventional data averaged on the whole wall thickness.ResultsICA demonstrated 36 patients with significant CAD. Their global stress average [1.61 (1.26, 1.87) mL·min−1·g−1], SEN [1.39 (1.2, 1.59) mL·min−1·g−1] and SEP [1.22 (0.96, 1.44) mL·min−1·g−1] MBF were significantly lower than in the 34 no-CAD patients: 2.05 (1.76, 2.52), 1.72 (1.53, 1.89) and 1.46 (1.23, 1.89) mL·min−1·g−1, respectively, all P < .005. In the 60 CAD vs. the 150 non-CAD territories, stress average MBF was 1.52 (1.10, 1.83) vs. 2.06 (1.69, 2.48) mL·min−1·g−1, SEN-MBF 1.33 (1.02, 1.58) vs. 1.66 (1.35, 1.93) mL·min−1·g−1, and SEP-MBF 1.07 (0.80, 1.29) vs. 1.40 (1.12, 1.69) mL·min−1·g−1, respectively, all P < .05. Using receiver operating characteristics analysis for the presence of significant CAD, the areas under the curve (AUC) were all significant (P < .0001 vs. AUC = 0.5) and similar: stress average MBF = 0.79, SEN-MBF = 0.75, and SEP-MBF = 0.73. AUC was 0.77 for the average CFR, 0.75 for SEN, and 0.70 for SEP CFR. The stress transmural perfusion gradient (TPG) AUC (0.51) was not significant. However, stress TPG was significantly lower in segments subtended by totally occluded arteries vs. those subtended by sub-total stenoses: 1.10 (0.86, 1.33) vs. 1.24 (0.98, 1.56), respectively, P < .005.ConclusionAutomatic assessment of SEN- and SEP-MBF (and CFR) using 13NH3 PET gives reasonable results that are in good agreement with the conventional average whole wall thickness data. Further studies are needed to examine the utility of layer measurements such as in patients with hibernating myocardium or microvascular disease.

Inter-reader variability of SPECT MPI readings in low- and middle-income countries: Results from the IAEA-MPI Audit Project (I-MAP)

Background Consistency of results between different readers is an important issue in medical imaging, as it affects portability of results between institutions and may affect patient care. The International Atomic Energy Agency (IAEA) in pursuing its mission of fostering peaceful applications of nuclear technologies has supported several training activities in the field of nuclear cardiology (NC) and SPECT myocardial perfusion imaging (MPI) in particular. The aim of this study was to verify the outcome of those activities through an international clinical audit on MPI where participants were requested to report on studies distributed from a core lab. Methods The study was run in two phases: in phase 1, SPECT MPI studies were distributed as raw data and full processing was requested as per local practice. In phase 2, images from studies pre-processed at the core lab were distributed. Data to be reported included summed stress score (SSS); summed rest score (SRS); summed difference score (SDS); left ventricular (LV) ejection fraction (EF) and end- diastolic volume (EDV). Qualitative appraisals included the assessment of perfusion and presence of ischemia, scar or mixed patterns, presence of transient ischemic dilation (TID), and risk for cardiac events (CE). Twenty-four previous trainees from low- and middle-income countries participated (core participants group) and their results were assessed for inter-observer variability in each of the two phases, and for changes between phases. The same evaluations were performed for a group of eleven international experts (experts group). Results were also compared between the groups. Results Expert readers showed an excellent level of agreement for all parameters in both phase 1 and 2. For core participants, the concordance of all parameters in phase 1 was rated as good to excellent. Two parameters which were re-evaluated in phase 2, namely SSS and SRS, showed an increased level of concordance, up to excellent in both cases. Reporting of categorical variables by expert readers remained almost unchanged between the two phases, while core participants showed an increase in phase 2. Finally, pooled LVEF values did not show a significant difference between core participants and experts. However, significant differences were found between LVEF values obtained using different software packages for cardiac analysis. Conclusions In this study, inter-observer agreement was moderate-to-good for core group readers and good-to-excellent for expert readers. The quality of reporting is affected by the quality of processing. These results confirm the important role of the IAEA training activities in improving imaging in low- and middle-income countries.

Prognostic role of baseline 18F-FDG PET/CT parameters in MALT lymphoma.

Mucosa‐associated lymphoid tissue (MALT) lymphoma is an indolent lymphoma with good prognosis and variable fluorine‐18 fluorodeoxyglucose (18F‐FDG) avidity. Many possible prognostic factors have been investigated with controversial results, but the possible prognostic role of 18F‐FDG positron emission tomography/computed tomography (PET/CT) remains unclear. Our aim was to evaluate the prognostic impact of qualitative and semiquantitative baseline PET/CT parameters on outcome of MALT lymphoma. We retrospectively enrolled 161 patients with histologically confirmed MALT lymphoma who underwent 18F‐FDG PET/CT before any treatment. PET images were qualitatively and semiquantitatively analyzed by measuring the maximum standardized uptake value body weight (SUVbw), lean body mass (SUVlbm), body surface area (SUVbsa), metabolic tumor volume (MTV), and total lesion glycolysis (TLG). The Kaplan‐Meier method was used to estimate the progression‐free survival (PFS) and overall survival (OS) times. Cox regression models were performed to determine the relation between PET/CT features and OS and PFS. Ninety‐eight patients had positive 18F‐FDG PET/CT showing 18F‐FDG uptake (mean SUVbw, 10.1; SUVlbm, 7.2; SUVbsa, 2.7; MTV, 88.8; and TLG, 526); the remaining 63 were not 18F‐FDG avid. 18F‐FDG avidity was significantly correlated with tumor size and Ki‐67 score. Relapse/progression of disease occurred in 47 patients with an average time of 40.2 months; death occurred in 12 patients with an average of 59 months. At a median follow‐up of 62 months, median PFS and OS were 52 and 62 months, respectively. Advanced tumor stage and extragastric site were demonstrated to be independent prognostic factors for PFS, while only tumor stage for OS. Instead, PET/CT parameters were not related to survival, despite positive correlation at univariate analysis between MTV and TLG with PFS and positive PET/CT with PFS and OS. In conclusion, a 61% rate of PET avidity in biopsy‐confirmed MALT lymphoma was found, and it was correlated with tumor size and Ki‐67 score. Only tumor stage and localization were independently correlated with PFS and OS.