Cerebral metabolic rate of glucose quantification with the aortic image-derived input function and Patlak method: numerical and patient data evaluation.

PURPOSE: Quantitative maps of cerebral metabolic rate of glucose (CMRGlu) from fluorine-18 fluorodeoxyglucose-PET are useful in brain studies, but are challenging to acquire because of technical constraints, which hinder their use in clinical routine. Aortic image-derived input functions (IDIFs) combined with Sokoloff's method were proposed as a suitable solution. However, Sokoloff's method requires the use of standard kinetic constants, which may produce biased estimates. Patlak's method would be more appropriate, but concern can arise when used with an aortic IDIF from unavailability of a complete brain curve acquired starting from injection. The aim of this study was to develop a CMRGlu quantification technique that combines Patlak's method with aortic IDIFs in a clinical setting. MATERIALS AND METHODS: A simple acquisition protocol for aortic IDIF measurement was developed and applied on a sample of patients with different degrees of hypometabolism (one healthy control, four patients with a neurodegenerative condition, and one coma patient). CMRGlu estimates in vivo were obtained with both the Sokoloff method and the Patlak method. Computer simulations were performed to assess the causes of bias affecting Sokoloff and Patlak estimates and interpret the results obtained in patients. RESULTS: Simulations showed that Sokoloff's method is less stable than Patlak's method as the extent of bias changed across different physiological states, potentially leading to misinterpretation of clinical data. In clinical patients, Sokoloff and Patlak estimates were correlated on the whole, but deviations emerged for critical physiological states. CONCLUSION: CMRGlu quantification with the Patlak method and aortic IDIF is feasible, easy to implement in clinical practice, and superior to Sokoloff's method from a personalized medicine perspective.

Evaluation of (123)I-orthoiodohippurate single kidney clearance rate by renal sequential scintigraphy in a large cohort of likely normal subjects aged between 0 and 18 years.

PURPOSE: Age-related values of (123)I-orthoiodohippurate (OIH) single kidney clearance rate (Cl) were estimated in a large cohort of likely normal children aged between 0 and 18 years. METHODS: Among 4,111 children examined in the past 10 years, 917 were selected with the following inclusion criteria: (a) mild ultrasonographic hydronephrosis with right differential renal function (DRF) <53% and >47% (498 pts), (b) known or suspected urinary tract infection with normal ultrasound, serum creatinine and DMSA and DRF <53% and >47% (419 pts). (123)I-OIH-Cl was assessed using a validated gamma camera method. Children were divided into 21 age classes: from 0 to 2 years, eight 3-month classes; from 2 to 14 years, twelve 1-year classes; from 14 to 18 years, one 4-year class. RESULTS: Cl, plotted against age, was fitted using an increasing function (y=a-be-cx). Mean (123)I-OIH-Cl of 1,834 kidneys was 306+/-22 ml/min/1.73 m(2) BSA. Mean (123)I-OIH-Cl of the right and left kidneys was 307+/-23 and 305+/-22 ml/min/1.73 m(2) BSA, respectively (p<0.002). The best-fitting (123)I-OIH-Cl growing function was: Cl=311-230e-0.69xAge (months). (123)I-OIH-Cl improved progressively starting from birth, reaching 96% and 98% of the mature value at 1 and 1.5 years, respectively. (123)I-OIH-Cl at birth (age=0) was 81 ml/min/1.73 m(2) BSA. After 18.6 days of life, the renal function had doubled its starting value, and it reached a plateau of 311 ml/min/1.73 m(2) BSA at 2 years. CONCLUSION: This work represents a systematic evaluation of ERPF by a gamma camera method in a large cohort of selected likely normal paediatric subjects.

Relationship of infarct size and severity versus left ventricular ejection fraction and volumes obtained from 99mTc-sestamibi gated single-photon emission computed tomography in patients treated with primary percutaneous coronary intervention.

The current technique of choice for perfusion imaging is gated single-photon emission computed tomography (SPECT), which allows the simultaneous assessment of perfusion and left ventricular (LV) function. We examined the relationships of infarct size and severity with LV ejection fraction (EF) and volumes in 215 myocardial infarction patients treated with primary percutaneous coronary intervention within 6 h of symptom onset. Patients were studied with resting gated SPECT 1 month later. Infarct size was expressed as LV percent, and infarct severity as the lowest activity ratio within the defect. LVEF, end-diastolic (ED) and end-systolic (ES) volume indexes (Vi) were calculated with commercial software. There was a significant correlation between infarct size and LVEF ( r=-0.68, P<0.00001), EDVi ( r=0.53, P<0.00001), and ESVi ( r=0.62, P<0.00001). Slightly lower correlations were demonstrated using infarct severity. LVEF and volumes were related to infarct location. A significantly higher correlation was observed between infarct size and LVEF in anterior than in non-anterior infarctions ( r=-0.75 vs -0.60, P<0.05). In multivariate analysis, infarct size and infarct location were significant predictors of LVEF ( R(2)=0.50) and ESV ( R(2)=0.40). Infarct size and infarct severity were significant predictors of EDVi ( R(2)=0.29). Infarct size (and severity) and LVEF (and volumes) derived from a single gated SPECT study correlate closely. Infarct location influences this relationship, with anterior infarctions showing a lower LVEF than inferior or lateral ones of the same extent.