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We present here a direct least-squares estimation (DLSE) method for the determination of renal kinetic parameters from sequences of very fast acquisitions performed with a three-headed single photon emission computed tomography (SPECT) system. A simple linear model for the behavior of the radiopharmaceutical, as well as a spatial model for its spatial distribution are defined. The model enables one to estimate the kinetic parameters directly from the projections, once the plasma concentration function is known. A new technique for the accurate reconstruction of time-radioactivity curves based on the direct reconstruction of the region-of-interest contents from a series of data from three-projections is presented. The technique is used to determine the plasma concentration function with a sub-second time resolution. The spatially-variant geometrical response is also included in the model to compensate for the spatial resolution of the SPECT system. Results obtained from simulations are presented. Basic spatial and time features of the simulations are derived from a patient study. Noise and segmentation errors are also simulated. The DLSE method is compared with the conventional one of deriving kinetic parameters from the time series of reconstructed images. The standard deviation of results given by DLSE is less than 2%, whereas with the conventional method it is between 5% and 6%. Within the limit of statistical fluctuations, DLSE results are unbiased whereas those of the conventional method are overestimated by 24%. Index Terms--Dynamic single photon emission computed tomography (SPECT), kinetic parameter estimation.

Age-related values of 123I-orthoiodohippurate (OIH) single kidney clearance rate (Cl) were estimated in a large cohort of likely normal children aged between 0 and 18 years. 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). 123I-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. Cl, plotted against age, was fitted using an increasing function ( % MathType!Translator!2!1!AMS LaTeX.tdl!TeX -- AMS-LaTeX! % MathType!MTEF!2!1!+- % feaaeaart1ev0aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbbjxAHX % garmWu51MyVXgatuuDJXwAK1uy0HwmaeHbfv3ySLgzG0uy0Hgip5wz % aebbnrfifHhDYfgasaacH8qrps0lbbf9q8WrFfeuY-Hhbbf9v8qqaq % Fr0xc9pk0xbba9q8WqFfea0-yr0RYxir-Jbba9q8aq0-yq-He9q8qq % Q8frFve9Fve9Ff0dmeaabaqaciGacaGaaeqabaWaaeWaeaaakeaaca % WG5bGaeyypa0JaamyyaiabgkHiTiaadkgacaWGLbGaeyOeI0Iaam4y % aiaadIhaaaa!400A! $$y = a - be - cx$$ ). Mean 123I-OIH-Cl of 1,834 kidneys was 306±22 ml/min/1.73 m2 BSA. Mean 123I-OIH-Cl of the right and left kidneys was 307±23 and 305±22 ml/min/1.73 m2 BSA, respectively ( p<0.002). The best-fitting 123I-OIH-Cl growing function was: Cl=311−230 e−0.69×Age (months). 123I-OIH-Cl improved progressively starting from birth, reaching 96% and 98% of the mature value at 1 and 1.5 years, respectively. 123I-OIH-Cl at birth (age=0) was 81 ml/min/1.73 m2 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 m2 BSA at 2 years. This work represents a systematic evaluation of ERPF by a gamma camera method in a large cohort of selected likely normal paediatric subjects. [ABSTRACT FROM AUTHOR]

Unlabelled: The value of (123)I-hippuran (OIH) renal sequential scintigraphy (RSS) in predicting the evolution of defects detected by (99m)Tc-dimercaptosuccinic acid (DMSA) scanning during a first episode of acute pyelonephritis (APN) was assessed., Methods: Fifty-eight children with APN underwent (99m)Tc-DMSA planar scanning and (123)I-OIH RSS during acute infection and at least 5 mo later. Renal lesions found by (99m)Tc-DMSA scanning were classified according to the following (99m)Tc-DMSA grading system: 0 = normal, 1 = 1 lesion, 2 = 2 lesions, and 3 = diffuse damage with renal parenchymal subversion. Renal scarring was diagnosed whenever a renal cortical defect detected at the first (99m)Tc-DMSA examination persisted on the follow-up (99m)Tc-DMSA examination. Single-kidney clearance rate (Cl) was evaluated by a method that was previously validated at our institution and is based on time-activity curves measured on the heart and kidney areas by the region-of-interest technique., Results: (99m)Tc-DMSA scanning showed renal damage in 76 kidneys and had negative findings for the remaining 40 kidneys (2 patients had bilaterally negative findings). (99m)Tc-DMSA scanning determined 40 kidneys to be grade 0, 49 to be grade 1, 21 to be grade 2, and 6 to be grade 3. For (99m)Tc-DMSA grades of 0-3, the corresponding Cl mean values (in mL/min/1.73 m(2) of body surface area [BSA]) were 292 +/- 33, 237 +/- 39, 210 +/- 54, and 140 +/- 53, respectively. The Spearman regression coefficient (R) demonstrated a significant correlation between (99m)Tc-DMSA grade and Cl (R = 0.69, P < 0.0001). Thirty-six of the lesions detected by staging (99m)Tc-DMSA were shown to have recovered on follow-up renal scans, whereas 40 developed scars. A significant difference in Cl was found between the 2 groups (P < 0.0002). The Cl cutoff value was determined by univariate discriminant analysis; a Cl value of 232 mL/min/1.73 m(2) of BSA discriminated best between scarred and nonscarred kidneys, with a specificity, sensitivity, positive predictive value, negative predictive value, and overall accuracy of 95%, 95%, 90%, 97%, and 95%, respectively., Conclusion: Cl evaluation, in the course of acute urinary tract infection, is highly valuable in predicting the fibrotic evolution of renal damage detected on acute (99m)Tc-DMSA scanning. Also, our data show close agreement between Cl and the grade determined by staging (99m)Tc-DMSA.

Unlabelled: The goal of this study was to evaluate the clinical reliability of the (131)I-6 beta-iodomethyl-norcholesterol ((131)I-NP-59) uptake semiquantitative evaluation method we propose for the characterization of adrenocortical masses in a selected population of patients with disease clinically classified as subclinical (SC) and preclinical (PC) Cushing's syndrome (CS) according to Reincke's definition., Methods: Forty-seven consecutive patients with incidentally discovered unilateral adrenal masses were examined by a triple-head SPECT system after intravenous injection of (131)I-NP-59. Abdominal SPECT was performed at 24, 48, 72, and, in selected cases, 96 h after tracer injection. Connected with adrenals and liver, a standard elliptic region of interest (ROI) was manually drawn, taking care to avoid the gallbladder region. The adrenal ROI integral count, obtained by summing the 24-, 48-, and 72-h counting values, was normalized by the hepatic integral count. Subsequently, the adrenal percentage of relative uptake (UPT%) was computed., Results: Discriminant analysis was performed on the variables UPT%, adrenocorticotropic hormone (ACTH) serum concentration, and CT mass dimension (CTMD) to determine the variable, or combination thereof, best discriminating between the SC-CS and PC-CS groups. Compared with both ACTH and CTMD variables, univariate analysis confirmed the UPT% variable as the most significant to discriminate between these 2 clinical groups. In fact, UPT% alone correctly classified 8 of 9 patients in the SC-CS group and 20 of 22 patients in the PC-CS group with 95% positive and 80% negative predictive values and with overall accuracy, sensitivity, and specificity equal to 90%, 91%, and 89%, respectively. When all 3 variables were submitted to stepwise discriminant analysis, the derived classification matrix, after cross-validation, correctly classified 9 of 9 patients in the SC-CS group and 18 of 22 patients in the PC-CS group with 100% positive and 69% negative predictive values and with overall accuracy, sensitivity, and specificity equal to 87%, 82%, and 100%, respectively., Conclusion: According to these initial results, use of the proposed semiquantitative approach associated with both laboratory screening for cortisol production and CTMD measure seems to be able to increase the clinical diagnostic accuracy of PC-CS. This approach could be used in the follow-up of adrenal mass function every time hormonal or clinical features are suggestive of adrenocortical hyperfunction.

The effects of medium-term antihypertensive treatment with the ACE inhibitor ramipril were studied on 10 hypertensive single-kidney patients in a double-blind study versus placebo. Patients with renovascular hypertension were excluded. Compared to placebo, ramipril induces a significant reduction of arterial blood pressure (p < 0.02 for systolic, p < 0.01 for diastolic, and p < 0.05 for mean blood pressure), renal vascular resistance (p < 0.005), and microalbuminuria (p < 0.005), but a significant rise of effective renal plasma flow (p < 0.01) and no significant variation of the glomerular filtration rate. The reduction of microalbuminuria was not related to arterial blood pressure variation. Our study shows that ramipril, in appropriately selected-kidney patients, is effective and safe in reducing arterial blood pressure, bringing about an improvement of renal function and reducing microalbuminuria, which is frequently observed in this condition.