Kinetic Evaluation of the Hypoxia Radiotracers ­ 18 FFMISO and ­ 18 F FAZA in Dogs with Spontaneous Tumors Using Dynamic PET/CT Imaging / 대한핵의학회잡지

Purpose@#We evaluated the kinetics of the hypoxia PET radiotracers, [18F]fluoromisonidazole ([18F]FMISO) and [18F] fluoroazomycin-arabinoside ([18F]FAZA), for tumor hypoxia detection and to assess the correlation of hypoxic kinetic parameters with static imaging measures in canine spontaneous tumors. @*Methods@#Sixteen dogs with spontaneous tumors underwent a 150-min dynamic PET scan using either [18F]FMISO or [18F] FAZA. The maximum tumor-to-muscle ratio ­(TMR max ) > 1.4 on the last image frame was used as the standard threshold to determine tumor hypoxia. The tumor time-activity curves were analyzed using irreversible and reversible two-tissue compartment models and graphical methods. T­MR max was compared with radiotracer trapping rate (k 3 ), influx rate (K i ), and distribution volume (V T ). @*Results@#Tumor hypoxia was detected in 7/8 tumors in the [18F]FMISO group and 4/8 tumors in the [18F]FAZA group. All hypoxic tumors were detected at > 120 min with [18F]FMISO and at > 60 min with [18F]FAZA. [18F]FAZA showed better fit with the reversible model. ­TMR max was strongly correlated with the irreversible parameters (k3 and Ki ) for [18F]FMISO at > 90 min and with the reversible parameter (V T ) for [18F]FAZA at > 120 min. @*Conclusions@#Our results showed that [18F]FAZA provided a promising alternative radiotracer to [18F]FMISO with detecting the presence of tumor hypoxia at an earlier time (60 min), consistent with its favorable faster kinetics. The strong correlation betwee TMR max over the 90–150 min and 120–150 min timeframes with [18F]FMISO and [18F]FAZA, respectively, with kinetic parameters associated with tumor hypoxia for each radiotracer, suggests that a static scan measurement ( ­TMR max ) is a good alternative to quantify tumor hypoxia.

Can distinction between the renalcortex and outer medulla onultrasonography predict estimatedglomerular filtration rate in caninechronic kidney diseases?

Background@#Quantitative evaluation of renal cortical echogenicity (RCE) has been tried anddeveloped in human and veterinary medicine. @*Objectives@#The objective of this study was to propose a method for evaluating RCEquantitatively and intuitively, and to determine associations between ultrasonographic renalstructural distinction and estimated glomerular filtration rate (eGFR) in canine chronickidney disease (CKD). @*Methods@#Data were collected on 63 dogs, including 27 with normal kidney function and 36CKD patients. Symmetric dimethylarginine and creatinine concentrations were measuredfor calculating eGFR. RCE was evaluated as 3 grades on ultrasonography images accordingto the distinction between the renal cortex and outer medulla. The RCE grade of each kidneywas measured. @*Results@#There was a significant difference in eGFR between the group normal and CKD (p< 0.001). As mean of RCE grades (the mean values of each right and left kidney's RCE grade)increases, the proportion of group CKD among the patients in each grade increases (p <0.001). Also, severity of RCE (classified as "high" if any right or left kidney evaluated as RCEgrade 3, "low" otherwise) and eGFR is good indicator for predicting group CKD (p < 0.001). @*Conclusions@#The degree of distinction between the renal cortex and the outer medulla isclosely related to renal function including eGFR and the RCE grade defined in this study canbe used as a method of objectively evaluating RCE.

Usefulness of a saline chaser to reduce contrast material dose in abdominal CT of normal dogs

Use of a saline chaser has been reported to allow reduction of contrast dose and artifacts during computed tomography (CT) examination in humans. This study assesses the extent of contrast dose by using a saline chaser in abdominal CT scans of normal dogs. Five beagles underwent abdominal CT scans. Three protocols were applied: 600 mg I/kg iohexol without saline chaser (protocol 1), 30% lower dose of iohexol (420 mg I/kg) followed by a 10 mL saline chaser (protocol 2), and 40% lower dose of iohexol (360 mg I/kg) followed by a 10 mL saline chaser (protocol 3). Attenuation values were obtained from aorta, portal vein, and liver parenchyma. The maximum enhancement values (MEVs) in protocol 2 were significantly higher than those in protocols 1 and 3 in the aorta; no difference was seen in the portal vein in all protocols. The liver parenchymal MEVs in protocols 1 and 2 were significantly higher than those obtained in protocol 3. In this study, the use of a saline chaser and a reduced dose of contrast material did not affect vessel enhancement. In conclusion, use of a saline chaser for abdominal CT of dogs is recommended because it allows a 30% reduction of contrast dose without decreasing vascular and hepatic parenchymal enhancement.