Kidney transplant donor glomerular filtration rate by iohexol clearance during computerized tomographic angiography of the kidneys.

BACKGROUND: Pre-transplantation living-donor kidney function determines remaining donor kidney function and significantly affects post-transplantation allograft function in the recipient. Few transplantation centers perform donor kidney function measurement owing to patient burden. A simplified method of glomerular filtration rate (GFR) measurement after angiographic procedures may facilitate more precise measurement of donor kidney function. METHODS: We evaluated the agreement between a simplified method of GFR measurement after renal computerized tomographic (CT) angiography (index GFR, 100 mL iohexol [350 mg/mL iodine]) and the reference GFR measurement with the use of iodinated radiocontrast media (5 mL bolus of iohexol [300 mg/mL iodine]) among 19 potential living kidney transplant donors. The 24-hour creatinine clearance and GFR estimation equations were additionally examined. Kidney lengths and total and segmented cortical kidney volumes were also measured. RESULTS: The index CT angiography GFR performed best with respect to the reference GFR with minimal bias (mean difference, -4 mL/min/1.73 m(2)), good precision (SD of the difference, 9.8 mL/min/1.73 m(2)), coefficient of determination (R(2)) of 0.74, narrow mean coefficient of variation (5% [range 1%-15%]), and high accuracy, with 100% of the values for the index test within 30% of the reference test. The 24-hour urine creatinine clearance values performed poorly. Kidney volumes and length did not significantly correlate with measured GFR. CONCLUSIONS: The CT angiographic GFR measurement could be a useful and more convenient method of donor kidney function evaluation and maintains minimal bias, high precision, and accuracy compared with the reference GFR measurement.

Scan length optimization for pulmonary embolism at CT angiography: analysis based on the three-dimensional spatial distribution of 370 emboli in 100 patients.

AIM: To determine the size and three-dimensional spatial distribution of pulmonary emboli (PE) at computed tomography angiography (CTA) to optimize the scan length. MATERIALS AND METHODS: Two experienced radiologists jointly reviewed 100 consecutive, positive PE CTA studies performed in the Emergency Department (53 women; age 61±17 years). All studies were conducted on a 16-detector row CT machine. In each case, the number of emboli was counted and the proximal and distal spatial coordinates of each embolus documented. Coordinates of the main pulmonary artery bifurcation (MPAb) and carina were recorded. For normalization, the thoracic cavity height (H)-from inlet to lowest hemidiaphragm-was measured. The minimal scan lengths for (a) capturing all emboli and (b) rendering a positive diagnosis were determined. RESULTS: Three hundred and seventy (370) emboli were detected. The average number of PE per patient was 3.7 (maximum 12, minimum 1). Their average length was 2.7 cm. Nine patients had saddle emboli (9%), and 71% of emboli were at or below the MPAb. An 18 cm (0.90×H) scan length, centred 4 cm (0.18×H) below the carina, captures all PE in this dataset while reducing z-axis coverage by 29% (34% for normalized data). Moreover, a 14.2 cm (0.78×H) scan length appropriately centred captures at least one embolus in all patients while reducing coverage by 44% (43%). Decreasing scan length to the lesser of 14.2 cm and 0.78×H per patient reduces coverage by 47%. CONCLUSION: Scan length at CTA for PE can be reduced by up to 47% while preserving diagnostic accuracy for PE detection.