Pitfalls and Limitations of Radionuclide Renal Imaging in Adults.

To understand pitfalls and limitations in adult renography, it is necessary to understand firstly the physiology of the kidney, especially the magnitude and control of renal blood flow, glomerular filtration rate and tubular fluid flow rate, and secondly the pharmacokinetics and renal handling of the three most often used tracers, Tc-99m-mercaptoacetyltriglycine (MAG3), Tc-99m-diethylene triamine pentaacetic acid (DTPA) and Tc-99m-dimercaptosuccinic acid (DMSA). The kidneys may be imaged dynamically with Tc-99m-MAG3 or Tc-99m-DTPA, with or without diuretic challenge, or by static imaging with Tc-99m-DMSA. Protocols are different according to whether the kidney is native or transplanted. Quantitative analysis of dynamic data includes measurement of renal vascularity (important for the transplanted kidney), absolute tracer clearance rates, differential renal function (DRF) and response to diuretic challenge. Static image reveals functional renal parenchymal damage, both focal and global, is useful in the clinical management of obstructive uropathy, renal stone disease and hypertension (under angiotensin converting enzyme inhibition), and is the preferred technique for determining DRF. Diagnosis based on morphological appearances is important in transplant management. Even though nuclear medicine is now in the era of hybrid imaging, renal imaging remains an important subspecialty in nuclear medicine and requires a sound basing in applied physiology, the classical supporting discipline of nuclear medicine.

Changes in the appearance of attenuation artefacts due to change in posture in myocardial perfusion imaging.

OBJECTIVE: Traditional supine imaging with arms raised for myocardial perfusion imaging (MPI) is uncomfortable for many cardiac patients. Seated imaging with arms resting at shoulder level is an attractive alternative. This study aimed to compare the patient comfort and image appearance of seated MPI with traditional supine MPI. METHOD: Sixty-seven patients (41 male, 26 female; body mass index (BMI) between 20.4 and 45.4) were imaged seated on the Mediso Nucline Cardiodesk gamma camera and supine on the GE Millennium VG gamma camera using our standard departmental MPI protocol. The images from each were compared and a questionnaire was used to determine patients' views of the relative comfort of the procedures. RESULTS: Strong patient preference for seated imaging was demonstrated. Perfusion patterns on seated and supine images were strikingly different with the changes seen being greatest and very striking in obese females with seven out of 12 (58%) showing changes of more than two grades. For a subset of 17 normal weight (BMI <25) male patients a significant reduction (P<0.05) in defect size was found in the inferior segment only, signifying a reduction in diaphragmatic attenuation in the seated position. CONCLUSION: Seated imaging offers considerable advantages in terms of patient acceptability. For non-obese men seated imaging also offers advantages in terms of reduced diaphragmatic attenuation artefacts. However, women and also obese men show significant differences in perfusion pattern from traditional supine imaging. A facility for accurate attenuation correction of seated images could provide useful information to elucidate these effects.