CLINICAL EVALUATION OF RENAL IMAGING BY ^99mTc-DMSA

Abstract

In the past, ²⁰³Hg-Neohydrin was commonly in use as a renal imaging agent. However, ²⁰³Hg-Neohydrin has such drawbacks as requiring high radiation dose to the patient. In an attempt to overcome this disadvantage, ¹⁹⁷Hg-Neohydrin and ^99mTc-labeled renal scanning agents have been evaluated.
In this report ^99mTc-dimerucaputosuccinic acid (^99mTc-DMSA: Medi-Physics) was evaluated for the clinical renal imaging. Ninety-seven cases consisted of 53 females and 44 males ranging from 12 to 89 years old (mean 60.4 years old) were studied by this new radiopharmaceutical.
Pho/Gamma 4 gamma camera with parallel hole high resolution and pinhole collimators and Graphic 5φ scanner were used. The images were obtained at 30min, 1, 2, 3, 4 and 6 hours after intravenous injection of 5mCi of ^99mTc-DMSA. In some cases, radioisotope angiogram was obtained after bolus injection of 10mCi of ^99mTc-DMSA.
In all cases, clear renal images were obtained up to 6 hours after injection. When the pinhole collimator was used in order to enlarge each kidney to full size of the field of view, more detail of renal image could be seen with improved resolution compared with images obtained by parallel collimator or Graphic scanner. When a breath-holding technique is applied it could minimize the image-degrading effect of respiratory movement of the kidneys.
Because this radiopharmaceutical accumulates in renal cortex and renal medulla demonstrates relatively cold area, normal variation of this new renal image was more marked than that of previous renal images. Normal renal image using ^99mTc-DMSA and pinhole collimator were classified into three paterns. In patients with chronic pyelonephritis, renal images usually demonstrated marked cortical atrophy. Renal infarct, polycystic kidney and renal cell carcinoma were also clearly depicted by the combination of ^99mTc-DMSA and pinhole collimator.
In conclusion, renal imaging by ^99mTc-DMSA combined with pinhole collimator was found to be the most useful method currently available for renal imaging. Improved image served for the readings of normal renal structure, characteristic findings of the cases with pyelonephritis and other space occupying lesions such as polycystic kidney, renal infarct, renal carcinoma and etc.