[Usefulness of low tube operating potential (TOP) for improved detection of minimally contrast-enhanced nodules CT].
OBJECTIVE
We recently observed that hepatic nodules which were only minimally enhanced on dynamic CT were much better visualized using a low TOP in spite of some increase of the background noise. The purpose of this study is to evaluate the potential superiority of low TOP in detecting minimally contrast-enhanced hepatic nodules on CT.


METHODS
A phantom was made of anger and contrast medium. Four anger columns were made four different concentrations of contrast media (0.8%, 1.0% 1.5% 1.8%). The phantom was scanned using different TOP (80, 100, 120, 140 kVp). Detectability of the columns were also evaluated contrast to noise ratio (CNR) and visually by radiologists in a doubleblind fashion. Weighted computed tomography dose index (CTDIw) was compared with different TOP. In the clinical study, seven patients were studied. The diagnostic usefulness of a TOP of 80 kVp was compared with that of 120 kVp in same patient by Dynamic CT which has better detectability of minimally contrast enhancing nodules.


RESULTS
With using lower TOP, CNR was increased. On visual evaluation by radiologists, images taken at 80 kVp achieved the highest detectability of the columns. CTDIw associated with the 80, 100, 120, 140 kVp at one scan were 5.78 mGy, 6.64 mGy, 8.13 mGy, 11.02 mGy, respectively. In the clinical study a lesion could be detected clearly with a low TOP of 80 kVp though the existence of the lesion could not be detected at 120 kVp. The existence of the HCC was proven with DSA, CTA and CTAP.


CONCLUSIONS
It was demonstrated in the phantom study that if up-to-date equipment is used, CT operated at a TOP of 80 kVp has potentially better detectability of minimally contrast-enhanced nodules than 120 kVp.
Fukui Medical University Hospital.
T
T
Ishida
K
K
Higashimura
H
H
Itou
D003287:Contrast Media; D019047:Phantoms, Imaging; D011856:Radiographic Image Enhancement / Q000379:methods*; D014057:Tomography, X-Ray Computed / Q000379:methods*
D003287:Contrast Media