Tadashi Ohsawa

CT pixel mapping in the diagnosis of small angiomyolipomas of the kidneys.

In six small renal angiomyolipomas (7–17 mm) the superiority of displaying the CT numbers of pixels within a lesion (pixel mapping) over the usual region of interest (ROI) measurement is described in the detection of small amounts of fat tissue. On precontrast 5 mm CT the ROI measurements were >0 in four cases whereas pixel maps revealed pixels with values <0 in six cases.

Effect of water fraction in selection of optimal TI value for STIR sequences.

Objective This article describes the effect of the water fraction in the selection of the optimal T1 value in a STIR sequence. This effect has been given little consideration in previous studies. Materials and Methods Therefore, using both STIR combined with the Dixon method (opposed-phase STIR) and conventional STIR (in-phase STIR), we have investigated the effect of the water fraction in the selection of an optimal TI value for the STIR sequence. Results Our findings have indicated that the water protons rather than the olefinic protons ( – CH = CH – ) play a major role in the opposed-phase effect in vivo. Conclusion Thus, it has been concluded that the most effective fat suppression can be achieved when the intravoxel phase cancellation effect between the water and lipid protons is maximal, rather than when the longitudinal magnetization of the lipid protons is minimal.

Intraarterial digital subtraction angiography in detection of hepatocellular carcinoma

To evaluate the usefulness of intraarterial digital subtraction angiography (IADSA) in hepatocellular carcinoma, IADSA was prospectively performed, combined with conventional film-screen angiography, in 40 patients in whom the tumor was histologically proven or highly suspected. Of the 16 main tumors less than 2 cm, IADSA detected 7 that were missed by film-screen angiography; 6 of these were less than 1 cm in size. With other diagnostic modalities including ultrasound; routine CT study, and CT after intraarterial Lipiodol injection, the detection rate of these tumors was low. IADSAs contribution is important in the detection of small hepatocellular carcinomas.

Orthopantomography of the Cervical Spine

The authors describe the application of orthopantomography to study of the intervertebral foramina of the cervical spine in patients with cervical spondylosis. Other structures such as the lateral mass of the cervical spine can be studied by altering the speed of the rotating film holder, which in two changes the width of the arch of the focal layer.