Twenty five cases of liver cell carcinoma were studied by subtraction technique using ⁶⁷Ga-Citrate and ^99mTc-Colloid. Ten cases were operated on, and 15 were not. Using computer processing system (Nova III), subtraction image were made by substracting ^99mTc image from ⁶⁷Ga image. They were very useful for detecting abnormal ⁶⁶Ga accumulations in the primary liver cell carcinoma. Twenty-four of 25 cases (96%) were easily diagnosed. In the remaining one, ⁶⁶Ga accumulation was recognized retrospectively on the substracted images. It was able to detect intrahepatic metastases even in the area where ordinary scintigram did not show any abnormality.
Setting regions of interest on the 80% substracted image, tumor to bone marrow ratio and lung to bone marrow ratio were calculated respectively. Average tumor to bone mar-row ratio was 2.56 whereas lung to bone marrow ratios were 0.73 in cases without cirrhosis and 1.07 with cirrhosis.
We found that subtraction scintigraphy was very useful not only for diagnosing prima-ry liver cell carcinoma but also for the dicision of operability on the basis of radioisotope imaging technique.

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When space-occupying lesion (SOL) is suspected on conventional ^99mTc-Sn-colloid liver scan, other radionuclide imaging studies, such as hepatobiliary scan, radionuclide liver angiography and 67Ga tumor imaging are often useful not only for distinguishing true SOL from false one but also for comprehending quality of SOL. This usefulness is true par-ticularly when SOL is located in the vicinity of physiologic fossae. First we investigated the frequency of defect like appearances in the vicinity of physiologic fossae, secondly evaluated the usefulness of combined radionuclide imaging studies.
Of 699 liver colloid scans for a year, defect like appearances in the vicinity of gall-bladder bed or porta hepatis were observed in 47% of the liver metastases suspected cases, in 50% of diffuse hepatic disease cases, in 46% of hepatoma cases and in 45% of other cases. Combined liver colloid and hepatobiliary scans were performed for 44 cases (20 liver metastases suspected cases, 18 diffuse hepatic disease cases and 6 other cases). Of these cases, defect and/or defect like appearances on liver colloid scan were located in physi-ologic fossae of 22 cases, in other site than physiologic fossae of 11 cases and in both sites of 11 cases. It means that 33 of 44 hepatobiliary scans were performed in order to clarify defect like appearances of physiologic fossae on liver colloid scan.
In 20 liver metastases suspected cases, combined radionuclide imaging studies were per-formed. Defect like appearances on colloid scans were confirmed to be exactly physiologic fossae in 10 cases by hepatobiliary scans. Hepatobiliary imaging were not obtainable due to hyperbilirubinemia in 4 cases. Of 6 cases which had multiple defects on hepatobiliary scans as well as liver colloid scans, hepatobiliary scans were of use for discriminating true SOL from physiologic fossae in 3 cases. Radionuclide hepatic angiography was performed in 6 cases. SOL had hypervascularity in 2 cases and hypovascularity to avascularity in 4 cases. In gallium scans of 6 liver metastases cases, SOL showed abnormal RI accumulation in 5 cases and no accumulation in one case.
Consequently, combined radionuclide imaging studies were very useful for diagnosing hepatic space-occupying lesions.

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Radionuclide Computed Tomography (RCT) was investigated using a rotating chair de-signed by us in combination with an ordinary scintillation camera (Ohio Nuclear Σ 410 S) and a computer (Scintipac 1200)
An image was first taken laterally, then the second one was taken after the chair was turned through 10 degrees, and so on. Finally, 36 images were taken, covering an entire circumference. The images were taken in a form of 64×64 elements and RCT images were finally displayed on a X-ray film in a form of 128×128 elements through the Micro Dot I mager.
At first, a cylindrical phantom having a diameter of 20 cm was filled with ^99mTc-solution, and the uniformity of the RCT image was checked applying 5 different formulae for count rate corrections on the data obtained. The final images were reconstructed by filtered back projection method with a Shepp and Logan's formula which was further modi-fied to eliminate high frequency noises. Then, we found that simple geometrical mean on the data from the two opposing directions was the best for the count rate corrections, which was exclusively used thereafter.
FWHM was found approximately 20 mm using a line phantom in the above-mentioned cylindrical phantom. Hot tubes having diameters of 4.0, 3.0, 2.0, and 1.0 cm in the phantom were all depicted, whereas the smallest cold tube depicted was 2.4 cm in diameter and 1.5cm was missed. The Alderson liver phantom was tested in air and both balls having diameters of 3.7 and 2.7 cm were well depicted as defects on the RCT images.
On the basis of these fundamental studies, we started applying this technique to the liver following exactly the above-mentioned procedure.
Thirty-seven patients were subjected to this study because of suspected intrahepatic masses. Eight mCi of ^99mTc-phytate was given to the each patient. The image quality was found to be good in 21 cases, fair in 12 and poor in 4. There were 21 cases on which RCT successfully depicted intrahepatic masses which were known to be present by other modalities such as X-ray CT, echography, scintigraphy, and surgery. The smallest nodule depicted on the RCT image was 2.5×1.8 cm on the surgical specimen, which was not de-picted on the ordinary scintigrams. There were 3 cases on which RCT failed to depict intrahepatic masses. In two of them the masses were located close to the diaphragmatic surface. In the remaining one the mass was in the posterior segment.
Considering that our method is a temporary expedient, the data seem to be fairly good at present. Better results could be expected from the machines made exclusively for RCT in the near future.

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With increasingly frequent request for a large number of radioimmunoassay, it requires to preparate in a limited short time. For this request, the Hitachi 4 Channel Radio-immunoassay Counting System (RMA-4A) has been designed specifically for the expanding needs in this field.
This system accomodates 12 samples racks. A NaI crystal with a side through-hole serves as radiation detector. It is located above the sample changer, and individual samples are elevated into it. Counting 4 samples at once and changing sample faster by moving the elevator results in a considerable time saving for large sample numbers. This arrangement provides better shielding as well as reduced volume dependence. An im-portant additional feature of this counting system is that permits counting of individual samples without interruption of the sample number sequence.
The calculated values in each 4 detectors are in good statistical agreement with those theoretical values, when their correcting coeficient for 4 channels are estimated.

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To evaluate the practical usefulness of RER and P. P. for quality control of RIA was studied in routine works at our laboratory.
The RER slope that was calculated for previous assays in each of fifteen kinds of RIA kits was compared with the coefficient of variation of antigen concentrations in replicates. In addition, P. P. was analysed in several RIA kits. From these results, it was supposed that there were three groups of RIA kits with different characteristics on quality control.
In a group, the good quality control was obtained with the criteria for rejection on the basis of the RER slope. In another group of RIA kits, quality control was possible with the RER slope except for the samples in low concentrations. In the others, the RER slope was able to minimized but there were a few samples that have a large error of deviation of concentrations.
It seemed that in practically the rejection criteria should not be established unflexible in as far as using commercial kits, because of difference of sensitivity of each kits and/or its clinical availability.

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The ultrasonic evaluation is the first choice of examination, once the biochemical studies have shown biliary system obstruction in the patient with jaundice. This article is directed at intra- and extrahepatic biliary duct dilatation and abnormalities of gall bladder.
(1) Malignancies-The vast majority of cases are shown to have already remarkable intrahepatic dilatation at the point when jaundice is found on clinical basis.
(2) Acute extrahepatic obstruction due to such as incarcerating stones-The common manifestations are markedly dilated extrahepatic duct frequently associated with stones in gall bladder.
(3) Intrahepatic cholestasis-The cavity of gall bladder is found small or obliterated in the absence of distended intrahepatic and hilar biliary tracts.

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Under the ultrasonic guidance, puncture, aspiration of fluid and injection of contrast medium were performed in 4 patients with various abdominal cystic lesions (congenital soli-tary hepatic cyst, hepatic hematoma, mesenteric cyst and congenital hydronephrosis, 1 case each). It permitted qualitative diagnosis and assessment of the expansion and adhesion to the surrounding organs of the cystic lesion. Furthermore, the examination of fluid -cytology, culture and labolatory test- made the diagnosis more accurate. This method is safe and useful for the diagnosis of abdominal cystic lesions, which was difficult by the conventional X-ray examination.

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The diagnosis of the abdominal organ by the CT image depends not only on the sign of the conture of the organ but also on the internal structure image of the organ. However. in the low contrast organ such as the liver or the pancreas, the difference of the ab-sorption between the normal part of the organ and the lesion is as low as few percent. The refore, the noise level may interfere the accuracy of the diagnosis.
The discussion have been made to the source of the noise, then allowable noise level to the image is estimated. On the other hand, for the examination of the abdominal organ, the region of interest should be choosen wider than the other such as a head region exami-nation, which may cause of increase the noise level.
From this point of view, following consideration should be taken;
1) The correction data should be taken with maximum exposure which obtainable by the apparatus.
2) Increase the number of the projection.
3) Increase the number of the detectors to strew the noise and reduce the granulation image as well.
4) Improvement of the X ray tube to obtain more dose. By these consideration the noise level might be kept less than 1% σ w.

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Evaluation of Octoson echography for the preoperative diagnosis was done on 95 patients with ovarian tumors.
An ultrasound examination is mandatory to show the existence of an ovarian tumor and to determine its characteristics. Computed tomography and angiography are valuable exami-nations and good supplements to ultrasound examination for differentiating malignant and benign lesions and to discriminate between ovarian and other site's tumors. The decision tree for the preoperative diagnosis of ovarian tumors is presented in the form of flow chart.

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Focal lesions of abdominal organs were studied and compared with scintigraphy and ultrasonography.
Scintigraphy was superior to ultrasonography showing global view of the liver. Ultra-sonography was superior to scintigraphy to distinguish true space-occupying lesion (SOL) from false one of physiologic fossae (porta hepatis, gall-bladder bed and hepatic vein), left lobe and inferior margin of the liver.
Qualitative diagnosis of SOL of abdominal organs were not so easy with scintigraphy. On the scintigraphic SOL, ultrasonography differentiated solid lesions from cystic ones by echogenecity.
Ultrasonography required the technical skill and diagnostic experiences by examiner.
As a result of these studies, scintigraphy and ultrasonography compensated each other. Combined radionuclide and ultrasound imaging were very useful for elevating the diagnostic accu racy.

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Ultrasound diagnostic equipment remarkably developed in recent years. Basic studies on the resolution of transducer of this equipment were performed. Utilized equipment was contact compound scanning system (PHO/SONIC SM).
Following results were obtained.
1) We determined axial and lateral resolution of each transducer with AIUM “Enclosed” test phantom. Since the resolution of transducer will be gradually falling down with use, it is very important to determine the resolution of each transducer at the purchase.
2) Lateral resolution and focal length of each transducer were fairly deviated from nominal values.
3) Water phantom with a cyst was prepared and phantom was scanned. A cyst was clearly demonstrated on the condition that transducer was positioned in the beam focal zone. However, recognition of a cyst was very difficult on the condition that same trans-ducer was positioned in the beam near or far field.

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U. I. OCTOSON improved by G. Kossoff is a full automatic water-coupling compound ultra-sonic echoscope. Eight transducers are located on the scanning arm submerged below a membrane. Patient lies prone on the membrane and ultrasonic beams are running through the water-bath. Ultrasonic beams are pulsed in sequence from each transducer (from 1 to 8) for each 0.5 msec so that 8 lines of sight are laid down for each 0.1° of sector movement of the transducers. Then the compound images are formed immediately in high quality grey scale echograms. Two hundred and sixteen cases were studied on experiences with Octoson echoscope. Details of these cases were as follows: gynecological disease (37%), digestive disease (32.90%), disease of mammary gland (24.2%), cardiovascular disease (2%) and urological disease(2%).
The rate of accuracy for diagnosis in gynecological disease, such as decision of abnor-malities in the position between placenta and fetus, hydatiden mole, ovarian tumor and myoma uteri was fairly high. It was also high in digestive disease, such as cholelithiasis, intra-hepatic tumor and hepatomegaly. Octoson was very useful for the diagnosis of cholelithiasis even in negative cases of DIC (drip infusion cholecystography). It was also useful for the diagnosis of breast tumor, aortic aneurysm and renal tumor.
Octoson provided with water-coupling allows the use of large aperture. Using the combination of eight transducers, both compound and simple scanning are possible. And high quality grey scale echogram is mechanically and continuously obtained without skillful-ness.
Octoson has been used broadly in many medical fields. The rate of accuracy for the diagnosis of it was good compared with that of manual contract compound scanning but it is less convenient in point of control of transducer's position.
There are a few of problems remained to be solved in the examination of Octoson. There is limits to examination time due to the aged and/or condition of the patient. Since the patients' position is prone in almost all cases, it is difficult to keep the same position during examination.
Hewever if correspondence with X-ray, CT (computerlized tomography), RI (radioisotope) and so on would be definite in future, Octoson would paly a more important role in the universal image diagnosis.

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