Monte Carlo estimates of absorbed dose rate in various tissues and organs

A computer program based on the Monte Carlo technique was developed for calculation of absorbed dose rate in various tissues and organs. The accuracy of the program was tested by reproducing Berger's values of the specific absorbed fractions for point isotropic sources in water, and a good agreement with those obtained by the moments method was found within an error of several percent. In comparing with experiment and other Monte Carlo results, good agreement was also obtained within the range of statistical error. The absorbed dose rate for an 123I, 124I, 125I, 126I and 99mTc point source and their specific dose constants in various tissues and organs were calculated using this program. This computer program has the mass energy absorption and attenuation coefficients for 69 tissues and organs as a database file, and can be extended to various radionuclides used in nuclear medicine by adding their nuclear data to the program.     

Tumor-antigen 4. Its immunohistochemical distribution and tissue and serum concentrations in squamous cell carcinoma of the lung and esophagus

The immunohistochemical distribution and concentrations of tumor-antigen 4 (TA-4) in tissues and serum were determined in patients with benign and malignant diseases, including 27 patients with squamous cell carcinoma (SCC; 15 in the lung and 12 in the esophagus). Tumor-antigen 4 immunoreactivity was present in the cytoplasm of many SCC tissues, especially in the hyperparakeratotic region, and in the cytoplasm of differentiated squamous cells of the intermediate layer of normal epithelia of various organs, but not in those of other types of lung cancers or benign pulmonary diseases. Consistent with the results of immunostaining, the TA-4 concentrations in SCC tissues of the lung, esophagus, and normal squamous epithelia were much higher than in those of lung cancer other than SCC, benign pulmonary diseases, normal lung, and submandibular gland tissues. The TA-4 concentration in SCC tissue tended to increase with increasing grades of differentiation. Serum TA-4 was elevated in 15 of 27 patients with SCC but in no patients with other types of lung cancer or benign diseases. These results indicate that TA-4 is an antigen related to the differentiation of squamous cells and that tumor cells of SCC can release a large amount of TA-4 into circulation whereas normal squamous epithelia cannot.     

Discordant pregnancy tests in detection of alpha-subunit--producing tumors

Ectopic production of isolated alpha-subunit of glycoprotein hormones was detected in a 32-year-old Japanese woman with metastatic lung tumor by a discordance in the immunologic pregnancy tests for native human chorionic gonadotropin (hCG) assays. Quantitative discrepancy of titrations among different types of pregnancy tests, ie, competitive (hemagglutination or latexagglutination inhibition) and noncompetitive (hemagglutination or latexagglutination) reactions, was also confirmed experimentally using a highly purified ectopic alpha-subunit from the patient's urine. Thus the discrepancy between the 2 types of assay systems was due, at least partly, to a cross-reaction of high concentrations (20,000 ng/ml) of ectopically secreted free alpha-subunit of glycoprotein hormones.     

Anti-Fas monoclonal antibody is cytocidal to human immunodeficiency virus-infected cells without augmenting viral replication.

A cytotoxic monoclonal antibody (anti-Fas mAb) against the 200-kDa cell surface Fas antigen, which is associated with the tumor necrosis factor (TNF) receptor, was examined for its in vitro activity on human immunodeficiency virus (HIV)-infected cells. It was found that both TNF and anti-Fas mAb selectively killed the chronically HIV-infected cells. Uninfected cells were less sensitive to the antibody than those infected with HIV. When the cells were cultured in the presence of anti-Fas mAb immediately after the HIV infection, the spread of HIV-infected cells was suppressed by the antibody. TNF augmented both the synthesis of HIV-specific mRNA in HIV-infected cells and formation of multinucleated giant cells. In contrast, the anti-Fas mAb did not augment HIV replication or enhance the HIV-induced formation of syncytia. The results indicated that anti-Fas mAb mimicks the cytocidal action of TNF but does not augment HIV replication.     

A unified computer program for assessment of attenuation correction and data acquisition methods in single photon emission computed tomography (SPECT)

A computer based simulation program was developed to assess the usefulness of various attenuation correction algorithms and data acquisition methods in single photon emission computed tomography (SPECT) in a unified approach. The program analytically calculated projection ray sums from a mathematical model with various distributions of activities and either uniform or non uniform attenuation coefficients by using the line integrals including the effect of attenuation. Data acquisition starting at arbitrary angles, various acquisition angles, including a 180° scan and a non circular orbit of a gamma camera, including an elliptical orbit can readily be taken into consideration in our simulation program. To simulate non circular orbit data acquisition, the resolution dependence on the object distance from the collimator surface was incorporated into the simulation. This computer based simulation program allows various combinations of attenuation correction algorithms such as hybrid methods, and data acquisition methods can be evaluated under a large number of study conditions. The usefulness of this computer based simulation program is shown with several representative examples.     

Single photon emission computed tomography (SPECT) with N-isopropyl-p-(123I) iodoamphetamine in partial epilepsy--evaluation of delayed image

Thirty eight patients with partial seizures in the interictal phase were studied using single photon emission computed tomography performed 30 min. (early image) and 4-4.5 hrs. (delayed image) after an injection of 111 MBq (3 mCi) N-isopropyl-p(123I) iodoamphetamine (IMP). Five types of distribution changes were observed on IMP-SPECT between the early and delayed images. Eight patients, Type 1, exhibited an unchanged distribution of IMP between the early and delayed images. Fifteen patients, Type 2, showed a smaller area of low uptake on the IMP-SPECT (delayed image) compared to that on the IMP-SPECT (early image)-redistribution. The Type 3 patients exhibited an initial uptake area on the IMP-SPECT (early image) which later became a lower uptake area on the IMP-SPECT (delayed image)-reversed redistribution. This type was further classified into three categories according to the initial uptake pattern including (a) Type 3A, 3 patients with increased uptake area, (b) Type 3B, 6 patients with normal uptake area, and (c) Type 3C, 6 patients with decreased uptake area. With Type 2, the epileptic findings on the present interictal electroencephalography (EEG) were shown in 11 of 15 patients. However, we could not find any other remarkable correlation among these 5 types and the clinical factors (the types of seizures, the X-CT findings, the present interictal EEG data, the present frequency of seizures, and the intervals from the last seizure). In 2 patients with Type 3B who suffered from simple partial seizures, a region of the normal distribution on the IMP-SPECT (early image) became a lower uptake area on the IMP-SPECT (delayed image), corresponding topologically to the ictal symptoms. In this experience, we determined that the IMP-SPECT (delayed image) could be useful in patients with the epileptic lesions unable to be detected on the IMP-SPECT (early image).     

Cocaine colitis

An unusual case of colitis in a 37-year-old cocaine addict is described. The patient presented with right-sided abdominal pain and diarrhea exacerbated by his use of cocaine. Significant antibiotic ingestion was denied. At laparotomy, an edematous cecum and ascending colon were found, the cut surface of which revealed diffuse superficial ulcerations and yellowish fibrinous material. Microscopic examination demonstrated findings consistent with pseudomembranous colitis with an ischemic component. A mechanism involving chathecholamine-induced mucosal ischemia is postulated to explain the findings seen in this patient.