Spatial resolution in the electrical impedance tomography for the local tissue.

Electrical impedance tomography (EIT) is one of the medical tissue diagnosis devices and it creates a two- or three-dimensional image of electrical impedance distribution in a living tissue. It is used for imaging the information of tissue structures, and physiological functions and states of the tissue. However, there are several problems to achieve the practical use of EIT, which are an inverse algorithm for estimating parameters and electrode structure and so on. EIT is calculated from impedance data, which is measured non-invasively by surface electrodes. Therefore, it is important to choose a proper electrode structure to realize a practical EIT measurement system. In this study, we used a electrode structure, called "divided electrode", which is proposed for a short time measurement of bio-impedance in a cross section of the local tissue. Its capability is examined by computer simulations, where a distributed equivalent circuit is used as a model for the cross section tissue. Estimation of impedance parameters is carried out by use of the Newton method. The objective of this study is to examine the spatial resolution on the circuit model. Moreover, the current flowing in the circuit model is examined.

Noninvasive measurement of the electrical bioimpedance of breast tumors.

The purpose of this study was to evaluate the possibility of differential diagnosis of tumors, such as breast cancer, by measuring the mammary electrical bioimpedance via the skin surface noninvasively and by examining the relationship between the tissue structure of the breast and electrical bioimpedance. The mammary electrical bioimpedance was measured in 24 patients with breast cancer. Taking into account the measurement results and the distribution of the mammary glands and fatty tissue, a breast model with tumors was proposed. Based on this model, the distributions of the electric potential and electric field in the tissue were theoretically analyzed by the three-dimensional finite element method. In clinical cases, the Re values of the diseased breast were significantly larger than those of the contralateral healthy breast. In theoretical analysis based on the breast model, the Re value of mammary electrical bioimpedance varied due to the structure of the breast, that is, the ratio of fatty tissue to mammary gland and the presence of mammary tumors. The results of the measurement agreed with the theoretical analyses. These results suggest that differential diagnosis of breast tumors is possible by measuring the mammary electrical bioimpedance using noninvasive electrodes on the skin.

Difference in thymidylate synthetase activity in involved nodes compared with primary tumor in breast cancer patients.

Thymidylate synthetase (TS) is a key enzyme as a methyl donor in the methylation reaction from dUMP to dTMP. TS activity was assessed in various tissue of mammary disorders. The descending order of TS activity was as follows: cancer-positive nodes, primary cancers, cancer-negative nodes, benign lesions, and normal parenchyma. Significant differences in TS activity were found between the positive nodes and each of the other tissues (p < 0.01). In node-positive cases, a significant correlation in TS activity was found between the primary cancers and positive nodes (r = 0.616, p = 0.033). There was no correlation between the nodal status and the TS activity in primary cancers. In 11 of 12 cases, the TS activity of positive nodes was higher than the 'calculated' TS activity of the primary cancer, which was defined as the TS activity per unit weight of cancer cells. A significant correlation was found between the calculated TS activity and the mitotic frequency in primary cancers (r = 0.697, p = 0.0001). On the other hand, a significant correlation could not be found between the TS activity and the mitotic frequency in positive nodes (r = 0.364, p = 0.244).

[Extravascular lung water in patients after cardiac surgery].

Extravascular lung water (EVLW) measured by a double indicator dilution method using thermal-dye indicator was evaluated in 204 patients after cardiac surgery during last 7 years. The measurement of EVLW was done at 2, 4, 8, 24 and 48 hours after extracorporeal circulation (ECC), EVLW showed no significant change except transient decrease at 4 hours after ECC, average of that was 7.62 +/- 3.58 ml/kg, EVLW of group I (MVR) and group III (AVR + MVR) were significantly higher than those of group II (AVR), group IV (noncyanotic congenital heart disease) and group V (A-C bypass). EVLW of 7 patients with postoperative pulmonary edema was 14.47 +/- 4.44 ml/kg, and that was significantly higher than those of others (7.54 +/- 3.06 ml/kg). EVLW of the patients using bubble oxygenator (8.60 +/- 3.90 ml/kg) was significantly higher than those of membrane oxygenator (7.15 +/- 3.40 ml/kg). Postoperative EVLW correlated with mean pulmonary artery pressure (mPAP), mean left atrial pressure (LAP) and microvascular hydrostatic pressure (PMV), and showed inverse correlation with cardiac index (CI). But there was no correlation of EVLW with duration of ECC. In the preoperative parameter, EVLW correlated with age, mPAP, mean pulmonary wedge pressure (mPAWP), PMV, serum BUN and serum creatinine, and showed inverse correlation with CI, %VC, FEV%, PSP test and creatinine clearance. We concluded that the patients with mitral valve disease who have high mPAP and LAP, respiratory and renal dysfunction and old aged preoperatively showed upward trend of EVLW. In perioperative management, care must be taken in such patients and membrane oxygenator was thought useful for prevention of pulmonary edema.(ABSTRACT TRUNCATED AT 250 WORDS)

Popliteal artery entrapment syndrome. Report of two cases.

We treated two patients with popliteal artery entrapment syndrome. In one, the popliteal artery was entrapped and obstructed in its abnormal course around the medial head of the gastrocnemius muscle, which was inserted into the femur laterally and cephalad (type II in Delaney's classification). In the other patient, the popliteal artery followed a normal course but was compressed laterally by the medial head of the gastrocnemius muscle, which was aberrantly inserted into the femur considerably higher and more lateral than usual, and was occluded. This could not be fitted into Delaney's or Insua's classification. Arterial reconstruction was successful with an autovein graft in the former case and an in situ bypass graft in the latter. We suggest a modification of type IV in Delaney's classification, so that when the popliteal artery is compressed by an aberrant muscular or tendinous structure in the popliteal fossa it can be included.