Population Genetics and Molecular Evolution of DNA Sequences in Transposable Elements. II. Accumulation of Variation and Evolution of a New Subfamily.

In order to understand how DNA sequences of transposable elements (TEs) evolve, extensive simulations were carried out. We first used our previous model, in which the copy number of TEs is mainly controlled by selection against ectopic recombination. It was found that along a simulation run, the shape of phylogeny changes quite much, from monophyletic trees to dimorphic trees with two clusters. Our results demonstrated that the change of the phase is usually slow from a monomorphic phase to a dimorphic phase, accompanied with a growth of an internal branch by accumulation of variation between two types. Then, the phase immediately changes back to a monomorphic phase when one group gets extinct. Under this condition, monomorphic and dimorphic phases arise repeatedly, and it is very difficult to maintain two or more different types of TEs for a long time. Then, how a new subfamily can evolve? To solve this, we developed a new model, in which ectopic recombination is restricted between two types under some condition, for example, accumulation of mutations between them. Under this model, because selection works on the copy number of each types separately, two types can be maintained for a long time. As expected, our simulations demonstrated that a new type arises and persists quite stably, and that it will be recognized as a new subfamily followed by further accumulation of mutations. It is indicated that how ectopic recombination is regulated in a genome is an important factor for the evolution of a new subfamily.

On the estimation of the insertion time of LTR retrotransposable elements.

It has been proposed that the insertion time of a long terminal repeat (LTR) retrotransposon can be estimated by the divergence between the two LTRs at the both ends because their sequences were identical at the insertion event. This method is based on the assumption that the two LTRs accumulate point mutations independently; therefore, the divergence reflects the time since the insertion event. However, if gene conversion occurs between LTRs, the nucleotide divergence will be much smaller than expected with the assumption of the independent accumulation of point mutations. To examine this assumption, we investigated the extent of gene conversion between LTRs by applying a comparative genomic approach to primates (humans and rhesus macaques) and rodents (mice and rats). We found that gene conversion plays a significant role in the molecular evolution of LTRs in primates and rodents, but the extent is quite different. In rodents, most LTRs are subject to extensive gene conversion that reduces the divergence, so that the divergence-based method results in a serious underestimation of the insertion time. In primates, this effect is limited to a small proportion of LTRs. The most likely explanation of the difference involves the minimum length of the interacting sequence (minimal efficient processing segment [MEPS]) for interlocus gene conversion. An empirical estimate of MEPS in human is 300-500 bp, which exceeds the length of most of the analyzed LTRs. In contrast, MEPS for mice should be much smaller. Thus, MEPS can be an important factor to determine the susceptibility of LTRs to gene conversion, although there are many other factors involved. It is concluded that the divergence method to estimate the insertion time should be applied with special caution because at least some LTRs undergo gene conversion.

Eradication of Myc-overexpressing small cell lung cancer cells transfected with herpes simplex virus thymidine kinase gene containing Myc-Max response elements.

Herpes simplex virus thymidine kinase (HSV-TK) gene was ligated with four repeats of the Myc-Max response elements (a core nucleotide sequence CACGTG), and its utility for gene therapy was examined by the treatment of either c-, L- or N-myc-overexpressing the small cell lung cancer (SCLC) cell line with ganciclovir (GCV). The chloramphenicol acetyltransferase assay demonstrated that the overexpression of any myc genes activated transcription from the CAT gene depending on the Myc-Max binding sites. The transduction of the HSV-TK gene ligated with the CACGTG core rendered all three SCLC lines to be more sensitive to GCV than parental ones in vitro. In addition, the growth of c- or L-myc-overexpressing SCLC cells containing the hybrid HSV-TK gene were significantly suppressed by GCV in vivo. When parental SCLC cells were mixed with HSV-TK-expressing tumor cells at a ratio of 1:3, GCV treatment inhibited tumor growth by 90% compared with parental cells only, indicating the existence of the "bystander effect." These data suggest that the CACGTG-driven HSV-TK gene may be useful for the treatment of SCLC overexpressing any type of myc family oncogenes.

Application of the Cre recombinase/loxP system further enhances antitumor effects in cell type-specific gene therapy against carcinoembryonic antigen-producing cancer.

A considerable number of studies of cancer have shown that the cell type-specific promoter is an effective tool for selective expression of foreign genes in tumor cells. However, few reports have demonstrated significant in vivo antitumor effects using this strategy thus far, possibly because the low activity of such a promoter results in insufficient expression of genes in cancer cells as well as in insignificant antitumor effects, even when the cells are infected by highly efficient gene transfer methods. To overcome this problem, we used the Cre/loxP system for the cell type-specific gene therapy against carcinoembryonic antigen (CEA)-producing cancer. We constructed a pair of recombinant Ads. One expresses the Cre recombinase (Cre) gene under the control of the CEA promoter (Ad.CEA-Cre). The other contains the herpes simplex virus thymidine kinase (HSV-TK) gene separated from the strong CAG promoter by insertion of the neomycin resistance (neo) gene (Ad.lox-TK). The HSV-TK gene of the latter Ad is designed to be activated through excisional deletion of the neo gene by Cre enzyme released from the former one only when CEA-producing cells are infected simultaneously with these Ads. Coinfection by these Ads rendered a human CEA-producing cancer cell line 8.4-fold more sensitive to ganciclovir (GCV) compared with infection by Ad.CEA-TK alone, the HSV-TK gene of which is directly regulated by the CEA promoter. On the other hand, coinfection with these Ads did not significantly change the GCV sensitivity of non-CEA-producing cells. Intratumoral injection of Ad.CEA-Cre combined with Ad.lox-TK followed by GCV treatment almost completely eradicated CEA-producing tumors established in the subcutis of athymic mice, whereas intratumoral injection of Ad.CEA-TK with GCV administration at most retarded the growth of inoculated tumors. These results suggest distinct advantages of the Cre/loxP system applied in the conventional cell type-specific gene therapy against cancer.

Association of Epstein-Barr virus with tumor cell proliferation: clinical implication in nasopharyngeal carcinoma.

Nasopharyngeal carcinoma (NPC) is characterized by its association with Epstein-Barr virus (EBV) infection. Unlike other upper aerodigestive tract squamous cell carcinomas, clinical and pathologic features are unable to predict outcome in NPC. EBV has been demonstrated to have transforming potential in B-cell systems so that its infection can rapidly and efficiently induce sustained lymphocyte proliferation in vitro. However, the relationship between cell proliferation and EBV infection in NPC has not been previously reported. This study was designed to determine the association of EBV infection and NPC tumor cell proliferation. Cell proliferation index, as measured by two markers, PCNA and Ki-67, were moderately correlated (r=0.534, p=0.033). Quantitative analysis of EBV positivity was highly correlated with both cell proliferation indices (r=0.802, p=0.0039 and r=0.720, p=0.0174 for PCNA and Ki-67, respectively). TNM staging did not demonstrate prognostic significance. NPC patients whose tumors were EBV positive demonstrated increased survival compared with patients whose tumors were EBV negative (p=0.043). These results indicate that EBV infection may regulate cell proliferation in NPC and the presence of EBV can be used as a positive prognostic factor.

Establishment of a CPT-11-resistant human ovarian cancer cell line.

A camptothecin analog, ((4s)-4,11-diethyl-4-hydroxy-9-[(4- piperidinopiperidino)carbonyloxy]dione hydrochloride trihydrate), (CPT-11), is a recently developed topoisomerase I (Topo I) inhibitor which attracts the attention of clinicians because of its high antitumor activity. We established a CPT-11-resistant human ovarian cell line, HAC2/CPT, from the parental HAC2 cell line. An in vitro drug sensitivity assay revealed that HAC2/CPT was 9.7 and 4.7 times as resistant as HAC2 to CPT-11 and 7-ethyl-10-hydroxy-CPT-11 (SN-38), an active metabolite of CPT-11, respectively. HAC2/CPT showed no cross-resistance to other drugs tested (adriamycin, etoposide, cisplatin and Taxol), suggesting that HAC2/CPT acquired a phenotype specifically resistant to the Topo I inhibitor. In order to elucidate the mechanism of the resistance, we measured Topo I activity of HAC2 and HAC2/CPT. The activity of Topo I of HAC2/CPT was reduced to half of that of the parental HAC2 cells. To determine the cause of the decreased activity of Topo I, the mutation of the Topo I gene was searched for by the polymerase chain reaction and the reverse transcriptase analysis. Topo I gene mutation was not detected. The amount of Topo I protein was measured by immunoblotting and a marked decrease of Topo I protein was observed in HAC2/CPT. These results suggest that the decreased protein content of Topo I causes the decreased activity of Topo I and the decreased sensitivity of HAC2/CPT to Topo I inhibitors.

Relationship between facial flushing and blood acetaldehyde levels after alcohol intake.

Normal subjects were divided into two groups, i.e., those showing, and those not showing, facial flushing after consuming a small amount of alcohol. In the flushing group, increases of pulse rate, facial skin temperature and carotid arterial pressure and blood flow rate, as well as changes of digital plethysmogram and electrocardiogram, were found together with a conspicuous rise in blood acetaldehyde levels after the drinking. However, significant changes of the signs as mentioned above and elevation of blood acetaldehyde did not occur in the non-flushing group. The maximum blood alcohol levels and the rate of alcohol elimination showed not difference between these two groups. Furthermore, urinary excretions of epinephrine and norepinephrine increased in the flushing cases after the drinking.

The discrepancy between 99Tcm-ECD dynamic and static SPET images in patients with ischaemic lesions corresponds to reduced vasoreactivity to acetazolamide.

We evaluated 99Tcm-N,N'-(1,2-ethylenediyl)bis-L-cysteine diethyl ester (99Tcm-ECD) dynamic and static SPET (single photon emission tomographic) images to examine 99Tcm-ECD kinetics under ischaemic cerebrovascular conditions. In 20 patients who showed arterial occlusion on magnetic resonance angiography, dynamic (0-10 min) and static (15-35 min) SPET images were acquired after the intravenous administration of 99Tcm-ECD. Thirteen of the patients had focal perfusion deficits that were more evident on the dynamic than on the static images; the other seven showed no such discrepancy. In those patients with a mismatch between the dynamic and static images, the extent corresponded to reduced vaso-reactivity to acetazolamide. Based on quantitative analysis of the ratio of tracer uptake in affected to that in unaffected areas, the patients with discrepant findings showed significantly different ratios on the dynamic and static images, whereas those with no such mismatch did not. Our results suggest that dynamic 99Tcm-ECD images provide circulatory information and that static images reflect a filling-in phenomenon of ECD metabolites in ischaemic lesions. 99Tcm-ECD dynamic and static SPET images offer an alternative method of detecting mild perfusion deficits without the need for acetazolamide challenge.

Left ventricular function at rest and during bicycle exercise in normal subjects: assessment by ECG-gated myocardial perfusion SPET with 99Tcm-tetrofosmin.

99Tcm-labelled myocardial perfusion tracers allow simultaneous assessment of myocardial perfusion and left ventricular function using ECG-gated SPET. The aim of this study was to evaluate left ventricular performance during exercise by means of ECG-gated myocardial perfusion SPET. After the administration of 99Tcm-tetrofosmin (555-740 MBq), eight healthy volunteers aged 27-49 years underwent ECG-gated myocardial perfusion SPET at rest and during supine submaximal exercise (75 and 125 W), for 3 min each. Using ECG-gated SPET data, left ventricular end-diastolic volume (LVEDV) demonstrated a biphasic response during exercise (from 106.4 +/- 17.5 to 119.9 +/- 19.9 to 108.1 +/- 19.2 ml). In contrast, left ventricular end-systolic volume decreased gradually and significantly during exercise (from 47.1 +/- 11.9 to 41.5 +/- 8.9 to 36.1 +/- 10.1 ml; P < 0.05), and left ventricular ejection fraction continued to increase at higher workloads (from 56.1 +/- 6.0 to 63.0 +/- 2.7 to 67.0 +/- 4.3; P < 0.01) despite a fall in LVEDV. There was a progressive increase in cardiac output during exercise, which reached a peak of 7.2 +/- 0.9 l.min-1. We conclude that ECG-gated myocardial perfusion SPET can assess left ventricular function during exercise and may provide useful information for the evaluation of patients with ischaemic heart disease.

Limitations of electrocardiography in the diagnosis of acute myocardial infarction--comparison with two-dimensional echocardiography.

In order to assess the sensitivity of the initial electrocardiogram (ECG) in diagnosing the first attack of acute myocardial infarction (AMI), we compared the findings on ECG and two-dimensional echocardiogram (2-D echo) in 74 patients with single vessel coronary artery disease. Group A consisted of 41 patients with infero-posterior AMI while group B consisted of 33 patients with antero-septal AMI. In group A, 12 patients showed normal ECGs, while 2-D echo failed to reveal abnormal left ventricular wall motion in only 2 patients. In those two patients, the quality of the echocardiogram was poor. In group B, only one patient showed a normal ECG, and all patients showed abnormal left ventricular wall motion on 2-D echo. We conclude that electrocardiography has limitations in diagnosing infero-posterior myocardial infarction especially during the acute phase, but 2-D echo is an additional useful diagnostic procedure.

Can heparin immobilized surfaces maintain nonthrombogenic activity during in vivo long-term implantation?

The authors previously demonstrated that heparin immobilized surfaces showed excellent nonthrombogenic properties for extracorporeal membrane oxygenation experiments as long as 168 hr. The characteristics of the heparin immobilized surfaces include high heparin bioactivity and prevention of platelet adhesion and complement activation. However, it is not known whether the heparin immobilized surfaces would be effective for in vivo long-term implantation. Heparin bioactivity may be lost because of complete degradation or blocking of binding sites on heparin by adsorbed proteins. This study attempted to elucidate the in vivo long-term fate of heparin immobilized surfaces. The blood contacting surfaces of the ventricular assist device (VAD) made from polyurethane was modified with heparin immobilization and evaluated in a long-term sheep left VAD (LVAD) model for as long as 3 months. After removal of the VAD, heparin bioactivity was measured by Factor Xa assay. The blood contacting surfaces were analyzed with a scanning electron microscope, and the adsorbed proteins on the surfaces of the diaphragm were analyzed by SDS-PAGE and Western blotting. The thickness of adsorbed proteins on the surfaces also was measured by a confocal laser microscope. For the control ventricular assist devices, thrombus formation was observed within 1 month, whereas heparin immobilized VADs were able to operate thrombus free for periods as long as 3 months. The control surfaces demonstrated a thick adsorbed protein layer on thin surfaces, whereas heparin immobilized surfaces maintained thinner adsorbed proteins on thin surfaces. Anti Factor Xa activity of the heparinized surfaces disappeared after 15 days, but the surfaces remained nonthrombogenic even after heparin bioactivity was completely lost. The protein composition analyzed by SDS-PAGE showed an albumin dominant pattern on the heparinized surfaces. The band of 110 kD corresponding to C3b was detected only on the control surfaces, which possibly activated complement, and subsequently activated platelets and coagulation. Immunoblot showed degradation products of fibronectin and vitronectin on the control surfaces, which probably were promoted by surface generated protease, whereas the heparinized surfaces showed minimal degradation throughout the experimental periods. These results suggest that the heparin moiety has an ability to control adsorbed proteins, thereby inhibiting thrombus formation during in vivo long-term implantation.

In vitro studies of immobilized heparin and sulfonated polyurethane using epifluorescent video microscopy.

In situ surface modification techniques to improve the blood compatibility of blood contacting surfaces of medical devices have been developed by the authors. The techniques include heparin immobilization and sulfonated polymer grafting onto a polyurethane (PU) surface by using either ozone oxidation or photo reaction. These modified PUs were evaluated using an epifluorescent video microscope combined with a parallel plate flow cell. The epifluorescent video microscope system measured the amount of platelet coverage on the PU surfaces using whole human blood containing mepacrine labeled platelets perfused at a wall shear rate of 100 sec-1 for 20 min. Platelet activation and complement activation were also measured. Both immobilized heparin and sulfonated PUs showed significantly lower levels of platelet adhesion than the control PU. The platelet activation levels of these modified PUs also correspond to the results of the platelet adhesion. As for complement activation, heparin the immobilized surface showed the least complement activation, while sulfonated PU and the control PU showed higher levels of complement activation. In situ surface modification techniques, which use either ozone oxidation or photo reaction, are useful in a variety of medical devices even of a complex design, such as membrane oxygenators or artificial hearts.

Terumo implantable left ventricular assist system: results of long-term animal study.

The research group of Terumo Corporation, NTN Corporation, and the Setsunan University have been developing an implantable left ventricular assist system (T-ILVAS) featuring a centrifugal blood pump with a magnetically suspended impeller (MSCP). The present study describes results of chronic animal experiments using the MSCP. The MSCP has been tested ex vivo and in vivo in 6 sheep as a left heart bypass between the left ventricular apex and descending aorta. Ex vivo chronic sheep experiments using Model I demonstrated long-term durability, nonthrombogenicity, low hemolysis (<6 mg/dl), and excellent stability of the magnetic bearing with long-term survival for up to 864 days. Average pump flow rate was 4 L/min at a fixed rotational speed of 2000 rpm. Power spectral analyses of heart rate, aortic pressure, and blood temperature maintained normal 1/f fluctuation during the study. The retrieved pump was completely free from thrombus formation and there was no evidence of infarct in major organs. The implantable Model II was evaluated ex vivo in two sheep and intra-thoracically implanted in a sheep. These experiments were terminated at 70, 79, and 17 days due to blood leakage through the connector system within the housing. No thrombus formation was observed in any of the retrieved pumps. A modified Model II with a new connector system was subsequently intra-thoracically implanted in a sheep. The sheep survived for 482 days without any sign of thromboembolic complication or hemolysis at a fixed rotational speed of 1700 rpm and an average pump flow rate of 5 L/min. There was no intra-device thrombus formation or infarct in major organs. The Model III system, consisting of an implantable controller and a new MSCP with a reduced input power of 13 W, has been developed and implanted in a chronic sheep model. The MSCP was implanted in the left pleural space and the controller in the abdominal wall. The experiment is still in progress for more than 30 days without any significant complication to date. These animal studies strongly suggest the feasibility of the MSCP for use as long-term circulatory assist.

Recent progress in the development of Terumo implantable left ventricular assist system.

The research group of the Terumo Corporation, the NTN Corporation, and Setsunan University (T. Akamatsu) has been developing an implantable left ventricular assist system (ILVAS) featuring a centrifugal blood pump with a magnetically suspended impeller (MSCP). The impeller of the MSCP is suspended by a magnetic bearing, providing contact-free rotation of the impeller inside the pump housing. Thus the MSCP is expected to provide years of long-term durability. Ex vivo chronic sheep experiments using the extracorporeal model (Model I) demonstrated long-term durability, nonthrombogenicity, and a low hemolysis rate (plasma free Hb <6 mg/dl) for more than 2 years. The prototype implantable model (Model II; 196 ml, 400 g) was evaluated ex vivo in 2 sheep and intrathoracically implanted in a small sheep (45 kg). These experiments were terminated at 70, 79, and 17 days, respectively, because of blood leakage through the connector system within the housing of Model II. There was no thrombus formation on the retrieved pump surfaces. A new connector system was introduced to the Model II pump (modified Model II), and the pump was intrathoracically implanted in a sheep. Pump flow rate was maintained at 3-7 L/min at 1700-1800 rpm. The temperature elevation on the surfaces of the motor and the electromagnet inside the pump casing was kept less than 6 degrees C. The temperature of the tissue adjacent to the pump casing became normal 10 days postoperatively. The sheep survived for more than 5 months without any sign of mechanical failure or thromboembolic complication. In vitro real-time endurance tests of motor bearings made of stainless steel and silicone nitride have been conducted for more than 1 year without any sign of bearing wear. The next prototype system (Model III), with an implantable controller and a new MSCP with reduced input power, has been developed with a view toward a totally implantable LVAS.

More than 1 year continuous operation of a centrifugal pump with a magnetically suspended impeller.

The authors have been developing a centrifugal pump with a magnetically suspended impeller (MSCP) designed for total artificial heart and long-term ventricular support. The MSCP consists of a magnetic bearing, an impeller and housing, and a driving motor. The impeller is suspended by a magnetic bearing, therefore providing contact free rotation of the impeller inside the pump. This study was designed to evaluate long-term durability and nonthrombogenicity of the MSCP in a chronic sheep model. The blood contacting surfaces of the pump and conduits were completely modified by a heparin immobilization technique (Hepaface). The MSCP was placed paracorporeally as a left heart bypass between left ventricle and descending aorta in three adult sheep. Coumadin was given orally to maintain prothrombin time at 15-20 sec. The coagulation and hematologic parameters, including plasma free hemoglobin, were periodically monitored throughout the experiment. Under daily movement in the cage, the pump could produce average flow rates of 3-6 L/min (50-100 ml/kg) at 1,700-2,000 rpm. Although the arterial pulse contour decreased, there was no physiologic deterioration. The axial impeller excursion monitored by a position sensor was < 25 microns. Plasma free hemoglobin level remained at < 5 mg/dl throughout the experiment. There was no increase in the motor current, which indicates no massive thrombus formation around the impeller. One experiment was terminated at 70 days due to Hall sensor dysfunction of the motor. The retrieved pump was entirely free from thrombus formation. There was no detectable thrombus formation inside the pump or the inflow and outflow conduits. Hematologic, renal, and hepatic parameters remained within the normal range throughout the experiment. The other two sheep have survived for more than 395 and 41 days without major complication. These studies demonstrated that the MSCP has significant potential for long-term use.

Comparison of Emory and Cedars-Sinai methods for assessment of left ventricular function from gated myocardial perfusion SPECT in patients with a small heart.

To evaluate the effect of left ventricular (LV) size on the calculation of LV function from gated myocardial SPECT with Emory and Cedars-Sinai programs, we performed 99mTc-tetrofosmin gated SPECT on 49 patients with ischemic heart disease. End-diastolic volume (EDV), end-systolic volume (ESV), and ejection fraction (EF) were semi-automatically calculated by each program. All patients underwent left ventriculography (LVG) within 3 months before and after the SPECT study. We grouped the patients into 22 with a calculated ESV obtained from LVG of over 50 ml (group A) and 27 with an ESV value of 50 ml or below (group B). We then compared the ESV values from gated SPECT with those from LVG in each group. In group A, the ESV from both Emory and Cedars-Sinai programs similarly correlated well with those from LVG (r = 0.92 and r = 0.93, respectively), but in group B, the ESV calculated from the Cedars-Sinai program correlated less with those from LVG (r = 0.53) than those from the Emory program did (r = 0.70). The calculated LV volumes had more errors in the Cedars-Sinai program than in the Emory program, when a patient had a small heart.

Simultaneous assessment of Tc-99m-sestamibi and I-123-BMIPP myocardial distribution in patients with myocardial infarction: evaluation of left ventricular function with ECG-gated myocardial SPECT.

123I-labeled 15-(p-iodophenyl)-3R,S-methyl pentadecanoic acid (BMIPP) is a branched-chain free fatty acid that is used to evaluate various cardiac diseases. The aim of the present study was to investigate the relationship between myocardial perfusion (99mTc-sestamibi) and BMIPP uptake, and to correlate perfusion and metabolic alterations with regional left ventricular dysfunction in patients with myocardial infarction (MI). ECG-gated dual-isotope myocardial SPECT was performed on 130 patients with MI with sestamibi (555 MBq) and BMIPP (148 MBq). The patients were classified into 3 groups according to PTCA therapy and the interval between the onset of infarction and RI injection (OR time). Group A (n = 56) included patients whose OR time was less than one month and who had undergone successful PTCA, Group B (n = 36) had OR times of less than one month and had conservative medical therapy, and Group C (n = 38) had OR times of over one month. The severity scores of the dual-isotope images were calculated from the defect scores in 9 segments. From the ECG-gated SPECT data with sestamibi, the left ventricular ejection fraction (LVEF; %) and regional wall motion were determined automatically using the QGS program LVEF obtained from gated SPECT correlated well with the severity scores for sestamibi and BMIPP (r = -0.68 and -0.76, respectively). The delta severity scores (BMIPP scores - sestamibi scores) of Group A were significantly higher than those of the other two groups (3.6 +/- 3.0 vs. 1.5 +/- 1.7 and 1.0 +/- 1.4, p < 0.001 ). The rate of dysfunctional segments with normal sestamihi distribution was significantly higher in Group A than in Group C (20.7% vs. 6.7%, p < 0.001). ECG-gated dual-isotope SPECT is useful since myocardial perfusion, fatty acid metabolism and left ventricular function can be analyzed during a single examination, so that this procedure has the potential to provide comprehensive information when evaluating patients with ischemic heart disease.

Rapid data acquisition protocol in ECG-gated myocardial perfusion SPECT with Tc-99m-tetrofosmin.

Into 25 patients with heart disorders, 99mTc-tetrofosmin 555-740 MBq was injected intravenously at rest. After 40 minutes, ECG-gated myocardial perfusion SPECT was performed with a two detector gamma camera VERTEX (ADAC), setting up two detectors to form a 90-degree angle. Sixteen frames per R-R interval were acquired during a 180 degree rotation from the RAO 45 degrees to the LPO 45 degrees. A pair of data sets with standard (SDA) and rapid data acquisition (RDA) protocols was collected. In an SDA protocol, SPECT imaging was performed for 50 sec per step in 5 degree angular steps (total acquisition time; 15 minutes). An RDA protocol was conducted with 12 sec per step, 6 degree angular steps (acquisition time, 3 minutes). LVEF (%) and LVEDV (ml) quantitated automatically with a QGS program showed excellent correlations between two protocols with correlation coefficients of 0.980 (p < 0.01) and 0.983 (p < 0.01), respectively. Subsequently visual assessment of regional wall motion based on a four-point grading system was carried out with a 3-D cine LV display. High complete agreement was gained with 158 (90.3%) out of total 175 segments, so that assessment of the global and regional LV function with the RDA protocol demonstrated high reliability and feasibility.

Classification of hematopoietic regions in out-of-phase T1-weighted images: a quantitative comparison study with T1-weighted and STIR images.

The hematopoietic regions were classified into two groups on the basis of out-of-phase T1-weighted images (op-T1WI): regions with lower intensity than that of muscle (LH) and regions with intensity equal to or higher than that of muscle (HH). We quantitatively evaluated the differences in signal intensity between LH and HH in order to examine this classification. Forty-two hematopoietic areas in aplastic anemia were classified into two groups of 23 LH and 19 HH. The signal ratios of hematopoietic areas to muscle on T1WI and STIR were calculated, and the differences between LH and HH were statistically evaluated. The signal ratios of LH were significantly higher on T1WI and lower on STIR than those of HH (unpaired t-test, p < 0.05). This result indicated that LH consisted of more hypocellular marrow than HH. Op-T1WI were useful in differentiating between LH and HH and defining the degree of hematopoiesis in aplastic anemia.