Search PubMed⌕ Search

Biomedical subjects

C Katoh

Publications and source records attributed to C Katoh.

At least 19 recordsLinked to original sources
PubMed2003

Effects of reduction of the number of primordial follicles on follicular development to achieve puberty in female rats.

Effects of reduction of the number of primordial follicles on follicular development and concentrations of circulating hormones were examined in immature female rat offspring of dams given busulfan intraperitoneally on day 14 of gestation. The offspring of dams treated with 5 mg busulfan kg(-1) showed vaginal opening at an age comparable with the offspring of dams treated with 2.5 mg busulfan kg(-1) or with corn oil as a control, although they exhibited an irregular oestrous cycle until week 14 after birth. The serum concentrations of immunoreactive inhibin and FSH on day 26 after birth of the offspring treated with 5 mg busulfan kg(-1) were similar to those of age-matched controls. On day 15 after birth, however, the concentration of their immunoreactive inhibin was markedly lower than that of controls, whereas the concentration of their FSH was increased inversely. Comparison of the numbers of ovarian follicles in the controls and groups treated with 2.5 mg busulfan kg(-1) and 5 mg busulfan kg(-1) revealed that prenatal treatment with busulfan reduced the number of follicles in the primordial or primary phase and in the preantral phase on day 7 after birth. Although the increase of the ratio of the number of preantral follicles during days 7-13 after birth tended to vary with the prenatal dose of busulfan, the number of preantral follicles in the group treated with 5 mg busulfan kg(-1) was still smaller than in the controls. The concentration of serum immunoreactive inhibin of the offspring treated with busulfan was reduced on day 7 after birth without alteration of the concentration of gonadotrophin. On day 13 after birth, the concentration of serum immunoreactive inhibin was reduced only in the offspring treated with 5 mg busulfan kg(-1), and the concentration of serum FSH of the offspring was increased inversely as found on day 15 after birth. These results indicate that a reduction in the number of primordial follicles decreases the number of follicles that enter the growing phase, a major source of circulating inhibin in the neonatal and infantile ovary, and that consequently increased circulating FSH may accelerate follicular development to achieve puberty.

Alkylating Agents↗
PubMed2002

Accuracy and reproducibility of left ventricular function from quantitative, gated, single photon emission computed tomography using dynamic myocardial phantoms: effect of pre-reconstruction filters.

We have investigated the accuracy and reproducibility of left ventricular (LV) functions using quantitative, gated, single photon emission computed tomography (SPECT) software dependent on critical frequencies of pre-reconstruction filters. This study incorporated dynamic myocardial phantoms (myocardial and cone shapes). Gated SPECT of 8-interval sets were pre-filtered with Butterworth filters (critical frequency varying between 0.16 and 1.16 cycles/cm, order 5) and with no filter. Phantoms were repositioned, and SPECT acquisitions were repeated. As the critical frequency increased, the estimated LV volume increased to reach a plateau at the level of the critical frequency, 0.54 cycles/cm. Conversely, the values of ejection fractions, wall motion and wall thickening with different filters which used critical frequency of > or =0.39 cycles/cm remained unchanged. However, LV functions and volumes were underestimated when any pre-reconstruction filter was used. Standard deviations of LV functions after repeated measurements were unaffected by different filters with critical frequencies of > or =0.39 cycles/cm. Standard deviations of LV volume, ejection fraction, wall motion and wall thickening were <2.2 ml, <0.9%, <0.6 mm and <8.7%, respectively. Therefore, with the exception of low critical frequencies, LV functions and volumes were highly reproducible when these routine reconstruction filters were used.

Algorithms↗
PubMed2002

Validation of left ventricular function from gated single photon computed emission tomography by using a scintillator-photodiode camera: a dynamic myocardial phantom study.

A scintillator-photodiode camera is able to acquire single photon emission computed tomography (SPECT) images by using a rotating chair system. We validated the left ventricular (LV) parameters of this camera system utilizing a dynamic myocardial phantom. Gated myocardial SPECT of a dynamic myocardial phantom (Hokkaido University type; end diastolic volume (EDV), 143 ml; end systolic volume (ESV), 107 ml; ejection fraction (EF), 25%) was performed with this scintillation camera. LV parameters were calculated using pre-installed software (Mirage Myocardial Perfusion SPECT) (study 1) and the other software (QGS; Cedars-Sinai) (study 2). For comparison, SPECT from a traditional Anger camera were processed by the QGS software (study 3). The estimated volumes were similar among the three studies (EDV, 110+/-8 ml in study 1, 112+/-2 ml in study 2 and 111+/-1 ml in study 3; ESV, 86+/-8 ml in study 1, 93+/-4 ml in study 2 and 91+/-2 ml in study 3). The estimated EFs were 23+/-3%, 17+/-2%, and 18+/-1%, respectively. The calculated volume within each study was underestimated by approximately the same degree. However, each estimated EF value for each study was close to the actual value. The estimated LV function using the scintillator-photodiode camera system may be considered as a suitable alternative to the traditional Anger camera system.

Algorithms↗
PubMed2002

Value and limitation of myocardial fluorodeoxyglucose single photon emission computed tomography using ultra-high energy collimators for assessing myocardial viability.

Single photon emission computed tomography (SPECT) using ultra-high energy collimators permits wide clinical application of (18)F-fluorodeoxyglucose (FDG) imaging without the use of expensive positron emission tomography (PET) cameras. This study was designed to evaluate the value of FDG SPECT using ultra-high energy collimators in assessing myocardial viability compared with FDG PET on a regional basis. We prospectively studied 33 patients with ischaemic heart disease. The patients were injected with 555 MBq of FDG under a hyperinsulinaemic glucose clamp, and FDG PET was performed 40 min later. FDG SPECT using ultra-high energy collimators was performed immediately after FDG PET. The images of the left ventricular myocardium were divided into nine segments and the regional defect score was assessed visually using a four-point scale (0=normal to 3=defect). Regional FDG uptake (%uptake) was quantitatively analysed using polar maps. In 297 segments of all the 33 patients, agreement between the defect scores based on FDG SPECT images and those based on FDG PET images was 70%, and agreement within one rank was 96% (kappa value=0.52). The %uptake based on FDG SPECT images significantly correlated with that based on FDG PET images (r=0.77, P<0.01). However, the defect scores in the inferior wall based on FDG SPECT images were higher (1.41+/-1.14) than those based on FDG PET images (1.06+/-1.12, P<0.01). When the viable region is defined as %uptake > or =50% in FDG PET studies, the optimal cut-off level of %uptake based on FDG SPECT images was 60% in the anterior wall, apex, septum and lateral wall (accuracies, 97%, 93%, 96% and 99%, respectively), and 45% in the inferior wall (accuracy, 99%). It is concluded that FDG SPECT using ultra-high energy collimators can be used for the assessment of myocardial viability as accurately as FDG PET. However, a slight difference was observed in the defect scores mainly due to attenuation in the inferior wall. Therefore, a slightly different cut-off level for assessing myocardial viability should be applied to the inferior wall when using FDG SPECT.

Adult↗
PubMed2001

Abnormal neuronal network in anorexia nervosa studied with I-123-IMP SPECT.

Single photon emission computed tomography was used to study 14 female patients with anorexia nervosa and 8 female normal comparison subjects. Automatic voxel-based analysis of the images was carried out using statistical parametric mapping (SPM) software. Statistics across the entire brain were displayed as Z scores (threshold: P<0.05). Compared with the normal comparison subjects, the anorectic patients were characterized by hypoperfusion in the medial prefrontal cortex and the anterior cingulate gyrus, and hyperperfusion in the thalamus and the amygdala-hippocampus complex. These results suggest that a dysfunction in neuronal circuitry may be related to anorexia nervosa.

Adolescent↗
PubMed2001

Use of [11C]acetate and [15O]O2 PET for the assessment of myocardial oxygen utilization in patients with chronic myocardial infarction.

Carbon-11 acetate positron emission tomography (PET) has been widely used to assess regional oxidative metabolism of the heart. However, the accuracy of [11C]acetate PET in assessing oxidative metabolism in infarcted myocardium remains controversial. Thirteen patients with stable coronary artery disease and old myocardial infarction were studied. The 15O-based PET studies yielded regional blood flow (rMBF, ml/min/g) and oxygen consumption (rMMRO2, ml/min/g), which was compared with the myocardial clearance rate constant (kmono) of [11C]acetate in segments with rMBF > or = 75% (group A), 50%-74% (group B) or < 50% (group C) of the normal reference segment. Mean MBF was 0.96 +/- 0.08 ml/g/min in group A, 0.67 +/- 0.06 ml/g/min in group B and 0.42 +/- 0.07 ml/g/min in group C segments. The segmental rMMRO2 correlated linearly with kmono (r = 0.89, P < 0.001, y = 0.61x + 0.026). The kmono/rMMRO2 ratio was comparable in the group A and B segments (0.99 +/- 0.19 vs 1.07 +/- 0.21, P = NS). However, the ratio was significantly higher in the group C segments (1.28 +/- 0.35, P = 0.037). It is concluded that kmono of [11C]acetate correlates linearly with rMMRO2 determined by [15O]O2 inhalation. However, kmono appears to yield higher rMMRO2 estimates than the [15O]O2 method in low-flow areas.

Acetates↗
PubMed2001

Clinical advantages of interictal SPECT coregistered to magnetic resonance imaging in patients with epilepsy.

PURPOSE: The aim of this study was to investigate the clinical value of coregistration of interictal SPECT and magnetic resonance imaging (MRI) in patients with partial epilepsy. MATERIALS AND METHODS: Seventeen patients with partial epilepsy were examined with I-123 IMP or Tc-99m ethyl cysteinate dimer SPECT during the interictal phase. The SPECT images were automatically coregistered to axial T1 weighted MRIs. Asymmetry indexes (AIs) were calculated in both nonregistered images and coregistered images. RESULTS: SPECT images showed areas of decreased tracer uptake in 12 patients. In two patients, the relation between the tumor and the extent of decreased uptake became more accurate in the coregistered images. In five cases, the coregistered images clearly showed that the decreased uptake was located in the sulcus. The AIs were significantly reduced from 14.29 +/- 7.23 to 5.86 +/- 3.48 (P < 0.001) after the images were coregistered in these cases. In five cases, the coregistered images indicated that the decreased areas were in agreement with the cortical findings. No significant differences in the AIs were observed in these cases (16.50 +/- 6.19 versus 17.83 +/- 4.45). Thus, the coregistered images were useful not only to differentiate actual hypoperfusion from artificial hypoperfusion resulting from partial volume effects but also to improve the accuracy of AIs. CONCLUSION: The coregistration of interictal perfusion SPECT and MRI is useful not only to provide precise functional and anatomic mapping but also to improve the accuracy of calculations of the semiquantitative analysis of regional cerebral blood flow parameters during the interictal state of epilepsy.

Adolescent↗
PubMed2001

Thalamic asymmetry on interictal SPECT in patients with frontal lobe epilepsy.

BACKGROUND: Interictal brain single photon emission computed tomography (SPECT) is useful for the detection of seizure focus. Recent reports indicate a hypoperfusion in the ipsilateral thalamus as a seizure focus on interictal SPECT in temporal lobe epilepsy. In frontal lobe epilepsy (FLE), however, the alteration of perfusion in the thalamus has not been well documented. This study aimed to assess whether perfusion analysis on the thalamus may add useful information for the detection of epileptic foci in patients with FLE. METHODS: Interictal brain SPECT was performed in 11 patients with FLE. The asymmetry index for the thalamus and frontal area in the SPECT image was calculated in order to compare the laterality of the seizure foci. RESULTS: Thalamic asymmetry was seen in seven patients (64%), while cortial asymmetry was seen in six patients (55%). The concordance with the lateralization of the seizure foci was 6/7 (86%) in the thalamus, and 4/6 (67%) in the frontal area. Four patients showed only thalamic asymmetry. Concordance with the lateralization of the seizure focus was found in all of them. CONCLUSION: These preliminary results suggest that hypoperfusion in the thalamus may have a complementary role to lateralize the epileptic foci in patients with FLE.

Adolescent↗
PubMed2001

Comparison of (18)F-FDG, (131)I-Na, and (201)Tl in diagnosis of recurrent or metastatic thyroid carcinoma.

UNLABELLED: There are several reports about the usefulness of (18)F-FDG PET in thyroid cancer. However, few studies have compared FDG PET with (131)I and (201)Tl scintigraphy. The aim of this study was to evaluate the clinical significance of whole-body FDG PET in differentiated thyroid cancer and to compare the results with those obtained from (131)I and (201)Tl scintigraphy. METHODS: Whole-body FDG PET was performed on 32 patients (10 men, 22 women; age range, 30-77 y; mean age, 54 y) with differentiated thyroid cancer (5 cases of follicular cancer and 27 of papillary cancer) after total thyroidectomy. An overall clinical evaluation was performed, including cytology, thyroglobulin level, sonography, MRI, and CT, to allow a comparison with functional imaging results for each patient. Metastatic regions were divided into five areas: neck, lung, mediastinum, bone, and other. Multiple lesions in one area were defined as one lesion. The tumor-to-background ratio (TBR) was measured for the lesions that were positive for both (201)Tl uptake and FDG PET uptake. RESULTS: The number of lesions totaled 47. Forty-one (87%) were detected by all scintigraphic methods. FDG uptake was concordant with (131)I uptake in only 18 lesions (38%). FDG uptake was concordant with (201)Tl uptake in 44 lesions (94%). Only one lesion was negative for FDG uptake and positive for (201)Tl uptake, and two lesions were positive for FDG uptake and negative for (201)Tl uptake. A significant correlation was seen between the TBR of (201)Tl and that of FDG (r = 0.69; P<0.05). CONCLUSION: These data indicate that for detecting metastatic lesions, FDG PET and (131)I scintigraphy may provide complementary information, whereas FDG PET may provide results similar to those of (201)Tl scintigraphy. Thus, the combination of (131)I scintigraphy and FDG PET (or (201)Tl scintigraphy) is the method of choice for detecting metastatic thyroid cancer after total thyroidectomy.

Adenocarcinoma, Follicular↗
PubMed2001

Low-dose dobutamine electrocardiograph-gated myocardial SPECT for identifying viable myocardium: comparison with dobutamine stress echocardiography and PET.

UNLABELLED: The identification of severely dysfunctional but viable myocardium is of particular importance for the selection of patients with depressed left ventricular function who will benefit from coronary revascularization. Assessment of inotropic reserve with dobutamine has recently been used for this purpose. This study compared the accuracy of low-dose dobutamine stress gated myocardial SPECT (DS SPECT) with the accuracy of dobutamine stress echocardiography (DSE) and resting perfusion SPECT for the identification of viable myocardium in patients with previous myocardial infarction. METHODS: Resting and low-dose dobutamine (7.5 microg/kg/min) gated (99m)Tc-tetrofosmin SPECT and echocardiography and resting (18)F-FDG PET were prospectively studied in 23 patients with previous myocardial infarction and severely depressed regional function. Twenty-one of them were successfully studied with each technique. The left ventricular wall was divided into 14 segments to assess wall motion using a 5-point scale. PET viability was defined as FDG uptake >/= 50% of the maximum uptake in a region with normal wall motion. For DS SPECT and DSE studies, viable myocardium was defined as hypokinetic areas with > or = 1 point improvement in wall motion. For resting perfusion SPECT, viable myocardium was defined as hypokinetic areas with a relative uptake > or = 50% of the maximum uptake. RESULTS: Of a total of 294 segments, 55 had severe resting dyskinesis. Thirty-four segments were identified as viable on FDG PET, and 21 segments were identified as nonviable. Eleven segments were inadequately visualized with DSE, including 5 segments in the apex. Sensitivities (78% vs. 76%) and specificities (94% vs. 100%) were similar for DSE and DS SPECT, with a concordance of 86% (kappa = 0.72). DS SPECT and perfusion SPECT did not significantly differ with respect to sensitivities (76% vs. 85%, respectively). However, specificity was significantly higher for DS SPECT than for perfusion SPECT (100% vs. 52%, respectively, P < 0.05). CONCLUSION: This study indicated that DS SPECT correlates well with DSE in the assessment of viability. In addition, gated SPECT can evaluate regional wall motion, even in areas inadequately assessed by echocardiography. DS SPECT may also provide additional information for identifying viable myocardium, which is often overestimated by routine perfusion scans.

Aged↗
PubMed2000

A new dynamic myocardial phantom for the assessment of left ventricular function by gated single-photon emission tomography.

Gated myocardial perfusion single-photon emission tomography (SPET) has been used for the measurement of left ventricular (LV) function and validated by means of comparison with other imaging modalities. We have designed a new dynamic myocardial phantom in order to validate the LV function as assessed by the use of gated myocardial perfusion SPET. The phantom consists of two half-ellipsoids (an endocardial surface and an epicardial surface) and a thorax. The myocardial space is filled with a radioactive solution. The endocardial surface moves continuously towards and away from the epicardial surface in the longitudinal axis to vary the LV volume [143 ml at end-diastole (ED), 107 ml at end-systole (ES)] and thickness (apex 8 mm at ED and 26 mm at ES, midplane 8 mm). The mean values of wall motion (WM) for the apical midplane region and the basal midplane region were 5 mm and 2 mm, respectively. Gated myocardial SPET was performed during 8 and 16 intervals. These projection data sets were processed using a Butterworth filter with an order of 5 and a critical frequency of 0.34 cycles/cm. LV function was calculated using the quantitative gated SPET (QGS) algorithm. The LV function values estimated by gated SPET during 16 intervals [22% for ejection fraction (EF), 3.7 mm for WM of the apical midplane, 1.7 mm for WM of the basal midplane] closely resembled actual LV functions [25% for EF, 5 mm for WM of the apical midplane, 2 mm for WM of the basal midplane]. However, the estimated values during 8 intervals were smaller than those during 16 intervals (19% for EF, 3.3 mm for WM of the apical-midplane, 1.1 mm for WM of the basal-midplane). The estimated LV volumes closely correlated with the actual volumes (r=0.99 for 16 intervals, r=0.95 for 8 intervals). Utilizing this phantom, LV function estimated using gated myocardial SPET can be compared with actual values.

Diastole↗
PubMed2000

Comparison between segmental wall motion and wall thickening in patients with coronary artery disease using quantitative gated SPECT software.

This study was performed to evaluate regional wall motion (WM) and wall thickening (WT) using gated myocardial perfusion single photon emission computed tomography (SPECT) and to determine their similarity and disparity in patients with coronary artery disease (CAD). A total of 44 patients underwent 1 day stress/rest (MIBI) gated SPECT. Commercially available quantitative analysis of gated SPECT (QGS) software was used to generate 3D surface display and cine-mode SPECT display. Left ventricle was divided into nine segments to score WM and WT from 0 (no abnormality) to 4 (severe abnormality) by six independent observers. Finally a mean score was calculated for each segment from the scores of six observers. There was fairly good correlation between WM and WT of individual segments (r = 0.62, p < 0.0001). Concordance rate (IWM - WTI < 1) was 85%. A large difference between WM and WT (WM - WT > or = 2) was observed in 15 segments, including 12 segments with greater WM abnormalities and 3 segments with greater WT abnormalities (lateral and inferior walls). Greater WM abnormalities were most commonly observed in anteroseptal segments especially in post coronary artery bypass grafting (CABG) patients. In conclusion, WM and WT showed similarity on QGS studies. However, these two parameters may be determined separately in gated SPECT studies for comprehensive and robust evaluation of the functional status of myocardium. Analyses based on WM assessment alone may lead to erroneous results especially in septal regions.

Aged↗
PubMed1999

Myocardial oxygen consumption is unchanged but efficiency is reduced in patients with essential hypertension and left ventricular hypertrophy.

BACKGROUND: Patients with hypertension and left ventricular hypertrophy (LVH) are prone to develop heart failure. We tested the hypothesis that compensatory LVH is associated with normalization of myocardial oxygen consumption and that this occurs at the expense of a decrease in the ratio between cardiac work and oxygen consumption (efficiency). METHODS AND RESULTS: Nine hypertensive men with LVH (LVH+) (age 42+/-2 years), left ventricular mass index (LVMI) 161+/-8 g/m(2), blood pressure (BP) 145+/-16/88+/-10 mm Hg (mean+/-SD); 8 hypertensive men without LVH (LVH-) (age 39+/-5 years, LVMI 107+/-15 g/m(2), BP 140+/-15/90+/-11 mm Hg); and 10 normotensive men (CONT) were studied. Myocardial blood flow, oxygen consumption, and glucose uptake were measured during euglycemic hyperinsulinemia using PET techniques. LV dimensions, volumes, and workload were determined by echocardiography, and efficiency was calculated. Myocardial workload (2.5+/-0.8 versus 3.0+/-0.6 versus 2. 3+/-0.5 mm Hg. mL. min(-1). g(-1) for CONT versus LVH- versus LVH+; P<0.05, LVH- versus LVH+), myocardial blood flow (0.84+/-0.16 versus 1.06+/-0.22 versus 0.81+/-0.09 mL. g(-1). min, respectively; P<0.05, LVH- versus other groups) and oxygen consumption (0.09+/-0.02 versus 0.14+/-0.03 versus 0.11+/-0.01 ml. g(-1). min(-1), respectively; P<0. 05, LVH- versus other groups) were increased in the LVH- group. Myocardial efficiency was reduced in the LVH+ group (18.1+/-4.1% versus 15.1+/-2.3% versus 13.5+/-1.9%, respectively; P<0.05, LVH+ versus CONT). CONCLUSIONS: Myocardial oxygen consumption per unit weight is increased in hypertensive patients without LVH but is normal in those with LVH. The normalization of oxygen consumption via hypertrophy occurs at the expense of efficiency, which may predispose hypertensive patients with LVH to heart failure.

Adult↗
PubMed1999

Validity of 99mTc-DMSA renal uptake by planar posterior-view method in children.

Renal uptake of 99mTc-DMSA has been quantified by various methods. The aim of this study is to obtain a normal value for 99mTc-DMSA renal uptake calculated by the posterior view method and age variation, and to assess its clinical validity. Scintigrams of 238 children (0-12 years) with 99mTc-DMSA were reviewed. All the children had a clinical history of primary vesicoureteral reflux and/or neurogenic bladder, ureteral or urethral anomalies. Their kidneys were divided into two groups, "normal" and "abnormal" according to their scintigraphic findings and split renal functions. Percent renal uptake per injected dose (% RU) was quantitated from planar images at 2 hours after injection of an age-adjusted dose (26-95 MBq) of 99mTc-DMSA. Calculated total % RU, individual % RU of the right and left kidneys (mean +/- sd) in patients with normal kidneys were 40.7 +/- 5.0%, 20.2 +/- 3.0%, 20.4 +/- 2.7%, respectively. There was no significant correlation between % RU and age (r = 0.231). Longitudinal variation in the % RU in 9 patients ranged from 1.2% to 18%. Our conventional method for quantifyng % RU is simple, practical and feasible in routine clinical practice, especially for children under follow up.

Adolescent↗
PubMed1999

Reappraisal of Tc-99m DMSA scintigraphy for follow up in children with vesicoureteral reflux.

We reviewed Tc-99m DMSA scintigraphy in children with vesicoureteral reflux (VUR) in order to assess whether repeated Tc-99m DMSA scans are necessary for the follow up of these patients. Ninety-seven children who were followed up for more than one year (1-7.4 years, average 2.8 years) after the first DMSA scan were included in the study. Fifty-one patients had been diagnosed as primary VUR and 46 as secondary VUR. Age at the first examination ranged from 0 to 14 years (average 5.1 years). Planar images were taken 2 hours after injection. The % renal uptake per injected dose (%RU) was calculated from posterior images. Kidneys in 11 patients (11.3%) changed morphologically during the follow up. Of these, new photon deficient areas (PD) were detected in only 4 patients (4.1%). All of these 4 patients had neurogenic bladder and were managed with self-catheterization. Of the remaining 7 patients, cortical thinning progressed in 5 patients (5.2%) and PDs resolved in 3 patients (3.1%). In one of these 7 patients, PD resolved in one kidney and cortical thinning progressed in the contralateral kidney. Of 97 patients reviewed, % RU decreased more than 20% during the follow up in 6 patients (6.2%). All were diagnosed as secondary VUR due to neurogenic bladder. %RU decreased only in the contracted kidneys at the initial scan. Two of them underwent renal transplantation because of severe renal failure. In conclusion, new PD rarely developed and % RU decreased in only a few patients during the follow up of children with VUR. Repeated Tc-99m DMSA scintigraphy therefore seems to have little benefit in the follow up of children with VUR. It should be performed in selected patients with high risk of urinary tract infection or renal failure.

Adolescent↗
PubMed1999

Myocardial blood flow, oxygen consumption, and fatty acid uptake in endurance athletes during insulin stimulation.

We have previously demonstrated reduced myocardial glucose uptake rates in hearts of endurance athletes, which could be due to increased use of alternative fuels or reduced energy demands. In the present study myocardial blood flow, oxygen consumption, and free fatty acid uptake were measured with [(15)O]H(2)O, [(15)O]O(2), [(18)F]FTHA, and positron emission tomography (PET) in 9 endurance athletes and 11 sedentary men during euglycemic hyperinsulinemia. Compared with sedentary men, athletes had 33% lower myocardial blood flow, 27% lower oxygen consumption, and 20% lower estimated myocardial work per gram of tissue. Myocardial fatty acid uptake rates were not significantly different in endurance athletes (0.83 +/- 0.29) and sedentary men (1.0 +/- 0.31 micromol. 100 g(-1). min(-1), P = 0.232). In conclusion, myocardial blood flow and oxygen consumption per unit mass of myocardium are reduced at rest in endurance athletes. This can be explained by reduced energy requirements per gram of tissue due to anatomic and physiological changes of the athlete's heart.

Adult↗
PubMed1999

Iterative reconstruction based on median root prior in quantification of myocardial blood flow and oxygen metabolism.

UNLABELLED: The aim of this study was to compare reproducibility and accuracy of two reconstruction methods in quantification of myocardial blood flow and oxygen metabolism with 15O-labeled tracers and PET. A new iterative Bayesian reconstruction method based on median root prior (MRP) was compared with filtered backprojection (FBP) reconstruction method, which is traditionally used for image reconstruction in PET studies. METHODS: Regional myocardial blood flow (rMBF), oxygen extraction fraction (rOEF) and myocardial metabolic rate of oxygen consumption (rMMRO2) were quantified from images reconstructed in 27 subjects using both MRP and FBP methods. For each subject, regions of interest (ROIs) were drawn on the lateral, anterior and septal regions on four planes. To test reproducibility, the ROI drawing procedure was repeated. By using two sets of ROIs, variability was evaluated from images reconstructed with the MRP and the FBP methods. RESULTS: Correlation coefficients of mean values of rMBF, rOEF and rMMRO2 were significantly higher in the images reconstructed with the MRP reconstruction method compared with the images reconstructed with the FBP method (rMBF: MRP r = 0.896 versus FBP r = 0.737, P < 0.001; rOEF: 0.915 versus 0.855, P < 0.001; rMMRO2: 0.954 versus 0.885, P < 0.001). Coefficient of variation for each parameter was significantly lower in MRP images than in FBP images (rMBF: MRP 23.5% +/- 11.3% versus FBP 30.1% +/- 14.7%, P < 0.001; rOEF: 21.0% +/- 11.1% versus 32.1% +/- 19.8%, P < 0.001; rMMRO2: 23.1% +/- 13.2% versus 30.3% +/- 19.1%, P < 0.001). CONCLUSION: The MRP reconstruction method provides higher reproducibility and lower variability in the quantitative myocardial parameters when compared with the FBP method. This study shows that the new MRP reconstruction method improves accuracy and stability of clinical quantification of myocardial blood flow and oxygen metabolism with 15O and PET.

Adult↗