Pulmonary clearance of inhaled 99mTc-DTPA: effect of the detergent dioctyl sodium sulfosuccinate in aerosol

Summary. The influence of the detergent dioctyl sodium sulfosuccinate on clearance from the lungs of inhaled technetium-99m-labelled dietylenetriamine pentaacetate (^99mTc-DTPA) was studied in twelve rabbits. An aerosol of dioctyl sodium sulfosuccinate or its vehicle alone was administered for 5 min prior to aerosolized ^99mTc-DTPA via a bag-in-bottle system. Time-activity curves were obtained from the right lung with a gamma camera. In rabbits given detergent, clearance of ^99mTc-DTPA was significantly faster than in rabbits given vehicle alone. No changes were seen in arterial Po₂ and compliance. Our data indicates that the transfer of ^99mTc-DTPA from alveoli to blood can be accelerated by administration of the detergent dioctyl sodium sulfosuccinate without any dramatic change in surface tension. Clearance of ^99mTc-DTPA may be a very sensitive indicator of altered surfactant function.     

Determination of 99mTc-DTPA clearance by a single plasma sample method

Summary. To derive a formula for determination of ^99mTc-DTPA clearance (Cl) from the radioactivity in a single plasma sample, the relation Cl=ECV/ was used, where ECV is the extracellular volume and I is the mean transit time of the tracer in the organism. By studying ^99mTc-DTPA time activity curves of 45 consecutive patients we found that ECV could be estimated from the body surface area, and that I could be calculated from the radioactivity in a single plasma sample. Cl calculated by the single sample method was almost identical to Cl calculated by a standard multiple sample method (r=0·987). It is concluded that the single sample method is accurate and that it may prove useful as a routine method provided that (a) the method is not used in patients with ^99mTc-DTPA clearance less than 30 ml min^-1, since this investigation includes only patients with Cl>30 ml min^-1; (b) the method is not used for children, since the test material did not contain any children; (c) the method is only used for plasma samples drawn at 180≤t≤300 min.     

Pulmonary clearance of 99mTc–DTPA and 99mTc-albumin in rabbits with surfactant dysfunction and lung injury

Summary. We measured the pulmonary clearance of inhaled ^99mTc-DTPA and “Tc-albumin in rabbits with surfactant dysfunction induced by dioctyl sodium sulphosuccinate and in rabbits with lung injury induced by oleic acid. The animals were tracheotomized and mechanically ventilated. After inhalation of ^99mTc-albumin in ten animals, clearance of the tracer from the lungs was monitored for 90 min. The first 30 min was a control period. Dioctyl sodium sulphosuccinate was then administered in aerosol and after another 30 min oleic acid was injected intravenously. Ten other rabbits were given ^99mTc-DTPA, and clearance was externally recorded for 60 min. Five animals inhaled detergent aerosol and five animals were given oleic acid intravenously after 30 min. Airway pressures, tidal volume, and arterial blood gases were measured before and after each intervention. The half-life of ^99mTc-albumin in the lung was 442 ± 123 min during the control period, 363 plusmn; 52 min after detergent administration, and 134 plusmn; 18 min after oleic acid administration (P<0.05 compared to control and P<0.01 compared to the period after detergent). The half-life of ^99mTc-DTPA was 94 plusmn; 16 min before and 10 plusmn; 0.6 min (P<0.01) after detergent administration and 75 plusmn; 12 min before and 18 plusmn; 1.8 min (P<0.01) after oleic acid administration. Gas exchange was not affected by administration of dioctyl sodium sulphosuccinate but markedly impaired after injection of oleic acid. Compliance of the respiratory system remained unaffected by detergent but decreased after injection of oleic acid. The results indicate that the rate limiting factors for the alveolo-capillary transfer of ^99mTc-albumin and ^99mTc-DTPA are different. Surfactant dysfunction affects the transfer of ^99mTc-DTPA but not ^99mTc-albumin. More extensive injury involving the alveolar epithelium may be required for the clearance of ^99mTc-albumin to increase.     

Biphasic pulmonary clearance of 99mTc-DTPA in smokers

Summary. We measured the pulmonary clearance of ^99mTc-labelled diethylene triamine penta-acetate (^99mTc-DTPA) for 3 h in 17 non-smokers and in 16 healthy smokers. We found the clearance of ^99mTc-DTPA to be well described by a mono-exponential equation in 14 non-smokers, the half-life being 66 ± 17 min (mean ± SD). In all smokers, a bi-exponential equation yielded a significantly better curve fit. The half-life of the slow and fast clearance components was 83 ± 19 and 13 ± 4 min, respectively. The relative amount of radioactivity cleared by the fast component was 57 ± 15% and correlated significantly with cumulated tobacco consumption (r= 0–58, P<0.02) and forced expiratory volume in 1 s in percentage of predicted value (r= - 0–60, P<0–02). We conclude that smoking induces a rapidly clearing pool of ^99mTc-DTPA in the lung, the size of which may be related to smoking habits.     

Pulmonary clearance of inhaled 99mTc-DTPA: effect of surfactant depletion in rabbits

Summary. We examined the effect of surfactant depletion on the rate of pulmonary clearance of inhaled ^99mTc-diethyl-triamino-penta-acetate (DTPA). ^99mTc-DTPA was administered as a fine aerosol to four control animals and to four animals after wash-out of pulmonary surfactant. Care was taken to minimize structural damage to the lavaged lungs. Clearance of ^99mTc-DTPA was measured over the right lung by external counting. The clearance rate was substantially increased in the lavaged animals compared to the control animals. We conclude that the pulmonary surfactant system is a rate-limiting factor for the absorption of inhaled ^99mTc-DTPA. Measurement of the pulmonary clearance of ^99mTc-DTPA may provide a new means for studying the pathogenetic role of the surfactant system in a variety of lung diseases.     

Comparison of simultaneous plasma clearance of 99mTc-DTPA and 51Cr-EDTA: can one tracer replace the other?

Abstract

Both ^99mTc-DTPA and ⁵¹Cr-EDTA are widely used to determine glomerular filtration rate (GFR), but few direct comparative studies exist. The shortage of ⁵¹Cr-EDTA makes a direct comparison highly relevant. The aim of the study was to investigate if there is any clinically relevant difference between plasma clearance of ^99mTc-DTPA and ⁵¹Cr-EDTA. Patients ≥18?years of age referred for routine GFR measurement by ⁵¹Cr-EDTA were prospectively enrolled. The two tracers (10 MBq ^99mTc-DTPA (CaNa₃-DTPA) and 2.5 MBq ⁵¹Cr-EDTA) were intravenously injected at time zero. A standard 4-sample technique was applied with samples collected at 180, 200, 220 and 240?min, if the estimated GFR (eGFR) was ≥30?mL/min. A comparison of single-sample GFR based on the 200?min sample was also conducted. Fifty-six patients were enrolled in the study. All patients had an estimated GFR >30?mL/min/1.73 m². No patients suffered from ascites or significant oedema. The mean ⁵¹Cr-EDTA plasma clearance was 82?mL/min (range 16–226). The plasma clearances determined by the two methods were highly correlated (r?=?0.993). The plasma clearance was significantly higher when measured by ^99mTc-DTPA than by ⁵¹Cr-EDTA (p?=?0.01), but the numerical difference was minimal (mean difference 1.4?mL/min; 95% limits of agreement (LOA) –6.6 to 9.4). The difference between the two methods was independent of the level of renal function. Similar results were found for one-sample GFR. No clinically relevant differences were found between the plasma clearance of ^99mTc-DTPA and that of ⁵¹Cr-EDTA. Therefore, ^99mTc-DTPA can replace ⁵¹Cr-EDTA when needed.     

Pulmonary clearance of inhaled 99Tcm-DTPA: significance of site of aerosol deposition

Summary. The aim of this study was to analyse how changes in the site of ⁹⁹Tc^m-DTPA aerosol deposition between central and peripheral parts of the lung influence routine measurement of pulmonary clearance of ⁹⁹Tc^m-DTPA (PCl). The study was performed in six ‘never-smokers’ and 10 smokers with bronchial hypersecretion. Changes in aerosol deposition was accomplished by changing the aerosol particle size and the velocity by which the subjects inhaled the particles. In the smokers with bronchial hypersecretion there was a significantly smaller PCI after central deposition (P< 0·01), than after peripheral deposition, while in the never-smokers, significance was not reached. The smokers with bronchial hypersecretion had a significantly higher PCI than the never-smokers (P<0·01) when the ⁹⁹Tc^m-DTPA had been deposited in the peripheral parts of the lung, but at the examination of central deposition, the difference was no longer significant. It is concluded that in smokers with bronchial hypersecretion measurement of regional PCl is influenced by the site of ⁹⁹Tc^m-DTPA deposition in the lung.     

99Technetiumm DTPA does not break down during ultrasound nebulization

Summary. For several years aerosolized ⁹⁹Tc^m-DTPA has been used for studies of pulmonary permeability. Comparable results have been obtained regardless of the ⁹⁹Tc^m-DTPA having been nebulized in an ultrasound nebulizer or a jet nebulizer. It was therefore surprising when in a recent study it was observed that more than 90% of a commercially available ⁹⁹Tc^m-DTPA (Squibb) was dissociated into ⁹⁹Tc^mO₄- and DTPA during ultrasound nebulization. To verify this observation we performed chromatography of seven commercially available DTPA-labelling kits (including that of Squibb). Four different test preparations of each of the kits were analysed: (1) stock solution of ⁹⁹Tc^m-DTPA; (2) heated (80°C) ⁹⁹Tc^m-DTPA; (3) ⁹⁹Tc^m-DTPA nebulized by a DeVilbiss ultrasound nebulizer; (4) ⁹⁹Tc^m-DTPA nebulized by a Varic ultrasound nebulizer. In no case were we able to demonstrate more than 1·0% reduced pertechnetate (⁹⁹Tc^mO₂) or more than 0·9% free ⁹⁹Tc^mO₄- after either heating or ultrasound nebulization. A maximum of 5·6%⁹⁹Tc^mO₂ could be demonstrated in the stock solution if chromatography was done immediately after the preparation, but only 15 min later no more than 0·9%⁹⁹Tc^mO₂ was present. We conclude that there is no essential chemical breakdown of ⁹⁹Tc^m-DTPA during ultrasound nebulization. Caution should be taken not to use the ⁹⁹Tc^m-DTPA until 15 min after its preparation.     

Increased colorectal permeability in patients with severe sepsis and septic shock

Objective To develop a method for the assessment of colorectal permeability in septic patients.Design and setting Observational study in ICUs at two university hospitals.Participants Nine patients with septic shock and abdominal focus of infection, 7 with severe sepsis and pulmonary focus and 8 healthy subjects.Measurements and results Colorectal permeability was assessed as the initial appearance rate of ^99mTc-DTPA in plasma after instillation into the rectal lumen and as the cumulative systemic recovery at 1 h. To calculate the latter, volume of distribution and renal clearance of ^99mTc-DTPA was estimated by an i. v. bolus of ⁵¹Cr-EDTA. The initial rate of permeability was increased in patients with septic shock and severe sepsis compared with controls [29.0 (3.7–83.3), 20.6 (3.6–65.5) and 6.0 (2.2–9.6) cpm ml⁻¹ min⁻¹, respectively, p < 0.05)] with a positive linear trend (r ² = 0.27, p = 0.01) and correlated to L-lactate concentrations in the rectal lumen (r ² = 0.39, p < 0.05). The cumulative permeability was also increased in patients with septic shock and severe sepsis compared with controls [2.07 (0.05–15.7), 0.32 (0.01–1.2) and 0.03 (0.01–0.06)‰, respectively, p < 0.01] and correlated to the initial permeability rate (r ² = 0.26, p = 0.01).Conclusions In septic patients, the systemic recovery of a luminally applied marker of paracellular permeability was increased and related to the luminal concentrations of L-lactate and possibly to disease severity. This suggests that the assessment of colorectal permeability by systemic recovery of ^99mTc-DTPA is valid and that metabolic dysfunction of the mucosa contributes to increased permeability of the large bowel in patients with severe sepsis and septic shock.     

Pulmonary clearance of inhaled [99Tcm]DTPA: effects of ventilation pattern

Summary. While a rise in lung volume is known to increase the pulmonary clearance of technetium-99m-labelled dietylene triamine pentaacetate ([⁹⁹Tc^m]DTPA), little interest has been focused on the effects of changes in ventilation frequency, tidal volume and airway pressure. We studied adult, anaesthetized and intubated rabbits during three ventilation patterns (VP) using pressure controlled ventilation (Servo Ventilator 900C). VP was either deep slow (f=20 min^-1, tidal volume (V_T) = 30 ± 4 ml kg^-1 and positive end-expiratory pressure (PEEP) = 0·2 kPa [VP 20/ 0·2, n= 8]) or rapid shallow (f=80 min^-1, V_T= 11 ±2 ml kg^-1 and PEEP = 0·2 or 0·4 kPa [VP 80/0·2, n= 6 and VP 80/0·4, n= 6]). The mean airway pressure was similar at VP 20/0·2 and VP 80/0·4. During administration of [⁹⁹Tc^m]DTPA aerosol all animals were ventilated under the same conditions (f=40 min^-1 and PEEP = 0·2 kPa). The pulmonary clearance rate expressed as the half-life time (T^1/2) of [⁹⁹Tc^m]DTPA was at VP 80/0·2 = 113 ± 31 min, at VP 80/0·4 = 70 ± 24 min (P < 0·01 compared to VP 80/0·2) and at VP 20/0·2 = 36± 18 min (P <0·001 compared to VP 80/0·2 and P <0·01 compared to VP 80/0·4). We conclude that the pulmonary clearance of [⁹⁹Tc^m]DTPA increases

• 1 during rapid shallow ventilation when PEEP is increased from 0·2 to 0·4 kPa;
• 2 during deep slow ventilation relative to rapid shallow ventilation even when the mean airway pressure is similar.

     

Pulmonary absorption of instilled and inhaled DTPA in smokers

Summary. Pulmonary absorption of DTPA (diamine-triethylene-penta-acetic acid) has been widely adopted as an index of pulmonary epithelial permeability. The aim of this study was to analyse:

• 1 if measurements of pulmonary absorption are influenced by the amount of fluid being administered to the lungs together with the DTPA; and
• 2 if all DTPA administered to the lungs is equally accessible for pulmonary absorption.

To this end DTPA was instilled into a lung segment of six smokers in association with a bronchoscopy. In six other subjects (five smokers and one ex-smoker) the DTPA was inhaled as an aerosol. Pulmonary absorption of DTPA was calculated from the plasma DTPA content, as determined for 4–10 h after the administration of the DTPA. We found that the mean transit time for the absorption of instilled DTPA, i(L), across the pulmonary membranes was significantly (P<0·05) longer (median 1498 min, range 955–2636 min) than the fi(L) of the absorption of the inhaled DTPA (median 131 min, range 44–512 min). Pulmonary clearance of the inhaled aerosolized DTPA tended to be faster when determined by external detection for 4 h, than when estimated from plasma samples, suggesting that not all pulmonary DTPA may be equally accessible for absorption from the pulmonary lining fluids. We conclude that pulmonary absorption of DTPA is influenced by the volume of fluid being administered to the lungs in association with the measurements. Not all pulmonary DTPA, however, is equally accessible for absorption, rendering external detection of pulmonary clearance of DTPA sensitive to a variety of factors other than pulmonary absorption.     

肾脏深度对SPECT测定肾小球滤过率的影响

目的 评估6种肾脏深度估算公式对^99mTc-DTPA肾动态显像测定肾小球滤过率(GFR)的影响。 方法 以232名北京地区健康居民为研究对象,分别采用双血浆法和^99mTc-DTPA肾动态显像法测定GFR(GFR_dt和GFR_Gates)。分析6种肾脏深度估算公式所得GFR_Gates与GFR_dt间的相关性及一致性。 结果 公式1和5所得肾脏深度显著低于其他公式,公式3和6所得GFR_Gates与GFR_dt的相关性最好(r=0.81)。公式1和5所得GFR_Gates与GFR_dt一致性最差,差值均值分别为(-23.62±18.60)ml/(min·1.73 m²)、(-20.66±18.00)ml/(min·1.73 m²);公式3和4所得GFR_Gates与GFR_dt一致性最好,差值均值分别为(-5.80±16.76)ml/(min·1.73 m²)和(-3.81±17.87)ml/(min·1.73 m²)。 结论 肾脏深度估算公式1、2、5准确性较差,其他公式结果差异较小;公式3、4和6均可用于临床,但公式3和4更优。     

肺灌注断层显像评价肺动脉血栓内膜剥脱术对慢性血栓栓塞性肺动脉高压的疗效

目的 采用⁹⁹Tc^m-人体大颗粒聚合白蛋白（⁹⁹Tc^m-MAA）肺灌注断层显像评价肺动脉血栓内膜剥脱术（PTE）对慢性血栓栓塞性肺动脉高压（CTEPH）的疗效。方法 对16例CTEPH患者分别于术前、术后6~12个月行肺灌注断层显像,观察术前、术后肺叶、肺段灌注病变及改善情况,计算全肺灌注缺损百分比（PPDs%）,并采用超声心动图观察术前、术后肺动脉收缩压（SPAP）的变化。结果 16例患者术后SPAP[（36.56±8.47） mmHg]较术前[（90.52±14.55） mmHg]明显减低（t=14.14,P<0.001）。PTE术前16例患者的96个肺叶中有86个（86/96,89.58%）存在灌注异常,术后完全改善、部分改善的肺叶分别为21个（21/86,24.42%）、65个（65/86,75.58%）;术前16例患者的304个肺段中,230个（230/304,75.66%）肺段灌注异常,术后完全改善、部分改善和未改善的肺段分别为73个（73/230,31.74%）、74个（74/230,32.17%）和83个（83/230,36.09%）。术前PPDs%为（56.79±14.54）%,术后6~12个月降低为（28.20±15.24）%（t=8.13,P<0.001）。PPDs%与同期SPAP呈正相关（r=0.68,P<0.001）。结论 PTE可使CTEPH患者的SPAP明显降低,肺血流灌注明显改善,肺灌注显像可有效评价PTE疗效。     

Single detector renography with 131I-Hippuran and 99mTc-DTPA: a comparison

Summary. ¹³¹I-Hippuran and ^99mTc-DTPA were injected intravenously within a few seconds. By appropriate dose and window selection, simultaneous Hippuran and DTPA renograms with discrete detectors were obtained from 33 kidneys (17 patients). Uptake and excretion ratios were significantly lower and peak time occurred slightly but significantly later in the DTPS than in the Hippuran renograms.     

Clearance and renal extraction of technetium-99m- L, L-ethylenedicysteine,I-131-ortho-iodohippurate and I-125-iothalamate in pigs

99mTc- L , L -ethylenedicysteine (^99mTc-EC) has been proposed as a ^99mTc-labelled alternative to radio-iodinated ortho-iodohippurate (OIH) for renal imaging and evaluation of renal function. The kinetics of this new renal function agent were studied by a single-injection plasma clearance technique in pigs. ^99mTc-EC, ¹³¹I-OIH and ¹²⁵I-iothalamate were injected and the plasma concentration of the three tracers was followed for 240 min. Renal, hepatic and total plasma clearance were calculated. There was no difference between the renal plasma clearance of ^99mTc-EC and ¹³¹I-OIH (175 ± 9 versus 178 ± 8 ml min^?1, P=0·43), whereas the difference between the total plasma clearance of ^99mTc-EC and ¹³¹I-OIH was highly significant (268 ± 16 versus 185 ± 9 ml min^?1, P=0·0001). ^99mTc-EC had a significant hepatic clearance of 83 ± 10 ml min^?1 whereas the hepatic clearance of ¹³¹I-OIH was negligible. Renal plasma extraction of both ^99mTc-EC and ¹³¹I-OIH decreased significantly between 2 and 240 min post-injection from 0·85 to 0·45% for ^99mTc-EC and from 0·93 to 0·57% for ¹³¹I-OIH. Red blood cell binding of ^99mTc-EC and ¹³¹I-OIH was 6·1% and 20%, respectively. The protein binding of ^99mTc-EC and ¹³¹I-OIH was 32% for both tracers. We conclude that ^99mTc-EC is not a suitable tracer for measuring renal function by the single-injection plasma clearance technique in pigs. This is due to a decreasing renal extraction and a significant hepatic clearance.     

99Tcm-HL91与99Tcm-MIBI肿瘤阳性显像在肺部肿块诊断中的对比研究

目的比较99Tcm-HL91和99Tcm-MIBI肿瘤阳性显像对肺部单发肿块的诊断效能和影像质量.方法 50例肺部结节或肿块患者,分为恶性组和良性组,术前分别行99Tcm-HL91和99Tcm-MIBI早、晚期平面及断层融合显像,对显像结果进行对照分析.结果①定性诊断HL91组的敏感性为97.30%(36/37例),特异性为69.23%(9/13例);MIBI组诊断的敏感性为83.78%(31/37例),特异性为76.92%(10/13例). 肺门及纵膈肿大淋巴结使用HL91检测的阳性率为91.30%(21/23个); MIBI法为73.91%(17/23个).② HL91法断层显像ROC曲线下的面积(0.953±0.034)较MIBI法(0.857±0.073)高约10%,以T/N值1.76为界点HL91诊断的敏感性为100%(37/37例),特异性为84.62%(11/13例);以1.66为界点MIBI组诊断的敏感性为86.49%(32/37例),特异性为76.92%(10/13例),以1.85为界点MIBI组诊断的敏感性为78.38%(29/37例),特异性为84.62%(11/13例).结论 99Tcm-HL91肺部病变亲肿瘤阳性显像在图像质量和诊断性能上均优于99Tcm-MIBI显像.     

Quantitative diffusion-weighted magnetic resonance imaging in the assessment of myocardial fibrosis in hypertrophic cardiomyopathy compared with T1 mapping

To identify myocardial fibrosis in hypertrophic cardiomyopathy (HCM) subjects using quantitative cardiac diffusion-weighted imaging (DWI) and to compare its performance with native T1 mapping and extracellular volume (ECV). Thirty-eight HCM subjects (mean age, 53?±?9 years) and 14 normal controls (mean age, 51?±?8 years) underwent cardiac magnetic resonance imaging (CMRI) on a 3.0T magnetic resonance (MR) machine with DWI, T1 mapping and late gadolinium enhancement (LGE) imaging as the reference standard. The mean apparent diffusion coefficient (ADC), native T1 value and ECV were determined for each subject. Overall, the HCM subjects exhibited an increased native T1 value (1241.04?±?78.50 ms), ECV (0.31?±?0.03) and ADC (2.36?±?0.34 s/mm²) compared with the normal controls (1114.60?±?37.99 ms, 0.24?±?0.04, and 1.62?±?0.38 s/mm², respectively) (p?<?0.05). DWI differentiated healthy and fibrotic myocardia with an area under the curve (AUC) of 0.93, while the AUCs of the native T1 values (0.93), (p?>?0.05) and ECV (0.94), (p?>?0.05) exhibited an equal differentiation ability. Both HCM LGE+ and HCM LGE? subjects had an increased native T1 value, ECV and ADC compared to the normal controls (p?<?0.05). HCM LGE+ subjects exhibited an increased ECV (0.31?±?0.04) and ADC (2.43?±?0.36 s/mm²) compared to HCM LGE? subjects (p?<?0.05). HCM LGE+ and HCM LGE? subjects had similar native T1 values (1250?±?76.36 ms vs. 1213.98?±?92.30 ms, respectively) (p?>?0.05). ADC values were linearly associated with increased ECV (R²?=?0.36) and native T1 values (R²?=?0.40) among all subjects. DWI is a feasible alternative to native T1 mapping and ECV for the identification of myocardial fibrosis in patients with HCM. DWI and ECV can quantitatively characterize the extent of fibrosis in HCM LGE+ and HCM LGE? patients.     

99Tcm-MIBI SPECT/CT显像诊断肺结节时本底的选取

目的 探讨行⁹⁹Tc^m-MIBI SPECT/CT断层显像时选取不同本底对鉴别诊断肺结节效能的影响。方法 回顾性分析38例患者共44个肺部可疑结节,根据病理结果将其分为恶性组和良性组;分别选取病灶对侧肺野(DL)、对侧软组织(NST)、肝顶(Liver)、心脏前壁(Cardiac)4种不同本底,计算病灶/本底(L/N)最大计数值(MAX)以及平均计数值(MEAN),比较组间差异、并采用ROC曲线评价其鉴别诊断良恶性病灶的效能。结果 以对侧肺野及对侧软组织作为本底,良恶性组间L/N最大计数值(MAX)以及平均计数值(MEAN)的差异均有统计学意义(P均< 0.05),而以肝顶及心脏作为本底时,良恶性组间L/N的差异均无统计学意义(P均> 0.05)。ROC曲线分析:以对侧肺野或对侧软组织作为本底,即L/DL-MAX、L/DL-MEAN、L/NST-MAX、L/NST-MEAN的AUC分别为0.78、0.78、0.74、0.77,两两比较,差异均无统计学意义(P均> 0.05)。在21个最大直径< 3 cm的肺部孤立病灶中,AUC分别为0.78、0.75、0.90、0.93,差异亦无统计学意义(P均> 0.05)。以AUC最大者、L/NST-MEAN=1.61为标准判断,灵敏度为88.89%(8/9),特异度为83.33%(10/12)。结论 采用⁹⁹Tc^m-MIBI SPECT/CT断层显像鉴别诊断肺结节时,对侧肺野及对侧软组织均可作为本底计算L/N比值。     

The role of serum cystatin C in estimation of renal function in survivors of critical illness

PurposeEstimating renal function by serum creatinine after critical illness is a challenging problem. However, the role of cystatin C for estimation of the renal function in survivors of critical illness is unknown. We aimed to compare the performance of serum cystatin C- and serum creatinine-based eGFR against a reference GFR using ^99mTc–diethylenetriaminepentaacetic acid (^99mTc-DTPA) in survivors of critical illness.Material and methodsSurvivors of critical illness with stable hemodynamics and renal functions were recruited. Their serum creatinine and cystatin C levels were measured. eGFR were calculated by using various equations: 1)CKD-EPI SCysC; 2) Thai eGFR SCysC; 3)CKD-EPI SCr; 4)Thai eGFR SCr; 5)MDRD Caucasian SCr; 6)CKD-EPI SCr-SCysC. The ^99mTc-DTPA plasma clearance was used as a standard eGFR.ResultsForty-two patients were included. The bias (median percentage difference) between standard GFR and SCysC-based eGFR were 41.97% (95%CI 33.1% to 48.5%) for CKD-EPI SCysC and 31.72% (95%CI 21.1% to 34.9%) for Thai eGFR SCysC. While, the bias between standard GFR and SCr-based eGFR were −11.37 (95%CI -20.9 to 1.6) for CKD-EPI SCr, −18.30 (95%CI -26.3 to −10.6) for Thai eGFR SCr, and −27.17 (−43.7 to −19.1) for MDRD Caucasian SCr.ConclusionIn survivors of critical illness, we demonstrated limitations of estimating GFR by both currently available SCysC and SCr-based equations. Therefore, further studies are still needed to develop better eGFR equations.     

Pulmonary clearance of [99mTc]DTPA and [99mTc]albumin in smokers

We measured the pulmonary clearance of [^99mTc]DTPA and [^99mTc]albumin for 3 h in 10 non-smokers and 10 healthy smokers. Seven of the non-smokers had a monoexponential clearance of [^99mTc]DTPA with a mean half-life of 66±18 min. The other three had a biexponential clearance of [^99mTc]DTPA with a fraction of radioactivity clearing rapidly (f_F) of 14±4%. Eight smokers had biexponential clearance of [^99mTc]DTPA. The half-life of the fast and slow clearance components was 1265 and 62611 min respectively. The f_F was 56±25%. Two of the smokers showed a monoexponential clearance of [^99mTc]DTPA with a half-life of 72 and 55 min. All non-smokers had monoexponential clearance curves for [^99mTc]albumin, compared with seven smokers. The half-life was 279±43 min in non-smokers and 236±64 min in smokers. The difference in half-life was not significant. In three smokers, the clearance curves of [^99mTc]albumin were significantly better described by a bi-exponential equation. The f_F was 22±9%. The effects of smoking on the clearance of [^99mTc]albumin appear to be qualitatively similar to those on the clearance of [^99mTc]DTPA. Clearance of [^99mTc]albumin seems less sensitive to the effects of smoking than clearance of [^99mTc]DTPA.