Solute transfer into the extravascular space: comparison of two non-invasive measurement techniques

Little clinical attention has been paid to the quantification of microvascular permeability to small hydrophilic solutes, probably because of a paucity of non-invasive techniques. We describe a technique using the gamma camera which measures the clearance of 99mTc DTPA, a molecule similar in size to sucrose, from the intravascular to the extravascular space in the lumbar tissues below the kidneys. This regional clearance (PSr) is analogous to the permeability-surface area (PS) product, a well established concept for describing solute transfer across the capillary. We found a value in subjects with normal renal function of 1.0 (SD 0.2) ml.min-1.100 ml-1 tissue, which is broadly similar to the values anticipated from published values of the extraction fraction of 51Cr EDTA and plasma flow of resting human skeletal muscle. We also describe an index, the t95, of whole body microvascular permeability. This is the time at which the second exponential of the bi-exponential plasma 99mTc DTPA clearance curve becomes equal to 95% of the total curve. The index reflects the rate of equilibration of DTPA between intravascular and extravascular spaces, and should reflect whole body microvascular permeability. The t95 showed a significant inverse correlation with regional clearance (t95 = -12 PSr + 98 min; r = -0.61; n = 60; p less than 0.001) confirming their mutual dependence on capillary DTPA transfer. These non-invasive techniques, with their advantages of simplicity, could prove useful in a variety of clinical settings.     

Increased lung permeability following long-term use of free-base cocaine (crack)

The clearance of inhaled 99mTc DTPA aerosol from the lungs is used as an index of lung epithelial permeability. Using the radioaerosol method, we investigated the effects of long-term "crack" (free-base cocaine) inhalation on lung permeability in 23 subjects. Eighteen control subjects (12 nonsmokers and 6 cigarette smokers) with no history of drug use were also studied. Subjects inhaled approximately 150 muCi (approximately 5.6 MBq) of 99mTc DTPA aerosol and quantitative gamma camera images of the lungs were acquired at 1-min increments for 25 minutes. Regions of interest (ROIs) were selected to include the following: (1) both lungs; (2) each individual lung; and (3) the upper, middle, and lower thirds of each lung. 99mTc DTPA lung clearance was determined from the slopes of the respective time-activity plots for the different RIOs. Radioaerosol clearance half-times (T1/2) for the seven nonsmoking crack users (61.5 +/- 18.3 minutes) were longer than for the seven cigarette-smoking crack users (27.9 +/- 16.9 minutes) and nine cigarette-smoking crack plus marijuana users (33.5 +/- 21.6 minutes). T1/2 for the nonsmoking crack users was significantly shorter (p less than 0.001) than for the nonsmoking control group (123.8 +/- 28.7 minutes). T1/2 for the cigarette-smoking drug users was similar to that of the cigarette-smoking control group (33.1 +/- 17.8 minutes), suggesting a similar mechanism of damage from the smoke of crack and tobacco. From these groups, one nonsmoker and 11 cigarette smokers displayed biexponential 99mTc DTPA clearances, indicative of greater lung injury than found in the usual cases of monoexponential clearance. The upper lungs of all crack users groups cleared faster than the lower lungs. The faster and biexponential clearance properties of inhaled 99mTc DTPA aerosol were the principal functional abnormalities found in all the drug users. In contrast, 19 of 23 crack users had normal spirometry and gas exchange. These results indicate that 99mTc DTPA may provide a sensitive and useful assay to evaluate the physiologic effects of cocaine inhalation in the lung.     

Dual pathway clearance of 99mTc-DTPA from the bronchial mucosa

Many studies have reported clearance rates of 99mTc-DTPA from the alveolar epithelial surface, but few have measured clearance of this solute from the bronchial mucosa. Those that have attempted such measurements have discounted the possibility that 99mTc-DTPA may be removed from the bronchial airways by mucocilliary transport as well as by absorption through the epithelium. This study was designed to better approximate the rate of 99mTc-DTPA absorption across the bronchial epithelium by correcting the measurements of total 99mTc-DTPA clearance for mucus transport. On two separate study days, each normal, nonsmoking subject (n = 8) breathed an aqueous aerosol (2.0 microns MMAD, sigma g = 2.0) containing 99mTc bound to DTPA or human serum ablumin (HSA) (a relatively nonpermeable solute that is cleared only by mucus transport over the period of measured clearance) while seated in front of a gamma camera. Breathing pattern was standardized to produce a similar central deposition of particles on both study days. From measurements of retention versus time over a 1-h period, exponential rate constants (Ktot and Km) were determined for the clearance of 99mTc-DTPA and 99mTc-HSA, respectively. By modeling the airways as a single compartment with two possible routes of clearance, we determined the permeability rate constant, Kp, as Ktot minus Km. Results showed that mucus clearance (Km) accounted for two thirds of the total rate of 99mTc-DTPA clearance (Ktot) (mean Ktot = 0.00985, Km = 0.00698, and Kp = 0.00287/min).(ABSTRACT TRUNCATED AT 250 WORDS)     

Non-invasive measurement of renal blood flow with 99mTc DTPA: comparison with radiolabelled microspheres

This technique for non-invasive measurement of renal blood flow is based on the principle of fractionation of cardiac output, and applicable with any recirculating gamma activity tracer. It effectively determines the count rate that would be recorded over the kidney if the tracer behaved like radiolabelled microspheres and was completely trapped in the kidney on first pass. After correction for kidney depth, the estimated first pass activity plateau, expressed as a fraction of the injected dose, is equal to the kidney's fraction of cardiac output. The principle of the technique was validated by comparison with renal blood flow based on radiolabelled microspheres. Nine separate comparisons were made in two anaesthetised dogs. A known dose of 99mTc radiolabelled microspheres (particle size 23-45 microns) was injected into the left ventricle and the count rate over each kidney recorded. A known dose of 99mTc diethylenetriaminepenta acetic acid (DTPA) was then given as an intravenous bolus and the data recorded dynamically with a gamma camera online to a computer. After subtraction of the stable signal arising from the preceding radiolabelled microspheres, the theoretical first pass activity plateau from the DTPA that would have been recorded if the DTPA, after reaching the systemic circulation, had behaved like radiolabelled microspheres and become completely trapped in the renal vascular bed, was estimated. Using doses based on syringe counts before and after injection the ratio of renal blood flow values given by the two techniques (DTPA:RLMS) was 1.14 (SD 0.22) for the left kidney and 1.1(0.17) for the right. Using doses based on whole body counts, corresponding ratios were 1.05(0.11) and 1.02(0.13).(ABSTRACT TRUNCATED AT 250 WORDS)     

Evaluation of 99mTc-albumin dilution curve with simultaneous injection of 99mTc- and 131I-albumins.

A critical comparison of radiocardiograms with 99mTc- and 131I-albumins was made to determine whether or not 99mTc-albumin can be used as a tracer for measuring blood volume (BV) and cardiac output (CO). Simultaneous injection of both isotopes was given to twenty-two patients to obtain radiocardiograms for each by means of a single scintillation counter with two pulse height analyzers. Such method allows for the determination of the energy levels for both 99mTc and 131I. The radiocardiographic pattern was somewhat different between 99mTc- and 131I-radiocardiograms: The ratio of left to right peak height was 16% on the average lower in the 99mTc-radiocardiogram in the 131I-one. The reason for the lower ratio is explained by greater absorption of 99mTc-radioactivity within the soft tissue interposing between the scintillation probe and heart. The values for 99mtc-derived blood volume were 7.4% on the average larger than those for 131I-derived blood volume (p less than 0.01), although the correlation was excellent (r = 0.98, p less than 0.01). There was no systemic difference between cardiac output determined by 99mTc- and 131I-albumins since the overstimation of blood volume can compensate for the understimation of CO/BV by 99mTc-study. In view of its rapid extravasation, 99mTc-albumin is not so appropriate tracer for accurate measurements of BV and CO/BV, although it may be used for measurement of cardiac output.     

Pneumocystis pneumonia increases the clearance rate of inhaled 99mTc DTPA from lung to blood

Despite no radiographic change, a patient with Pneumocystis pneumonia showed increased clearance of inhaled 99mTc DTPA from lung to blood. Gas transfer for carbon monoxide was also reduced, but improved with treatment. This was paralleled by serial increase in the t1/2 LB.     

Effects of common therapeutic concentrations of oxygen on lung clearance of 99mTc DTPA and bronchoalveolar lavage albumin concentration

We studied the effects of oxygen concentrations (21 to 50%) considered clinically "safe" on clearance of inhaled technetium-labeled diethylene triamine pentaacetate (99mTc DTPA) and the concentration of albumin in bronchoalveolar lavage (BAL) fluid of normal subjects. We also measured several markers of cell injury and inflammation in the BAL fluid including total and differential cell counts, lactate dehydrogenase, alkaline phosphatase, extracellular potassium, and several eicosanoids. Subjects inhaled oxygen (50, 40, 30, or 21%) for a mean of 45 h; there were no symptoms or bronchoscopic signs of oxygen toxicity. The concentration of albumin in BAL fluid was increased compared with baseline measurements in a dose-dependent manner in subjects exposed to 30% oxygen and above. Clearance of 99mTc DTPA was increased only in subjects who inhaled 50% oxygen. There were no significant changes in BAL fluid volume or total and differential cell counts after oxygen exposure. A trend towards an increased percentage of polymorphonuclear leukocytes was noted in the 50% oxygen group. We found no evidence of cell injury or inflammation in the BAL fluid. Supplemental humidity did not appear to influence the findings in the 50% oxygen group. Thus, oxygen in concentrations considered clinically "safe" increases clearance of 99mTc DTPA and BAL albumin concentration in normal subjects after a relatively short time of exposure.     

An improved noninvasive method for measurement of cardiac output and evaluation of left-sided cardiac valve incompetence

A time-saving method was developed to label red blood cells in vitro with 99mTc while avoiding centrifugation. After tin incubation, extracellular tin was oxidized by sodium hypochlorite, and EDTA was added for stabilizing the complex prior to 99mTc incubation. Labeling yields were 95%, and in vivo decay showed a high stability with a mean biologic half-life of eleven hours. The first-passage radionuclide technique for determination of cardiac output using the above-mentioned tracer was evaluated by using the left ventricle as area-of-interest with individual background correction after complete mixing of the tracer. This technique showed a high level of agreement with invasive methods. By combining this method for measurement of the forward stroke volume with the multigated equilibrium principle for determination of the total left ventricular stroke volume using similar background corrections, an exact evaluation of regurgitation fractions was obtained. In patients with aortic and mitral valve disease the noninvasive radionuclide technique gave similar but probably more accurate results as compared with contrast aortography and ventriculography. The radionuclide technique may be suitable for monitoring and selecting patients for surgical treatment.     

Acute paraquat intoxication: using nuclear pulmonary studies to predict patient outcome.

STUDY OBJECTIVES: Paraquat, a widely used herbicide, has been shown to cause severe and often fatal pulmonary fibrosis in humans and laboratory animals. Although paraquat is known to be directly cytotoxic to lung parenchyma, changes in routine lung scintigraphy results after acute paraquat intoxication have not been reported. The objective of this project was to investigate changes in lung ventilation (LV) and alveolar permeability (AP) in patients with paraquat intoxication, using 99mTc diethylenetriamine pentaacetate (DTPA) radioaerosol lung scintigraphy. DESIGN: Prospective, blinded study. SETTING: Nuclear medicine and toxicology departments in two university-affiliated teaching hospitals. PATIENTS OR PARTICIPANTS: Thirteen patients with acute paraquat intoxication were included in this study. Ten volunteers without acute paraquat intoxication were studied for comparison. MEASUREMENTS AND RESULTS: 99mTc DTPA aerosol inhalation and 99mTc macroaggregated albumin (MAA) perfusion lung scintigraphies were performed to determine LV, AP, and lung perfusion (LP). Five of the 13 patients (38%) had significant LV abnormalities; 3 of these 5 patients also showed abnormal LP. Of the 13 patients, 4 patients (31%) showed normal AP and survived. The remaining 9 patients (69%) showed abnormal AP and died. The mean values for AP were statistically different (p < 0.01) between survivor (0.72 +/- 0.16%) and nonsurvivor (1.52 +/- 0.40%) groups. Data from the normal volunteers and survival patients showed a 99mTc clearance slope < 1.00%. Data from patients who died showed a clearance slope > 1.00%. CONCLUSION: These results indicate that AP, measured by 99mTc DTPA aerosol inhalation lung scintigraphy, may help predict outcome in patients with paraquat intoxication.     

Radioaerosol lung clearance in patients with active pulmonary sarcoidosis

Pulmonary radioaerosol clearance rate of 99mTc diethylenetriamine pentacetate (DTPA) in 14 patients with untreated sarcoidosis was compared with 67Ga lung scan and increased lymphocytes in the bronchoalveolar lavage (BAL) fluid. Nine healthy nonsmoking subjects had a mean DTPA clearance rate of 1.18%/min (range, 0.54 to 1.60%/min). Eight of 14 patients with sarcoidosis had clearance rates greater than 1.60%/min. Of those 8 patients with abnormal DTPA clearance, 4 had positive gallium scans, 4 had more than 17% lymphocytes in the BAL fluid, and 3 had both tests positive. To study the cause of abnormal DTPA clearance, 23 subjects (including 3 normal controls, all 14 patients with sarcoidosis, and 6 patients with localized disease on chest roentgenogram) underwent both DTPA clearance studies and BAL for quantitation of the amount of albumin in lung fluid. There was a positive correlation between the rate of DTPA clearance and the albumin concentration in lung fluid (r = 0.87, p less than 0.01).     

Carboplatin dosing based on measurement of renal function — experience at the Peter MacCallum Cancer Institute

Background: Carboplatin is used in treating many types of cancer. Because renal excretion is the major variable determining the pharmacokinetics of this drug, a dosing formula based on glomerular filtration rate (GFR) has been proposed and is being increasingly used in carboplatin dosing. This method of dosing is critically dependent on accurate measurement of GFR. Aims: To report the experience at a single major oncology centre of carboplatin dosing based on GFR, and comparisons of different methods of measuring renal function for use in this dosing method. Methods: An initial group of patients (n=24) was studied where GFR was measured by Cr⁵¹EDTA clearance and compared to Tc^99mDTPA clearance, measured 24 hour urine creatinine clearance and the Cockcroft and Gault formula. The carboplatin area under the plasma concentration versus time curve (AUC) was calculated using total platinum measured in a single blood sample assayed by flameless atomic absorption spectrophotometry. A subsequent patient group (n=16) was then studied using Tc^99mDTPA clearance to measure GFR. Results: Carboplatin dosing using Cr⁵¹EDTA clearance to measure GFR was accurate (<25% difference between planned and measured AUC) in 87% of samples. Estimation of renal function using the Cockcroft and Gault formula correlated with Cr⁵¹EDTA clearance only in patients with GFR <100 mL/minute. The measured 24 hour urine creatinine clearance did not correlate with Cr⁵¹EDTA clearance. Using Tc^99mDTPA clearance to measure GFR, carboplatin dosing was accurate in 81% of samples. Across a GFR range of 42–239 mL/minute, the Cr⁵¹EDTA and Tc^99mDTPA clearances were closely correlated (r=0.98, slope of regression line=1.02). Conclusions: Carboplatin dosing using a pharmacological formula based on GFR produces accurate targeting of the carboplatin AUC. Tc^99mDTPA clearance can be used to measure GFR instead of Cr⁵¹EDTA clearance, which is both more convenient and has potential cost savings. Estimates of renal function using the Cockcroft and Gault formula or measured 24 hour creatinine clearance are insufficiently accurate to use for carboplatin dosing.     

Haemophilia, AIDS and lung epithelial permeability

Lung 99mTc DTPA transfer was measured in HIV antibody-positive haemophiliacs (11 smokers, 26 nonsmokers, 5 patients with Pneumocystis carinii pneumonia (PCP]. Lung 99mTc DTPA transfer as a marker of lung epithelial permeability was measured as the half time of transfer (from airspace into blood). This half time was faster in smokers compared to nonsmokers and the transfer curve was monoexponential. In nonsmokers no difference was observed between asymptomatic HIV-positive haemophiliacs and normal subjects, with the exception of the lung bases. At the lung bases in HIV-positive haemophiliac nonsmokers the transfer was faster than in normal individuals, implying increased alveolar permeability. Pneumocystis carinii pneumonia resulted in a rapid transfer of 99mTc DTPA (mean T50 of 2 minutes) and the transfer curve was biphasic, confirming previous observations in homosexual HIV antibody-positive patients with PCP. These changes returned to a monoexponential profile by 6 weeks following successful treatment. The DTPA lung transfer study may enable clinicians to instigate therapy for PCP without the need for initial bronchoscopy and provide a noninvasive method for the reassessment of patients should further respiratory signs or symptoms develop. This method is considered to be highly cost-effective in that it obviates the use of factor VIII concentrates required to cover bronchoscopic procedures and, with its early application and ease of use as a follow-up investigation, permits the evaluation of patients on an outpatient basis, thus reducing hospital costs.     

Diffusion kinetics in blood during haemodialysis and in vivo clearance of inorganic phosphate

Contradictory data are reported in the literature concerning the diffusion kinetics of inorganic phosphates (iPh) between red blood cells and plasma during haemodialysis. Accordingly, we performed mass balance and equilibration studies to analyze the diffusion kinetics of iPh in vivo and in vitro. Mass balance analysis shows that iPh is only cleared from the plasma volume and thus that it practically does not diffuse from red blood cells to plasma during the short time lapse of blood transit through the haemodialyzer. In vitro equilibration studies of blood drawn at the filter outlet show that at room temperature there is a slow, limited, and almost linear net efflux of iPh during the 4 h that follow blood drawing. Our results point out: (1) that the in vivo clearance of iPh should be exclusively determined as plasma clearance, and (2) that for accurate clearance determinations the iPh concentrations should be measured in blood samples centrifuged within at most 1 h after blood drawing. Whole-blood clearance determinations--as well as the in vitro dialyzer data--largely overestimate (>30%) the real in vivo dialyzer performance.     

Acute cigarette smoke exposure alters lung eicosanoid and inflammatory cell concentrations in rabbits

We studied lung clearance of technetium-labeled diethylenetriamine pentaacetic acid [( 99mTc]DTPA), plasma and bronchoalveolar lavage fluid (BALF) concentrations of 6-keto-PGF1 alpha (stable metabolite of prostacyclin, prostaglandin I2, PGI2), TxB2 (stable metabolite of thromboxane A2, TxA2), and leukotriene B4 (LTB4), and inflammatory cells as indices of lung injury in rabbits exposed to cigarette smoke (CSE). Thirty-one rabbits were randomly assigned to four groups: control sham exposure (SS, n = 6), sham smoke ibuprofen-pretreated (SS-I, n = 7), CSE (n = 6), and CSE ibuprofen-pretreated (CSE-I, n = 12). Ibuprofen, a cyclooxygenase eicosanoid inhibitor, was administered as a single daily intramuscular injection (25 mg/kg) for 7 d before the experiment. Cigarette or sham smoke was delivered by syringe in a series of 5, 10, 20, and 30 tidal volume breaths with a 15-min counting period between each subset of breaths to determine [99mTc]DTPA biological half-life (T1/2). The CSE-I group was retrospectively divided into rabbits who survived the 30-breath subset (CSE-IL, n = 6) and those who died during the 30-breath CSE (CSE-ID, n = 6). In the CSE, CSE-IL, and CSE-ID groups, [99mTc]DTPA T1/2 as well as BALF LTB4 levels were significantly decreased. Plasma and BALF 6-keto-PGF1 alpha increased in CSE rabbits compared to the other groups. Alveolar macrophages were lower in the CSE-ID rabbits than in the CSE-IL group. CSE and CSE-IL BALF lymphocyte levels were decreased compared to SS values. Our data indicate that acute CSE is associated with significant increases in 6-keto-PGF1 alpha and decreases in LTB4 as well as a significant reduction in lymphocytes. Furthermore, pretreatment with ibuprofen before CSE was associated with severe lung injury in half of the rabbits. The severity of lung injury may be related to a combination of a lower number of alveolar macrophages and blockade of lung PGI2.     

Intestinal permeability in gastrointestinal disorders

This study examined intestinal permeability in gastrointestinal disorders by measuring urinary recovery following oral administration of [99mTc]DTPA in 117 subjects. The mean percent of the ingested dose excreted in a 24-hr urine sample was 2.8 +/- 1.6% in 11 healthy controls, 10.8 +/- 10.2% (P less than 0.001) in 21 ulcerative colitis patients, 8.0 +/- 4.7% (P less than 0.001) in 35 Crohn's disease patients, 5.1 +/- 2.9% (P less than 0.01) in 17 patients with heterogeneous digestive disease diagnoses, and 3.2 +/- 4.7% (P greater than 0.05) in 33 patients with hepatobiliary diagnoses. Among ambulatory patients, Crohn's disease subjects, but not ulcerative colitis patients, had greater urinary recovery than the controls (P less than 0.05). The Crohn's disease activity index correlated positively with the radionuclide recovery in Crohn's subjects (r = 0.455, P less than 0.02). In a heterogeneous sample of subjects simultaneous ingestion of [99mTc]DTPA and [51Cr]EDTA produced urinary levels that were correlated positively (r = 0.556, P less than 0.001). Increased absorption of [99mTc]DTPA relative to [51Cr]EDTA, however, was noted in ulcerative colitis patients (P less than 0.05). In conclusion, increased intestinal permeability has been demonstrated by utilizing [99mTc]DTPA in Crohn's disease and ulcerative colitis patients. Although this observation appears to be a nonspecific indicator of injury, the test provides a simple objective means of establishing disease activity, which possibly may be utilized for therapeutic and investigative studies.     

A comparison between estimates of GFR using [99m– Tc]DTPA clearance and the approximation of Cockcroft and Gault

Background: The formula of Cockcroft and Gault, relating age, weight, sex and plasma creatinine is widely used to estimate glomerular function. Its ability to predict [^99mTc]DTPA clearance, an accepted measure of GFR, is therefore of interest. Aim: To test prospectively the reliability of the formula in predicting the [^99mTc]DTPA clearance in subjects with normal and sub-normal renal function. Methods: The 24 hour creatinine clearance (Ccr), the derived clearance using the formula (C_der), and the [^99mTc]DTPA clearance have been compared in 47 male and 47 female subjects, aged between 15 and 71 years. Obese and non-obese subjects (males >90 kg, females >80 kg body weight) were considered separately. Results: Across the range of [^99mTc]DTPA clearance studied (14 to 125 mL/minute), in non-obese subjects, both Ccr and C_der were correlated similarly with [^99mTc]DTPA clearance in males and females. In obese subjects as a group, C_der was also closely correlated with [^99mTc]DTPA clearance but the scatter of data was wider. Among non-obese subjects, correlations were high between either Ccr or C_der and [^99mTc]DTPA clearance values < 101 mL/minute but were not significant at [^99mTc]DTPA clearance values > 100 mL/minute. For [^99mTc]DTPA clearance values between 14 and 100 mL/minute, C_der was a more direct and more precise predictor of [^99mTc]DTPA clearance [DTPA clearance = 1.01(C_der) + 2.34, with 95% confidence limits of ± 18 mL/minute] than of Ccr [Ccr= 1.34(C_derC)- 10.86, confidence limits ±28 mL/minute]. Conclusion: For very mild through to moderate renal failure, the formula of Cockcroft and Gault can evidently be used as a reasonable estimate of GFR. (Aust NZ J Med 1993; 23: 494–497.)     

Differential renal function during angiotensin converting enzyme inhibition in renovascular hypertension

Renal function was measured sequentially in 32 patients with proven renovascular hypertension who were treated with the oral angiotensin converting enzyme inhibitor captopril. Renal function was assessed by serial measurement of serum creatinine. Six patients showed acute rises in serum creatinine concentration compatible with acute renal failure. Acute renal failure was confined to those patients with stenosis to a solitary kidney (transplant or native, occurring in 3 of 8 patients) or bilateral renal artery stenosis (occurring in 3 of 13 patients). No rise in serum creatinine concentration was observed in 11 patients with unilateral renal artery stenosis during long-term angiotensin converting enzyme inhibitor therapy. Acute renal failure during angiotensin converting enzyme inhibitor therapy was not related to the degree of blood pressure fall or the plasma angiotensin II level. Eleven patients with renovascular hypertension were followed prospectively with estimation of renal function by 99mTc-diethylenetriaminepentaacetic acid (DTPA) clearance (determined by computer analysis of scintillation camera renography). In six patients with unilateral renal artery stenosis, total 99mTc-DTPA clearance and serum creatinine level remained constant following angiotensin converting enzyme inhibitor therapy, while in five patients with bilateral renal artery stenosis 99mTc-DTPA clearance fell from 40 +/- 9 to 27 +/- 5 ml/min (p less than 0.05). Split renal function studies revealed that 99mTc-DTPA clearance fell in most kidneys with stenosed arteries during angiotensin converting enzyme inhibition, including the stenosed kidney from patients with unilateral renal artery stenosis (16 stenosed kidneys studied; change in Tc-DTPA clearance, -7.5 +/- 2.7 ml/min).(ABSTRACT TRUNCATED AT 250 WORDS)     

18F-FDG与99mTc同时心肌显像对不同缺损大小的模型研究

目的本研究通过模型试验旨在评价18F-FDG及99mTc同时心肌显像(DISA)的准确性.方法应用标准心脏模型进行心肌断层采集.模型内部备有不同大小的缺损块,模拟心肌梗死,分别为整个心肌容积的3%、5%、10%及15%.模型内部注入99mTc-O4-74 MBq(2mCi)及18F-FDG11.1MBq(300μCi).使用配备超高能准直器的Varicam双探头SPECT,行双核素心肌DISA.采用滤波反投影法,进行重建,产生双核素图像(99mTc,18F-FDG).采用5×5像素大小的感兴趣区,计算缺损区放射性计数,及与最大心肌计数的比值.结果所得图像中,缺损清晰可见.18F-FDG的图像中,缺损部位的放射性计数明显高于99mTc的图像,在小到中度缺损时尤其显著,而在大面积的缺损则差别减小.结论此项技术可能高估存活心肌的大小,在灌注显像显示小或中等的缺损时,代谢显像可能会产生部分假的不匹配.因此,应考虑到此影响的存在,定量分析可能会提高DISA评价心肌灌注-代谢估价的准确性.     

Technetium 99m-diethylene triamine penta-acetic acid aerosol clearance in the evaluation of pulmonary involvement in sickle cell disease

BACKGROUND: Pulmonary clearance of inhaled technetium (Tc) 99m-labeled diethylene triamine penta-acetic acid (DTPA) aerosol is a sensitive non-invasive marker of alveolar permeability and patients with interstitial lung diseases show enhanced clearance. However, a previous study in adult patients with diabetes mellitus showed delayed clearance. OBJECTIVES: To investigate DTPA clearance in steady-state, otherwise healthy adult sickle cell disease (SCD) patients and correlate it with pulmonary function tests (PFTs), hematologic and clinical parameters. MATERIALS AND METHODS: The subjects were randomly selected from the Hematology Clinic of Mubarak Hospital, Kuwait. Hematologic and pulmonary function data were collected with standard methods. DTPA radio-aerosol clearance studies were performed using ultrafine nebulizer containing 35 mCi (1295 MBq) of Tc 99m-DTPA in its reservoir and t(1/2) clearance in minutes was determined. Average values for both lungs were calculated and compared with normal values for our population. RESULTS: Forty-three subjects (24 SS and 19 S-beta(0)thal) aged between 16 and 45 yr (mean of 27.1 +/- 9.7) were studied. Twenty-two subjects (51.2%) had delayed, while only 10 (23.3%) showed enhanced DTPA clearance. Patients with enhanced clearance showed better PFTs than those with normal or delayed clearance. There was significant negative correlation of DTPA clearance with forced expiratory volume in 1 s, forced vital capacity and total lung capacity and significant positive correlation with age. CONCLUSIONS: Majority of adult SCD patients have delayed DTPA clearance unlike in inflammatory lung diseases, but similar to diabetes mellitus. DTPA clearance may be a useful modality for monitoring pulmonary involvement in SCD.