Comparison of radionuclide estimation of glomerular filtration rate using technetium 99m diethylenetriaminepentaacetic acid and chromium 51 ethylenediaminetetraacetic acid

Simultaneous measurements of the clearance rates of technetium 99m diethylenetriaminepentaacetic acid (^99mTc-DTPA) and chronium 51 ethylenediaminetetraacetic acid (⁵¹Cr-EDTA) were performed in 30 patients with a range of renal function (glomerular filtration rates between 9 and 120 ml/min). Using multiple blood samples, the two clearance values correlated well (r=0.991, standard error 3.9 ml/min), but DTPA clearance was systematically higher by 7.6%. For each radiopharmaceutical, an equation was derived to correct clearance values obtained using only plasma samples taken at 2 and 4 h for the systematic error inherent in this technique compared with analysis of the complete plasma concentration-time curve. The root mean square error remaining after application of these equations was 1.9 ml/min for both the EDTA and DTPA data. The corresponding errors obtained using the equation derived by Brochner-Mortensen for EDTA plasma clearance were 2.2 ml/min and 1.9 ml/min, respectively, these values were not significantly different from those obtained using the equations derived in this study.     

Glomerular filtration rate in relation to extracellular fluid volume: Similarity between99mTc-DTPA and inulin

The rate constant ( ₂) of the terminal exponential of the technetium-99m diethylene triamine pentaacetic acid (DTPA) plasma clearance curve is close to the ratio of glomerular filtration rate (GFR) to extracellular fluid volume (ECV) and is therefore a convenient, already normalised, measure of filtration function. Since ₂ depends on the distribution volume of the tracer, our aim was to compare ₂ from inulin and^99mTc-DTPA and also to compare the equilibration kinetics of the two filtration markers. Fifty millititres of^99mTc-DTPA (250 MBq) and inulin (10%), mixed in the same syringe, were given by intravenous injection in 15 patients undergoing routine^99mTc-DTPA renography for a variety of clinical indications. Frequent antecubital venous blood samples were taken up to about 4 h after injection to construct plasma clearance curves from which GFR, ECV and GFR/ECV (i.e. the reciprocal of mean transit time through the distribution volume) were calculated.^99mTc-DTPA/inulin concentration ratio curves were also constructed after normalisation to the ratio in the syringe. GFR given by the two markers correlated closely (DTPA=0.98·inulin—0.4ml/min;r=0.98).^99mTc-DTPA had the same distribution volume as inulin, had a similar transit time through it and gave the same value of ₂ (r=0.98). GFR/ECV from^99mTc-DTPA accordingly correlated closely with GFR/ECV from inulin (DTPA=0.75·inulin+0.99 ml/min;r=0.95). Even though the distribution volumes and the times to equilibration (i.e. to reach the terminal exponential) were similar, the distribution volume of^99mTc-DTPA at about 10 min after injection was, after subtraction of the plasma volume, about twice that of inulin.We confirm the validity of^99mTc-DTPA for measuring GFR. ₂ is a convenient measure of GFR, can be based on the terminal exponential of inulin of^99mTc-DTPA curves and can be converted to GFR/ECV with an appropriate scaling factor. The kinetics or the two clearance curves with respect to anatomical correlates of the exponentials and the rates of diffusion throughout the respective distribution volumes requires further study.     

Measurement of the ratio of glomerular filtration rate to plasma volume from the technetium-99m diethylene triamine pentaacetic acid renogram: comparison with glomerular filtration rate in relation to extracellular fluid volume

Individual kidney glomerular filtration rate (IKGFR) can be measured from the renogram from the rate of uptake of technetium-99m diethylene triamine penta-acetic acid (^99mTc-DTPA). A blood sample is required to derive IKGFR in millilitres per minute, which is then usually normalised to body surface area. We describe a technique which does not require a blood sample, is already normalised for plasma volume and uses the robust Patlak plot for measuring renal uptake. The rate of kidney uptake, dR(t)ldt, at time = 0, as a fraction of the injected dose, is equal to the fraction of the plasma volume (PV) filtered per minute, i.e. IKGFR/PV. The gradient dR(0)/dt cannot be accurately measured directly but is equal to [ · LV(0)], where is the renal uptake constant (proportional to IKGFR) and LV is the count rate over a left ventricular ROI. LV(0) was obtained by extrapolation of LV(t), while a is the slope of the Patlak plot up to 3 min. GFR/PV (i.e. right plus left kidneys) in patients with normal renal function was about 0.04 min^–1, as would be expected from normal values of GFR (120 ml/min) and plasma volume (3 l). GFR/PV correlated significantly with the ratio of GFR to extracellular fluid volume (ECV), measured from the terminal exponential of the plasma clearance curve (GFR/PV = 3.2.GFR/ECV + 5.3 ml/min/1 [r = 0.82,n = 82]). GFR/PV (r = 0.74) and GFR/ECV (r = 0.82) both correlated inversely and non-linearly with plasma creatinine in 43 studies where the measurement was made within 1 week of the^99mTcDTPA study. They also correlated significantly with the plasma cyclosporin trough level in 14 patients with dermatomyositis on the 30 occasions when this measurement was made within 1 week of the renogram (r = –0.38,P < 0.05 for GFR/PV andr = –0.77,P < 0.001 for GFR/ECV). The ratio of GFR/PV to GFR/ECV is the ratio of extracellular fluid volume to plasma volume, and this was 4.0 (SD 0.99). We conclude that both GFR/PV and GFR/ECV can be easily measured with^99mTc-DTPA and are physiologically valid expressions of GFR. Although GFR/PV and GFR/ECV correlate with each other, the question is raised as to which of the two fluid volumes is the most appropriate for normalising GFR. Correspondence to: A.M. Peters     

A Comparison of the Accuracy of Different Single Plasma Sample Methods for Measuring Glomerular Filtration Rate Using <Superscript>51</Superscript>Cr-EDTA in Children

Purpose

Among the different methods of measuring glomerular filtration rate (GFR) using ⁵¹Cr-ethylenediaminetetraacetic acid clearance, the two-plasma-sample method (TPSM) is widely used, and highly accurate. The single-plasma-sample method (SPSM) is occasionally used for simplicity, at the expense of accuracy. Our aims were (1) to investigate the correlation and (2) to compare the accuracy of six known SPSMs in pediatric patients in reference to TPSM.

Methods

We retrospectively reviewed 122 pediatric cases (65 boys, age 7.3?±?4.6 years) and analyzed 307 GFR measurements. SPSMs included Groth and Aasted at 120 min, Ham at 120 min, Christensen and Groth at 120 and 240 min, and Jacobsson at 120 and 240 min. Reference GFR (GFR_ref) was defined using TPSM GFR corrected by the Jodal and Brochner-Mortensen equation. GFR_ref?<?30 mL min^?1 1.73 m^?2 were excluded. The standard error of the estimate (SEE) and the number of cases with differences >?10% (N_10%) were used to evaluate accuracy.

Results

SPSMs generally correlated well with GFR_ref (r?=?0.92~0.99) and were relatively accurate (SEE?=?9.21~15.60). Groth and Aasted showed the smallest SEE, while Jacobsson at 240 min showed the smallest N_10% for all GFR_ref ranges. As for the decreased GFR_ref, Ham was most accurate followed by Jacobsson at 240 min.

Conclusions

Jacobsson at 240 min provided good accuracy in all GFR_ref ranges and was well correlated with TPSM. Jacobsson at 240 min might be the most appropriate method to substitute for TPSM in pediatric patients. Ham could be an alternative in patients with impaired renal function.

     

Extravascular chest wall technetium 99m diethylene triamine penta-acetic acid: implications for the measurement of renal function during renography

Measurement of individual kidney glomerular filtration rate (IKGFR) from the gamma-camera technetium 99m diethylene triamine penta-acetic acid (^99mTc-DTPA) renogram requires a continuous measurement of arterial activity. This is usually based on a region of interest (ROI) placed over the cardiac blood pool on the posterior view, with the assumption of negligible contamination from activity in the extravascular space of the chest wall. By injecting a small dose of technetium 99m human serum albumin (HSA) before the^99mTc-DTPA in 12 patients undergoing routine renography, the contribution of extravascular activity to the total signal recorded over the cardiac blood pool was calculated to be 11.0% (SE 2.1%) 1.5 min after DTPA injection, rising to 35.1% (SE 2.5%) at 15 min. Subtraction of the time-activity curve recorded from a ROI of the same size over the right lung generated a pure blood signal as shown by almost identical HSA/DTPA signal ratios recorded in blood samples taken 5 min after HSA and 15 min after DTPA and from the gamma-camera at the corresponding times. The effect of using a cardiac blood pool time-activity curve uncorrected for extravascular activity was to overestimate IKGFR by an average factor of 1.17 (SE 0.03). Offprint requests to: A.M. Peters     

99mTc-DTPA gamma-camera renography: Normal values and rapid determination of single-kidney glomerular filtration rate

A method for ^99mTc-diethylenetriaminepentaacetate (DTPA) gamma-camera renography is presented. From each renogram, an uptake index (UI) proportional to the single-kidney glomerular filtration rate (SKGFR) is defined. If the proportionality factor between UI and SKGFR is the same in all patients, UI can be used as an accurate measure of SKGFR. In order to test this, ^99mTc-DTPA renography was performed in 101 patients with glomerular filtration rates (GFR) varying between 4 and 172 ml/min. The sum of the right-and left-kidney UIs correlated well with the total GFR calculated from the simultaneously measured plasma clearance of ^99mTc-DTPA after a single injection. The correlation coefficient was 0.97. The method was tested in a prospective study of 57 patients. The total GFR estimated from the renograms was not significantly different from the GFR calculated from the plasma clearance of ^99mTc-DTPA. The coefficient of variation—a combination of inaccuracy and imprecision in the estimates as well as in the reference values — was 11.8% at a GFR of 100 ml/min. It is concluded that, in adults, the SKGFR can be calculated as part of the clinical routine from ^99mTc-DTPA gamma-camera renography without determining the injected dose or collecting urine or blood samples. Normal values for some parameters of the renogram obtained in 25 normal subjects are given.     

Assessment of alveolar epithelial permeability in Behçet’s disease with <Superscript>99m</Superscript>Tc-DTPA aerosol scintigraphy

Objective

Behçet’s disease (BD) is a multisystem disorder characterized by vasculitis, and consists of a triad of recurrent ulcers of the oral and genital mucosa with relapsing uveitis. The prevalance of pulmonary involvement varies in the range of 1–10% in various studies and its complications are severe and life threatening. In this study, we investigated the changes of pulmonary epithelial permeability of patients with BD using technetium-99m diethylene triamine penta-acetic acid (^99mTc-DTPA) aerosol scintigraphy, so as to begin the therapy regimen as soon as possible.

Methods

Twenty-one nonsmoking patients with BD (8 women, 13 men; mean age 38.67 ± 8.86 years) and 15 healthy volunteer nonsmoking controls (8 women, 7 men; mean age 50.87 ± 12.45 years) underwent ^99mTc-DTPA aerosol inhalation scintigraphy and pulmonary function tests (PFTs). Subjects inhaled 1480 MBq of ^99mTc-DTPA for 4 min in the supine position. Scintigraphic data were recorded dynamically (1 frame/min) in the posterior projection on a 64 × 64 matrix for a 30-min period using a double-headed gamma camera (Infinia, GE, Tirat Hacarmel, Israel) equipped with a low-energy all-purpose parallel hole collimator. Half time of ^99mTc-DTPA clearance (T _1/2) was calculated by placing a mono-exponential fit on the curves. Penetration index (PI) was also calculated by dividing the peripheral total counts by the sum of the peripheral and central total counts on the first minute image, in order to quantify the distribution of the inhaled aerosol.

Results

The clearance half time of ^99mTc-DTPA radioaerosols in the BD patients (24.81 ± 6.22 min) was faster than in the normal control group (46.53 ± 22.41 min) (P = 0.004). There was also a significant difference between PI of the patients with BD (0.15 ± 0.03) and that of the controls (0.21 ± 0.06) (P = 0.002). No correlation was found between the mean T _1/2 values of ^99mTc-DTPA clearance or the spirometric measurements in the BD patients. Penetration indices were not correlated with PFT in the BD patients.

Conclusions

Lung epithelial permeability of the patients with BD was significantly higher than that of the normal subjects. The results of this study demonstrated that the assessment of lung epithelial permeability using ^99mTc-DTPA aerosol scintigraphy could predict the presence of lung involvement in the early stages of BD.

     

Different kinetics of lung clearance of technetium-99m labelled diethylene triamine penta-acetic acid in patients with sarcoidosis and smokers

The rate of clearance from the lungs of inhaled technetium-99m labelled diethylene triamine penta-acetic acid (^99mTc-DTPA) is often increased in interstitial lung disease as well as in smoking. In smokers a bi-exponential clearance course of ⁹⁹mTc-DTPA when measured over 3 h has previously been shown. This study was performed to compare the kinetics of clearance of ^99mTc-DTPA, measured for 3 h, in sarcoid patients and healthy smokers. Forty-one never-smoking patients with sarcoidosis and radiological signs of intrathoracic disease were studied. The results were compared with those of 16 healthy current smokers and of 14 healthy never-smokers reported previously. A mono-exponential clearance equation described the clearance in 22 of the sarcoid patients and all normal never-smokers, but with a shorter average tracer half-life in the patients (P<0.05). In 19 patients and all smokers a bi-exponential equation gave a significantly better curve fit. The rate of clearance of the slow component was higher in patients with sarcoidosis than in smokers (P< 0.05). The fraction of the tracer cleared by the fast clearance component was smaller in patients with sarcoidosis than in smokers (P<0.01). Differences in kinetics of clearance of ^99mTc-DTPA in sarcoidosis and smoking could thus be demonstrated, suggesting that the abnormal clearance is caused by diverging pathophysiological mechanisms.     

99mTc-DTPA clearance measured by a dual head gamma camera in healthy subjects and patients with sarcoidosis

^99mTc-DTPA clearance was studied in ten healthy non smokers, five asymptomatic smokers and nine non smoking patients with sarcoidosis in the supine position with a dual head gamma camera allowing simultaneous information of regional clearance rates in frontal and dorsal projections. In the patients with sarcoidosis, a bronchoalveolar lavage was performed prior to the clearance study. DTPA clearance rate was measured during 60–90 min and data were corrected for recirculating radioactivity. The coefficients of variation for measurements on 2 consecutive days in the 10 healthy non smokers were 9%–11% for the right and left lung, anterior and posterior projections. The T_1/2 calculated from total lung projections were 90–92 min for the anterior view and 84–85 min for the posterior view. Regional measurements did not add further information. No apico-basal difference was found but there was a significant fronto-dorsal gradient in^99mTc-DTPA clearance in the supine position. Smokers had significantly (P<0.01) faster clearance rates (T_1/2 28±10 min) than healthy controls. In the sarcoidosis group clearance rates were increased in four patients and no relationships were found between DTPA clearance rates and inflammatory markers (lymphocytes, albumin, ACE) in the bronchoalveolar lavage fluid.     

Measurement of glomerular filtration rate with 99mTc-DTPA: A comparison of gamma camera methods

A comparison has been made between three gamma camera methods for estimation of glomerular filtration rate (GFR) using ^99mTc-DTPA in a group of 27 patients with widely different renal function. Plasma clearance of ^99mTc-DTPA by multiple blood sampling was used as the reference. Percentage uptake of chelate in the bladder and kidneys at 20 min after injection gave the lowest standard error of 8.0 ml/min. Techniques using early uptake of isotope in the kidneys at 2 min after injection gave less accurate estimates. Correction for the vascular activity in the renal region of interest improved the results for the 2 min uptake technique. Gamma camera techniques provide rapid estimates of GFR which are less accurate than those obtained by plasma clearance of labelled chelate.     

Spectral analysis applied to dynamic single photon emission computed tomography studies with N-isopropyl-p-(123I)iodoamphetamine

This study was performed to evaluate the usefulness of spectral analysis (SA) applied to dynamic single photon emission computed tomography studies with N-isopropyl-p-(¹²³I)iodoamphetamine (IMP). The unidirectional clearance of IMP from the blood to the brain tissue (K₁) obtained by SA (y (ml/g/min)) agreed well with that obtained from a two-compartment model using the nonlinear least-squares (NLSQ) method (x (ml/g/min)) (y = 0.994x + 0.003, r = 0.999, standard error of the estimate (SEE) = 0.005 ml/g/min). The rate constant for back diffusion of IMP from the brain tissue to the blood (k₂) obtained by SA (y (min^?1)) also agreed well with that obtained by the NLSQ method (x (min^?1)) (y = 0.985x + 0.000, r = 0.948, SEE = 0.001 min^?1). The brain vascular volume (Vo) obtained by SA (y (ml/g)) correlated well with that obtained by the NLSQ method (x (ml/g)) (y = 1.138x + 0.000, r = 0.867, SEE = 0.012 ml/g). These results indicate that SA is applicable and useful for quantification of the kinetic parameters of IMP in the human brain, and can be an alternative approach to compartment analysis.     

Accurate assessment of long-term nephrotoxicity after peptide receptor radionuclide therapy with 177Lu-octreotate

Purpose

Renal radiation during peptide receptor radionuclide therapy (PRRT) may result in glomerular damage, a potential reduction of glomerular filtration rate (GFR) and ultimately lead to renal failure. While reported PRRT nephrotoxicity is limited to data derived from serum creatinine—allowing only approximate estimates of GFR—the aim of this study is to accurately determine PRRT-induced long-term changes of renal function and associated risk factors according to state-of-the-art GFR measurement.

Methods

Nephrotoxicity was analysed using ^99mTc-diethylenetriaminepentaacetic acid (DTPA) clearance data of 74 consecutive patients with gastroenteropancreatic neuroendocrine tumours (GEP NET) undergoing PRRT with ¹⁷⁷Lu-octreotate. The mean follow-up period was 21 months (range 12–50) with a median of five GFR measurements per patient. The change of GFR was analysed by linear curve fit. Potential risk factors including diabetes mellitus, arterial hypertension, previous chemotherapy, renal impairment at baseline and cumulative administered activity were analysed regarding potential impact on renal function loss. In addition, Common Terminology Criteria for Adverse Events (CTCAE) v3.0 were used to compare nephrotoxicity determined by ^99mTc-DTPA clearance versus serum creatinine.

Results

The alteration in GFR differed widely among the patients (mean ?2.1?±?13.1 ml/min/m² per year, relative yearly reduction ?1.8?±?18.9 %). Fifteen patients (21 %) experienced a mild (2–10 ml/min/m² per year) and 16 patients (22 %) a significant (>10 ml/min/m² per year) decline of GFR following PRRT. However, 11 patients (15 %) showed an increase of >10 ml/min/m² per year. Relevant nephrotoxicity according to CTCAE (grade ≥3) was observed in one patient (1.3 %) with arterial hypertension and history of chemotherapy. Nephrotoxicity according to serum creatinine was discordant to that defined by GFR in 15 % of the assessments and led to underestimation in 12 % of patients. None of the investigated factors including cumulative administered activity contributed to the decline of renal function.

Conclusion

Serious nephrotoxicity after PRRT with ¹⁷⁷Lu-octreotate is rare (1.3 %). However, slight renal impairment (GFR loss >2 ml/min/m² per year) can frequently (43 %) be detected by ^99mTc-DTPA clearance assessments. Cumulative administered activity of ¹⁷⁷Lu-octreotate is not a major determinant of renal impairment in our study.     

Bone marrow transplantation: effects of conditioning and cyclosporin prophylaxis on microvascular permeability to a small solute (technetium 99m diethylene triamine penta-acetic acid)

Microvascular permeability to small diffusible solutes has rarely been measured at a clinical level. We have developed a simple non-invasive technique for measuring the permeability surface area (PS) product, which is suitable for clinical use. We illustrate its potential value in six subjects who underwent bone marrow transplantation for chronic myeloid leukaemia. These patients received high-dose cyclosporin A (CyA) for prevention of graft versus host disease (GVHD) and sustained an easily measurable increase in microvascular permeability to technetium 99m diethyltriamine penta-acetic acid (^99mTc-DTPA). This was measured as the PS product, which increased from 1.1 (SD 0.3) to 2.2 (0.4) ml/min per 100 ml tissue between baseline and treatment with CyA for prevention of GVHD (P<0.01). The increase broadly correlated with nephrotoxicity which was measured, from the plasma DTPA clearance, as global glomerular filtration rate (GFR). This decreased from 106 (11.1) to 49 (6.7) ml/min (P<0.001). These abnormalities, both in PS product and GFR, were sustained for several months, after which they tended to return towards baseline levels. We conclude firstly that this technique has a potential clinical role and secondly that endothelial abnormalities due to CyA deserve further study.     

Determination of glomerular filtration rate (GFR) by analysis of capillary blood after single shot injection of 99mTc-DTPA

^99mTc-DTPA was prepared from a kit produced by the Institute of Atomic Energy, Oslo, Norway. Radiochemical purity as determined with gel chromatography ranged from 98.5–99.7% (n=7). The radiopharmaceutical showed no red cell uptake and not more than 0.2% protein binding in in vitro biokinetic studies.The clearance of ^99mTc-DTPA was compared to the clearance of ¹²⁵I-Iothalamate simultaneously using single shot intravenous injection and biexponential analysis of plasma activity disappearance rate according to Sapirstein et al. (1955). ¹²⁵I-Iothalamate was found to have a higher second volume of distribution than ^99mTc-DTPA, but there was no statistically significant difference in clearance.GFR calculated from capillary serum ^99mTc-DTPA count rates was in all subjects investigated virtually identical with GFR calculated from simultaneously collected venous plasma samples.Estimation of GFR on the basis of plasma activity curves obtained from sampling in two hours gave higher values than estimation from four hours sampling irrespective of kidney function and whether ^99mTc-DTPA or ¹²⁵I-Iothalamate was used.It is concluded that ^99mTc is almost entirely bound to DTPA after intravenous injection of the ^99mTc-DTPA complex, and that the complex is a suitable agent for determination of glomerular filtration rate, using both venous and capillary blood sampling.     

Measurement of separate kidney clearance by means of 99mTc-DTPA complex and a scintillation camera

A new radioisotopic method of determining the separate glomerular clearance of the kidneys is described. After injection of ^99mTc-DTPA, the data from a scintillation camera are recorded by computer. The renal curves are corrected for extrarenal activity and the plasma curve is obtained from a precordial curve. At each instant the slope of the renal curve divided by the corresponding plasma concentration gives the separate clearance value, in the period extending from 80 to 180 s after injection of the tracer. The error and correction factors introduced are discussed. Normal values are established on 25 patients and correspond to inulin clearance values. Left kidney: 60 ml/min (SD=13). Right kidney: 57 ml/min (SD=12). The method is simple for the patient, takes only 20 min, is not dangerous, is particularly applicable to young children and can be repeated frequently in the same patient.     

In vivo labelling of RBC with 99mTc for blood pool imaging using different stannous radiopharmaceuticals

The in vivo ^99mTc-RBC labelling efficiency and stability of labelling was assessed after pretinning with a high-stannous content DTPA kit (Sn DTPA) in comparison with Sn-pyrophosphate (Sn PPi) and a low-stannous DTPA kit (DTPA). The distribution in Sprague Dawley rats showed that similar fractions of administered ^99mTc remained within the blood pool after pretinning with Sn DTPA and Sn PPi when equal quantities of stannous ions (15 g/kg) and equal time intervals (30 min) between successive IV injections of pretinning agent and ^99mTc-pertechnetate were used. Significantly lower fractions were found when DTPA (1.9 g Sn²⁺/kg) was used for pretinning. The rate of ^99mTc elution emphasises the importance of the Sn²⁺ concentration used, not only for labelling efficiency but also for stability of the labelling. Satisfactory intravascular activity, exceeding 80% during the first hour post-injection, was demonstrated in three volunteers after ^99mTc injection, when Sn DTPA was used for pretinning. Left ventricular ejection fractions (LVEF) measured by equilibrium radionuclide angiography angiography after pretinning with Sn DTPA in 24 patients correlated well (r=0.98) with those obtained by contrast angiographies over a broad spectrum of values (0.14–0.72). Four repeated LVEF measurements at 45-min intervals in six additional patients at rest showed excellent reproducibility in each patient: maximum variation was less than 6%.     

Use of a standardized uptake value for parametric in vivo imaging of benzodiazepine receptor distribution on [<Superscript>11</Superscript>C]flumazenil brain PET

To simplify the acquisition protocol of carbon-11 labeled flumazenil (FMZ) positron emission tomography (PET) for distribution volume (DV) images, we attempted to obtain standardized uptake value (SUV) images compatible with DV images, and assessed the applicability of this method in patients with unilateral cerebrovascular diseases (CVD). [¹¹C]FMZ PET was performed in ten normal subjects. A DV image and ten sequential 5-min SUV images were generated for each subject. We investigated the correlation coefficient (r) and standard estimation of error (SEE) between the latter ten static images and the DV image using the pixel-by-pixel method, thereby determining the optimum acquisition phase. The same FMZ PET procedure was performed in 15 patients with unilateral CVD. Twenty regions of interest (ROIs) were positioned both in lesioned areas and in symmetrical regions. DV and SUV in the optimum phase for each ROI were calculated to compare the lesion-to-normal (L/N) ratio of DV and that of SUV. The highest r and a low SEE (r=0.957, SEE=633) were observed from 30 to 35 min after tracer administration in the study of normal subjects. A high r (0.945) and a low SEE (0.0438) between the DV L/N ratio and the SUV L/N ratio were obtained in the study of patients. Our study suggests that SUV images acquired from 30 to 35 min after FMZ administration are a suitable alternative to DV images not only in normal subjects but also in patients with unilateral CVD. This simple method seems to be valuable for the identification of altered neuronal activity in patients with CVD.     

<Superscript>99m</Superscript>Tc-DTPA dynamic SPECT and CT volumetry for measuring split renal function in live kidney donors

Objectives  

Split renal function (SRF) estimated from the posterior view of ^99mTc-diethylenetriaminepentaacetic acid planar scintigraphy (DTPA/P) is not sufficiently accurate even after correction for kidney depth by computed tomography (CT). To obtain more accurate SRF using ^99mTc-DTPA, dynamic SPECT method was carried out for the initial 5 min after bolus injection of ^99mTc-DTPA (DTPA/SPECT). Also SRF was evaluated from the renal volume measured by CT. We compared the results with ^99mTc-dimercaptosuccinic acid SPECT (DMSA/SPECT).     

Comparison of radionuclide estimation of glomerular filtration rate using technetium 99m diethylenetriaminepentaacetic acid and chromium 51 ethylenediaminetetraacetic acid

Simultaneous measurements of the clearance rates of technetium 99m diethylenetriaminepentaacetic acid (99mTc-DTPA) and chronium 51 ethylenediaminetetraacetic acid (51Cr-EDTA) were performed in 30 patients with a range of renal function (glomerular filtration rates between 9 and 120 ml/min). Using multiple blood samples, the two clearance values correlated well (r = 0.991, standard error 3.9 ml/min), but DTPA clearance was systematically higher by 7.6%. For each radiopharmaceutical, an equation was derived to correct clearance values obtained using only plasma samples taken at 2 and 4 h for the systematic error inherent in this technique compared with analysis of the complete plasma concentration-time curve. The root mean square error remaining after application of these equations was 1.9 ml/min for both the EDTA and DTPA data. The corresponding errors obtained using the equation derived by Brochner-Mortensen for EDTA plasma clearance were 2.2 ml/min and 1.9 ml/min, respectively, these values were not significantly different from those obtained using the equations derived in this study.     

Assessment of intra- and interobserver reproducibility of rest and cold pressor test-stimulated myocardial blood flow with <Superscript>13</Superscript>N-ammonia and PET

Purpose We investigated the intraobserver reproducibility of myocardial blood flow (MBF) measurements with PET at rest and during cold pressor test (CPT), and the interobserver agreement. Methods Twenty normal volunteers were studied. Using ¹³N-ammonia, MBF was measured at rest and during CPT and measurement was repeated in a 1-day session (short-term reproducibility; SR). After a follow-up of 2 weeks, MBF was measured again at rest and during CPT and compared with the initial baseline measurement (long-term reproducibility; LR). In addition, adenosine-induced hyperemic MBF increases were assessed. Results Assessment of the SR did not show a significant absolute difference in MBF at rest, MBF during CPT or the endothelium-related change in MBF from rest to CPT (ΔMBF) (0.09 ± 0.10, 0.11 ± 0.09, and 0.08 ± 0.05 ml/g/min; p = NS), and they were linearly correlated (r = 0.72, r = 0.76 and r = 0.84; p < 0.0001). Corresponding values for standard error of the estimate (SEE), as indicative for the range of MBF measurement error, were 0.14, 0.14, and 0.09 ml/g/min. The LR yielded relatively higher but non-significant absolute differences in the MBF at rest, MBF during CPT and ΔMBF (0.10 ± 0.10, 0.14 ± 0.10, and 0.19 ± 0.10 ml/g/min; p = NS), and paired MBFs significantly correlated (r = 0.75, r = 0.71, and r = 0.60; p < 0.001). Corresponding SEEs were 0.13, 0.15, and 0.16 ml/g/min. The interobserver analysis yielded a high correlation for MBF at rest, MBF during CPT, and hyperemic MBF (r = 0.96, SEE=0.04; r = 0.78, SEE=0.11; and r = 0.87, SEE=0.28; p < 0.0001, respectively), and also a good interobserver correlation for ΔMBF (r = 0.62, SEE=0.09; p < 0.003). Conclusion Short- and long-term MBF responses to CPT, as an index for endothelium-related coronary vasomotion, can be measured reproducibly with ¹³N-ammonia PET. In addition, the high interobserver reproducibility for repeat analysis of MBF values suggests the measurements to be largely operator independent. Thomas H. Schindler and Xiao-Li Zhang contributed equally to this paper.