Renal vascular transit time and tubular transit time dispersion for 99Tcm-MAG3

Renal transit time usually refers to tubular transit time, as introduced by Taplin, but other measures of renal transit have been proposed. Here we examine the vascular transit time (VTT, following Rutland) and the standard deviation of tubular transit time (SDTT, following Britton) in a group of 30 patients having baseline and ACE-inhibitor 99Tcm-MAG3 renography prior to arteriography. A same-day, low-dose/high-dose protocol was used for renography; only the post-captopril dose was high enough to measure VTT. Pre-captopril, the Spearman rank correlation coefficient for SDTT was rho = 0.52 (n = 53 kidneys; P < 0.0002); post-captopril, rho = 0.54 (n = 49 kidneys; P < 0.0002). For VTT, the post-captopril value was rho = 0.24 (n = 30 kidneys; N.S.). For comparison, the same statistics were calculated for Taplin's original measure of transit time: the time from injection to maximum count rate (peak time). Pre-captopril, for peak time, rho was 0.47 (n = 53 kidneys; P < 0.001); post-captopril, rho was 0.39 (n = 50 kidneys, P < 0.01). These findings confirm the diagnostic value of SDTT but not of VTT. SDTT correlated better than peak time with the arteriographic findings.

Intraperitoneal radioimmunotherapy of ovarian cancer with 177Lu-CC49: a phase I/II study

BACKGROUND

Twenty-seven ovarian cancer patients who failed chemotherapy entered a phase I/II trial of intraperitoneal 177Lu-CC49 antibody.

METHODS

Patients had disease confined to the abdominal cavity +/- retroperitoneal lymph nodes, adequate organ function, and no previous radiation.

RESULTS

The most common side effects were delayed, transient arthralgia (10/27) and marrow suppression with 1.665 GBq/m2 (45 mCi/m2), which was considered the maximum tolerated dose. One of thirteen patients with gross disease had >50% tumor reduction after therapy, whereas most others with gross disease progressed (one went off study with stable disease at 11 weeks). Seven of nine patients with <1-cm nodules progressed in < or =21 months, and two of nine remain without evidence of disease at 4 to 5 months. Of patients with microscopic or occult disease, one relapsed at 10 months and four of five remain without evidence of disease at >6 to 35 months.

CONCLUSIONS

Marrow suppression was the dose-limiting toxic effect of intraperitoneal immunotherapy with 177Lu-CC49. Antitumor effects were noted against chemotherapy-resistant ovarian cancer, even at lower dose levels, and resulted in prolonged disease-free survival of most patients with microscopic disease. This form of treatment deserves further study.

Health Care Financing Administration/American Society for Cytotechnology inspections: government assessment of cytology laboratory practice under the regulations of the Clinical Laboratory Improvement Amendments of 1988

Since 1988, the American Society for Cytotechnology has performed inspections of 206 cytology laboratories in the United States under contract to the Health Care Financing Administration. These surveys are conducted by a team of supervisory-qualified cytotechnologists, including a specially trained survey team leader. A board-certified anatomic pathologist is assigned to each team and is on call for each survey. Laboratories are assessed for compliance with the regulations of the Clinical Laboratory Improvement Amendments of 1988 and, in particular, the area of quality control in cytology. These surveys are unique in that a sample of at least 0.1% of a laboratory's annual case volume is reevaluated by the survey team. Of the 206 laboratories surveyed, 116 were found to be in substantial compliance with the regulations while 90 were found to have Condition level deficiencies. Of those with Condition level deficiencies, 8 have had their Clinical Laboratory Improvement Amendments of 1988 certificates limited for cytology, and 16 have been terminated from Medicare participation.

Phase II study of dual 131I-labeled monoclonal antibody therapy with interferon in patients with metastatic colorectal cancer

The combination of COL-1 (anti-CEA) and CC49 (anti-TAG-72) has shown an increase in binding and distribution in colon cancer by immunoperoxidase staining compared to either antibody alone. To overcome tumor heterogeneity and allow delivery of higher radiation dose, 131I-labeled COL-1 and CC49 at a total dose of 75 mCi/m2 (2775 MBq/m2) were simultaneously administered to 14 patients with metastatic colon cancer. alpha-IFN (3 x 10(6) IU) was given s.c. on days -5 to +3 to increase carcinoembryonic antigen and TAG-72 antigen expression. Most patients had mild symptoms during IFN therapy, including mild neutropenia, fever, and malaise, which rapidly subsided after IFN cessation. No acute allergic reactions occurred with radioimmunotherapy; two patients experienced transient, delayed grade 2 arthralgias. Transient neutropenia and/or thrombocytopenia, which was maximal at 4-6 weeks, were consistent side effects without adverse events. All patients had tumor localization, and 13 of 14 patients achieved 4+ (highest grade) localization readings to at least one known site of disease. No objective responses occurred; 4 patients were stable and 10 progressed. Tumor dose estimates varied from 393 to 1327 cGy, including liver and extrahepatic sites. Combining two complementary antibodies and IFN administration appeared to increase localization intensity and radiation doses at tumor sites as compared to historical controls. The amount of radiation delivered to tumor sites was still below that required to cause tumor regressions in metastatic colorectal cancer.

Intraperitoneal radioimmunotherapy of ovarian cancer with lutetium-177-CC49

Twelve ovarian cancer patients who failed chemotherapy entered a Phase I trial of intraperitoneal 177Lu-CC49 antibody.

METHODS

Patients had disease confined to the abdominal cavity +/- retroperitoneal lymph nodes, adequate organ function and no previous radiation.

RESULTS

Side effects included mild discomfort with administration (1/12), delayed transient arthralgia (2/12), and mild marrow suppression (calculated marrow doses of 11-54 cGy). The maximum tolerated dose has not been reached with levels of 10, 18, 25 and 30 mCi/m2. Radioimmunoscintigraphy revealed localization consistent with tumor in 11 of 12 patients. One of eight patients with gross disease had > 50% tumor reduction after therapy, while six progressed and one went off study with stable disease. Of patients with microscopic or occult disease, one relapsed at 10 mo and three remain without evidence of disease after 18 mo.

CONCLUSION

Intraperitoneal radioimmunotherapy with 177Lu-CC49 is well tolerated and appears to have antitumor activity against chemotherapy-resistant ovarian cancer in the peritoneal cavity.

Measurement of renal function with technetium-99m-MAG3 in children and adults

A single-injection, single-sample procedure for measuring 99mTc-MAG3 clearance is presented that incorporates scaling for patient size and is valid for both children and adults.

METHODS

The procedure is based on an empirical formula in which all measurements are expressed in dimensionless combinations. The formula was obtained by fitting data collected from 122 adults and 80 children at several centers.

RESULTS

All results were scaled to standard adult surface area and are presented in units of ml/min/1.73 m2. For adult subjects, the residual standard deviation (r.s.d.) calculated from a single sample at 45 min was found to be 23, using the plasma clearance calculated from a multi-sample clearance curve as a reference. This did not differ significantly from the value of 22 obtained with our previous formula, which was valid for adults only. For pediatric subjects, an r.s.d. of 24 was calculated by the new formula from a single sample at 35 min; a comparable value of 33 was found using a pediatric formula previously published.

CONCLUSION

The new clearance formula is recommended as a replacement for the formula we previously published, since it is based on a larger and more diverse subject population, and since it now holds for children as well, with no loss of accuracy for adult subjects.

Techniques for measuring renal transit time

A variety of techniques have been used for quantitative estimation of renal transit time. We compared different indices of transit time in a group of 30 patients having baseline and ACE inhibitor technetium-99m mercaptoacetyltriglycine (MAG3) renography prior to arteriography: peak time, mean transit time, and the ratio of background-subtracted counts at 20 min to those at 3 min. Each index was calculated from whole-kidney ROI, cortical ROI, and cortical factor (by factor analysis). The strongest correlations between angiographic percent of stenosis and transit time index were observed for the peak time (Spearman p=0.469, n=53, P <0.005) and for the R20/3 (again p=0.469, n=53, P <0.005) using the whole-kidney ROI and using only the baseline data without captopril. (Spearman's p is simply the correlation coefficient calculated from rank in list, which allows for nonlinear correlation.) Thus simple indices of transit time (whole-kidney peak time and R20/3) correlated as well with the observed pathology as did more complicated methods that required deconvolution, factor analysis, or selection of a cortical ROI.

Comparison of single-injection multisample renal clearance methods with and without urine collection

Single-injection renal clearance methods based on plasma clearance alone, without urine collection, are sometimes met with skepticism. They require data extrapolation to infinite time, which is hard to justify a priori. It has been asserted that they are less accurate for rapidly cleared tubular agents than for slowly cleared glomerular filtration rate agents. In this study, we compare urine-based and urine-free methods for the tubular agents 99mTc-MAG3 and 131I-OIH.

METHODS

In 18 patients, dual-tracer plasma data were obtained from 4 to 90 min after injection (nine samples). Urine was also collected for 90 min (in two voidings). The urine counts wre corrected for residual bladder activity by pre- and postvoid dual-channel gamma camera images.

RESULTS

When comparing the two methods of clearance calculations, the difference between urine-based and urine-free measurements 1 +/- 5 ml/min for 99mTc-MAG3 and 23 +/- 8 for 131I-OIH (mean +/- s.e. of the mean). For 99mTc-MAG3, the regression line did not differ significantly from the line of identity. The correlation coefficient was 0.94 for both agents.

CONCLUSION

Urine collection is not necessary to measure renal clearance, even for the rapidly cleared tubular agents, except at low clearance levels (when the small absolute error corresponds to a large percentage error).

A single-injection, two-sample method for measuring renal 99mTc-MAG3 clearance in both children and adults

We present a method for estimating 99mTc-MAG3 clearance from both a single injection and two blood samples that is valid for both adults and children. It was obtained by fitting a scaled two-compartment model (having only two adjustable parameters) to adult and pediatric data from multiple centers.

Radionuclide evaluation of renal transplants

Chronic renal failure caused by hypertension or by parenchymal kidney disease is a very common global health problem. Patients with chronic renal failure have two therapeutic options, dialysis and transplantation, of which transplantation has become a preferred modality. This review article is an update of a more comprehensive previous review (Semin Nucl Med, 181-198, 1988) and concentrates on the changes that have taken place in this field in recent years. These changes comprise new criteria for the selection of transplant candidates, newer techniques for the diagnosis of medical and surgical complications after transplantation, the use of new tracers (Tc-99m MAG3), and new antirejection regimens.

Treatment of metastatic prostate carcinoma with radiolabeled antibody CC49

A Phase II trial of 75 mCi/m2 131I-anti-TAG-72 high-affinity antibody CC49 was studied in 15 patients with hormone-resistant metastatic prostate cancer.

METHODS

Patients had adequate renal, liver and hematopoietic function. No previous cytotoxic chemotherapy was allowed and previous radiation was limited to 20% of the active bone marrow.

RESULTS

No acute adverse reactions occurred, but all patients had evidence of an immune response to CC49 by 4 wk. Six of 10 symptomatic patients had bone pain relief, but no patients met the radiographic or PSA criteria for objective response. Positive imaging of bone and/or soft-tissue lesions was noted for 13 of the 15 patients.

CONCLUSIONS

CC49 had a high frequency of tumor localization with evidence of anti-tumor effects (pain relief).

Quantitation of renal parenchymal retention of technetium-99m-MAG3 in renal transplants

When imaging renal transplants with tubular agents, such as mercaptoacetyltriglycine, marked parenchymal retention is a hallmark of acute rejection (AR) or acute tubular necrosis (ATN). (AR can be distinguished from ATN by the time course on serial studies.) The quantitative relationship of retention to uptake can be measured by dividing the background-corrected renal activity at 20 min by that at 3 min.

METHODS

The diagnostic value of this ratio (R20/3) was tested in a series of 555 renograms. Because patients with mild disease have minimal abnormalities, the patients were ranked by their estimated severity of disease (1-4 for abnormal and 0 for normal).

RESULTS

R20/3 was found to correlate strongly with severity of ATN (Spearman's rho = 0.879, p < 0.001, n = 168) and also with severity of AR (rho = 0.888, p < 0.001, n = 267). There were two (3%) false-positive results in 64 normal patients.

CONCLUSION

If 0.8 is taken as the upper limit of normal for R20/3, then among patients with disease severity 3 or 4, there were no false-negative findings in 104 patients with ATN or in 203 patients with AR. R20/3, despite its simplicity, is an effective diagnostic parameter.

Lipoprotein lipase regulation by insulin and glucocorticoid in subcutaneous and omental adipose tissues of obese women and men

There are marked variations in the activity of lipoprotein lipase (LPL) among adipose depots, particularly in women. Consistent with data on LPL activity, the level of expression of LPL mRNA was lower in omental (OM) than subcutaneous (SQ) adipose tissue of women. To investigate the cellular basis of these differences, OM and SQ adipose tissues obtained at surgery from obese men and women were placed in organ culture for 7 d with varying concentrations of insulin and dexamethasone. Insulin increased levels of LPL mRNA and LPL activity in abdominal SQ but not OM adipose tissue. Dexamethasone also increased LPL mRNA and LPL activity, and these effects were more marked in the OM adipose tissue, particularly in men. When insulin and dexamethasone were added together, synergistic increases in LPL activity were seen in both depots, and this was in part explained at the level of LPL mRNA. The SQ depot was more sensitive to the effects of submaximal doses of dexamethasone in the presence of insulin. The maximum activity of LPL induced by insulin or insulin plus dexamethasone was higher in the SQ than in the OM depot of women, and this was associated with higher levels of LPL mRNA. Rates of LPL synthesis paralleled LPL mRNA levels. These data show that insulin and glucocorticoids influence human adipose tissue LPL activity at the level of LPL gene expression, as well as posttranslationally, and that responsiveness to these hormonal effects is dependent on adipose depot and gender.

Optimum sample times for single-injection, multisample renal clearance methods

The best choice of sample times for measuring renal function in adults by single-injection multisample plasma clearance methods was determined by Monte Carlo simulation, using a two-compartment model with parameters chosen to fit average values (from published clinical studies) for each of the three radiopharmaceuticals 99mTc-MAG3, 99mTc-DTPA and 131I-ortho-iodohippurate. Random errors were added and the simulated data were then fit to a two-exponential model using a weighted nonlinear curve fitting method. The calculated clearance values were compared with the original values to determine random and systematic errors for different selections of sample time for each radiopharmaceutical at various levels of renal function. The results show that for research-level accuracy with a GFR agent such as 99mTc-DTPA, plasma sampling must begin by 10 min after injection and continue at least 3 hr (in adults). With an ERPF agent such as 99mTc-MAG3 or 131I-OIH, sampling must begin by 5 min and continue for at least 90 min. Six logarithmically distributed samples are sufficient.

Direct localization comparison of murine and chimeric B72.3 antibodies in patients with colon cancer

To compare radiolocalization of murine B72.3 (m-B72.3) and mouse/human chimeric B72.3 (ch-B72.3) antibodies, five patients with biopsy confirmed adenocarcinoma of the colon received both radiolabeled antibodies 4 or 7 days before laparotomy. Following antibody administration, preoperative gamma camera images showed localization to sites of disease in four of the five patients. Autoradiography of resected specimens showed that both labeled antibodies localized specifically to the tumor with only minimal amounts in normal tissues. Radioactivity from each isotope in biopsy specimens of tumor and normal tissues was quantitated by scintillation gamma counting. Comparison of the percentages of injected activities for each antibody in resected tumor and normal tissue yields tumor to normal tissue radiolocalization ratios of 2.7-13.3 and 0.9-6.3 for murine and chimeric antibodies, respectively. The higher ratios for murine antibody were due to lower normal tissue levels, reflecting its faster clearance from the circulation, whereas the quantitative uptake of labeled antibody was always greater with the chimeric antibody. The chimera to murine antibody ratios in tumor of 1.1-2.7 suggest modest enhancement of tumor localization with chimeric antibody because of its longer half-life.

Renal transplant hypertension caused by iliac artery stenosis

A captopril renal study performed with both radiohippuran and 99mTc-MAG3 demonstrated the typical changes of a hemodynamically significant renal artery stenosis in a hypertensive renal allograft recipient. Arteriography demonstrated high grade stenosis not of the renal artery but of the iliac artery. After successful angioplasty, the patient's hypertension resolved.

Phase I trial of iodine-131-chimeric B72.3 (human IgG4) in metastatic colorectal cancer

Twelve patients with metastatic colorectal cancer participated in a Phase I trial of 131I-labeled chimeric B72.3 (human IgG4). Consecutive groups of patients received 18 mCi/m2, 27 mCi/m2 and 36 mCi/m2. No acute side effects related to antibody administration were noted. Bone marrow suppression was the only side effect; it was dose-dependent and correlated with whole-body radiation dose estimates. The lowest dose level produced no marrow suppression, whereas 27 mCi/m2 resulted in Grade 1 and 2 marrow suppression in two of three patients. The maximum tolerated dose was 36 mCi/m2 with all six patients at this dose level having at least Grade 1 and two patients with Grade 3 and 4 marrow suppression. Eight of 12 patients had radioimmune imaging of tumor sites at 5-22 days. Seven patients had an antibody response to initial infusion. On retreatment, whole-body kinetics and imaging were altered for patients with a high anti-ch-B72.3 response. Thus, chimeric B72.3 (IgG4) has limited utility as a means of delivering multiple therapeutic doses of 131I in the majority of patients; alternative strategies including second generation anti-TAG-72 monoclonal antibodies, other radioisotopes and other chimeric human isotypes will need to be pursued.

Diagnosis of renovascular hypertension after renal transplantation

Hypertension in renal transplant recipients is an important risk factor for graft function and cardiovascular morbidity and mortality. The mechanisms of posttransplant hypertension are not well understood. Most of the time, the nature of this hypertension is multifactorial. Rejection, both acute and chronic, recurrent renal disease, graft renal artery stenosis, native kidney disease and drug therapy with steroids and cyclosporin have all been implicated. Where a single cause can be identified, the therapy can be rational and often very successful. For this reason, the diagnosis of graft renal artery stenosis is important, because percutaneous transluminal angioplasty or surgery can lead to the cure of hypertension and improvement of the graft function. Noninvasive testing, using captopril renography for the diagnosis of hemodynamically significant renal artery stenosis, presently yields encouraging results.

Simplified methods for renal clearance in children: scaling for patient size

Development and validation of simplified renal clearance methods has required a research data base of multiple blood samples drawn over a substantial time interval, which is difficult to obtain for children. While the medical risks entailed in drawing multiple samples may be negligible, the problems of parental and institutional consent make such studies more difficult in the pediatric population. Scaling for patient size permits combining data from patients of different age and limits the number of studies required. A scaling technique is presented and evaluated here. With scaling, adult data can be used successfully to predict pediatric responses and to develop pediatric methods based on adult data alone. Inclusion of pediatric data improves the fit and permits development of generic methods that work with both adults and children.

Pharmacokinetics, immune response, and biodistribution of iodine-131-labeled chimeric mouse/human IgG1,k 17-1A monoclonal antibody

Pharmacokinetics, immunogenicity, and biodistribution of a 131I-labeled mouse/human chimeric monoclonal antibody (C-17-1A) was studied in six metastatic colon cancer patients. Pharmacokinetics obtained from serum radioactivity or chimera concentration were identical after 5 mCi of 131I-C-17-1A with mean alpha half-lives of 17.6 +/- 2.3 and 19.7 +/- 2.9 and mean beta half-lives of 100.9 +/- 16.1 and 106.4 +/- 14.1 hr, respectively. HPLC analysis documented the monomeric chimeric 17-1A without evidence of immune complexes or free 131I. None of the patients developed antibody after 131I-chimeric 17-1A exposure. Radiolocalization occurred in known areas of disease greater than 4 cm in all patients. The half-life of total-body radioactivity was 58 +/- 7 hr by whole-body counts and 64 +/- 13 hr by urine measurements. Whole-body and bone marrow dose estimates ranged from 0.75-1.03 and 0.76-1.05 rad/mCi, respectively. These studies confirm the prolonged circulation and reduced immunogenicity of chimeric 17-1A versus murine 17-1A. Marrow radiation exposure using antibodies with prolonged circulation is a critical factor in planning for radioimmunotherapeutic applications.

Measurement of renal parenchymal transit time of 99mTc-MAG3 using factor analysis

Renal parenchymal transit time of the recently introduced radiopharmaceutical 99mTc-MAG3 (mercaptoacetylglycylglycinel) was measured in 37 kidneys, using factor analysis to separate parenchymal activity from that in the collecting system. A new factor algorithm was employed, based on prior interpolative background subtraction and use of the fact that the initial slope of the collecting system factor time-activity curve must be zero. The only operator intervention required was selection of a rectangular region enclosing the kidney (by identifying two points at opposite corners). Transit time was calculated from the factor time-activity curves both by deconvolution of the parenchymal factor curve and also by measuring the appearance time for collecting system activity from the collecting system factor curve. There was substantial agreement between the two methods. Factor analysis led to a narrower range of normal values than a conventional cortical region-of-interest method, presumably by decreasing crosstalk from the collecting system. In preliminary trials, the parenchymal transit time did not well separate four obstructed from seventeen unobstructed kidneys, but it successfully (p less than 0.05) separated six transplanted kidneys with acute rejection or acute tubular necrosis from 10 normal transplants.

Measurement of renal function with radionuclides

For the nuclear physician who wants to measure renal function, the biggest problem may be having to choose among the dozens of methods that have been proposed. An overview will be presented here. The final selection must depend upon the needs of each clinic as well as its technical and financial resources. Except at very low levels of renal function, almost any of these methods can be more reliable than creatinine clearance.

Estimation of technetium-99m-MAG3 plasma clearance in adults from one or two blood samples

Technetium-99m mercaptoacetyltriglycine (MAG3) clearance is strongly correlated with effective renal plasma flow and can be used directly as a measure of renal function. For these reasons, formulas were developed for estimation of [99mTc]MAG3 clearance based on one or two plasma samples. A two-exponential model provided an excellent fit for 8-point plasma clearance curves obtained from 35 patients having a wide range of renal function. The 8-point [99mTc]MAG3 clearance could be estimated from a single point at 43 min with an error of 19 ml/min (residual s.d.) or from two samples at 12 and 94 min with an error of 7 ml/min. The relative errors with MAG3 are thus comparable to those reported for similar techniques used with [131I]orthoiodohippurate, [99mTc]diethylenetriaminepentraacetic acid and [51Cr]ethylenediaminetetraacetic acid.

The kidney: imaging with Tc-99m mercaptoacetyltriglycine, a technetium-labeled analog of iodohippurate

A new renal imaging agent, technetium-99m mercaptoacetyltriglycine (MAG3, mertiatide), is currently undergoing clinical trials. Like iodine-131 orthoiodohippurate (OIH)--and unlike all other available agents--it is avidly secreted by the renal tubules. Fifty patients underwent simultaneous renal imaging studies with I-131 OIH and Tc-99m MAG3. The superior physical properties of the Tc-99m label led to better image quality in all cases, largely due to count rates that were 50-fold better. In two patients, lesions were seen with MAG3 that were not visible with OIH. The biological properties of the two agents were found to be so similar that conventional diagnostic criteria for I-131 OIH could be used for Tc-99m MAG3 with only minor modifications.

Estimation of ERPF in adults from plasma clearance of 131I-hippuran using a single injection and one or two blood samples

The plasma clearance of [131I]o-iodohippurate, which is an estimate of effective renal plasma flow, can be measured from one or two blood samples drawn after an i.v. bolus of tracer. The most widely used method is based on a single sample. Here, it is shown that the error (relative to a complete curve of six or more blood samples) can be halved by using two samples rather than one. Since the one-sample method is satisfactory for most clinical purposes, the two-sample method is recommended only when special accuracy is needed.

Quantitation of renal function with technetium-99m MAG3

The technetium-labeled hippuran analog [99mTc]MAG3 was compared with [131I]hippuran in 50 patients using a quantitative renal function protocol that includes: (a) estimation of effective renal plasma flow by a single-injection, single-sample plasma clearance method, (b) determination of relative function of right and left kidney from the initial count rate over each kidney, and (c) comparison of recovered urine activity with plasma disappearance. This protocol is suitable for routine clinical use, and, in fact, has been used heavily at our clinic for a number of years. By slight modification of the formulas, the results obtained with [99mTc]MAG3 agreed well with those using [131I]hippuran. We conclude that [99mTc]MAG3 can be substituted for [131I]hippuran in the quantitative protocol, with the better image quality and lower radiation dose (in abnormals) of a technetium-labeled agent.

Abnormal captopril renogram with a technetium-99m-labeled hippuran analog

A case of renovascular hypertension is presented in which the [131I]hippuran renogram was initially normal, but became strikingly abnormal upon administration of the angiotensin converting enzyme (ACE) inhibitor captopril. The patient presented with fibromuscular dysplasia of the renal arteries, which was shown by hippuran renography to be functionally significant on the right side. She became normotensive after angioplasty of the right renal artery. Hypertension recurred a year later, at which time the renogram was normal without captopril, but showed functionally significant left renal artery stenosis with captopril challenge. Both the conventional agent, [131I]hippuran, and an experimental new 99mTc-labeled hippuran analog, [99mTc]MAG3, were used. Angiography confirmed progression of disease on the left side, which was successfully treated by angioplasty. Functionally significant unilateral renal artery stenosis was thus demonstrated first on the right side and then, 1 yr later, on the left side, using hippuran and [99mTc]MAG3. Anatomic progression of disease was documented by angiography.

Radionuclide evaluation of renal transplants

In this review article, the following topics are treated: the radiopharmaceuticals 99mTc-diethylenetriaminepentaacetic acid (DTPA), 131I-orthoiodohippurate (OIH), 99mTc-mercaptoacetyltriglycine (MAG3), 67Ga-citrate, radioiodinated fibrinogen, 99mTc-sulfur colloid, 111In-labelled white cells and platelets; gamma camera methods based on images, on first pass and on tubular transit; blood clearance methods; and the diagnosis of surgical complications, acute rejection (AR), acute tubular necrosis (ATN), chronic rejection (CR), and cyclosporine-A (CYA) toxicity.

Comparison of technetium-99m MAG3 with iodine-131 hippuran by a simultaneous dual channel technique

Technetium-99m MAG3, a technetium-labeled analog of hippuran, was compared with [131I] hippuran using a simultaneous dual isotope study in 20 patients. The plasma clearance for MAG3 was lower than that of hippuran, but its plasma concentration was higher, resulting in similar rates of excretion and similar renal time-activity curves. Apart from better statistics with the technetium-labeled agent, there were no clinically significant differences in this group of patients.

Clinical use of a standard kit-preparation of radiolabeled monoclonal antibody 96.5 in the diagnostic imaging of metastatic melanoma

We studied the efficiency of a standard-kit preparation using 1 mg 111In-labeled 96.5 monoclonal antibody in combination with 19 mg of unlabeled antibody in the diagnostic imaging of 27 patients with documented metastatic melanoma. Twenty-three of 26 patients (88%) demonstrated immunoscintigraphic localization of tumor. Of 104 metastatic sites previously documented by conventional studies, 62 (60%) were identified by immunoscintigraphy. A total of 77 sites demonstrated localization of radiolabeled antibody. Fifty-four (70%) corresponded to known sites of disease; eight sites (10%) were "discovered" by immunoscintigraphy and subsequently confirmed by conventional studies; 15 imaged sites (20%) could not be confirmed by conventional studies. Size and location of metastasis appear to be important features that influence imaging efficiency. Tumor size (greater than or equal to 2 cm v less than 2 cm) appears to be the statistical dominant determinant. The feasibility and potential clinical use of radioimmune imaging of tumors is discussed.

Estimation of extracellular fluid volume from plasma clearance on technetium-99m DTPA by a single-injection, two-sample method

A simple method is presented for estimating extracellular fluid volume from the plasma clearance of [99mTc])DTPA or [169Yb]DTPA. Two plasma samples are required, at 1 and 3 hr, following a single intravenous injection. (The same plasma samples can be used for measurement of glomerular filtration rate.) Using the complete plasma clearance curve as a reference (eight samples at 10 to 240 min), the error of the two-sample method in 40 patients was 1.5 I for [99mTc]DTPA, 2.1 I for [169Yb]DTPA (residual standard deviation).

Estimation of glomerular filtration rate using 99mTc-DTPA and the gamma camera

Two methods of glomerular filtration rate estimation have been evaluated, based on the intravenous administration of 99mTc-DTPA and the measurement of renal time activity curves by means of a computer linked gamma camera. A single 20 min plasma sample was also required. These methods were designed to minimize the component of error arising from decay statistics. One method was based on using a constant fraction of the cardiac activity in lieu of a perirenal region of interest for the background correction, the other was based on deconvolution by a constrained least squares technique. The first method, based on modifying the background correction, led to poor results (residual standard deviation 18.9 ml/min when compared with the plasma clearance method). The second method, based on constrained least squares deconvolution, worked as well as previously reported methods (residual standard deviation 14.5 ml/min) and appears suitable for clinical use.

Quality control of technetium-99m DTPA: correlation of analytic tests with in vivo protein binding in man

When [99mTc]DTPA is administered, a small fraction of the activity (presumably an impurity) is bound to plasma proteins. This causes an error in the calculation of glomerular filtration rate from plasma clearance. This paper presents two methods of laboratory quality control for measuring the fraction that binds to plasma proteins. One method involves in vitro binding to human serum albumin followed by gel filtration. The other method involves descending paper chromatography on wet pre-equilibrated anion exchange paper. In a series of 80 patients, correlation was demonstrated between laboratory characteristics and actual clinical performance of the [99mTc]DTPA preparation. Both laboratory methods appear suitable for routine quality control.

Measurement of glomerular filtration rate: single injection plasma clearance method without urine collection

Glomerular filtration rate (GFR) can be calculated from the plasma clearance of any of several radiopharmaceuticals that are excreted by glomerular filtration. Simplified methods have been proposed that require only one or two plasma samples in lieu of a more complete clearance curve. We examined the error introduced by this simplification. Forty patients were studied using a dual-isotope technique employing [99mTc]DTPA and [169Yb]DTPA, obtaining eight plasma samples for each clearance curve at intervals from 10 to 240 min after injection. Data were fit to several empirical or semiempirical formulae and also to a two-compartment computer model that permitted GFR estimation from only one or two data points. The computer model gave good fit, but so did several simpler methods. The error that results from replacing the complete clearance curve by a single 3-hr sample was about 8 ml/min (residual s.d.). By using two samples (at 1 and 3 hr), the error could be reduced to 4 ml/min. Recommended one- and two-sample methods are presented.

Measurement of glomerular filtration rate using 99mTc-DTPA and the gamma camera: a comparison of methods

A variety of methods have been proposed to estimate the glomerular filtration rate (GFR) from the renal uptake of technetium Tc 99m-DTPA using a gamma camera. To compare alternative methods, we calculated the GFR in several different ways from measurements in 33 patients and compared the results with an independent GFR measurement based on eight-point plasma clearance of ytterbium Yb 169-DTPA. The best agreement was obtained using an algorithm that has not been described previously, in which correction was made for overlap of the kidneys by the liver and spleen. The correlation coefficient was 0.958, and the residual standard deviation was 12.1 ml/min. This method required a single 20-min blood sample as well as the camera data. The best method not requiring a blood sample was significantly less accurate, with a correlation coefficient of 0.837 and a residual standard deviation of 23.1 ml/min. The accuracy of these methods was comparable to that reported for creatinine clearance, the most commonly used estimate of the GFR in current clinical practice.

Mean ionic charge on two components of technetium pyrophosphate prepared using stannous chloride

Ionic charge, complexation equilibria, and acid-base equilibria can be measured at tracer concentrations by ion-exchange chromatography. To characterize better the principal components found in [99mTc]pyrophosphate preparations used for diagnostic bone and heart scanning, these were studied in two ion-exchange chromatographic systems: (A) DEAE-cellulose in pyrophosphate form at pH 6.0-7.5, and (B) DEAE-cellulose in perchlorate form at pH 3.7-4.8. The chromatographic retention times were measured as a function of pH and electrolyte concentration, and compared with those of trisoxalatochromium(III) complex, which was chosen as reference ion because of its similarity in charge and retention to the Tc-pyrophosphate complexes. The pyrophosphate complexes were even more sensitive to electrolyte concentration than was the triply negative reference ion: the calculated mean net charge in the mobile phase for the two principal Tc-pyrophosphate species were -4.5 +/- 0.5 and -4.9 +/- 0.5 at pH 4.3, and -11.2 +/- 1.3 and -10.1 +/- 1.0 at pH 7.0. It can be concluded that the two principal radioactive components in clinical Tc-pyrophosphate preparations both bear a high, pH-dependent negative charge.

Quality control of Tc-99m DTPA for measurement of glomerular filtration: concise communication

When technetium-99m DTPA is used to measure glomerular filtration rate (GFR), the accuracy depends on the supplier of the radiopharmaceutical. The error in GFR is due to protein binding, as we have shown by direct measurement. In 19 patients, GFR measured with Tc-DTPA and corrected for protein binding agreed with that measured simultaneously using Yb-169 DTPA (correlation coefficient 0.991). Without correction, Tc-DTPA gave falsely low values in patients having good renal function, in whom unbound activity cleared rapidly while bound activity remained in the circulation. When Tc-DTPA is used to measure GFR, the in vivo protein binding should be measured and used to correct the data.

Iminodiacetate complexes of technetium: an electrochemical study

Iminodiacetate complexes of technetium are used extensively in diagnostic medical imaging, but their chemical structure and properties are yet uncertain. We studied formation of technetium-99 complexes with diethylenetetraminepentaacetate (DPTA), ethylenediaminetetraacetate (EDTA), N-(2-acetamido)iminodiacetate (ADA), and N-(2,6-dimethylphenylcarbomoylmethyl)iminodiacetate (HIDA) by tast (sampled DC) polarography, reverse-pulse polarography, controlled-potential coulometry, and amperometric titration. The products, often mixtures, varied with reaction conditions and ligand; this can explain apparent contradictions in previous studies.

Quantitation of renal function with glomerular and tubular agents

Quantitative methods to measure the glomerular and tubular function of the kidneys with radionuclides have been available for many years. They have not been widely used because the techniques and the calculations exceeded the scope of routine nuclear medicine practice. Validation of simplified methods and the introduction of computer technology have made measurement of the effective renal plasma flow (ERPF) and the glomerular filtration rate (GFR) simple enough so that they can be performed reproducibly in most nuclear medicine departments. The estimation of ERPF with radioiodinated OIH and GFR with 99mTcDTPA can be achieved in many ways, all of which yield clinically useful results. How to get the best results using the simplest methods is still unclear. The required accuracy depends on the intended clinical use. Our preference at the present time is to use a single or double plasma sample to calculate global ERPF or GFR, and to use the 1-2 min OIH or 1-3 min Tc-DTPA uptake to calculate relative function of the two kidneys (split function ERPF or GFR). The choice of method will be influenced by local factors, such as the nature of the patient population, the case volume, and the resources available. A desirable goal for future studies is to document carefully the capabilities and limitations of each alternative method, so that the choice can be rational.

Complexes of technetium with hydroxycarboxylic acids: gluconic, glucoheptonic, tartaric, and citric

Technetium complexes of several hydroxycarboxylic acids are used for medical imaging. To determine the oxidation state of technetium in these agents, we studied the reduction of pertechnetate (Tc-99) in 0.1 M solutions of four hydroxycarboxylic acids, using polarography and amperometric titration with Sn(II). In D-gluconate below pH 6, Tc(III) and Tc(V) complexes were identified with certainty, Tc(IV) questionably; at pH 6 to 10, Tc(IV) and Tc(V) were formed; above pH 10, Tc(III), Tc(IV), and Tc(V). In D-glucoheptonate below pH 6, Tc(III) and Tc(V) were formed, and questionably Tc(IV); at pH 6 to 10, Tc(V); above pH 10, Tc(III), Tc(V), and probably Tc(IV). In L-tartrate below pH 6, Tc(III), Tc(IV), and Tc(V) were formed; above pH 6, Tc(IV) and Tc(V). In citrate below pH 10, Tc(III), Tc(IV), and Tc(V) were formed; above pH 10, Tc(IV) and Tc(V). For all four ligands the initial product of reduction by Sn(II) at pH 3 to 9 was Tc(V). In freshly prepared tin-labeled imaging agents of this class, the oxidation state is probably Tc(V). Lower stable oxidation states exist, attainable by using reducing agents stronger than tin; these may show altered imaging properties.

Determination of net ionic charge on Tc-99m DTPA and Tc-99m EDTA by a column ion-exchange method

The net charge on a stable complex ion is conveniently measured at tracer levels by studies of ion-exchange equilibrium. Previous applications to radiopharmaceuticals have used a batch equilibrium method, but such measurements are affected by any radiochemical impurities present. Since technetium pharmaceuticals are often heterogeneous, it is of value to have a technique that is directly applicable to a mixture of different species. Such a method is presented here: a column method to determine the net charge on the technetium-99m complex of diethylenetriaminepenta-acetic acid (DTPA), and also on the principal component in a mixture of species formed by reducing pertechnetate in the presence of ethylenediaminetetra-acetic acid (EDTA). The net charge was calculated from the effect of eluent concentration on retention time. The net charge on Tc-DTPA was found to be -2 at both pH 4.6 and 7.0. The net charge on the Tc-EDTA complex, measured at pH 7.0 only, was also -2.

Complexes of technetium with pyrophosphate, etidronate, and medronate

The reduction of [99Tc]pertechnetate was studied as a function of pH in complexing media of pyrophosphate, methylene diphosphonate (MDP), and ethane-1, hydroxy-1, and 1-diphosphonate (HEDP). Tast (sampled d-c) and normal-pulse polarography were used to study the reduction of pertechnetate, and normal-pulse polarography (sweeping in the anodic direction) to study the reoxidation of the products. Below pH 6 TcO4-was reduced to Tc(III), which could be reoxidized to Tc(IV). Above pH 10, TcO4-was reduced in two steps to Tc(V) and Tc(IV), each of which could be reoxidized to TcO4-. Between pH 6 and 10 the results differed according to the ligand present. In pyrophosphate and MDP, TcO4- was reduced in two steps to Tc(IV) and Tc(III); Tc(III) could be reoxidized in two steps to Tc(IV) and TcO4-. In HEDP, on the other hand, TcO4- was reduced in two steps to Tc(V) and Tc(III), and could be reoxidized to Tc(IV) and TcO4-. Additional waves were observed; they apparently led to unstable products.

Value of gallium-67 citrate scanning in Crohn's disease: concise communication

A frequent problem in Crohn's disease is the distinction between exacerbated inflammation of the bowel, which can be treated medically, and intra-abdominal abscess, a common complication that requires surgical management. We present evidence that the gallium scan is of value in making this distinction. From a series of 11 studies, negative gallium scans correctly excluded abscess in over half. All patients were symptomatic at the time of the scan. Most patients with active Crohn's disease do not have abnormal gallium uptake and in these patients the gallium scan is useful to exclude the possibility of abscess.