Radionuclide investigations of the urinary tract in the era of multimodality imaging

This article presents the role of nuclear medicine procedures in investigating renal and parenchymal disease, as well as upper urinary tract abnormalities. More specifically, the use of scintigraphy is described in the exploration of urinary tract dilatation and UTIs, vesicoureteric reflux, renovascular hypertension, and renal transplants. With a low radiation burden and the absence of sedation, these nuclear medicine procedures are easy to perform and can provide clinicians with valuable data on renal perfusion and the function of individual kidneys, as well as on urinary tract dynamics. However, knowledge of limitations and technical pitfalls is essential in understanding the role of scintigraphy among contemporary imaging methods and the unique information it supplies in nephrourology.

In vivo radionuclide uptake quantification using a multi-pinhole SPECT system to predict renal function in small animals

PURPOSE

In vivo quantification of radiopharmaceuticals has great potential as a tool in developing new drugs. We investigated the accuracy of in vivo quantification with multi-pinhole single-photon emission computed tomography (SPECT) in rats.

METHODS

Fifteen male Lewis rats with different stages of renal dysfunction were injected with 50 MBq 99mTc-dimercaptosuccinic acid. Four to six hours after injection, SPECT of the kidneys was acquired with a new four-headed multi-pinhole collimator camera. Immediately after imaging the rats were sacrificed and the kidneys were counted in a gamma-counter to determine the absorbed activity. SPECT data were reconstructed iteratively and regions of interest (ROIs) were drawn manually. The absolute activity in the ROIs was determined.

RESULTS

Uptake values ranging from 0.71% to 21.87% of the injected activity were measured. A very strong linear correlation was found between the determined activity in vivo and ex vivo (r2=0.946; slope m=1.059).

CONCLUSION

Quantification in vivo using this multi-pinhole SPECT system is highly accurate.

A dynamic renal phantom for nuclear medicine studies

Dynamic radionuclide renal study (renography) provides functional and structural information of the kidney and urinary tract noninvasively. Our purpose in this study is to describe the construction and test results of a dynamic renal phantom with different clinical features of radionuclide renography. The phantom consisted of five pieces of different shaped Plexiglas boxes: Two kidneys, one liver, two square shaped boxes (one heart and one bladder). The bladder was internally divided into two compartments in order to collect each kidney output separately. The dynamic circulation of the phantom was maintained under a hydrostatic pressure approximately equal to 13.3 kPa (average human blood pressure). The standard dose distribution among different organs and different renographic parameters were calculated from series of normal patients study (91 with 99mTc-DTPA, 68 with 99mTc-EC). All the studies were performed with same camera (Siemens Orbiter Digitrac 7500) equipped with LEAP (low energy all purpose) collimator using ADAC Pegasys II analytic package program under the same clinical procedure. Different regions of interest (ROIs) were drawn for concerning organs and counts per second (CPS) were collected for each ROI. The series of renogram curves were generated by phantom-studies with different flow rates for left kidney (LK) and right kidney (RK). The renal index (RI) for an individual study was calculated as the product of two indexes: "Relative Renal Function" (RRF) (water-volume of LK/RK) and "Relative Renal Time" (RRT) (Tmax of LK/RK). The most significant correlation was found in total CPS for LK and RK between the EC group and phantom studies (p < 0.001). The calculated RI values were used to simulate the patients' study with different clinical features. The dynamics were found reproducible. The phantom is suitable for using in calibration and quality control protocols of the renogram procedure used in Nuclear Medicine.

The gamma camera as an absolute measurement device: Determination of glomerular filtration rate in 99mTc-DTPA renography using a dual head gamma camera

AIM

The aim of this study was to design a general nuclear medicine method for fast, accurate and direct determination of the clearance of a radioactive indicator provided that all uptake compartments of the radioactive indicator could be included in the field of view of the gamma camera.

METHODS

The data material for clearance calculation in the gamma camera method (GCM) comprises: (1) a transmission map of a part of the body using a water filled flood field phantom with a uniform distribution of the radioisotope, (2) the background corrected activity curves in the anterior and posterior views over all uptake compartments following the injection of the radioactive indicator, and (3) the activity of the radioactive indicator in at least two blood samples drawn during the examination. With a view to determining glomerular filtration rate (GFR) in 99mTc-DTPA renography the gamma camera method was tested in a group of 26 adult subjects in whom GFR was determined simultaneously using the simplified multiple samples method (MSM) with plasma samples drawn 3-5 h following the injection of 51Cr-EDTA.

RESULTS

For values of GFR above 30 ml.min(-1) the regression line of GFR in the MSM versus GFR in the GCM was not significantly different from the line of identity. The reliability of the GCM alone was about 14%, 11% and 6% for GFR values of 30, 60 and 120 ml.min(-1) and, therefore, the reliability of the GCM and the simplified MSM for prediction of GFR was almost the same.

CONCLUSION

Since the recording of the renal count rates in the anterior and posterior views permits an accurate determination of the split renal function, the GCM yields reliable estimates also of the single kidney GFR.

New automated physical phantom for renography

Physical phantoms have been used to test the diagnostic proficiency of nuclear medicine professionals and the accuracy of their equipment in external quality assurance surveys. No dynamic renal phantoms are commercially available. A new renal phantom, presented in this paper, was constructed and patented in the United States.

METHODS

The organs to be simulated by the phantom were in the form of containers filled with radioactive solution, and the device further comprised movable steel and lead plates between the containers and the gamma-camera. The detectable radiation was regulated in accordance with automated computer-controlled step motors to move the attenuators to simulate a given patient situation. The reproducibility of the phantom measurements was defined as a coefficient of variation. Four different kidney-function simulations were repeated 3 times, and 6 parameters were compared.

RESULTS

The average root mean square deviation of the coefficient of variation was 6.7% for the perfusion integral, 1.3% for time to reach the maximum activity, 19.7% for mean transit time, 3.3% for function (Patlak [%]), 1.0% for outflow index (%), and 6.5% for time to reach the half-activity from maximum.

CONCLUSION

With this phantom, the true values of most parameters measured are well known; it closely approaches true extraction, washout, and attenuation properties and curves, and the images produced are similar to those of patient studies. Compared with the first manual version, this new automated phantom is easy to use. Any desired clinical situation can be programmed. It is a promising tool for quality assurance and calibration of renography.

[Morphologic and functional assessment of renal artery stenosis: use of combined MR angiography and MR renography--preliminary report]

PURPOSE

To assess the possibility of use of multiphase magnetic resonance angiography for simultaneous acquiring of angiographic images and curves of contrast enhancement of renal cortex, medulla and pyelocalyceal system and evaluation of quality of obtained images.

MATERIAL AND METHODS

Twenty-four patients suspected of having renal artery stenosis underwent power-injection of 30 ml of Gd-DTPA (3 ml/sec). From 10 to 360 seconds after the beginning of the injection, 3D MRA sequence was performed multiple times. Acquisition time of single phase of MR examination was 7.5-8 sec (TR = 5 ms, TE = 1:6 ms, single 7 cm thick slab with 35 partitions, 164 x 512 matrix). First three phases were used to obtain angiographic images. All phases were used to obtain curves of renal cortical, medullary and pyelocaliceal enhancement. Two readers evaluated quality of MRA images, as well as, quality of enhancement curves.

RESULTS

21 of 24 MRA examinations were of good, 2 of fair and none of poor quality. Quality of enhancement curves was good in 22 cases. It was suboptimal in 2 cases because of irregular breath-holding. Maximum number of acquisitions per minute was 4-5. Eight accessory, 2 obstructed and 9 stenosed renal arteries were visualized. Renographic curves were abnormal in 8 patients.

CONCLUSIONS

MRA sequence with short acquisition time enables simultaneous acquisition of angiographic images and renographic curves of good quality. With further reduction in acquisition time it may be possible to obtain more points on MR renographic curves.

Administered activity of 99Tcm-MAG3 for gamma camera renography in children

A method of calculating the activity of 99Tcm-MAG3 to be administered to children of different ages has been developed and evaluated. The suggested administered activity schedule is only valid for estimation of split renal function. The activity required to obtain the same count rate over the kidneys for all ages was calculated as a fraction of the activity administered to an adult by using a biokinetic model and taking attenuation effects into account. The activity schedule is based on the age of the child and was tested using renograms from patients of different ages. Statistical noise was added to the smoothed renograms simulating an injected activity corresponding to 45 MBq for an adult. The precision in the determination of split renal function calculated with four different methods was determined for 500 simulated renograms. The precision was approximately the same for all ages, but varied with the method used. The activity to be administered to a very small child is 90% of the adult activity, decreases to less than 50% between 2 and 5 years of age, and then slowly increases to 100% as the child grows to adulthood.

Consensus on renal cortical scintigraphy in children with urinary tract infection. Scientific Committee of Radionuclides in Nephrourology

A questionnaire related to cortical scintigraphy in children with urinary tract infection was submitted to 30 experts. A wide consensus was reached on several issues related to planar images: 99mTc dimercapto succinic acid (DMSA) appears as the most appropriate tracer for renal imaging; dynamic tracers are considered to be inferior, in particular 99mTc diethylenetriaminepentaacetate, which is not recommended. The general opinion is that DMSA scintigraphy is not feasible with a minimal dose below 15 MBq, whereas the maximum dose should not be higher than 110 MBq. The dose schedule generally is based on body surface area, and sedation is only exceptionally given to children. Images are obtained 2 to 3 hours after injection, preferably with high resolution collimators; pinhole images are used by only half of the experts. Posterior and posterior oblique views are used by most of the experts, and the posterior view is acquired in supine positions. At least 200.000 kcounts or 5 minute acquisition is required for nonzoomed images. As a quality control, experts check the presence of blurred or double outlines on the DMSA images. Color images are not used and experts report on film or directly on the computer screen. As far as normal DMSA images are concerned, most experts agree on several normal variants. Hydronephrosis is not a contraindication for DMSA scintigraphy but constitutes a pitfall. Differential renal function generally is measured, but no consensus is reached whether or not background should be subtracted. Most of the experts consider 45% as the lowest normal value. A consensus is reached on some scintigraphic aspects that are likely to improve and on some others that probably represent persistent sequelae. There is a wide consensus for the systematic use of DMSA scintigraphy for detection of renal sequelae, whereas only 58% of the experts are systematically performing this examination during the acute phase of infection.

A dynamic phantom for radionuclide renography

The aim of the study was to develop and test a dynamic phantom simulating radionuclide renography. The phantom consisted of five partly lead covered plastic containers simulating kidneys, heart, bladder and background (soft tissues, liver and spleen). Dynamics were performed with multiple movable steel plates between containers and a gamma camera. Control of the plates is performed manually with a stopwatch following exact time schedules. The containers were filled with activities (99mTc) which produce count rates close to clinical situations. Count rates produced by the phantom were compared with ten clinical renography cases: five 99mTc MAG3 and five 99mTc DTPA examinations. Two phantom simulations were repeated three times with separate fillings, acquisitions and analyses. Precision errors as a coefficient of variation (CV) of repeated measurements were calculated and theoretical values were compared with the corresponding measured ones. A multicentre comparison was made between 19 nuclear medicine laboratories and three clinical cases were simulated with the phantom. Correlations between count rates produced by the phantom and clinical studies were r = 0.964 for 99mTc MAG3 (p < 0.001) and 0.961 for 99mTc DTPA (p < 0.001). The precision error was 4.5 +/- 3.2% and the percentage difference between theoretical and measured values for Tmax was 4.0 +/- 1.6%. Images and curves of the scanned phantom were close to a real patient in all 19 laboratories but calculated parameters varied: the difference between theoretical and measured values for Tmax was 6.8 +/- 6.2%. The difference between laboratories is most probably due to variations in acquisition protocols and analysis programs: 19 laboratories with 18 different protocols and 8 different programs. The dynamics were found to be repeatable and suitable for calibration purposes for radionuclide renography programs and protocols as well as for multicentre comparisons.

[Kidney function based on dynamic nephroscintigraphic data in the late period after extracorporeal lithotripsy]

Dynamic nephroscintigraphy (DSG) was performed in 112 patients aged 14 to 76 years who had undergone 1 to 6 sessions of EL for unilateral or bilateral nephrolithiasis. A total of 254 EL sessions on 119 kidneys were performed. DSG was conducted before EL and at least 12 months after elimination of the stone fragments. The improvement of secretory renal function occurred in 68(57%) patients, aggravation was registered in 17(14.3%), unchanged renal function was in 34(28.6%) patients. Out of 17 cases of aggravation EL was responsible for only 3 of them. The others were due to other factors (progressive chronic pyelonephritis, acute pyelonephritis, hematoma, etc.). The conclusion is made that EL is a low-traumatic treatment of urolithiasis which is a method of choice in making decision on therapeutic policy in urolithiasis.

Effect of administered activity on precision in the assessment of renal function using gamma camera renography

Split and total renal function are commonly assessed from time-activity curves obtained from gamma camera renography with 99Tcm-diethylenetriamine pentaacetate (99Tcm-DTPA) and 99Tcm-mercaptoacetyl-triglycine (99Tcm-MAG3). The impact of the statistical noise associated with these curves on the total precision in split and total renal function impairment was studied at different levels of administered activity by simulation. The simulation consisted of generated time-activity curves, with statistical noise corresponding to the administration of 10-400 MBq 99Tcm-DTPA or 7.5-150 MBq 99Tcm-MAG3. Our results indicate that the error induced by statistical noise in split renal function calculations is generally very low (< 3% at 100 MBq 99Tcm-DTPA or 75 MBq 99Tcm-MAG3) and only affects precision slightly in calculations at 45-50 MBq 99Tcm or more. Similar results were obtained for precision in GFR calculations, where the total error increased from 12.3% at 100 MBq 99Tcm-DTPA to 12.8% at 50 MBq, but decreased to 12.0% at 400 MBq. Consequently, statistical noise has a minor effect on the precision in split and total renal function calculations at commonly used activity levels when it is reduced to approximately 50 MBq.

[The use of dynamic renal scintigraphy for studying kidney functional disorders in patients with different forms of hypercorticism]

Results are submitted of studying the function of the kidneys in 34 patients with Itsenko [correction of Icenko]-Cushing disease and syndrome, who were evaluated by dynamic renoscintigraphy besides routine clinical procedures. Dynamic renoscintigraphy was found to be an important diagnostic acid enabling one to disclose function disorders of the kidneys in the preclinical stage under normal routine investigations. In this setting, there have been revealed disturbances both in secretory-filtrational and excretory and aggregate functions of the kidneys practically in all the patients irrespective of the type of hypercorticoidism. Surgical treatment of hypercorticoidism does not lead to normalization of the function of the kidneys. And what is more, function disorders of the kidney on the side of the surgical intervention appear to be even more serious.

[The use of a new method for determining the ratio of the glomerular filtration rate to circulating plasma volume in patients with arterial hypertension]

Renal scintigrams with 99Tc-DTPA were analysed retrospectively in 19 patients with essential hypertension. Glomerular filtration rate (GFR) was measured by Gates technique. Ratio GFR to plasma volume (PV) was quantified by A. M. Peters' technique (1994). PV was calculated as the relation of these two indices. Total GFR in hypertensive patients widely ranged (from 76.8 ml/min to 165.7 ml/min). Three groups were selected taking into account hypertension duration: patients with decreased, normal and increased values of basal GFR. The severity of hypertension did not affect the GFR, but showed positive and strong correlation with PV (r = 0.91; p < 0.05). GFR/PV was decreased in hypertensive patients. Factors affecting the GFR in hypertensive subjects are discussed.

Determination of the relative glomerular filtration rate of each kidney in man. Comparison between iohexol CT and 99mTc-DTPA scintigraphy

Iohexol and 99mTc-DTPA were used in 43 patients to determine the relative glomerular filtration rate (GFR), i.e., the GFR of each kidney in percent of total GFR. The amount of any GFR marker accumulating in Bowman's space, tubuli and renal pelvis within a few minutes after i.v. injection, before any marker had left the kidney via the ureter, was defined as proportional to the GFR of that kidney. The renal accumulation of iohexol was determined by CT using 10 slices of 8-mm thickness 1 to 4 minutes after injection. The renal accumulation of 99mTc-DTPA was determined with a gamma camera within 2 minutes after injection. The correlation coefficient between the two methods was 0.98. Due to the higher radiation dose from CT than from 99mTc-DTPA injection, relative GFR determination with CT should be performed when there is also a diagnostic need to reveal morphology.

DMSA scintigraphy in renal duplex system

During a 4-year period 40 children (13 boys and 27 girls) with renal duplex system were examined with DMSA scintigraphy. The age at the investigation varied from 18 days to 9 years, mean 2.5 years. Duplicated system existed in 52 kidneys, bilaterally in 12 cases, right-sided in 10 and left-sided in 18 cases. The renal DMSA scintigraphy of the 52 duplicated kidneys revealed insignificant parenchymal damage in 19 kidneys. Moderate parenchymal damage existed in 10 kidneys. In the remaining 23 kidneys, severely deteriorated function of the upper moiety was found in 15 cases and of the lower pole in 9 cases, as both moieties were affected in one kidney. The function of the severely deteriorated moiety varied between 0% and 14%, mean 5.7% of the total renal function. All the 23 cases with severely deteriorated function were operated upon, 22 with heminephrectomy and one with nephrectomy. The assessment of parenchymal function of the separate parts of the kidney with duplex system by DMSA scintigraphy is of great value in the decision of management and surgical procedure.

Inaccuracies in quantitative radionuclide renal imaging due to patient position or diverging collimation

Radionuclide renal studies with quantitative measurements in patients confined to intensive care units usually require the use of a 10-inch field-of-view mobile gamma camera and a diverging collimator to image both kidneys simultaneously. The patient must frequently be in the lateral decubitus position so imaging can be performed in the posterior projection. Due to spatial distortion caused by the diverging collimator, variations in detector angulation and kidney depth produce different detection efficiencies for each kidney. Counts in regions of interest over the kidneys were compared as a function of detector angulation and patient position (prone and lateral decubitus). Substantial variations were observed comparing the diverging collimator data to 15-inch field-of view parallel hole acquisitions. Significant variation can also be obtained with parallel hole collimators when the patient's position is changed.

A dose-attenuation shield for use in glomerular filtration rate computations. A method for combined renal scintiangiography and functional quantification

Renal perfusion and function can be determined by renography using Tc-99m DTPA. However, the high dose of tracer necessary for scintiangiography may result in inaccurate syringe-count determinations when measured by the gamma camera necessary for calculating the glomerular filtration rate by a camera technique. This report describes a syringe shield, constructed at minimal cost, which allows for suitable count attenuation and use of high doses of tracer for assessment of both renal perfusion and function.

[A comparison of two algorithms for determining renal whole body clearance following simultaneous acquisition with a partially shielded whole-body counter and a gamma camera]

The influence of instrumentation, algorithm, and the time of blood sampling on whole-body renal clearance as defined by effective renal plasma flow (ERPF) was investigated. The study involved simultaneous sampling with a partially shielded whole-body counter (WBC) and a gamma camera to assess ERPF. The results obtained using two different analysis algorithms for each modality are compared. Although ERPF as determined by the Oberhausen technique was significantly higher than that obtained using an algorithm developed by the authors, for each algorithm there was no significant difference between the WBC and gamma camera-derived values within the range of 100 to 800 ml/min. Furthermore, positioning of the ROI was not critical for gamma camera-derived ERPF (SD less than 1% for multiple crescentic ROIs and approximately 4% for multiple rectangular ROIs). However, the time of blood sampling did appear more important since the average ERPF derived from the 10- and 20-min samples compared with that from the 15- and 25-min samples differed significantly for both analysis algorithms. The methodology which we have validated provides a more precise tool for further investigations of the influence of medication, posture, and exercise stress on renal function.

[A comparative evaluation of iodine-131 OIH and technetium-99m MAG3 in the study of renal function]

A new renal imaging agent, 99mTc mercaptoacetyltriglycine (MAG3), has been recently proposed in the nuclear medicine evaluation of renal function. Just like 131 orthoiodohippurate (OIH), 99mTc MAG3 is removed mainly by the renal tubules. An heterogeneous group of 39 patients underwent a radioisotopic study with the simultaneous injection of OIH (131I) and 99mTc MAG3. Image quality was found to be better with 99mTc MAG3 than with OIH (131I), because the former always allowed renal regions of interest (ROI) to be clearly demonstrated, even in case of severe renal impairment. A quantitative analysis was also carried out: effective renal plasma flow (ERPF) values were compared with renographic peak times evaluated by using both radiotracers. Our results demonstrate a firm correlation to exist between the informative content yielded by 99mTc MAG3 and by OIH (131I). Absolute ERPF value was higher with MAG3, but the correlation index (r = 0.98) allowed a simple correction factor to be introduced. In conclusion, MAG3 appears to be a good alternative to OIH.

Renal scans in pregnant transplant patients

This study demonstrates the normal technetium-99m diethylenetriaminepentaacetic acid ([99mTc]DTPA) renal scan in pregnant patients with transplanted kidneys. Five pregnant renal transplant patients had seven [99mTc]DTPA renal studies to assess allograft perfusion and function. All scans showed the uteroplacental complex. The bladder was always compressed and distorted. The transplanted kidney was frequently rotated to a more vertical position. In all patients allograft flow and function were maintained. There was calyceal retention on all studies and ureteral retention activity in three of five patients. Using the MIRD formalism, the total radiation absorbed dose to the fetus was calculated to be 271 mrad. This radiation exposure is well within NRCP limits for the fetus of radiation workers and an acceptable low risk in the management of these high risk obstetric patients.

[Determination of effective renal plasma flow based on data from dynamic renoscintigraphy with 131I-hippuran]

The paper is concerned with a comparative study of 2 methods of calculation of the separate effective renal plasma flow (ERPF)--by hippuran clearance and hippuran absorption by the kidneys on the 2nd minute of renoscintigraphic investigation. The latter one was characterized by some advantages: the use of routine scintigraphy, the absence of blood and urine tests, rapid performance, the accuracy of the results obtained was no inferior to that of ERPF calculation by clearance. The method was included in an application package for scintigraphy data processing. A study of the ERPF was conducted in 140 patients with nephroureterolithiasis in the time course of surgical treatment. The results have shown that the ERPF can be used not only for the control of therapeutic efficacy but also for the prognosis of postoperative restoration of affected kidney function. The determination of the total ERPF and a degree of asymmetry of its distribution is of great prognostic importance.

[Use of the Renodinamika-81 automated system of acquisition, storage and processing of radionuclide renography data in mass screening studies]

An automated Renodinamika-81 system was used for examination of 212 students to detect latent pathology of the urinary system. Renography by a common method with simultaneous data recording on a punched tape was performed. The software was based on the FORTRAN language for SM-4 computers. Changes were detected in 20.7% of the students. The Renodinamika-81 system was recommended for early examination of patients identified as a risk group during mass screening of the population.

A trial of automatic kidney detection in a dynamic renal study

We developed an automatic kidney detection procedure designed to do away with extraneous margins such as the liver or spleen while leaving the kidney margins intact using Laplacian operations and concurrence calculations. We evaluated the detectability of kidneys using our procedures and found that the renal margins were successfully detected in 84 cases of 100 subjects (84%) including 176 kidneys out of a total of 198 kidneys (89%). It was shown that as the renal function decreased the detectability of the renal margin decreased. In eight cases (16 kidneys) out of 9 patients who later resultantly received hemodialysis even manual settings of the renal ROI were very difficult. After excluding these 8 cases the detectability was 92% for all the cases and 95% for the kidneys. It was our conclusion that this method is sufficient for clinical application.

Micturition detection switch

Micturating renograms often need to be carried out on children, with whom difficulty may be experienced in synchronizing onset of micturition with camera and computer acquisition. A flow detection system has been developed which will automate these acquisitions, resulting in far fewer false starts or lost studies. The unit was developed specifically for the camera/computer system in our department (IGE 400T and DEC 11/34) but with only minor modifications would be suitable for interfacing to other equipment. It is a free standing unit which requires no modifications of the camera or computer circuitry apart from access to the remote start buttons.

[Automation of renographic studies using a microcomputer]

The paper is concerned with the results of the automation of renogram storage and processing. The computer system 15 VUMS-28 (on the basis of the ELEKTRONIKA-60 computer) fitted out with storage on the magnetic tape (KML) AZII-4, two 3-channel renographs (NP-356 and NP-307), manufactured in Hungary, and a plotter N-306 were interfaced by means of the KAMAK apparatus. The REN-1 program in the QUASIC language ensuring simultaneous storage and processing of renograms from two renographs was developed. The maximum time (Tmax) and semiexcretion time (T 1/2) as well as a system of indicators based on a linear chamber model of hippuran transport were used for analysis of renograms.

[Radionuclide evaluation of the function of the operated kidneys]

Altogether 68 patients were examined in early and late periods after operations on the kidneys. Function of the operated kidney was checked up by the results of two-indicator renal scintigraphy with 99mTc-DTPA and 131I-hippuran. When the kidney preserved its secretory capability and the suppression of organ function was caused by inhibited urine passage via the upper urinary tract, therapy aimed at the restoration of the kidney integrity and the elimination of the urine discharge obstruction, resulted in a rapid and complete recovery of all renal functions. Operative treatment of prolonged urological diseases complicated by chronic pyelonephritis, helped to accelerate secretory-excretory processes and slightly improved function of unchanged nephrons. A progressive decrease in the actively functioning parenchyma was recorded on scintigrams in 28% of the cases of the formation of the arteriosclerotic kidney. The authors found radionuclide investigations appropriate in the postoperative period not only in the development of complications and recurrences of urological diseases. Two-indicator renal scintigraphy with glomerulotropic and tubulotropic radiopharmaceuticals made it possible to give an objective assessment of the efficacy of surgical intervention.

The individual kidney function. A comparison between frame summation and deconvolution

A variety of methods have been developed to estimate the individual kidney function. Many methods use a scintillation camera the data from which are processed in a computer system. To compare two of these methods, the principles of which are completely different, such as the 'Oberhausen' method of frame summation and background subtraction and a method that uses deconvolution, the scintillation camera data of 121 patients have been collected. A computer program was written to calculate the individual kidney function by which both methods were used. It is often asserted that specific techniques of frame summation and background subtraction are not suitable to define the individual kidney function. To see if this assertion is true, two different methods have been compared using the contribution of the left kidney to the individual kidney function. An excellent correlation between the two methods was found (R = 0.9808, n = 121) which proves the ability of both the 'Oberhausen' method and the method that uses deconvolution. However, it is also seen that the 'Oberhausen' method may give false results, caused by an increasing background count outside the kidneys in patients with a large difference in function between the two kidneys.

Estimating the effective renal plasma flow from the hippurate renogram

A method for estimating the effective renal plasma flow (ERPF) from renograms is presented. Renograms obtained in 91 patients were used to test the method. The clearance values derived from renography were compared with those obtained with infusion clearance. It was shown that the ERPF was able to be estimated from the renogram with a standard error of +/- 94 ml min-1.

A comprehensive analysis of renal DTPA studies. I. Theory and normal values

Gamma camera renograms, using DTPA, were analysed to obtain flow rates and transit times during the initial arterial phase (0-36 s) and the later glomerular phase (37 s onwards). This paper outlines the underlying theory, and the effect of age on all the variables, calculated from patients with normal renal function.

A microprogrammed data acquisition system for renography

The purpose of this project was to design an efficient, low cost, and portable system for renography suitable for clinical use. The principles involved in the renographic test, and the procedures and calculations which act on the design of our system, are given. The system consists of an Apple II Plus computer equipped with 48K memory, two disk drives with diskettes of 143K each, a thermal printer with graphic capability, the Microsoft Z80 card, and an interface which is specifically designed for renographic data acquisition.

[Radionuclide studies with a dynamic kidney phantom]

Altogether 120 studies with a dynamic kidney phantom (DKP) were conducted permitting one to imitate the normal functioning of the kidneys or different pathological states of the organ. The studies were conducted with the help of a gamma-chamber of MV-9100 type using a computer system SEGAMS (Hungary) and a chronoscope RIKh-5M-01. On completion of the experiment the activity-time curves were plotted characterizing the time course of the passage of a radioactive tracer through phantom cylinders that imitate the kidneys. The results obtained have demonstrated DKP potentialities for the imitation of various renal functional states. Studies with a DKP make it possible to select an optimum regimen for research and to assess the quality of performance of nuclear medical diagnostic equipment.

[Determination of the amount of functioning renal parenchyma based on multipositional scintigraphy data]

The paper is concerned with mathematical calculations of two methods to determine the amount of the functioning renal parenchyma using the polyposition statistic scintigraphy data. These methods are used to determine the depth of kidney location from the body surface in the lumbar region. An analysis of polyposition scintigraphy of 122 patients without tumor lesion has shown that in 41.7% of the cases the difference in the depth of location was over 1 cm. in 13.1% over 2 cm and in 5.7% over 3 cm. If one of the kidneys is shifted forward by 3 cm, in scintigraphy gamma-irradiation from this kidney for 99mTc will be weakened more than 1.5 times, and for 197Hg more than 1.75 times. It is only in renal insufficiency and in obese patients that the method of estimated RPD accumulation in the kidneys with regard to lateral projections is the best as compared to that using the results of scintigraphy of front and back projections.

Scintillation camera renography with 99mTc-DTPA and 131I-Hippuran

Two different indicators for scintillation camera renography, 99mTc-DTPA and 131I-Hippuran, were compared directly in 37 patients. Quantitative data were obtained by means of a small digital computer. 99mTc-DTPA gave better kidney image quality, but also higher background than 131I-Hippuran. The two indicators gave renographic curves of slightly different shape, those after DPTA being flatter, but estimations of separate kidney function were not significantly different. Early kidney uptake of indicators was roughly proportional to glomerular filtration rate, but with a wide scatter.

Background correction factors in renography with single probe detectors

The background correction factor was determined with [131I]albumin, FA, in eighty-six patients with various nephro-urological diseases, with [131I]hippuran in eighty unilaterally nephrectomized patients (FH), and in twenty-five patients in whom the renogram showed background configuration, FH, B. FH was approximately the same on the left and the right side, the mean values being 1.39 and 1.35, respectively. FA showed a significant side difference, the mean values being 1.30 and 1.19 on the right side, respectively. FH, B was higher than FH, which shows that some uptake of hippuran can take place in apparently non functioning kidneys.

A simple method of background subtraction in two-detector renography

To increase the accuracy in the routine measurement of the side distribution of kidney function from 131I-Hippuran renograms, a simple method of background subtraction has been developed. Principally a background curve was adapted to the renogram on each side, assuming an initial amplitude corresponding to the amplitude of phase I of the renogram. The amplitudes of the renogram over background after 2 min is recognized as a measured of kidney function and a background quotient was calculated by dividing the background curve amplitude at 2 min with its initial amplitude. Mean values of the background quotient recorder over thorax was 0.62 and over an empty kidney region 0.73. It was found that a quotient of 0.70 could be used generally, thus omitting the need for a background curve registration at each renographic examination.

Methodological aspects of renography in children

Kidney function in children by renography has been evaluated. For reproducible results a high degree of standardization with respect to position, hydration and dosage was necessary. The wide range of kidney size and depth in children requires age-adapted collimators. For practical use for different size have been constructed for the age-groups: less 1 year, 1-5 years, 6-9 years and 10-15 years. A reduction in the surrounding activity of the kidneys is thereby obtained and disturbing influence from the bladder or contralateral kidney is prevented. Kidney function variables from the renogram are presented in terms of uptake and excretion ratios. The correlation between sum of uptake ratios and clearance measurements is good in cases with slight or moderate difference in kidney size. The standardized renographic technique has many advantages for kidney function measurements in children. The method is applicable in all ages, it is simple and reliable without extensive preparations and requires a low radiation dose. Also in children we can confirm the previous opinion obtained in adults that renography is a clinical valuable method of measuring kidney function.

A method for subtraction of the extrarenal "background" in dynamic 131I-hippurate renoscintigraphy

Using a Toshiba GC-401 gamma camera with MDS computer Trinary a new method was developed for subtracting the extrarenal (extracanalicular) "background" from the count rate recorded over the kidneys after intravenous administration of 131I-hippurate. Mean subtraction factors of the "blood" activity curve were calculated from a study of 27 patients who were given 51Cr-HSA for purposes of conventional renography with "background" subtraction. The values of the mean subtraction factors FR,L for the right and left kidney, by which a blood count rate should be multiplied amounted to 0.86 +/- 0.12 and 0.79 +/- 0.13, respectively. A comparison of the coefficients of variation of the pure renal signal when mean vs. individually determined subtraction factors were used, and the verification of the method in unilaterally nephrectomized patients have demonstrated that determination of the factors, FR,L, for each patient individually is not required and sufficient precision can be obtained by using the method and factors reported in this study.

Renography in the foetal and newborn lamb

Hippuran renography indicates kidney function as reflected in a substance handled mainly by the tubules. The working conditions of the kidneys undergo a fundamental change at birth with the cessation of placenta circulation, and these organs become responsible for waste elimination. 131I-hippuran renography was performed on foetal and newborn lambs using a gamma camera and a computer. The intervals of the maximum- and half-time renal activity were determined. These decreased by a half from mean foetal value of Tm=7 mi and T12=19 min in 1 to 1.5 days and reached the full-grown level in 2 to 5 weeks. No sudden change occurred as a result of the first breath.