Concentration of orally administered and chronically fed 95mTc in Japanese quail eggs

A chronic feeding study using 95mTc incorporated into alfalfa and an acute study where 95mTc was amended to alfalfa showed that about 8.4% of ingested Tc was transferred to eggs. After 10 days of chronic feeding, 80% of the Tc was in yolk, 20% in albumin and less than 1% in shell and associated membranes. At necropsy, technetium concentrations in the three largest oocytes were nearly equal. The biological half-time for Tc was about one to two days in acute studies. Results from the chronic feeding study also indicated that Tc levels in albumin reach a maximum between three and five days while maximum yolk concentration is attained in about six to seven days. Albumin concentrations declined about 20-50% after Day 6.

Radioactive implant induced x-ray emission technique for noninvasive determination of iodine content in thyroid: experimental study

A new technique, radioactive implant x-ray emission spectrometry to determine the in vivo iodine content of the human thyroid is proposed. The variations of counting rate and effective excitation efficiencies of I K alpha (28.6 keV) with iodine content, thyroid volume and skin-thyroid distance were studied for the 201Tl source to examine the properties of excitation and photon attenuation. As a result, the gland depth and volume could be estimated from the peak ratios of 30.7 keV/167.6 keV and 28.6 keV/167.6 keV. Using a 1 MBq 201Tl implant source, the detectable minimum iodine concentration found was approximately 70 micrograms/g for 2000 s measuring time in the phantom experiment. The effectiveness of the RIXE technique is discussed. It was concluded that the 201Tl RIXE spectrometry might serve to determine the in vivo iodine content of the human thyroid.

Single injection techniques in determining age-related changes in porcine renal function

Glomerular filtration rate (GFR) and effective renal plasma flow (ERPF) were determined in 32 anaesthetised female Large pigs, aged 4-24 months, from the plasma disappearance curves of [99mTc]DTPA and [131I]hippuran respectively. Clearance was also monitored by external counting over the heart. GFR and ERPF increased markedly with age in pigs up to 12 months old, reaching mean values of 242.06 +/- 5.89 and 919.39 +/- 79.01 mL/min. In pigs aged 12-24 months ERPF increased slightly, but renal function remained essentially unchanged after 1 yr of age. These results for renal function were similar to previous estimates, using continuous infusion techniques inferring that GFR and ERPF could be accurately monitored using single injection procedures.

A direct comparison between subcutaneous and intralymphatic injections for lymphoscintigraphy

Lymphoscintigraphy using 99mTc colloids has been proposed as a simple adjunct to lymphangiography. To validate the technique of subcutaneous injection we performed a direct comparison between intralymphatic and subcutaneous administration of 99mTc-antimony colloid. In all cases excellent correspondence was obtained between the two techniques. Lymphoscintigraphy does not provide the same morphological information as lymphangiography, but can provide useful data regarding lymphatic obstruction.

Intraperitoneal injection of technetium-99m sulfur colloid in visualization of a peritoneo-vaginalis connection

Ten minutes after an intraperitoneal infusion of Tc-99m sulfur colloid, a gamma camera was used to obtain anterior abdominal views. This visualized a peritoneoscrotal communication in an 80-yr-old patient. He had developed extensive edema of the genitals and lower limbs after about 6 wk of continuous ambulatory peritoneal dialysis. At operation the communication was confirmed and closed. A repeat test verified the success of operation.

[Clinical usefulness of lymphoscintigraphy by rectal submucosal injection of radioactive colloid]

Lymphoscintigraphies about 27 cases were examined by the methods of 11 cases of anal subcutaneous and 17 cases of rectal submucosal injections of 99mTc-rhenium colloid. Para-aortic nodes and common iliac nodes were visualized in more than 70% out of the 27 cases by these methods, and those images were superior to images obtained by the conventional methods with pedal subcutaneous injections. Internal iliac nodes were visualized in 78.1% by the rectal injection method while in 27.3% by the anal injection method. It was concluded that the transrectal injection method should be used to visualize internal iliac nodes. Examination efficacies of lymphoscintigraphies by these methods on detection of lymph nodes metastases which were confirmed by autopsy, operation, contrast lymphoangiography and/or X-ray CT. As for 131 regions of rectal and anal injected cases, sensitivity was calculated at 84.0% and specificity was at 89.6%. When the cases in which more than one definite defect was detected were scintigraphycally diagnosed as positive to metastasis and when calculated case by case, sensitivity was calculated at 90.9% and specificity was at 62.5% in the 27 cases. Lymphatic systems were seen specifically and systematically by using lymphoscintigraphies. Though the sensitivity was not enough for a screening test of lymph node metastases and the specificity was not enough for a test to rule out lymph node metastases, lymphoscintigraphies are clinically very useful as supplementary examinations. The lymphoscintigraphy by the method of rectal submucosal injection is much more useful as it is convenient and is the only one method to visualize the internal iliac nodes systematically.

Extravasation from venous catheter: a serious complication potentially missed by lung imaging

Three patients were referred for lung ventilation and perfusion (V/Q) imaging with symptoms strongly suggestive of pulmonary embolus (PE). Chest roentgenograms and xenon ventilation studies on all three were normal, save for prominent mediastinal silhouettes and effusions. Technetium-99m macroaggregated albumin (Tc-99m MAA), when injected through the central venous catheter (CVP), revealed mediastinal localization, whereas antecubital injections showed normal pulmonary perfusion. Contrast fluoroscopy introduced through the venous catheter in the first patient defined the extravasation. For patients under strong suspicion of PE, with a venous catheter whose distal tip is seen about the level of the heart on chest radiograph, we recommend administering the perfusion agent slowly through the central catheter to exclude catheter-induced complications. When extravasation is detected, injection of Tc-99m MAA by peripheral vein should be used to exclude PE.

[Radiation dosage to staff during administration of pharmaceutical preparations labeled with 99m Tc]

The paper is concerned with the characteristics of irradiation doses the staff-members are exposed to at one of the most important stages of a radiodiagnostic study: administration of 99mTc-labeled radiopharmaceutical drugs. Proceeding from an analysis of technological peculiarities of this stage the authors propose recommendations to decrease dose exposures of the hands and body of the staff-members engaged in the administration of radiopharmaceutical drugs.

Myocardial perfusion imaging with 99mTc-DMPE in man

Technetium-99m DMPE (99mTc-DMPE) is a newly synthesized myocardial perfusion imaging agent that shows intense myocardial accumulation in the dog. In the present study, dosimetry and potential clinical usefulness of this agent were assessed in four human subjects. Absorbed radiation doses were low, with the highest doses consisting of 200 mrad/mCi (54 microGy/MBq) to the gallbladder and 160 mrad/mCi (43 microGy/MBq) to the liver. No evidence of clinical toxicity was found. Technetium-99m DMPE did image the myocardium, but the ratio of target to nontarget activity was less favorable than that observed in the dog. Intense hepatic 99mTc-DMPE activity interfered with clinical imaging of the cardiac apex in two of the four subjects. We conclude that the prototype radiopharmaceutical, 99mTc-DMPE, is capable of myocardial perfusion imaging in man but the planar myocardial images produced are of inferior quality compared with 201Tl myocardial images. Further work is justified to develop related compounds to overcome the clinical limitations described.

Radiation dose estimates for oral agents used in upper gastrointestinal disease

Radiation dosimetry was calculated for a number of orally administered radiopharmaceuticals used for study of upper gastrointestinal function. These include: Tc-99m sulfur colloid in water, in a cooked egg, and in chicken liver labeled in vivo; In-111 DTPA; Tc-99m DTPA; In-113m DTPA; Tc-99m ovalbumin in cooked egg; and In-111 colloid in chicken liver labeled in vivo. Radiation burdens to the stomach, small intestine, upper and lower large intestine, ovaries, testes, and total body are calculated for each preparation.

Radiation dose calculations for inhalation of Tc-99m sulfur colloid radioaerosol

The radiation dose to the lung from the administration of Tc-99m sulfur colloid aerosol (for ventilation investigations) has been calculated. The dose to the ciliated airway epithelium varies between 0.34 to 2.5 rads, compared with 0.31 rads to the lung parenchyma. The calculation was normalized to a total of 1 mCi of Tc-99m deposited in the lung.

Mean transit time image--a new method of analyzing brain perfusion studies

Point-by-point calculation of the mean transit time based on gamma fit was used to analyze brain perfusion studies in a vertex view. The algorithm and preliminary results in normal brain and in different stages of cerebral perfusion abnormality (ischemia, stroke, migraine, tumor, abscess) are demonstrated. In contrast to the traditional methods using fixed, a priori defined regions of interest this type of mapping of the relative regional cerebral perfusion shows more clearly the irregular outlines of the disturbance. Right to left activity ratios in the arterial part of the time-activity curves showed significant correlation with the mean transit time ratios (Qt = 1.185 - 0.192 Qa, n = 38, r = 0.716, P less than 0.001).

Early behaviour of 99mTc-pertechnetate in the head after intravenous bolus injection: its relevance to the cerebral blood circulation

The relative differences between the behavior of 99mTc-pertechnetate (Tc) and both, non-diffusible and diffusible reference tracers in the head were evaluated by a statistical comparison of their time-activity curves in blood, brain and some tissues underlying the brain, after IV injection in the rat. This study showed that the particular cephalic behaviour of Tc was neither similar to that of diffusible tracers (even with restricted diffusion) nor equivalent to that of a non-diffusible tracer in the whole head. Although Tc is not an intravascular tracer in the entire cephalic volume, it was demonstrated that the initial peak characterizing the dilution of this tracer in the head is exclusively generated by its first passage in the cerebral circulation, even if the blood flow rate is changed. To extract from this initial peak a first dilution curve relevant to the cerebral circulation, Tc kinetics in the head were considered as a two compartmental model. Assuming that the maximum uptake of tracer was reached at the same time in both compartments of this model, the disappearance of Tc from the fast compartment approximates the first dilution curve of Tc in the fast cerebral circulation, if the slope of the Tc disappearance curve from the slow compartment is assimilated to a plateau.

[Advantages of the combined use of nuclear medicine procedures in the diagnosis of coronary disease]

Investigations on 106 patients with coronary artery disease were performed to improve the diagnosis of myocardial ischemia by combining myocardial scintigraphy and gated blood studies. The results show that it is possible to enhance the detection of coronary artery disease and to classify haemodynamic efficiency. In addition we found that in investigations performed on patients with arrhythmia and under stress conditions the "hybrid-technique" is superior to the framemode acquisition method.

The isotope clearance technique for measuring skin blood flow

The measurement of skin blood flow using the isotope clearance technique has been investigated in pig skin. The isotope used was technetium-99m; this was shown to be freely diffusible in skin. The volume injected (0.02 to 0.3 ml) did not affect the clearance parameters. Bi-exponential clearance curves were always obtained in normal pig skin. An analysis of what parameters of blood flow are indicated by the two exponents has been made by correlating changes in clearance parameters (animal age and depth of injection) with changes in vascular density and dermal thickness. It is suggested that the fast and slow clearance parameters are derived from clearance by capillaries in the papillary and reticular regions of the dermis respectively. Further evidence in support of this hypothesis was derived from the application of the clearance technique in skin traumatised by surgery (pedicle skin flaps) or x-irradiation. The value of the isotope clearance technique in the measurement of nutrient flow in the dermis is discussed.

[Ventilation scintigraphy of the lung with 99mTc-DTPA or with 99mTc-sulfur colloid?]

Ventilation scintigraphy of the lung, obtained with sufficiently small 99mTc-labelled aerosol particles, provides an image of ventilation distribution that is acceptable in clinical routine. Whether 99mTc-DTPA or 99mTc-sulfur colloid is more suitable as a carrier was studied in 6 smokers and 8 non-smokers with chronic obstructive pulmonary disease. 99mTc-sulfur colloid was not absorbed by the bronchial mucosa and therefore appears to be an almost ideal agent. In contrast, 99mTc-DTPA was absorbed by the bronchial mucosa in all smoking patients more rapidly and inhomogenously than in non-smokers. The quantitative and qualitative comparison of the two dorsal ventilation scans taken both immediately after inhalation and 20 min later, showed in all 6 smoking patients after 20 min significant differences which influenced the diagnosis result. 99mTC-DTPA is therefore not recommended for use in ventilation lung scintigraphy, especially in smoking patients.

Deconvolution analysis of radionuclide angiocardiography curves: problems arising from fragmented bolus injections

Deconvolution analysis of radionuclide angiocardiography time-activity curves (TAC) in the cases of fragmented bolus injections was studied by using a new deconvolution technique based on the maximum a posteriori estimator. This method was first tested by simulation studies which showed its capability for accurate handling of deconvolution both for single and double peak input functions. These simulations have proved this technique to have advantages over a Fourier transform division method used with a low-pass filter. In patient studies, deconvolution of pulmonary TAC by superior vena caval TAC produced poor results in double peak (fragmented) bolus injections, compared with single peak bolus injections (SPBI). This discrepancy seems to be due to the fact that the postulates of linearity and invariance, on which deconvolution analysis is based, do not hold for the 'cardiopulmonary system' which extends from the superior vena cava to the lung. The differences between the model and the real system appear unimportant for SPBI. However, differences become apparent for fragmented bolus injections. Deconvolution analysis should be avoided with this type of input function in this cardiopulmonary system.

Evaluation of renal function parameters with simultaneously administered 99mTc-DTPA and 131I-hippuran

The present study aimed at comparing two renal function tests using 99mTc-DTPA (diethylene triamine penta acetic acid) and 131I-labeled hippuran (o-hippuric acid). A mixture of 80 MBq 99mTc-DTPA and 7.4 MBq 131I-hippuran in a total volume of 1.5 ml or less was injected into an arm-vein. Both radiopharmaceuticals have identical initial distributions in the blood pool when injected in this manner. Seventy-two patients were studied with the present dual radionuclide technique. The following parameters were derived from the renogram: area under curve, uptake ratio, Tmax, decrease ratio, excretion ratio, and rate of decrease. The parameters for 99mTc-DTPA and 131I-hippuran were compared for various kidney groups. Generally the renographic parameters were well correlated. Apart from the systematic differences due to different modes of renal excretion, the curve patterns virtually agreed. The differences that were observed between the two tracers lacked clinical significance.

Rapidly reversible alterations of pulmonary epithelial permeability induced by smoking

A radioaerosol procedure using 99mcTc-DTPA (diethylene triamine penta acetate) was used to evaluate the permeability of the pulmonary epithelium in smokers and nonsmokers. The average clearance of this indicator from the lungs of smokers without significant airway obstruction exceeded that found in normal subjects by an average factor of more than five. This abnormality was observed throughout all lung regions. 99mTc-DTPA clearance decreased rapidly during the week after smoking was discontinued. It is concluded that smoking results in a rapidly reversible increase in pulmonary epithelial permeability.

Radiation dose estimates for interstitial radiocolloid lymphoscintigraphy

The spatial distribution of radioactivity in the injection site, and its rate of clearance, have been measured in patients undergoing various types of interstitial radiocolloid lymphoscintigraphy using 99mTc-antimony sulfide colloid. The clearance of radioactivity from the injection site, and the expansion with time of the localized radioactivity vary considerably for different sites of injection. Maximum absorbed dose estimates of 45.6 rads to the center of the injection site (rectus sheath) and 21 rads to individual lymph nodes have been calculated for patients undergoing internal mammary lymphoscintigraphy with 450 mu Ci injected radioactivity. Absorbed dose estimates for finger web, toe web, and perianal injection sites are also presented.

Iliopelvic lymphoscintigraphy

In patients with genitourinary cancers, it is critically important that lymph node metastases be detected prior to surgery. Information regarding the status of these nodes will influence the type and extent of therapy. Radiologic tests currently available for lymph node imaging--contrast lymphangiography, ultrasound, and computed tomography--are sometimes associated with a high false-negative rate. Iliopelvic lymphoscintigraphy, when performed following bilateral perianal injections of 99mTc-antimony trisulfide colloid, offers a physiologic method for visualizing these nodes and allows demonstration of the internal iliac chain, often not visualized on contrast lymphangiographic studies. Additionally, data from initial patient trials suggest that this technique offers a clinically acceptable level of sensitivity and specificity. This article details the methodology of the technique, and addresses reproducibility, sensitivity, specificity, and image interpretation.

Lymphoscintigraphy in gynecologic malignancies

Lymphoscintigraphy is an easily performed noninvasive procedure that offers the potential to detect small numbers of ascitic tumor cells and early diaphragmatic tumor involvement. Moreover, it can be used to delineate and define abnormalities in lymph nodes that are not routinely visualized by bipedal contrast lymphangiography, ultrasound or computed tomography. Lymphoscintigraphy is recommended as an important investigative and adjunctive procedure in diagnosing gynecologic malignancies; there does not appear to be sufficient sensitivity and specificity to justify its routine clinical use.

Control of the carcinogenic potential of 99mTechnetium by the immunologic hormone lymphotoxin

Immunologic prevention of the carcinogenicity of the diagnostic gamma-emitting radionuclide 99mTechnetium (99mTc) by lymphotoxin was evaluated using an in vivo-in vitro assay of carcinogenesis. Pregnant Syrian golden hamsters received 125-2,300 microCi 99mTc/kg body weight by injection, and 7 days later colonies of morphologically transformed cells were quantitated in vitro. The transformation frequency increased directly with the radionuclide concentration, and cells derived from transformed colonies produced tumors in athymic nude mice. The total absorbed 99mTc dose was 0.20 rad following injection of 250 microCi 99mTc/kg hamster body weight; this compares with an exposure of 0.13 rad following injection of 143 microCi 99mTc/kg body weight in humans. Intravenous injection of purified hamster lymphotoxin immediately after 99mTc caused a dose-dependent reduction in the transformation frequency. Transformation was essentially completely prevented (97%) by injection of 8,000 U of lymphotoxin. Thus, the immune system, through the action of lymphotoxin, has the potential to prevent carcinogenesis induced by gamma-radiation from 99mTc. This emphasizes the importance of considering the recipient's immune and other homeostatic mechanisms as part of a complete diagnostic or therapeutic gamma-radiation regimen.