Technetium-99m antimony sulphide colloid lymphoscintigraphy of the prostate by direct transrectal injection

Laterality of prostatic lymphatic drainage was successfully assessed in nine patients with prostatic carcinoma after direct unilateral transrectal injections of 99Tcm-antimony sulphide colloid by Franzen needle. Pelvic lymphatic drainage was equally divided between ipsilateral, contralateral and bilateral patterns. The frequent observation of radiocolloid migration to contralateral lymph node groups in patients with prostate carcinoma, including those with primary disease localized clinically to a single lobe of the prostate, indicates the potential for contralateral pelvic lymph node metastases in this population. This finding may be important in determining the appropriate surgical staging and treatment of patients with prostate carcinoma. The clinical applicability of lymphoscintigraphy in the evaluation of metastatic spread and in lymph node biopsy planning requires further study.

Tc-99m RBC imaging for demonstrating intermittent intestinal bleeding

A case of intestinal bleeding caused by multiple ulcerations near the terminal ileum is presented. Abdominal scanning with Tc-99m tagged red blood cells (Tc-99m RBC) demonstrated the intermittent bleeding in short intervals. Selective angiography did not demonstrate the bleeding site. Exploratory laparotomy showed 3 ulcers on the ileum at a site near the terminal ileum, with bleeding from one site. Tc-99m RBC abdominal scanning was very useful in this case for localization of the site of gastrointestinal bleeding before laparotomy.

A model of the peritoneal cavity for use in internal dosimetry

Several therapeutic and diagnostic techniques involve injection of radioactive material into the peritoneal cavity. Estimation of the radiation dose to the surface of the peritoneum or to surrounding organs is hampered by the lack of a suitable source region in the phantom commonly used for such calculations. We have modified the Fisher-Snyder phantom to include a region representing the peritoneal cavity which may be employed to estimate such radiation doses. A geometric model is described which is coordinated with the existing organ regions in the phantom. Specific absorbed fractions (derived by Monte Carlo techniques) for photon emissions originating within the cavity are listed. Photon S-values for several radionuclides which have been administered intraperitoneally are shown. Dose conversion factors for electrons irradiating the peritoneal cavity wall, from either a thin plane or volume source of activity within the cavity, are also given for several nuclides.

The particle size distribution of technegas and its influence on regional lung deposition

The size distribution of the aerosol produced by a technegas generator has been measured with a screen diffusion battery. The median diameter of the active aerosol was found to be of the order 140 nm and not to vary with the delay between generation and use. The measurements indicate that about 20% of the aerosol should be deposited in deep lung with about 5% deposited in the upper airways.

Gastrointestinal scintiscanning: dosimetry

Calculations of the dosimetry associated with orally administered 99mTc labeled cellulose fibres and 111In labeled plastic particles were performed for adult standard man using MIRD methodology. The applied gastrointestinal transit parameters of these radiopharmaceuticals probably reflect the ranges of these parameters, regarding nondigestible components used for gastrointestinal transit studies. However, the critical organ for both radiopharmaceuticals was the large intestine.

Scintigraphic evaluation of gastric emptying: are radiolabeled solids necessary?

A standard, dual-isotope meal (Tc-99m-egg sandwich and In-111 DTPA in water) was administered to 14 normal volunteers and 37 patients, who had not undergone gastric surgery, to determine if the emptying characteristics of the liquid phase alone could accurately predict delayed solid emptying. Delayed gastric emptying was defined clinically as a solid half-emptying time more than two standard deviations greater than the mean for normal volunteers. Linear regression analysis was performed on the natural logarithm of liquid fractional retention at each time interval to yield a slope and y-intercept for each subject. There was no significant difference (0.6 less than P less than 0.8) between volunteers and patients with normal solid emptying for the liquid slope. In patients who exhibited delayed gastric emptying for solids, the liquid slopes were significantly different from the normal values (P less than .001). There was a high correlation of liquid slope to solid half-emptying time in all patients and volunteers (r = -0.80, P less than .001). Comparison of the liquid slope measurement to solid half-emptying time criteria revealed a sensitivity of 96%, a specificity of 100%, and a predictive value of 100% for the slope test. These results suggest that delayed gastric emptying can be accurately detected with a liquid-solid meal using only a single-liquid label.

Effect of liposome surface charge on the stability of technetium (99mTc) radiolabelled liposomes

Using liposomes radiolabelled by the 99mTechnetium-stannous chloride technique we have investigated the effect of surface charge on the stability of the isotope in vitro and in vivo. Dialysis of 99mTc-labelled positive, negative and neutral liposomes, which had been incubated in either saline or normal rat serum showed no significant loss of the isotope from the liposome surface with only 2 per cent of the isotope dialysed. A comparison of gel chromatography with dialysis confirmed that most of the isotope remained attached to the liposome surface, but it did reveal greater loss of the isotope, between 15 and 23 per cent. The liposome clearance rates obtained from 125I-egg phosphatidylcholine (EPC) and 99mTc dual-labelled positive or neutral liposomes were significantly different. The 99mTc marker was cleared five times faster from the positive liposomes and twice as fast from the neutral liposomes as the 125I-EPC integral membrane marker. The 99mTc attached to liposomes with a negative surface charge was stable in vivo and had the same clearance rate from the circulation as the 125I-EPC marker. These results indicate that the commonly used in vitro techniques for assessing liposome radiolabel stability are unsuitable for predicting the stability of the 99mTc in vivo.

The effect of eating on transit through the small intestine

The effect of eating on the transit of radiolabelled particles through the small intestine has been monitored in eight healthy subjects dosed after an overnight fast. Each subject participated on three occasions and either remained fasting for 9 h after dosing or consumed a meal at 1.5 h or 4 h. The mean +/- 1 S.D. small intestinal transit time during the fasting study was 5.5 +/- 2.1 h and during the 1.5h and 4 h fed studies 4.8 +/- 2.9 h and 4.7 +/- 2.2 h, respectively. These times were not significantly different, nor were the rates of entry of the particles into the colon. These findings indicate that once in the small intestine the efficacy of orally administered pharmaceutical preparations is unlikely to be affected by eating.

The retention of [99mTc]-d,l-HM-PAO in the human brain after intracarotid bolus injection: a kinetic analysis

[99mTc]-d,l-HM-PAO (HM-PAO) was injected rapidly into the internal carotid artery and its retention in the brain was recorded by external scintillation cameras in eight human subjects. A model is described based on three compartments: the lipophilic tracer in the blood pool of the brain, the lipophilic tracer inside the brain, and the hydrophilic form retained in the brain. The retention curve initially drops abruptly, corresponding to the nonextracted fraction of the injectate leaving the brain; it then falls exponentially towards the asymptotic level of the fractional steady-state retention R. Cerebral blood flow (F) was measured using the xenon-133 intracarotid injection method. The first-pass extraction E of HM-PAO was calculated from F using an empiric regression equation. The residue curves for the whole brain after intracarotid HM-PAO injection were analyzed to yield a retention fraction (R') and the brain clearance backflux constant of lipophilic HM-PAO (k). From the kinetic model and the measured values of R', k, and F, the following parameter values could be calculated: the average retained fraction of all tracer supplied to the brain, R = 0.38 +/- 0.05 (mean +/- SD), the conversion rate constant (lipophilic to hydrophilic tracer) in the brain k3 = 0.80 +/- 0.12 min-1, the efflux rate constant (brain to blood) k2 = 0.69 +/- 0.11 min-1, the conversion/clearance ratio alpha = k3/k2 = 1.18 +/- 0.25, the influx (blood clearance) constant K1 = 0.45 +/- 0.11 ml/g/min, and the brain/blood partition ratio lambda = K1/k2 = 0.67 +/- 0.23 ml/g. Using the kinetic model and assuming constancy of alpha, an algorithm was developed that corrects for the blood flow dependent backflux of HM-PAO and results in a more linear relation between regional cerebral blood flow (rCBF) and HM-PAO distribution.

Comparison of technetium-99m pyrophosphate and technetium-99m DTPA aerosols for SPECT ventilation lung imaging

Although [99mTc] diethylenetriaminepentaacetic acid (DTPA) is currently the most widely used radioaerosol, rapid alveolar clearance limits its usefulness for single photon emission computed tomography (SPECT) ventilation lung imaging. Previous research has shown that [99mTc]phosphate compounds have high alveolar deposition and slow clearance and thus provide suitable aerosols for pulmonary ventilation studies. We have compared the pulmonary retention and blood levels of [99mTc]pyrophosphate (PYP) and [99mTc]DTPA in eight normal nonsmoking male volunteers. These two radioaerosols have comparable pulmonary deposition. Technetium-99m PYP, however, has a much slower pulmonary clearance which allows sufficient time (20 or more minutes) for SPECT data acquisition using a single-headed rotating gamma camera. While the radiation absorbed dose to the lungs for [99mTc]PYP (0.31 rad/mCi) is greater than for [99mTc]DTPA (0.11 rad/mCi), it is at a clinically acceptable and safe level.

The infiltrated radiopharmaceutical injection: dosimetric considerations

A small proportion of radiopharmaceutical administrations are extravasted from the injection site to the surrounding tissue. Of interest is the resulting absorbed dose. This investigation was undertaken to determine the biologic behavior and subsequent dosimetry of selected radiopharmaceutical infiltrations using a rat model. Subcutaneous injection of 99mTc-microspheres, 99mTc-MDP, 67Ga-citrate, and 201Tl-chloride were studied. Three adult male Sprague-Dawley rats were injected subcutaneously at three separate sites on the shaven backs of the animals for each agent studied (i.e., nine sites per agent). The rats were imaged and the resulting data were analyzed by computer immediately after injection and at various intervals up to 5-6 h, and again at 24 h. Particulate subcutaneous 99mTc-microspheres exhibit essentially no diffusion of tracer from the injection site, whereas non particulates showed a biexponential release pattern. Radiation burdens in rad/mCi (mGy/MBq) due to an infiltrate volume uniformally distributed over a 5 g mass for 99mTc-microspheres, 99mTc-MDP, 67Ga-citrate and 201Tl-chloride were 59.4(16.0), 13.6(3.7), 32.9(8.9) and 92.2(24.9), respectively. The radiobiological risk associated with these radiation burdens are below that needed to produce severe skin reactions when distributed within a 5 g mass.

Investigations to determine the optimum conditions for radiolabelling human platelets with 99Tcm-hexamethyl propylene amine oxime (99Tcm-HM-PAO)

99Tcm-hexamethyl propylene amine oxime (99Tcm-HM-PAO) has been evaluated as an agent to radiolabel human platelets in vitro. The rate of uptake of this lipophilic complex, the effect of HM-PAO, plasma and platelet concentration were measured to determine the optimum conditions for radiolabelling platelets for short-term clinical investigations of thromboses. The complex was made according to the manufacturer's instructions and immediately added to isolated platelets in vitro. The rate of labelling was slower than for leucocytes, reaching a plateau after approximately 40 min at room temperature (RT). Increasing the temperature to 37 degrees C did not increase the labelling efficiency (LE). Addition of plasma to platelets at a cell concentration of 1 x 10(9) [corrected] ml-1 reduced the LE from 66% in saline to 52% in 20% ACD-plasma. However, increasing the platelet concentration from 5 x 10(8) to 2 x 10(9) ml-1, increased the LE from 9 to 76% for platelets labelled in 20% plasma for 30 min at RT. The in vitro stability of the 99Tcm in the labelled cells showed that 7% of the radioactivity were immediately released from the platelets and a further 13% were eluted during a 60 min incubation in plasma at 37 degrees C. It has been concluded that incubation of platelets at RT with 99Tcm-HM-PAO containing 80 micrograms ml-1 HM-PAO at a cell concentration of 1 x 10(9) ml-1 or greater, results in a high LE, with more than 85% of the 99Tcm being retained by the platelets during a 60 min incubation in plasma.

IV radionuclide total-body arteriography: a new noninvasive whole-body screening procedure--a case report

Recently the authors introduced a new technique of intravenous (IV) radionuclide total-body arteriography. The major arterial system, multiple organs of the whole body, and cardiac function can be evaluated with one small IV injection in the arm. After analyzing more than 1000 cases, they have found that many pathologies can be detected and/or confirmed in this procedure. This new technique may be used as a general whole-body screening test for those patients at high risk for disease.

[Pulmonary scintigraphy with radioaerosol in idiopathic scoliosis]

The study of respiratory function is of key importance for the clinical evaluation of patients with idiopathic scoliosis. Such study has been traditionally based on classical pulmonary function tests and arterial blood gas analysis. However, neither procedure gives any information on the topographical distribution of abnormalities, and both might be suboptimal as far as sensitivity is concerned. The preliminary results obtained with radioaerosol lung scintigraphy in 11 patients with scoliosis are here presented. They lead to the conclusion that radioaerosol lung scintigraphy, besides being an useful adjunct to more traditional diagnostic procedures, can yield unique information on the localization of convective ventilation derangements induced by the dynamic abnormalities of the rib cage.

Myocardial perfusion imaging with 99mTc-methoxy-isobutyl-isonitrile (MIBI): comparison of short and long time intervals between rest and stress injections. Preliminary results

Unlike 201Tl, 99mTc-methoxy-isobutyl-isonitrile (99mTc-MIBI) does not redistribute in the myocardium after injection. Thus, two separate injections of this new myocardial perfusion agent are required to differentiate ischemia from scar. An injection at stress followed by a 2nd injection at rest performed 24 h later, or the inverse, has been proposed. This protocol is not ideal in clinical practice. It would be preferred if both injections were performed on the same day. Fifteen patients with significant coronary artery disease demonstrated by coronary angiography and with at least one ischemic segment on the myocardial 201Tl study were evaluated within two weeks with the following protocol. On the same day (short time interval protocol), 3 images, each of 10 min duration (anterior, 45 degrees LAO and 70 degrees LAO views) were performed between 30 to 60 min after the injection at rest of 7-10 mCi 99mTc-MIBI. On completion of the rest study, the patient received 25-30 mCi 99mTc-MIBI at stress and images were again obtained 30 to 60 min later. Two days later (long time interval protocol) a stress study alone was repeated using 10 mCi 99mTc-MIBI with the same imaging time. Qualitative and quantitative comparisons between the short and the long time interval studies were performed by four experienced observers. Both protocols showed the same number of ischemic segments (52/225) and fixed defects (19/225). The diagnostic information of images was judged similar in nine patients while the short protocol was judged superior to the long protocol in five patients and inferior in 1.(ABSTRACT TRUNCATED AT 250 WORDS)

Scintigraphy of inflammation with nanometer-sized colloidal tracers

The biodistribution of a nanometer-sized colloid was tested in three groups of rats, one with a turpentine-induced abscess and one with a histamine-induced oedema in the musculature of a hind leg. The third group served as a control. A 99Tcm-labelled colloid with a mean particle size of 30 nm was administered to each group intravenously. The biodistribution of the tracer, studied 1 h after injection, demonstrated that the colloid accumulated to a very limited extent in oedematous tissue, whereas the uptake in inflamed muscle was high. The colloid was subsequently administered to patients with arthritis, osteitis and osteomyelitis. All sites of inflammation accumulated the radiopharmaceutical and could be visualized scintigraphically 45 min after its administration. The results were in agreement with 67Ga-citrate or 111In-leukocyte scintigraphy, and/or other diagnostic modalities. Hyperaemia alone was not sufficient to cause uptake. We conclude that the mechanism of uptake is regional spilling of the tracer into the extravascular space through gaps in the damaged basement membrane, and that nanometer-sized 99Tcm-labelled colloid may constitute a convenient radiopharmaceutical for detecting inflammation in the extremities.

Technetium-99m DTPA aerosol and gallium scanning in acquired immune deficiency syndrome

In 11 non-smoking AIDS patients suspected of pneumocystis carinii pneumonia (PCP), the results of Tc-99m DTPA aerosol clearances, gallium scans, and arterial blood gases were compared with those of bronchoalveolar lavage (BAL). Nine patients had PCP. All had increased clearances five times higher than the normal (5.6 +/- 2.3% X min-1 vs 1.1 +/- 0.34% X min-1, N = 10, P less than 0.001), suggesting an increased alveolar permeability. Gallium scans were abnormal in six patients but normal or slightly abnormal in the three others. Four of these nine patients had normal chest x-rays. In two of these the gallium scan was abnormal, but in the two others, only the increased Tc-99m DTPA clearances showed evidence of lung disease. Two patients had normal BAL, with normal clearances and gallium scans. Four out of the nine patients with PCP were studied after treatment. Three recovered and had normal clearance and gallium scans. One still had PCP with increased clearance but normal gallium scan. Gallium scanning and Tc-99m DTPA clearance are useful for detecting lung disease in AIDS patients with suspected PCP and for prompting BAL when chest x-rays and PaO2 levels are normal. Due to its high sensitivity, a normal Tc-99m DTPA clearance could avoid BAL.

Suppression by perchlorate of technetium-99m and iodine-123 secretion in milk of lactating goats

Lactating goats were infused with either technetium-99m (99mTc) or iodine-123 (123I) together with chlorine-36 (36Cl) through an indwelling catheter previously placed in an external pudic mammary artery. The radioisotope infusions were repeated together with 100 mg of sodium perchlorate. There was a rapid transfer of 99mTc and 123I into milk, reaching a peak concentration 30 min after a 15-min infusion. The fractional secretion of 99mTc and 123I in milk was reduced by 70%-80% and 60%-66%, respectively, by perchlorate. The fractional secretion of 36Cl was not affected by perchlorate, and the shape of the 36Cl secretion curve differed from those of 99mTc and 123I, which were similar. It is probable, therefore, that the latter nuclides were secreted by a transport route different from that of chloride. Available data describing the secretion of 99mTc in human milk after pertechnetate administration was reviewed, and it was concluded that perchlorate pretreatment significantly reduced the secretion of 99mTc in human breast milk.

Quantitative scintigraphy with deconvolutional analysis for the dynamic measurement of hepatic function

A mathematical technique known as deconvolutional analysis was used to provide a critical and previously missing element in the computations required to quantitate hepatic function scintigraphically. This computer-assisted technique allowed for the determination of the time required, in minutes, of a labeled bilirubin analog (99mTc-disofenin) to enter the liver via blood and exit via bile. This interval was referred to as the mean transit time (MTT). The critical process provided for by deconvolution is the mathematical simulation of a bolus injection of tracer directly into the afferent blood supply of the liver. The raw data required for this simulation are obtained from the intravenous injection of labeled disofenin, a member of the HIDA family of radiopharmaceuticals. In this study, we perform experiments which document that the simulation process itself is accurate. We then calculate the MTT under a variety of experimental conditions involving progressive hepatic ischemia/reperfusion injury and correlate these results with the results of simultaneously performed BSP determinations and hepatic histology. The experimental group with the most pronounced histologic findings (necrosis, vacuolization, disorganization of hepatic cords) also have the most prolonged MTT and BSP half-life. However, both quantitative imaging and BSP testing are able to identify milder degrees of hepatic ischemic injury not reflected in the histologic evaluation. Quantitative imaging with deconvolutional analysis is a technique easily adaptable to the standard nuclear medicine minicomputer. It provides rapid results and appears to be a sensitive monitor of hepatic functional disturbances resulting from ischemia and reperfusion.

Pulmonary epithelial clearance of 99mTc-DTPA after thrombin-induced pulmonary microembolism

We investigated the effect of thrombin-induced pulmonary microembolism on the pulmonary clearance rate of aerosolized 99mTc diethylenetriamine pentaacetic acid (99mTc-DTPA) in awake, chronically prepared sheep. Chest activity was recorded after administration of a 0.44 micron aerosol of 99mTc-DTPA. Decay-corrected data were fit to an exponential and expressed as percent decrease per min (%/min). Sheep were given alpha-thrombin intravenously (80 U/kg for 10 min) 60 min after the aerosol administration. The clearance rate prior to alpha-thrombin was 0.35 +/- 0.05 %/min (mean +/- SEM). During alpha-thrombin administration, the clearance rate increased to 5.84 +/- 0.70 %/min (p less than 0.001 from baseline), but returned to 0.41 +/- 0.06 %/min within 30 min after the end of the thrombin infusion. The increased clearance rate during alpha-thrombin administration was not due to increased lung volume since alpha-thrombin did not change functional residual capacity. Moreover, the clearance rate was unchanged during gamma-thrombin administration, which does not induce coagulation, or during alpha-thrombin challenge in defibrinogenated animals. alpha-thrombin administration in neutrophil-depleted sheep caused a transient increase in DTPA clearance similar to that in control sheep, suggesting that the increase occurred independently of neutrophils. The results indicate that alpha-thrombin causes a large, transient increase in 99mTc-DTPA clearance, which may be the result of increased epithelial permeability. This response is dependent on the activation of intravascular coagulation.

99mTc-DTPA and 99mTc-rhenium sulfur aerosol compared as adjuncts to perfusion scintigraphy in patients with suspected pulmonary embolism

Two radiopharmaceuticals, 99mTc-DTPA (D) and 99mTc-rhenium sulfur (R), were evaluated with a nebulizer delivering submicronic particles. Seventy-seven patients were examined (42 D, 35 R). For all patients, the examination began with a ventilation study. Immediately after the last ventilation view, 99mTc MAA was injected. Aerosol performance was assessed in 37 D and 17 R. Nebulization yield was 8.98% for D and 9.31% for R. A lung clearance study was performed in 12 patients for D and in 12 different patients for R. The lung clearance was 0.22%/min for R and 2.35%/min for D. The quality of ventilation and the quantification of bronchial and gastric activity were evaluated; the difference between the two groups was not statistically significant. It may be concluded that radioaerosols allow good quality images to be obtained. The yield of the nebulizer is adequate, so that nebulization of 20 mCi delivers approximately 2 mCi of aerosol activity to the lung. When pulmonary embolism is being investigated, R, due to its slower lung clearance, would appear to be preferable to D for patients suspected of increased bronchoalveolar permeability, especially if the time between nebulization and recording is greater than 10 min.

Permeability of human brain tumor to 99mTc-gluco-heptonate and 99mTc-albumin. Implications for monoclonal antibody therapy

The variable penetration of chemotherapeutic drugs into brain and tumor is more dependent upon lipid solubility than upon size. In contrast, the molecular weight of virus- and tumor-specific monoclonal antibodies appears to limit uptake. The authors have studied eight patients with malignant brain tumors in order to compare tumor uptake of an iodinated contrast agent evaluated by computerized tomography scanning with uptake of the low and high molecular weight imaging agents technetium-99m (99mTc)-glucoheptonate and 99mTc-albumin, respectively, measured by radionuclide brain scanning. The agent 99mTc-labeled albumin was chosen for evaluation because its molecular weight (68,000) is similar to that of the most clinically promising monoclonal antibody fragment, the immunoglobulin (Ig) G Fab monomeric fragment. The radionuclide brain scans in the eight patients showed highly variable permeability of brain tumor to these markers, with uptake of the high molecular weight marker in the tumor being much less than that of the low molecular weight radionuclide. A clinical implication of these studies is that the success of monoclonal antibody therapy in the treatment of malignant brain tumors may require techniques to increase permeability of the blood-brain barrier and blood-tumor barrier to protein.