Clearance of Tc-99m DTPA aerosol in mismatched and matched pulmonary perfusion defects

PURPOSE: To evaluate clearance changes of Tc-99m DTPA aerosol in mismatched and matched pulmonary perfusion defects. MATERIALS AND METHODS: Twenty-one patients (14 women, 7 men; mean age, 51 +/- 14 years) with possible pulmonary embolism were included in the study. On the day after perfusion (Q) scintigraphy with 5 mCi Tc-99m MAA, radioaerosol inhalation scintigraphy was performed using 45 mCi Tc-99m DTPA. Immediately and 45 minutes after the inhalation, early and delayed inhalation images (EI and DI, respectively) were obtained. Group 1 included 11 patients with mismatched defects who had a high probability of pulmonary embolism according to the Q/EI scan results. Group 2 included 10 patients with matched defects who had a low probability of PE. Contralateral normal lungs of 7 patients in group 2 served as controls (group 3). In groups 1 and 2, regions of interest were drawn over the mismatched and matched perfusion defects where they were best visualized, and this region of interest was mirrored to the same region on EI and DI images. For the control group, this was done in the contralateral normal lung. Mean counts in each region of interest were used for quantitative analysis, and the percentage clearance ratio was calculated using the following formula: early counts - late counts/early counts x 100. RESULTS: The average percentage clearances for the three groups were as follows: group 1, 37% +/- 10%; group 2, 21% +/- 4%; group 3, 24% +/- 7%. Differences between groups 1 and 3 were significant, as were those between groups 1 and 2 (P < 0.05). Patients with mismatched perfusion defects had increased DTPA clearance compared with the control group and those with matched defects. CONCLUSIONS: Vascular occlusion may lead to impairment of the alveolar-capillary barrier and consequently an increase in the clearance of Tc-99m DTPA aerosol in embolized regions. Immediately after inhalation, Tc-99m DTPA imaging should be started in the projection where perfusion defects are best seen to avoid potential misinterpretation of pulmonary embolism.     

Breast-milk radioactivity after a Tc-99m DTPA aerosol/Tc-99m MAA lung study

Measurements were made of the concentration of Tc-99m activity in samples of breast milk following an administration of Tc-99m DTPA aerosol for a lung ventilation image and one of Tc-99m MAA for lung perfusion. The activity was 222 nCi/ml of milk (8.2 kBq/ml) at 2 hr after the MAA injection, and it was found to be excreted exponentially with an effective half-life of 4.6 hr. There was a small incorporation of Tc-99m into breast-milk protein. We conclude that the combined use of these two Tc-99m agents did not indicate the interruption of breast feeding beyond 24 hr after administration of the MAA, and that for an aerosol ventilation study alone, breast feeding need not be interrupted for more than 4 hr after the test.     

Clinical experience with technetium-99m DTPA aerosol with perfusion scintigraphy in suspected pulmonary embolism

To evaluate the clinical value of radioaerosol imaging, 156 patients with suspected pulmonary embolism (PE) were studied. In 25 patients, a preperfusion xenon-133 (Xe-133) study was compared with a postperfusion study using Tc-99m DTPA aerosol. It was found that they were of equal value most of the time (56%), but that the aerosol study was more often helpful. Because of this, and the technical ease of using six standard views with radioaerosol, the series was completed using perfusion scintigraphy followed by radioaerosol images. In 19 patients the perfusion scintigraphy with Tc-99 macroaggregated albumin (Tc-99m MAA) was normal or nearly normal and no aerosol study was required. Tc-99m DTPA aerosol images were satisfactory when the count rate was at least twice and preferably three times that of the previous perfusion study. There were 17 studies (11%) classified as intermediate. There were 26 patients classified as high probability for PE, and angiographic or autopsy correlation was available in 14. All of the 14 proved to have PE. In the 113 patients classified as low probability, there were ten with angiographic or autopsy correlation. In the ten, there was one patient with a small pulmonary embolus found at autopsy. Clinical follow-up for over two months confirmed the absence of PE in the remainder of this group. Aerosol studies have proven technically easier to perform and a satisfactory substitute for xenon imaging in suspected PE.     

Tc-99m HMPAO scintigraphy in amiodarone-induced acute lung toxicity: comparison with Tc-99m DTPA inhalation scintigraphy

PURPOSE: This case demonstrates the use of Tc-99m HMPAO scintigraphy in amiodarone (AD)-induced lung toxicity. The aim of this presentation is also to discuss different scintigraphic modalities in the diagnosis and follow up in AD-induced lung toxicity. MATERIALS AND METHODS: A 77-year-old man, with a suspicious AD-induced acute lung toxicity, underwent Tc-99m DTPA aerosol inhalation scintigraphy and Tc-99m HMPAO scintigraphy. RESULTS: Rapid alveolar clearance of Tc-99m DTPA was found during AD therapy and increased lung uptake of Tc-99m HMPAO was also demonstrated. These findings supported the diagnosis AD lung toxicity. After cessation of therapy, Tc-99m DTPA alveolar clearance was decreased. Although there was some decrease in L/H and L/B ratios of Tc-99m HMPAO after 3 weeks of stopping therapy, Tc-99m HMPAO uptake in the lungs was still continued. This finding may be the result of ongoing pulmonary inflammation as a result of the long half-life of AD. CONCLUSION: Compared with Tc-99m DTPA aerosol inhalation scintigraphy, Tc-99m HMPAO scintigraphy may have a role in the diagnosis of AD lung toxicity. Nevertheless, there is a need for longitudinal studies investigating patients under AD therapy using follow-up Tc-9m HMPAO scintigraphy.     

Evaluation of lung epithelial permeability in the volatile substance abuse using Tc-99m DTPA aerosol scintigraphy

Aim  

Chronic inhalant use is associated with significant toxic effects, including neurological, renal, hepatic, and pulmonary damage. However, there is a paucity of reports regarding respiratory complications in inhalant abusers. The aim of this study was to evaluate pulmonary epithelial permeability in the volatile substance abuse (VSA) using Tc-99m DTPA aerosol scintigraphy.     

Evaluation of alveolo-capillary permeability in thyrotoxicosis using Tc-99m DTPA aerosol scintigraphy

Surfactant secreted from type II pneumocytes plays an important role in alveolo-capillary permeability. In thyrotoxicosis, high levels of T3 receptors detected at these cells might affect the alveolo-capillary permeability due to increased serum thyroid hormone levels. The results by CO-diffusion capacity measurement in thyrotoxicosis are conflicting. Changes in alveolo-capillary membrane permeability resulting from thyrotoxicosis are not well established yet. This prompted us to investigate the alveolo-capillary permeability in thyrotoxic patients in comparison with CO-diffusing capacity. For this aim twenty-two non-smoking thyrotoxic patients (before treatment) and fifteen healthy voluntary controls underwent 99mTc-DTPA aerosol scintigraphy. CO-diffusing and pulmonary function tests were performed in all subjects. After ventilation of radiotracer through a nebulizer for 15 minutes, 30 dynamic images (1 frame/minute) were taken from both lungs. ROI's were drawn over both lung areas, and the time-activity curves were generated. Then clearance half time (CT1/2) for radioaerosol was obtained. CT1/2 of thyrotoxic patients did not differ from that of the controls: 77.9 +/- 25.9 min vs. 79.4 +/- 22.3 min; p > 0.05. Similar result was found for CO-diffusion parameters. Also there was no significant correlation between CT1/2 and CO-diffusion parameters. We concluded that in patients with thyrotoxicosis, the alveolo-capillary permeability is unaffected. Further experimental research is needed to establish the possible effects of thyroid hormones on alveolo-capillary membrane.     

Generation of parametric images during routine Tc-99m PYP inhalation/Tc-99m MAA perfusion lung scintigraphy. Technical note.

A simple technique is described for generating ventilation/perfusion ratio and perfusion/ventilation ratio images from the posterior Tc-99m PYP aerosol inhalation and Tc-99m MAA perfusion images obtained during routine lung scintigraphy. These images highlight areas of ventilation/perfusion incongruence--mismatch or reverse mismatch--that may sometimes be difficult to detect on conventional images.     

Evaluation of alveolar clearance by Tc-99m DTPA radioaerosol inhalation scintigraphy in welders

OBJECTIVES: The welding process produces metal fumes and gases which may affect respiratory health. Technetium-99m diethylenetriaminepentaacetic acid (Tc-99m DTPA) dynamic lung scanning is an easy, noninvasive method to assess disorders of alveolar-capillary barrier permeability secondary to epithelial damage. We aimed to investigate the alveolar clearance by Tc-99m DTPA radioaerosol inhalation scintigraphy in welders, to assess additive effects of exposure to welding fumes and cigarette smoking on clearance rate of alveolar epithelium and to determine the correlation between Tc-99m DTPA aerosol lung scintigraphy and spirometric measurements. METHODS: Nine nonsmoking welders, 9 smoking welders, and a control group of 6 nonsmokers and 6 smokers were accepted to the study. Tc-99m DTPA radioaerosol inhalation scintigraphy was performed in all subjects. Clearance half time (Tl/2) was calculated by placing a monoexponential fit on the curves. Penetration index (PI) was also calculated on the first minute image. Pulmonary function tests of welders and control group were compared. RESULTS: The mean T1/2 values of Tc-99m DTPA of the nonsmoking welders were significantly higher than those of the nonsmoking control group (82.1+/-24.3 min and 48.1+/-9.7 min, respectively; p = 0.003). The mean T1/2 values of Tc-99m DTPA of the smoking welders were higher than those of the smoking control group (53.3+/-24.5 min and 44.5+/-9.7 min, respectively; p = 0.510). PI of the nonsmoking welders was significantly higher than that of the nonsmoking control group (0.46+/-0.38 and 0.39+/-0.46 respectively; p = 0.004). PI of the smoking welders was significantly higher than that of smoking control group (0.43+/-0.38 and 0.37+/-0.45, respectively; p = 0.019). There was a negative correlation between T1/2 value and FEV1% (r = -0.468, p = 0.016), FVC% (r = -0.442, p = 0.024) and FEF25-75% (r = -0.391, p = 0.048) in the welders and control group. No statistically significant differences were found in the values of the standard pulmonary function tests of any of the subjects. CONCLUSIONS: Welding seems to decrease alveolar clearance which causes an increase in the penetration index. This was considered to be due to fibrotic changes and increased number of alveolar macrophages induced by welding fumes.     

Detection of alveolar epithelial injury by Tc-99m DTPA radioaerosol inhalation lung scan in rheumatoid arthritis patients

Rheumatoid arthritis (RA) is a systemic autoimmune disorder primarily involving the joints. Lung alterations in RA may be primary or secondary to pharmacological treatments and may involve the alveoli, interstitium, airways and/or pleura. Technetium-99m diethylenetriaminepentaacetic acid (Tc-99m DTPA) aerosol inhalation scintigraphy is a sensitive and noninvasive test commonly employed to assess pulmonary epithelial membrane permeability. The purpose of the this study was a) to investigate the changes of pulmonary alveolar epithelial permeability in patients with RA, b) to determine the relationship between the clearance rate of Tc-99m DTPA and pulmonary function test (PFT) results, and c) to determine the relationship between the clearance rete of Tc-99m DTPA and clinical parameters of disease. Twenty-five patients with RA but without lung alterations were included in the study. The patients were 22 females, and 3 males; mean age 53.6 +/- 8.7 years. Technetium-99m DTPA aerosol inhalation scintigraphy was performed on the study and healthy control groups. Clearance half times (T1/2) were calculated by placing a mono-exponential fit on the curves. Penetration index (PI) was calculated on the first-minute image. There were no significant differences in the mean T1/2 or mean PI values between the RA patients and control subjects. No correlation was found between the mean T1/2 values of Tc-99m DTPA clearance and activity of RA, clinical values, or the spirometric measurements except FEV1/FVC and functional status in RA patients (p = 0.02, p = 0.01, respectively). However, a weak correlation was found between duration of disease and T1/2 values of Tc-99m DTPA clearance (p = 0.006). PI values tended to correlate with FEF25-75, although, this was not statistically significant (p = 0.057). This study shows that no changes occur in alveolar-capillary permeability in RA patients without lung alterations.     

Dissociation of Tc-99m DTPA in a nebulizer

An unexpected biodistribution of nebulized Tc-99m diethylene triamine pentaacetic acid was detected after the ventilation of a patient referred for diagnosis of pulmonary embolism. Radiochemical purity testing of the stock vial showed more than 95% labelling. Further investigation indicated that the problem was possibly associated with a cleaning agent used for the nebulizer, leading to the dissociation of the Tc-99m diethylene triamine pentaacetic acid. Manufacturer's instructions for cleaning of the nebulizer specify the use of 70% denatured ethanol solution, but a chlorine-based agent had been used inadvertently.     

Extrarenal abnormalities in Tc-99m DTPA renal perfusion studies due to hypervascularized tumors

In cases of impaired renal perfusion and/or function, Tc-99m DTPA renal flow studies are often used as screening procedures. Besides the demonstration of pathological changes in renal perfusion and/or function, various extrarenal abnormalities may sometimes be detected. Three cases of hypervascular tumors were detected during the course of Tc-99m DTPA renography. These findings stimulated further diagnostic clarification revealing extended extrarenal lesions associated with several different etiologies: angiomyolipoma in tuberous sclerosis, extramedullary manifestations of plasma-cytoma, and metastasis of renal carcinoma. One should be aware of these extrarenal abnormalities in renal flow studies since these three tumor entities frequently exhibit increased vascularity.     

Tc-99m erythromycin lactobionate inhalation scintigraphy in parenchymal lung diseases

We have investigated Technetium 99m erythromycin lactobionate (Tc 99m EL) clearance from the lungs after inhalation, in the presence of an alveolitis. Eighteen patients (6 sarcoidosis, 7 idiopathic fibrosis, and 5 miliary tuberculosis) were imaged after the patients inhaled 1,110 MBq of Tc 99m EL. Clearance half time for the first 45 min, for 24 h, and retention at 24 h correlated with percentage of lymphocytes in bronchoalveolar lavage fluid (BAL) (r = .729, r = .883, and r = .826, respectively). There was a positive correlation between peripheral penetration (PP) and forced expiratory volume in 1 s (FEV1) (r = .806) and forced vital capacity (FVC) (r = .781). Retention was more marked in sarcoidosis compared with tuberculosis (0.025 < p < or = 0.05). Radioaerosol lung imaging may reflect the pulmonary function impairment in parenchymal lung diseases. Retention of Tc 99m EL may be related to number of BAL cells or presence of a lymphocytic alveolitis. Long residency time of Tc 99m EL in the lungs implies that erythromycin can also be administered by inhalation for therapeutic purposes.     

Localization of Tc-99m DTPA in a chordoma.

The authors report a patient with chordoma that was demonstrated as a photopenic region on Tc-99m MDP bone imaging but that localized Tc-99m DTPA intensely. An explanation for the discrepancy is discussed. Complementary Tc-99m DTPA imaging in the preoperative evaluation of sacral tumors is suggested.     

The bronchoalveolar epithelial permeability in house painters as determined by Tc-99m DTPA aerosol scintigraphy

PURPOSE: Isocyanates are highly reactive chemicals used in a number of industries including paints. Therefore, house painters are known to be at risk for occupational exposure to isocyanates. Our objectives in this study were: (1) to investigate the possible effects of isocyanate exposition on the bronchoalveolar epithelial permeability in house painters by using Tc-99m DTPA radioaerosol lung scintigraphy; (2) to assess whether or not some differences exist between asthmatic and non-asthmatic house painters, and (3) to determine the relationship between Tc-99m DTPA radioaerosol lung scintigraphy and the spirometric measurements, and the work duration of house painters. MATERIALS AND METHODS: Ten non-smoking house painters (28.8 +/- 8.8 yrs) and ten healthy volunteers underwent Tc-99m DTPA radioaerosol lung scintigraphy. Following inhalation of radiotracer through a nebulizer for 5 minutes, dynamic scintigrams (1 frame/min, up to 10 min) were taken from both lungs. ROI's were drawn over the both lung area, and time-activity curves were obtained, from which the half-time (T1/2) of Tc-99m DTPA clearance was calculated. Spirometric lung function test was measured in all house painters. RESULTS: Mean T1/2 values (min +/- SD) were 93.74 +/- 32.79 for house painters, and 90.96 +/- 40.02 for control subjects. There was no significant difference in T1/2 values of Tc-99m DTPA clearance between house painters and controls, and between asthmatic and non-asthmatic house painters as well. No correlation was observed between T1/2 values of Tc-99m DTPA clearance and spirometric measurements. In house painters, there was a positive correlation between T1/2 values of Tc-99m DTPA clearance and work duration (r = 0.73, p = 0.016). CONCLUSIONS: Our findings indicate that in house painters, occupational exposure to isocyanates has no effect on bronchoalveolar epithelial permeability, and the rate of Tc-99m DTPA clearance shows no difference between asthmatic and non-asthmatic house painters. The positive correlation between the rate of Tc-99m DTPA clearance and work duration needs to be confirmed in larger cohorts.     

Comparison of technetium-99m aerosol and krypton-81m in ventilation studies for the diagnosis of pulmonary embolism

A new method of producing aerosols (technegas) in which 99Tcm is bound to carbon atoms (99Tcm-C) was evaluated by comparing 99Tcm-C images with those obtained with 81Krm in the same patients. Twenty-five patients with suspected pulmonary embolism (PE) were studied. Immediately after the last 99Tcm-C view, the patients remained in supine position and inhaled 81Krm at tidal volume. Immediately after the 81Krm ventilation views were recorded, 4-7 mCi of MAA were injected IV. The same four views (ant, lop, rop, post) were recorded after inhalation of 99Tcm-C and 81Krm (200 kcounts) and 99Tcm MAA injection (400 kcounts). The mean penetration index of 99Tcm-C (0.91) was lower than that of 81Krm (1.04) (P less than 0.03). The apex to base lung distribution of 99Tcm-C and 81Krm appeared to be similar. The mean heterogeneity of 99Tcm distribution was 23, greater than that of 81Krm (14) (P = 10(-4)). The 99Tcm-C ventilation image quality was considered very good for 16 patients and good for 6 others. Significant foci of high bronchial uptake were infrequent. Interpretation of the examinations performed after inhalation of 99Tcm-C and 81Krm was concordant in all cases. No patient had an 81Krm/99Tcm MAA examination suggestive of PE when 99Tcm-C/99Tcm MAA indicated a low probability of PE, and vice versa. 99Tcm-C aerosols enable good quality ventilation images to be obtained in nearly all cases. Thus 99Tcm-C aerosols could be used in preference to 81Krm in ventilation studies for the diagnosis of PE.