Technetium-99m-DTPA aerosol scintigraphy in amiodarone induced pulmonary toxicity in comparison with Ga-67 scintigraphy

Acute amiodarone toxicity causing respiratory failure

A 66-year-old male patient was referred to our clinic with severe pneumonia. Bronchoscopy was performed due to clinical worsening despite antibiotics and diuretic therapy, respiratory failure and radiographic progression. Because bacterial cultures of the bronchoalveolar lavage fluid were negative and after using amiodarone for almost one month, we eliminated amiodarone from his medication regimen due to suspicion of amiodarone toxicity. Accordingly, we also initiated systemic steroid therapy. Chest X-ray done after 72 hours showed a significant resolution of lung consolidations and the patient exhibited significant clinical improvement, with decline of his oxygen requirements.

Physiological imaging of the lung: single-photon-emission computed tomography (SPECT)

Emission tomography provides three-dimensional, quantitative images of the distribution of radiotracers used to mark physiological, metabolic, or pathological processes. Quantitative single photon emission computed tomography (SPECT) requires correction for the image-degrading effects due to photon attenuation and scatter. Phantom experiments have shown that radioactive concentrations can be assessed within some percentage of the true value when relevant corrections are applied. SPECT is widely spread, and radiotracers are available that are easy to use and comparably inexpensive. Compared with other methods, SPECT suffers from a lower spatial resolution, and the time required for image acquisition is longer than for some alternative methods. In contrast to some other methods, SPECT allows simultaneous imaging of more than one process, e.g., both regional blood flow and ventilation, for the whole lung. SPECT has been used to explore the influence of posture and clinical interventions on the spatial distribution of lung blood flow and ventilation. Lung blood flow is typically imaged using macroaggregates of albumin. Both radioactive gases and particulate aerosols labeled with radioactivity have been used for imaging of regional ventilation. However, all radiotracers are not equally suited for quantitative measurements; all have specific advantages and limitations. With SPECT, both blood flow and ventilation can be marked with radiotracers that remain fixed in the lung tissue, which allows tracer administration during conditions different from those at image registration. All SPECT methods have specific features that result from the used radiotracer, the manner in which it is administered, and how images are registered and analyzed.

Technetium-99m hexamethylpropylene amine oxime lung scintigraphy findings in low-dose amiodarone therapy

Amiodarone (AD)-induced pulmonary toxicity is one of the major complications of long-term AD therapy. Technetium-99m-labeled D: ,L: -hexamethylpropylene amine oxime (Tc-99m HMPAO) scintigraphy has been used to assess lung injury. We designed this study to clarify lung uptake changes of Tc-99m HMPAO using low doses of AD (5 mg/kg/day) during long-term therapy in a rabbit model. Group 1 consisted of 7 rabbits fed with AD by gavage for 6 months. To investigate the effect of ketamine on Tc-99m HMPAO uptake, 5 rabbits were included in Group 2 as a control group. Tc-99m HMPAO scintigraphy was performed in both Group 1 and Group 2 at baseline and after 2, 4, 6, 8, and 12 weeks of AD intake. After 16, 20, and 24 weeks of drug intake, Tc-99m HMPAO scintigraphy was repeated only in group 1. One-min anterior images were acquired 30 min after the injection of 37 MBq of Tc-99m HMPAO. For semiquantitative evaluation, the mean count values were obtained and lung/background and liver/background ratios were calculated. Histopathologic evaluation was performed. No increase in lung and liver uptake of Tc-99m HMPAO was found 2, 4, 6, 8, and 12 weeks after drug intake. There was no significant increase in L/B and H/B ratios of Tc-99m HMPAO in Group 1 compared with Group 2. Both scintigraphic studies and histopathologic examinations showed nonspecific changes. Longitudinal studies investigating Tc-99m HMPAO lung uptake may be planned in patients carrying risk factors for AD-induced lung toxicity.

Pulmonary epithelial permeability in patients treated with bleomycin containing chemotherapy detected by technetium-99m diethylene triamine penta-acetic acid aerosol (99mTc-DTPA) scintigraphy

PURPOSE

To evaluate pulmonary epithelial permeability using 99mTc-DTPA scintigraphy in patients treated with bleomycin-containing regimens.

MATERIAL AND METHODS

Twelve non-smoking chemotherapy-naïve patients with no clinical or radiological evidence of pulmonary disease and treated with bleomycin-containing chemotherapy were tested with 99mTc-DTPA scintigraphy before the first cycle and every 3 weeks until the third month after the end of chemotherapy (total cumulative dose of bleomycin 347.9 mg).

RESULTS

Pretreatment values (T1/2 74.93 minutes) of 99mTc-DTPA scintigraphy were significantly higher than those obtained after the total dose of bleomycin (T1/2 51.00 minutes) (p < 0.001). This difference was more important in the later evaluations especially, on the third week and third month measures after discontinuing treatment (p < 0.001). All the tests of Within-Subjects Effects were significant (p < 0.001). Comparing pretreatment and post-treatment scintigraphies the mean T1/2 99mTc-DTPA values decreased as the bleomycin dose increased.

CONCLUSION

We conclude that cumulative bleomycin doses are related to increased pulmonary epithelial permeability at a dose of 256.5 mg. However, whether this is related to clinical toxicity is uncertain and large, multi-center prospective studies are needed.

Use of iodine-123 metaiodobenzylguanidine scintigraphy for the detection of amiodarone induced pulmonary toxicity in a rabbit model: A comparative study with technetium-99m diethyltriaminepenta acetic acid radioaerosol scintigraphy

The purpose of the study was; (i) to determine whether 123I-MIBG scintigraphy is sensitive for detection of amiodarone induced pulmonary toxicity (AIPT) and (ii) to compare it with 99mTc-DTPA radioaerosol. Twelve white New Zealand rabbit with initial mean body weight 4.24 +/- 0.47 g were divided into two groups. AIPT group (n = 7) was administered amiodarone (20 mg/kg BW). The control group (n = 5) received the same amount of 0.9% saline. All animals underwent 123I-MIBG and 99mTc-DTPA radioaerosol scintigraphy at the end of the treatment period. 123I-MIBG static thorax images were obtained during 10 minutes at 15 minutes and 3-hours after intravenous injection of the radiopharmaceutical. Lung to heart ratios (LHR) and lung to mediastinum ratios (LMR), and retention index (LRI) of 123I-MIBG were determined. Two days after 123I-MIBG scintigraphy, 99mTc-DTPA radioaerosol scintigraphy was performed, and clearance from the lungs was measured for 10 min (1 min/frame) following termination of inhalation. 123I-MIBG lung retention index (LRI) was significantly higher in the AIPT group than the control (61 +/- 4.6 vs. 40 +/- 4.5, p = 0.01). Early LHR and LMR were significantly lower in the AIPT group than in the control group (p = 0.04, p = 0.01, respectively), whereas those of late LHR and LMR were not significantly different. T1/2 values of DTPA clearance were significantly increased in AIPT group according to the control group (55 +/- 7.2 vs. 86.6 +/- 18.5, p = 0.02). 123I-MIBG scintigraphy is a valuable tool for detecting AIPT in a rabbit model. Additionally, 99mTc-DTPA radioaerosol scintigraphy is an excellent comprehensive investigational tool for detecting AIPT with the added advantage of lower cost.