Altered kinetics of 123I-IMP in irradiated rabbit lungs

Reversed Intrapulmonary Right-to-Left Shunt After Banding of the Patent Ductus Venosus

Diffuse pulmonary microvascular arteriovenous communication developed in an 8-year-old girl with a patent ductus venosus. Tc-99m macroaggregated albumin (MAA) pulmonary perfusion scintigraphy with total-body imaging demonstrated multiple lung perfusion deficits and abnormal tracer uptake in systemic organs with hepatic radioactivity greater than the kidneys, suggesting the presence of right-to-left shunt and abnormal hepatic hemodynamics. I-123 iodoamphetamine transrectal portal scintigraphy revealed a large portosystemic venous shunt. The follow-up Tc-99m MAA perfusion scans after banding of the patent ductus venosus revealed partial improvement of the perfusion deficits and right-to-left shunt, indicating the possible reversibility of this pulmonary shunt complication.

Potential of noncontrast electrocardiogram-gated half-fourier fast-spin-echo magnetic resonance imaging to monitor dynamically altered perfusion in regional lung

RATIONALE AND OBJECTIVES

The potential of a noncontrast, electrocardiography (ECG)-gated fast-spin-echo (FSE) MR imaging (MRI) to monitor dynamically altered regional lung perfusion was assessed in acute and temporal pulmonary embolic and airway obstruction dog models.

MATERIALS AND METHODS

After acquisition of ECG-gated multiphase FSE MR images during one cardiac cycle, the two phase images of the minimal lung signal intensity (SI) during systole and the maximal SI during diastole were acquired in the lower lung levels in six normal dogs, in 13 dogs before and for 35 minutes after temporal microvascular embolization in regional lungs with gradually degradable starch microspheres of spherex, and in 12 dogs before and for 45 minutes after bronchial occlusion with a balloon catheter. In three of the 13 embolic models, the opposite lung areas, however, were permanently embolized with enbucrilate. Subtraction between the diastolic and systolic images yielded a perfusion-weighted image. The results were compared with a gadolinium diethylenetriaminepentaacetic acid (Gd-DTPA)-enhanced dynamic perfusion MRI, which was subsequently performed after the ECG-gated MRI in each animal.

RESULTS

The multiphase FSE images provided cardiac-dependent pulsatile lung SI changes, and the subtracted perfusion-weighted images provided a uniform perfusion map in normal lungs. In all the embolic models, the subtracted perfusion-weighted images showed gradual disappearance of the spherex-induced perfusion deficits, while the enbucrilate-induced perfusion deficits persistently remained in the three animals. In all airway obstruction models, these images showed gradually decreased perfusion in the hypoventilated areas. These results were consistent with the matched Gd-DTPA-enhanced pulmonary arterial perfusion phase images in each animal.

CONCLUSION

This noncontrast perfusion MRI may have excellent potential for continuously monitoring dynamically changed regional lung perfusion within a short time on its high spatial resolution cross-sectional images.

Perfusion characteristics of radiation-injured lung on Gd-DTPA-enhanced dynamic magnetic resonance imaging

RATIONALE AND OBJECTIVES

A contrast-enhanced dynamic magnetic resonance (MR) study was performed experimentally and clinically to describe perfusion characteristics of radiation-injured lung according to pathologic phases.

METHODS

The MR study was performed before and at 0.5, 1, 2, 3, 4, and 7 months after 40 Gy-dose irradiation to the right hemithorax in 8 dogs, and clinically in 12 lung lesions of 9 patients with acute or fibrotic radiation pneumonitis. Altered Gd-DTPA kinetics in the affected lungs was assessed by time-signal intensity curves. MR findings were correlated with lung histology and CT images.

RESULTS

Within 1 month after irradiation, the irradiated animal lungs showed focal and persistent contrast enhancement relative to nonirradiated lungs. This abnormality was pronounced during the next 2 months. After 4 months, irradiated lungs conversely showed lower enhancement during the Gd-DTPA first-pass but were followed by persistently greater enhancement during Gd-DTPA redistribution phase. Similar differences in enhancement abnormalities between acute and fibrotic radiation pneumonitis were clinically observed.

CONCLUSION

These findings indicate that Gd-DTPA kinetics can be altered according to the histopathologic change in early/acute radiation pneumonitis and radiation fibrosis and that the contrast-enhanced perfusion MRI may help differentiate the phases of radiation pneumonitis.

Lung perfusion impairments in pulmonary embolic and airway obstruction with noncontrast MR imaging

A noncontrast electrocardiography (ECG)-gated, fast-spin-echo magnetic resonance imaging was applied to noninvasively define perfusion impairments in pulmonary embolic and airway obstruction dog models. Two-phase ECG-gated lung images of the minimal lung signal intensity during systole and maximal signal intensity during diastole were acquired by using optimized R-wave triggering delay times in seven dogs anesthetized with pentobarbital sodium before, soon after, and 2 mo after embolization with enbucrilate and in another eight dogs before and after bronchial occlusion with balloon catheters, in combination with a gadolinium diethylenetriaminepentaacetic acid-enhanced dynamic study. An ECG-gated subtraction image between the two-phase lung images provided a uniform but gravity-dependent perfusion map in normal lungs. Furthermore, it defined all 13 variable-size perfusion deficits associated with pulmonary embolism and the dynamically decreased perfusion with time after bronchial occlusion in all the airway obstruction models. These results were consistent with contrast-enhanced pulmonary arterial perfusion phase images. This noncontrast imaging could be equivalent to a contrast-enhanced dynamic study in the definition of regionally impaired pulmonary arterial perfusion in pulmonary embolism and airway obstruction.

Regional lung functional impairment in acute airway obstruction and pulmonary embolic dog models assessed with gadolinium-based aerosol ventilation and perfusion magnetic resonance imaging

RATIONALE AND OBJECTIVES

Gadolinium diethylenetriaminepentaacetic acid (Gd-DTPA)-based aerosol ventilation and perfusion magnetic resonance (MR) images were used to define regional functional impairment in acute airway obstruction (AO) and pulmonary embolic (PE) dog models.

METHODS

The aerosol study was performed in 10 anesthetized normal dogs in a supine position during 20-minute spontaneous inhalation of an aerosol of 100- or 200-mmol-Gd/L Gd-DTPA solute produced by an ultrasonic nebulizer in an open-circuit delivery system, combined with a dynamic perfusion study after a 3-second intravenous bolus injection of a 0.1 mmol/kg dose of Gd-DTPA. These MR studies were also performed in the same 10 dogs approximately 30 minutes after obstructing the segmental (n = 6) or lobar (n = 4) bronchus with a balloon catheter, and in another six dogs after segmental (n = 6) and lobar (n = 4) pulmonary arterial embolization with enbucrilate. Regional lung enhancement was assessed on time-signal intensity (SI)-curves and ventilation- and perfusion-weighted images produced by a subtraction technique.

RESULTS

The normal lungs were gradually and gravity-dependently enhanced with time after Gd-DTPA aerosol inhalation regardless of the respiratory SI changes, except for three animals with the fastest breathing rate. The averaged maximal relative lung SI increase against the baseline in the successful animals was significantly greater in the slowly and deeply breathing animals than in the fast and shallow breathing animals, regardless of the difference in Gd-concentration (100 mmol Gd/L: 153.3% +/- 69.7% vs. 54.2% +/- 23%; P < 0.001; and 200 mmol Gd/L: 189.7% +/- 68.0% vs. 75.6% +/- 42.2%; P < 0.0001, respectively). There was an additional enhancement of 382% +/- 101 in the ventral lung and 722% +/- 160 in the dorsal lung on the pulmonary arterial phase perfusion image even in the slowly and deeply breathing animals who inhaled 200-mmol-Gd/L aerosol, and the enhancement effect was significantly greater compared with that with the aerosol (P < 0.0001). The ventilation- and perfusion-weighted images clearly defined the regionally matched perfusion-ventilation deficits in all the AO models, and the regionally mismatched perfusion-ventilation in all the PE models.

CONCLUSION

Gd-based aerosol can provide efficient lung enhancement in spontaneously and adequately breathing animals, using a relatively noninvasive aerosol delivery system. The combined use of Gd-based perfusion MR imaging may be acceptable for defining regionally impaired function associated with acute AO and PE.

Liver involvement in hereditary haemorrhagic telangiectasia: assessment with 99Tcm-phytate radionuclide angiography and 123I-IMP transrectal portal scintigraphy

Abnormal hepatic haemodynamics and function in a 43-year-old woman with hereditary haemorrhagic telangiectasia (HHT) were evaluated using 99Tcm-phytate angiography and iodine-123-iodoamphetamine transrectal portal scintigraphy. Radionuclide angiography demonstrated hyperdynamic perfusion of the liver owing to intrahepatic arteriovenous fistulae (AVF), entry of tracer into the systemic circulation through intrahepatic portosystemic shunts and an increase in recirculating blood flow caused by these vascular disorders. Heterogeneous distribution of tracer also suggested the presence of chronic hepatic injury. Transrectal portal scintigraphy showed large portosystemic shunts. Other imaging techniques confirmed the presence of the AVF but failed to identify the portosystemic shunts. Non-invasive radionuclide studies are helpful in the evaluation of hepatic involvement of HHT.

On clinical usefulness of Tl-201 scintigraphy for the management of malignant soft tissue tumors

The purpose of this study was to investigate Tl-201 as a tumor scanning agent in patients with malignant soft tissue sarcomas and to establish the sensitivity of this type of scintigraphy concerning local recurrences or metastases that may remain clinically suspected. Seventy-eight patients with malignant soft tissue sarcomas and 22 with benign soft tissue tumors were studied. Of these 78 malignant soft tissue sarcomas patients, the sensitivity of Tl-201 (81.2%) was higher than that of Ga-67 (68.8%). Thirty-three out of 78 patients received a total of 95 consecutive scintigraphic follow-up examinations. Therapeutic effects was assessed by comparing the results of Tl-201 examinations with the clinical findings. Of these 33 patients, the therapeutic effects observed were as follows: complete remission 1, partial remission 8, progress of disease 1, and no remarkable change 23. Tl-201 scintigraphy has proved itself very useful not only in clinically detecting the malignant soft tissue sarcomas and in assessing therapeutic effects on these diseases, but also in assessing the follow-up patients with malignant soft tissue sarcomas.

I-123 IMP scintigraphy in two patients with primary pulmonary malignant lymphoma

123I-IMP lung scintigraphy was performed in two patients with primary malignant lymphoma, whose radiographic features were difficult to differentiate from inflammatory or atelectatic lesions. 123I-IMP scans revealed a defect in the lesions on the delayed (24 hr) image, suggesting a tumorous lesion. 123I-IMP scan may contribute to differential diagnosis of this rare tumorous entity from benign disorders having a different appearance.