Pulmonary clearance of 99mTc-HMPAO aerosol

The clearance rate of inhaled aerosols of a lipophilic substance, 99mTc-HMPAO (Hexamethyl propylene amine oxime) was studied and compared to that of hydrophilic substances in 6 normal volunteers and 18 patients with lung diseases. The subject in sitting position inhaled a single deep breath of 99mTc-HMPAO aerosols, and held his breath about 30 sec. Then he continued to breath aerosols again for about 3 min. Radioactivity rapidly falls down during breath holding, to about 60% of the peak value (fast phase), with T 1/2 of 3.75 +/- 2.22 sec in 6 normal volunteers. This rapid phase was not appeared in hydrophilic aerosols with 99mTc-DTPA and 99mTc-pertechnetate and in lipophilic aerosol with 123I-IMP aerosol. The clearance of residual activity of 99mTc-HMPAO was slow with T 1/2 of 17.4 +/- 4.0 min. The T 1/2 of 99mTc-DTPA, 99mTc-pertechnetate and 123I-IMP were 50.2 +/- 20.9 min, 11.4 +/- 4.3, and 62.5 +/- 20.8 min respectively. 99mTc-HMPAO may cross transcellularly using the whole alveolar surface. The clearance of aerosols in the fast phase is rapid and depend on the regional perfusion. On the other hand, hydrophilic aerosol pass by an intercellular pathway and the clearance will be diffusion limited. As conclusion, inhalation study of 99mTc-HMPAO might be a new method to evaluate perfusion following ventilation study.     

Investigation of pulmonary epithelial permeability in patients after hyperbaric oxygen therapy by 99mTc diethylenetriaminepentaacetic acid aerosol inhalation lung scintigraphy

The aim of this study was to evaluate the possibility of pulmonary epithelial permeability damage in patients after hyperbaric oxygen therapy (HBOT) by 99mTc diethylenetriaminepentaacetic acid (99mTc-DTPA) aerosol inhalation lung scintigraphy. Twenty-five controls and 21 patients with normal chest X-rays and no cigarette smoking for at least 1 year were recruited for the study. 99mTc-DTPA aerosol inhalation lung scans were performed after 20 HBOT sessions in 21 patients with refractory osteomyelitis or diabetic foot. The HBOT with 100% oxygen at 2.5 atm absolute for 100 min was performed five times a week. Clearance rates (%/min) of 99mTc-DTPA aerosol in each lung field were calculated from the dynamic images for 30 min. Clearance rates of 99mTc-DTPA aerosol were compared between patients and controls by the unpaired t test. Thirteen patients who had 99mTc-DTPA aerosol lung scans before and after HBOT therapy studies were tested for statistical significance by using the paired t test. There was no statistically significant difference (P>0.05, unpaired t test) between patients and controls in every lung field. For the 13 patients who had 99mTc-DTPA aerosol studies both before and after 20 HBOT sessions, the results also showed no statistically significant difference (P>0.05, paired t test). It is concluded that there was no demonstrable pulmonary epithelial permeability change under current clinical HBOT protocol.     

SPECT images after intravenous injection of 99mTc-DTPA in lung tumors--comparison with delayed 123I-IMP lung scintigraphy

The aim of this study was to assess the efficacy of SPECT imaging of the thorax with 99mTc-DTPA, which accumulates at sites of increased capillary permeability and expanded extracellular space, by comparing it with delayed 123I-IMP lung scintigraphy. We have previously reported that increased uptake on delayed 123I-IMP lung scintigraphy was associated with atelectasis and inflammation. Thirteen patients with lung cancer (4 with atelectasis and 3 with pleurisy), one patient with malignant lymphoma complicated by pneumonia and pleurisy, and one patient with pneumonia were studied. 99mTc-DTPA scintigraphy was performed twice, 20-160 minutes and 2-4 hours after the intravenous administration of 370 MBq of 99mTc-DTPA. 123I-IMP scintigraphy was performed 24 hours after the intravenous injection of 111 MBq of 123I-IMP. SPECT images were obtained with both types of scintigraphy. 99mTc-DTPA scintigraphy was compared with 123I-IMP scintigraphy for its ability to detect atelectasis and pneumonia. All patients showed increased accumulation corresponding to the lesions on both 123I-IMP and 99mTc-DTPA scintigraphy. 123I-IMP scintigraphy showed a defect corresponding to the tumor with increased accumulation around the tumor, whereas 99mTc-DTPA scintigraphy showed accumulation corresponding to the tumor. Ten of 11 tumors showed accumulation of an intensity equal to that of the soft tissue of the chest wall on 20-60 min 99mTc-DTPA images. The 2-4 hr images showed that 99mTc-DTPA leaked from the periphery of the tumor toward its center. All the patients with pleurisy showed increased accumulation in effusion on 2-4 hr 99mTc-DTPA scintigraphy.(ABSTRACT TRUNCATED AT 250 WORDS)     

Urine excretion of inhaled technetium-99m-DTPA: an alternative method to assess lung epithelial transport

Technetium-99m DTPA clearance (99mTc-DTPA) clearance measured by a gamma camera or a scintillation probe not only reflects epithelial transport, but is also influenced by an unknown amount of mucociliary clearance depending on particle size and aerosol deposition. This is confirmed by factor analysis of dynamic inhalation studies. Assessment of epithelial absorption by urinary excretion of inhaled 99mTc-DTPA is largely independent of aerosol lung deposition. Twenty-four-hour excretion reflects the amount of aerosol cleared by absorption, while two-hour excretion is a quantitative measure of the aerosol absorption rate from the epithelium into blood. Urinary 99mTc-DTPA excretion of two aerosols with different particle size correlated significantly (p less than 0.001) with analysis of lung clearance curves. A very similar regression in the form of a cumulative exponential function was found with both aerosols. Two-hour urine values of nonsmokers differed significantly from those of smokers or patients with active interstitial or infectious lung disease. This alternative procedure is suited as a bedside test and holds promise for patient monitoring and follow-up.     

Radiographic and neuro-SPECT imaging in an immature third ventricle teratoma: case report.

We report a case of an immature teratoma of the third ventricle, which was preoperatively thought to be a choroid plexus papilloma. The diagnosis was made by biopsy since the radiographic (CT, MRI), angiographic and scintigraphic findings ([99mTc]pertechnetate, 99mTc-DTPA, 99mTc-HMPAO brain SPECT) were nonspecific. Disruption of the blood-brain barrier is the mechanism for radionuclidic and contrast tumoral uptake and is demonstrated by marked contrast enhancement on CT and focal concentration on [99mTc]pertechnetate and 99mTc-DTPA images. No suppression of [99mTc]pertechnetate tumor uptake was observed following the administration of potassium perchlorate. Increased concentration of tumor protein is suggested by the increased signal on the T1-weighted magnetic resonance images and high [99mTc]pertechnetate uptake. The tumor's detection on the 99mTc-HMPAO brain SPECT was due to its intraventricular location. A number of potential mechanisms for brain tumor localization of 99mTc-HMPAO are discussed.     

Pulmonary clearance of 99mTc-DTPA aerosol in patients with progressive systemic scleroderma]

Alveolar epithelial permeability was assessed in 32 patients with progressive systemic scleroderma (PSS), using 99mTc-DTPA aerosol. Immediately after the inhalation of 99mTc-DTPA aerosol for 3 to 6 minutes under normal tidal breathing, lung was imaged sequentially for 30 minutes from the posterior by a gamma camera and exponential fitting was processed on the time activity curve. T1/2 (min) was used as a parameter for the evaluation of permeability of alveolar epithelium. Patients with collagen disease showed shorter T1/2 (T1/2 = 43.7 +/- 23.8 min) than the normal volunteers (T1/2 = 76.8 +/- 8.7 min). No significant difference was observed between patients with or without interstitial changes on the chest CT. Significant correlation was not observed between T1/2 and %VC or %DLco. In 8 cases, studies were repeated in the interval of 3 to 19 months. Improvement of T1/2 was seen in 4 cases, independent of CT findings. These results suggest that 99mTc-DTPA aerosol clearance study provides information independent from other lung examinations, and may be useful for the assessment of lung interstitial changes in patients with PSS.     

Pulmonary inhalation scintigraphy using N-isopropyl-p-[123I]iodoamphetamine (123I-IMP) aerosol

N-isopropyl-p-[123I]iodoamphetamine (123I-IMP) is lipophilic substance and permeates through the alveolar epithelium via intracellular transport, whereas 99mTc-DTPA is water-soluble substance and permeates through the alveolar epithelium via paracellular transport. We performed inhalation lung imaging using 123I-IMP and 99mTc-DTPA in order to assess alveolar epithelial permeability in 4 patients with restrictive ventilatory impairment, and 5 volunteers including one smoker. The time-activity (T/A) curves of 123I-IMP were well fitted into two compartments, first and slow, by least-squares fit technique, in contrast to 99mTc-DTPA fitted well with one compartment. In 4 normal volunteers, the T/A curves of the lower pulmonary fields declined faster than those of other pulmonary fields. In 99mTc-DTPA studies, the Kep values of patients with restrictive ventilatory impairment (n = 4) were higher than those of normal volunteers (n = 4) (2.14 +/- 0.30 x 10(-4) vs 1.48 +/- 0.41 x 10(-4), p less than 0.005). On the other hand, in 123I-IMP studies, the Kep values of the patients were much lower than those of normal volunteers (6.79 +/- 0.55 x 10(-5) vs 1.52 +/- 0.45 x 10(-3), p less than 0.005).     

Determining the influence of biocompatible oxygenators during cardiopulmonary bypass by 99m Tc-DTPA aerosol assessment of pulmonary permeability

Changes in pulmonary permeability provide a partial measure of the clinical impact of biocompatible oxygenator use during cardiopulmonary bypass surgery. Previous research has shown that the clearance rate of 99mTc-labelled diethylene triamine penta-acetic acid (99mTc-DTPA) aerosol from the lungs is increased following cardiopulmonary bypass, resulting from an increase in pulmonary permeability. The aerosol clearance rate has been shown to return to normal after a period of 7 days. A blind trial was set up to assess the clinical impact of a biocompatible, Trillium-coated oxygenator compared with a standard oxygenator. In a group of 25 patients 99mTc-DTPA aerosol studies were carried out prior to cardiopulmonary bypass surgery for mitral valve surgery. Repeat studies were undertaken 3-4 h and 24-28 h after surgery. Analysis of the rates of pulmonary clearance reproduced the trends seen in earlier research. There was however no statistically significant difference in the variation of serial clearance times between the groups of patients undergoing surgery using the Trillium-coated oxygenators and those using the standard oxygenators.     

Dynamic pulmonary scintigraphy with Tc99m radioaerosol for the evaluation of the permeability of the alveolo-capillary barrier

Pulmonary clearance of small droplet 99mTc-DTPA radioaerosol was studied in 100 patients (12 normal subjects, N; 10 asymptomatic healthy smokers, FA; 31 patients with interstitial lung diseases, IP; 47 patients with chronic obstructive lung disease, BPCO). The first seven minutes of clearance were described with the function At = Ao*exp (-K*t) and the time constant K was considered representative of the 99mTc-DTPA clearance rate and hence of the alveolar-capillary barrier permeability. Groups FA, IP and BPCO showed a significant (p less than 0.05) or a highly significant (p less than 0.01) increase in permeability when compared to group N. No correlation was found between permeability and bronchial obstruction tests. The following conclusions were drawn: --99mTc-DTPA dynamic lung scanning is an easy, non-invasive method to assess derangements of alveolar-capillary barrier permeability secondary to epithelial damage; --permeability increase is a very early effect of cigarette smoke damage to the epithelium; --other mechanisms of epithelial injury are present in diffuse lung disease; --while the clinical role of this new pathophysiological test is not yet clear, it is likely that it may become a very early marker of pulmonary epithelial damage in diffuse lung disease.     

Clinical assessment of 99mTc-HMPAO scintigraphy in thoracic tumors]

99mTc-hexamethylpropylene amineoxime (99mTc-HMPAO) scintigraphy was performed in 15 malignant tumors in 11 patients and a patient with bronchopneumonia. A high 99mTc-HMPAO affinity for the tumors was observed on SPECT, however, the mean tumor/contralateral normal lung ratios of 99mTc-HMPAO activity (1.26) was lower than that of 201Tl-chloride (2.29). 99mTc-HMPAO uptake was seen not only in the tumors but also in the bronchopneumonia, atelectasis, and irradiated lung (containing radiation fibrosis). Moreover, a diffuse uptake in the lung was seen in a patient received repeated chemotherapy. Therefore, it is emphasized that there is a non-specific 99mTc-HMPAO uptake in those various pulmonary conditions.     

Different uptake of 99mTc-ECD adn 99mTc-HMPAO in the same brains: analysis by statistical parametric mapping

The purpose of this study was to investigate the differences between technetium-99m ethyl cysteinate dimer (99mTc-ECD) and technetium-99m hexamethylpropylene amine oxime (99mTc-HMPAO) uptake in the same brains by means of statistical parametric mapping (SPM) analysis. We examined 20 patients (9 male, 11 female, mean age 62+/-12 years) using 99mTc-ECD and 99mTc-HMPAO single-photon emission tomography (SPET) and magnetic resonance imaging (MRI) of the brain less than 7 days after onset of stroke. MRI showed no cortical infarctions. Infarctions in the pons (6 patients) and medulla (1), ischaemic periventricular white matter lesions (13) and lacunar infarction (7) were found on MRI. Split-dose and sequential SPET techniques were used for 99mTc-ECD and 99mTc-HMPAO brain SPET, without repositioning of the patient. All of the SPET images were spatially transformed to standard space, smoothed and globally normalized. The differences between the 99mTc-ECD and 99mTc-HMPAO SPET images were statistically analysed using statistical parametric mapping (SPM) 96 software. The difference between two groups was considered significant at a threshold of uncorrected P values less than 0.01. Visual analysis showed no hypoperfused areas on either 99mTc-ECD or 99mTc-HMPAO SPET images. SPM analysis revealed significantly different uptake of 99mTc-ECD and 99mTc-HMPAO in the same brains. On the 99mTc-ECD SPET images, relatively higher uptake was observed in the frontal, parietal and occipital lobes, in the left superior temporal lobe and in the superior region of the cerebellum. On the 99mTc-HMPAO SPET images, relatively higher uptake was observed in the medial temporal lobes, thalami, periventricular white matter and brain stem. These differences in uptake of the two tracers in the same brains on SPM analysis suggest that interpretation of cerebral perfusion is possible using SPET with 99mTc-ECD and 99mTc-HMPAO.     

Brain single-photon emission CT studies using 99mTc-HMPAO and 99mTc-ECD early after recanalization by local intraarterial thrombolysis in patients with acute embolic middle cerebral artery occlusion

BACKGROUND AND PURPOSE: The brain distribution of 9mTc-hexamethylpropyleneamine oxime (HMPAO) correlates with regional brain perfusion, whereas 99mTc-ethyl cysteinate dimer (ECD) reflects not only perfusion but also the metabolic status of brain tissue. We compared 99mTc-ECD single-photon emission CT (SPECT) with 99mTc-HMPAO SPECT early after recanalization by local intraarterial thrombolysis (LIT) in patients with acute embolic middle cerebral artery occlusion. We also assessed the predictive value of 99mTc-HMPAO and 99mTc-ECD SPECT for the development of ischemic brain damage. METHODS: 99mTc-HMPAO and consecutive 99mTc-ECD SPECT studies were performed in 15 patients within 3 hours of LIT. The two SPECT studies were obtained independently using a subtraction technique. SPECT evaluation was performed using semiquantitative region-of-interest analysis. Noninfarction, infarction, and hemorrhage were identified by follow-up CT or MR imaging. RESULTS: Forty-five lesions were identified (21 noninfarctions, 19 infarctions, and five hemorrhages). Regardless of 99mTc-HMPAO SPECT findings, lesions showing isoactivity (count rate densities of 0.9 to 1.1 as compared with the contralateral side) on 99mTc-ECD SPECT were salvaged. Lesions with hypoactivity (values < 0.9) on 99mTc-ECD SPECT developed irreversible brain damage. Hemorrhage appeared in lesions with both hyperactivity (values > 1.1) on 99mTc-HMPAO SPECT and hypoactivity on 99mTc-ECD SPECT. CONCLUSION: The brain distribution of 99mTc-ECD in a reperfused area identified by 99mTc-HMPAO SPECT early after recanalization of acute ischemic stroke is dependent on cerebral tissue viability. By combining 99mTc-ECD and 99mTc-HMPAO SPECT, performed within the first few hours of LIT, it is possible to identify patients at risk for hemorrhagic transformation reliably.     

Pulmonary clearance of technetium 99m diethylene triamine penta-acetic acid aerosol in patients with amiodarone pneumonitis

Amiodarone pneumonitis is a serious complication that may lead to fatal lung fibrosis. In an attempt to diagnose this condition as early as possible, the technetium-99m-labelled diethylene triamine penta-acetic acid (99mTc-DTPA) aerosol washout rates of 10 non-smoking normal volunteers (group 1), 10 non-smoking patients on a long-term amiodarone regimen with dilated cardiomyopathy but no congestive heart failure (group II) and 10 patients with amiodarone pneumonitis (group III) were compared. Spirometric measurements, as percentage predicted, were higher in group I than in group III (P less than 0.05). The global mean effective half-lives of 99mTc-DTPA aerosol for both lungs together in minutes were 65 +/- 14, 55 +/- 16 and 27 +/- 4 for groups I, II and III, respectively. Group III values were significantly lower than those of groups I and II (P less than 0.05). Our results demonstrated that amiodarone pneumonitis alters the alveolar-capillary membrane permeability to hydrophilic molecules. The pulmonary clearance of 99mTc-DTPA aerosol is a useful test in the differentiation of patients on a long-term amiodarone regimen without side effects from patients with amiodarone pneumonitis. The test is rapid, easy to perform and has the potential for playing an important role in deciding which patients should discontinue therapy.     

Hypofixation and hyperfixation of 99mTc-hexamethyl propyleneamine oxime in subacute cerebral infarction.

The relationship between hypofixation and hyperfixation of 99mTc-hexamethyl propyleneamine oxime (99mTc-HMPAO) remains unclear. The purpose of this study was to compare 99mTc-HMPAO SPECT with regional cerebral blood flow (CBF) imaging using 133Xe inhalation in patients with subacute cerebral infarction and to investigate the behavior of 99mTc-HMPAO in the infarct area using dynamic SPECT. METHODS: 133Xe and consecutive 99mTC-HMPAO SPECT studies, the latter of which consisted of dynamic and static scanning, were performed on 51 patients (22 women, 29 men; age range, 40-83 y; mean age, 61 y) with cortical infarction in the middle cerebral artery territory 13-15 d after stroke onset. One region of interest (ROI) was drawn in the infarct area. The control ROI was mirrored to the contralateral side, and the same set of ROIs was applied to all SPECT studies. Fractional fixation of 99mTc-HMPAO in the infarct area was evaluated relatively as the ratio of the infarct-to-control region in 99mTc-HMPAO static tomograms/the ratio of the infarct-to-control region in CBF images using 133Xe inhalation and was classified as hyperfixation when this value was >1.1 and hypofixation when this value was <0.9. To investigate the behavior of 99mTc-HMPAO in the infarct area, the second (36-72 s after tracer injection) and eighth (252-288 s after tracer injection) of 8 dynamic scans were selected, and the washout rate was calculated using the formula: 1 - (mean count in the eighth scan/mean count in the second scan). RESULTS: The infarct area showed hyperfixation of 99mTc-HMPAO when CBF in the area was 35 mL/100 g/min or less and showed hypofixation when CBF was >45 mL/U100 g/min. The washout rate was usually negative when CBF imaging using 133Xe inhalation was <20 mL/100 g/min but was positive when it was >45 mUL/100 g/min. The washout rate was negative when the infarct area showed hyperfixation of 99mTc-HMPAO but was positive when it showed hypofixation. CONCLUSION: 99mTc-HMPAO SPECT underestimates CBF in high-flow regions and overestimates CBF in low-flow regions of subacute cerebral infarction. 99mTc-HMPAO hypofixation and hyperfixation are associated with backdiffusion from the brain to blood and gradual accumulation of hydrophilic metabolites, respectively. Dynamic images should be useful for discriminating between 99mTc-HMPAO hypofixation and hyperfixation.     

Detection of alveolar epithelial injury by<Superscript>99m</Superscript>Tc-DTPA radioaerosol inhalation lung scan following blunt chest trauma

DTPA clearance rate is a reliable index of alveolar epithelial permeability, and is a highly sensitive marker of pulmonary epithelial damage, even of mild degree. In this study, 99mTc-DTPA aerosol inhalation scintigraphy was used to assesss the pulmonary epithelial membrane permeability and to investigate the possible application of this permeability value as an indicator of early alveolar or interstitial changes in patients with blunt chest trauma. A total of 26 patients was chest trauma (4 female, 22 male, 31-80 yrs, mean age; 53+/-13 yrs) who were referred to the emergency department in our hospital participated in this tsudy. Technetium-99m diethylene triamine pentaacetic acid (DTPA) aerosol inhalation scintigraphy was performed on the first and thirtieth days after trauma. 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. On the first day, mean T1/2 value of the whole lung was 63+/-19 minutes (min), and thirtieth day mean T1/2 value was 67+/-21 min. On the first day, mean PI values of the lung and 30th day mean PI value were 0.60+/-0.05, and 0.63+/-0.05, respectively. Significant changes were observed in radioaerosol clearance and penetration indices. Following chest trauma, clearance of 99mTc-DTPA increased owing to breakdown of the alveolar-capillary barrier. This increase in the epithelial permeability of the lung appears to be an early manifestation of lung disease that may lead to efficient therapy in the early phase.     

Ventilation scintigraphy with lipophilic cationic compounds

OBJECTIVE: On the basis of our hypothesis that lipophilic cations may be more suitable for ventilation lung scintigraphy than the conventional technetium-99m diethylenetriamine penta-acetic acid (Tc-DTPA), comparative studies were carried out. BASIC METHODS: The nebulization potential of nine routine radiopharmaceuticals was compared on medical and scintigraphy-specific nebulizers. This was followed by ventilation scintigraphy in 14 patients with chronic obstructive airway disease (n=13) or pulmonary embolism (n=1) where either 99mTc-methoxyisobutylisonitrile (n=10) or Tc-tetrofosmin (n=4) was used. Same-patient comparison with 99mTc-DTPA ventilation scan was available in six patients using the same acquisition protocol. Comparison with 99mTc-DTPA was made with respect to the nebulization rates, radioactivity delivered per unit of radioactivity available for inhalation, and regional distribution of inhaled counts. RESULTS: Lipophilic cation solutions had a significantly higher nebulization rate compared with 99mTc-DTPA using the medical nebulizer (235%, P<0.01) and 370% on scintigraphy-specific nebulizer (P<0.01). More than three times the counts of 99mTc-methoxyisobutylisonitrile or 99mTc-tetrofosmin was deposited in the body compared with Tc-DTPA aerosol per megabecquerel activity inhaled (1.5 vs. 0.4 kcounts/MBq) (P<0.001), preferentially in the lungs (75.2 vs. 65.2%), at the expense of oropharynx and stomach. Within the lungs, about 50% more counts were deposited in the outer one-third lung with lipophilic cations. Overall, therefore, more than 12 times the radioactivity deposition was achieved in the peripheral one-third of the lungs with the lipophilic cations. CONCLUSION: Ventilation lung scanning with lipophilic cations is a viable substitute of nanoparticle scintigraphy (technegas and pertechnegas, which are expensive and technically far more demanding).     

Impaired lung epithelial permeability in hepatitis C virus antibody positive patients detected by 99mTc-DTPA aerosol scintigraphy

Chronic hepatitis C virus (HCV) infection has been recently identified as an aetiological agent in idiopathic pulmonary fibrosis. The present study was designed to determine the pulmonary clearance rate of 99mTc-diethylenetriaminepentaacetic acid (99mTc-DTPA) in asymptomatic HCV antibody positive (HCV Ab+) patients and the role of 99mTc-DTPA aerosol scintigraphy in the early detection of lung involvement. Twenty-six non-smoker HCV Ab+ and HCV-RNA (+) patients (20 female, six male; aged 43+/-11 years), with no clinical pulmonary symptoms, and normal radiological findings, were studied. Thirty-one healthy non-smoker volunteers (24 female, seven male; aged 40+/-10 years) were taken as a control group. 99mTc-DTPA aerosol inhalation scintigraphy and pulmonary function tests were performed in all patients and in controls. On the basis of the scintigrams the percentage decline in activity per minute (Kep) was evaluated, which represented an accurate parameter of lung membrane permeability. The mean Kep values of healthy controls (0.78+/-0.13 for left lung, 0.79+/-0.14 for right lung) were significantly lower than HCV Ab+ patients (1.10+/-0.31 for left lung, 1.11+/-0.34 for right lung, P<0.001). But no significant change was observed in PFT (P>0.05). We conclude that subclinical alveolitis and/or interstitial lung disease may be present in patients with HCV Ab+, since it is known that an increase in the epithelial permeability of the lung is an early manifestation of interstitial disease.     

Evaluating the changes in alveolar permeability and lung ventilation in patients with chronic renal failure after haemodialysis using 99mTc-DTPA radioaerosol inhalation lung scan

Hypoxaemia occurring in patients with chronic renal failure (CRF) during haemodialysis (HD) has long been known. Several mechanisms of pathogenesis have been proposed. Before and after regular HD, lung ventilation (LV) and alveolar permeability (AP) were measured in 24 male patients with CRF (age, 61-75 years). LV and AP were determined by 99mTc-diethylenetriaminepentaacetic acid (99mTc-DTPA) radioaerosol inhalation lung scan (99mTc-DTPA lung scan). The LV images were visually interpreted according to established criteria, including the presence or absence of an inhomogeneous distribution, inverted base to apex gradient and segmental hypoventilation. The degree of AP in the total right lung was presented as the clearance rate (K; %.min-1) of the time-activity curve from dynamic total right lung images. Ten male normal controls (age, 62-76 years) were enrolled in the study for comparison. Ten of 24 (42%) cases showed an inhomogeneous distribution and eight of 24 (33%) cases showed hypoventilation on equilibrium LV images. After regular HD for 5 h, no significant changes in the LV images were found. Before HD, the CRF patient group (K=1.14+/-0.36%.min-1) had a significantly faster clearance rate than that of normal controls (0.75+/-0.14%.min-1, P<0.05). Moreover, the clearance rate after HD was significantly slower (0.87+/-0.15%.min-1, P<0.05) than that before HD. CRF can predispose patients to LV change and AP damage. After HD, the damage to AP is significantly improved. However, after HD, the change in LV is not significant.     

"Luxury perfusion" with 99mTc-HMPAO and 123I-IMP SPECT imaging during the subacute phase of stroke

To compare the merits of 123I-isopropyl-iodoamphetamine (123I-IMP) and 99mTc-HMPAO in showing abnormal brain uptake distribution during cerebral ischemia, we studied ten patients during the subacute phase of their stroke, a period where metabolism and blood flow are frequently uncoupled. SPECT imaging was performed using both radiopharmaceuticals in the 10 patients from 48 h to 4 weeks after onset of symptoms. Two patients out of the 10 had similar defects with 123I-IMP and 99mTc-HMPAO SPECT, the location of the defects corresponding to the area of infarction observed on CT. Six patients had normal 99mTc-HMPAO SPECT and abnormal 123I-IMP SPECT with defects in the area of infarction shown by CT. The remaining 2 patients had hyperactive abnormalities on 99mTc-HMPAO in areas corresponding to defects on the 123I-IMP images. Two of the patients with SPECT mismatches were studied again more than 1 month after onset. On reexamination, 99mTc-HMPAO SPECT which was previously normal or hyperactive became hypoactive with a focal area of decreased activity corresponding to the defect on 123I-IMP. Crossed cerebellar diaschisis was found in 7 patients with 99mTc-HMPAO and was absent for both 123I-IMP and 99mTc-HMPAO in 3. We suggest that SPECT with 99mTc-HMPAO could show transient hyperemia not demonstrated by 123I-IMP whereas in some cases cerebral infarction would be more difficult to demonstrate with 99mTc-HMPAO than with 123I-IMP. SPECT with both tracers is recommended to follow the evolution of strokes in terms of regional cerebral blood flow and tissue metabolism.     

Assessing adequacy of collateral circulation during balloon test occlusion of the internal carotid artery with 99mTc-HMPAO SPECT.

A balloon test occlusion of the internal carotid artery was performed in 11 patients with internal carotid artery aneurysms. Tolerance by patients was assessed by a combination of clinical examination; angiography; electroencephalography; 99mTc-hexamethylpropyleneamine oxime (99mTc-HMPAO) single-photon emission computed tomography (SPECT) with relative quantification; and, in four patients, 99mTc-HMPAO SPECT with absolute quantification of cerebral blood flow. During test occlusion, angiography showed a patent circle of Willis in all patients. No patient developed new clinical findings or electroencephalographic changes. The SPECT studies of five patients in whom 99mTc-HMPAO was injected during test occlusion demonstrated changes from their baseline SPECT studies. The internal carotid artery was permanently occluded in two of these patients, neither of whom became symptomatic because of the occlusion. Three patients who demonstrated no changes between baseline and test occlusion SPECT studies underwent permanent occlusion of the internal carotid artery without incident, and postoperative SPECT images were unchanged from baseline. Our preliminary results suggest that patients who have no changes between baseline and test occlusion 99mTc-HMPAO SPECT studies should have adequate collateral circulation to sustain cerebral blood flow after occlusion of the internal carotid artery if no thromboembolic episodes occur. In contrast, a patient's tolerance of permanent occlusion cannot be consistently and reliably predicted if there are changes between baseline and test occlusion SPECT studies. In these patients, absolute quantitation of cerebral blood flow is important. Greater numbers of patients are required to confirm these initial results.