Diagnostic value of ventilation/perfusion single-photon emission computed tomography/computed tomography for bronchiolitis obliterans syndrome in patients after lung transplantation

Administered dosage and effective dose estimated from 81Rb-rubidium hydroxide for lung ventilation scintigraphy using 81mKr noble gas

The aim of this study was to estimate the administered dosage of 81mKr noble gas as calculated by the radioactivity of 81Rb-rubidium hydroxide (81RbOH). The administered dosage was regarded as the total amount of 81mKr noble gas. The radioactivity of 81mKr was calculated using the radioactivity of 81RbOH at the examination, the beginning of inhalation, the inhalation duration and the attenuation volume from the generator to the patient for 81mKr noble gas. In addition, we created an Internet survey and asked National University Hospital in Japan to respond to questions regarding the parameters of concern. Survey responses were provided by 38 hospitals (response rate was 90.5%). Twenty-seven hospitals (64.3%) examined lung ventilation scintigraphy using 81mKr noble gas. The mean administered dosage and the effective dose of lung ventilation scintigraphy using 81mKr noble gas were 35.8 ± 22.1 GBq and 0.97 ± 0.60 mSv, respectively.

Relative Lung Perfusion on Ventilation-Perfusion Scans After Double Lung Transplant

BACKGROUND

Pulmonary blood flow can be assessed on ventilation-perfusion (VQ) scan with relative lung perfusion, with a 55% to 45% (or 10%) right-to-left differential considered normal. We hypothesized that wide perfusion differential on routine VQ studies at 3 mo posttransplant would be associated with an increased risk of death or retransplantation, chronic lung allograft (CLAD), and baseline lung allograft dysfunction.

METHODS

We conducted a retrospective cohort study on all patients who underwent double-lung transplant in our program between 2005 and 2016, identifying patients with a wide perfusion differential of >10% on a 3-mo VQ scan. We used Kaplan-Meier estimates and proportional hazards models to assess the association between perfusion differential and time to death or retransplant and time to CLAD onset. We used correlation and linear regression to assess the relationship with lung function at time of scan and with baseline lung allograft dysfunction.

RESULTS

Of 340 patients who met inclusion criteria, 169 (49%) had a relative perfusion differential of ≥ 10% on a 3-mo VQ scan. Patients with increased perfusion differential had increased risk of death or retransplantation ( P  = 0.011) and CLAD onset ( P  = 0.012) after adjustment for other radiographic/endoscopic abnormalities. Increased perfusion differential was associated with lower lung function at time of scan.

CONCLUSIONS

Wide lung perfusion differential was common after lung transplant in our cohort and associated with increased risk of death, poor lung function, and CLAD onset. The nature of this abnormality and its use as a predictor of future risk warrant further investigation.

[Impact of Residual Radioactivity Rate of 99mTc-macro Aggregated Albumin (MAA) in Syringes and Administration Routes with a Focus on Pediatric Nuclear Medicine Examinations]

PURPOSE

The purpose of this study was to evaluate the residual radioactivity in the syringe and route of administration of a low fluid volume 99mTc-macro aggregated albumin (MAA) intended for pediatric nuclear medicine examinations.

METHOD

We evaluated the residual characteristics, as the effect of elapsed time from drawing up of radiopharmaceuticals to plastic syringe to administration, and the effect of volume of 99mTcO4- solution to be labeled, the effect of rinsed times of plastic syringe, effect of dose of calculated by consensus guidelines for pediatric nuclear medicine and residual location in injection sets with 99mTc-MAA. Residual radioactivity was measured using planar images obtained by the gamma camera.

RESULTS

Residual radioactivity rate of 99mTc-MAA, 99mTc-MAG3, 123I-IMP showed 41.3±1.6%, 14.4±0.6%, 14.6±2.0%, respectively. 99mTc-MAA clearly showed a higher residual rate. Residual radioactivity rate increased with the extension of the elapsed time, and reached a high value of 41.3% in 30 minutes. Residual radioactivity rate was dependent on the different volume of 99mTcO4- to be labeled (4.0 ml and 8.0 ml). Residual radioactivity rate did not change when the number of rinsed was more than one. Residual rate was around 40% at all doses of calculated by consensus guidelines for pediatric nuclear medicine.

CONCLUSION

99mTc-MAA showed the highest residual radioactivity rate among radiopharmaceuticals used in pediatric nuclear medicine examinations. The factor that most affected the residual radioactivity rate of 99mTc-MAA was the elapsed time from draw up to the plastic syringe to administration.

Noninvasive methods for detection of chronic lung allograft dysfunction in lung transplantation

Lung transplantation (LTx) is the only therapeutic option for end-stage lung diseases. Chronic lung allograft dysfunction (CLAD), which manifests as airflow restriction and/or obstruction, is the primary factor limiting the long-term survival of patients after surgery. According to histopathological and radiographic findings, CLAD comprises two phenotypes, bronchiolitis obliterans syndrome and restrictive allograft syndrome. Half of all lung recipients will develop CLAD in 5 years, and this rate may increase up to 75% 10 years after surgery owing to the paucity in accurate and effective early detection and treatment methods. Recently, many studies have presented noninvasive methods for detecting CLAD and improving diagnosis and intervention. However, the significance of accurately detecting CLAD remains controversial. We reviewed published studies that have presented noninvasive methods for detecting CLAD to highlight the current knowledge on clinical symptoms, spirometry, imaging examinations, and other methods to detect the disease.

Post-infectious Bronchiolitis Obliterans: HRCT, DECT, Pulmonary Scintigraphy Images, and Clinical Follow-up in Eight Children

Background: Bronchiolitis obliterans (BO), first mentioned in 1901, is a severe and rare chronic lung disease in children. BO has various etiologies and the most common in children is post-infectious BO (PIBO). High resolution CT (HRCT) is an often-used image tool for the diagnosis of BO, and pulmonary scintigraphy is an alternative tool that can functionally evaluate BO. Recently, dual-energy computed tomography (DECT) have also been applied to BO for its accuracy and safety. Here we described the characteristics of HRCT, pulmonary scintigraphy, DECT, and the clinical profiles of patients with PIBO. Methods: This is a retrospective and descriptive study. Data were collected from patients diagnosed with PIBO from 2014 to 2019 in the Pediatric Cardiopulmonary Outpatient Clinics of Kaohsiung Medical University Hospital. The diagnosis was based on clinical, chest X-ray, and HRCT findings. Clinical profile, radiological characteristics, and images of pulmonary scintigraphy were documented. Results: Eight children (4 boys and 4 girls) were diagnosed with PIBO at a mean age of 25.8 months (range 15 to 41 months). Two of our patients developed pulmonary hypertension. The most common HRCT finding is mosaic pattern, where match ventilation/perfusion (V/Q) defects is a general feature in pulmonary scintigraphy. DECT pulmonary blood vasculature images revealed various degrees of decreased perfusion and is compatible with the decreased perfusion on pulmonary scintigraphy. Conclusion: The therapeutic strategy of PIBO is still lacking of standardization. HRCT and V/Q scans are important image tools in diagnosis and follow-up of BO. DECT may be used in BO patients as it has no additional radiation exposure and add value on functional information of HRCT.