First week of life respiratory management and pulmonary ventilation/perfusion matching in infants with bronchopulmonary dysplasia: a retrospective observational study.

OBJECTIVE: To investigate the association between early neonatal respiratory management in infants with bronchopulmonary dysplasia (BPD) and the degree of pulmonary ventilation perfusion-matching (V/Q) at term. METHODS: 30 preterm infants with a diagnosis of BPD who were initially treated with either controlled mechanical ventilation/continuous positive airway pressure (CMV/CPAP) (n = 14) or high-frequency oscillatory ventilation (HFOV) using a high lung-volume strategy (n = 16) were retrospectively included in this study. All infants underwent pulmonary V/Q single photon emission computed tomography at a median postmenstrual age of 37 weeks. RESULTS: Infants treated with HFOV had significantly larger proportion of the lung with matched V/Q as compared to infants treated with CMV/CPAP, median (interquartile range) 60.4% (55.5-66.0%) and 45.8% (37.8-53.1%) respectively (p = 0.01). CONCLUSIONS: In infants who needed mechanical ventilation the first week of life and later developed BPD an association was observed between treatment with a HFOV and better pulmonary V/Q matching at near-term age.

Primary hyperparathyroidism, a machine learning approach to identify multiglandular disease in patients with a single adenoma found at preoperative Sestamibi-SPECT/CT.

Objective: Successful preoperative image localisation of all parathyroid adenomas (PTA) in patients with primary hyperparathyroidism (pHPT) and multiglandular disease (MGD) remains challenging. We investigate whether a machine learning classifier (MLC) could predict the presence of overlooked PTA at preoperative localisation with 99mTc-Sestamibi-SPECT/CT in MGD patients. Design: This study is a retrospective study from a single tertiary referral hospital initially including 349 patients with biochemically confirmed pHPT and cured after surgical parathyroidectomy. Methods: A classification ensemble of decision trees with Bayesian hyperparameter optimisation and five-fold cross-validation was trained with six predictor variables: the preoperative plasma concentrations of parathyroid hormone, total calcium and thyroid-stimulating hormone, the serum concentration of ionised calcium, the 24-h urine calcium and the histopathological weight of the localised PTA at imaging. Two response classes were defined: patients with single-gland disease (SGD) correctly localised at imaging and MGD patients in whom only one PTA was localised on imaging. The data set was split into 70% for training and 30% for testing. The MLC was also tested on a subset of the original data based on CT image-derived PTA weights. Results: The MLC achieved an overall accuracy at validation of 90% with an area under the cross-validation receiver operating characteristic curve of 0.9. On test data, the MLC reached a 72% true-positive prediction rate for MGD patients and a misclassification rate of 6% for SGD patients. Similar results were obtained in the testing set with image-derived PTA weight. Conclusions: Artificial intelligence can aid in identifying patients with MGD for whom 99mTc-Sestamibi-SPECT/CT failed to visualise all PTAs.

Pulmonary translocation of ultrafine carbon particles in COPD and IPF patients.

OBJECTIVE: Epidemiological studies indicate association between elevated air pollution and adverse health effects. Several mechanisms have been suggested, including translocation of inhaled ultrafine carbon (UFC) particles into the bloodstream. Previous studies in healthy subjects have shown no significant pulmonary translocation of UFC-particles. This study aimed to assess if UFC-particles translocate from damaged alveolar compartment in subjects suffering from chronic obstructive pulmonary disease (COPD) and idiopathic pulmonary fibrosis (IPF). METHODS: Eleven COPD and nine IPF subjects were exposed to a 100 nm UFC-particle-aerosol labeled with Indium-111. Activity in the body was followed up for 10 days using gamma camera planar-imaging as well as in blood and urine samples. RESULTS: The pulmonary central to periphery activity ratio was significantly higher for COPD as compared to IPF subjects at exposure, 1.8 and 1.4, respectively and remained constant throughout the test period. Ten days after exposure, the estimated median pulmonary translocation of UFC particles was 22.8 and 25.8% for COPD and IPF, respectively. Bound activity was present in blood throughout the test period, peaking at 24-h postinhalation with a median concentration of 5.6 and 8.9 Bq/ml for the COPD and IPF, respectively. Median bound activity excreted in urine (% of inhaled) after 10 days was 1.4% in COPD and 0.7% in IPF. Activity accumulation in liver and spleen could not be demonstrated. CONCLUSIONS: Our results suggest that UFC particles leak through the damaged alveolar barrier to the bloodstream in COPD and IPF patients probably distributing in a wide spectrum of whole-body tissues.

The preoperative localisation of small parathyroid adenomas improves when adding Tc-99m-Sestamibi SPECT to multiphase contrast-enhanced CT.

OBJECTIVES: To investigate the incremental value of Sestamibi SPECT combined with a non-enhanced and contrast-enhanced CT, using SPECT/CT, for the preoperative localisation of small parathyroid adenomas (PTA). METHODS: Retrospectively, 147 patients surgically cured from primary hyperparathyroidism, as verified by biochemistry 6 months postoperatively, were included. All patients had preoperatively undergone a dual time 99mTechnetium-Sestamibi SPECT (S) with multiphase CT including native (N), arterial (A) and venous (V) phases. Independently, two radiologists blinded from both the surgical and the preoperative imaging reports, sequentially performed PTA localisation starting with either [A] or [V], thereafter [A + N] or [V + N] and finally with the complete [A + N + S] or [V + N + S]. PTA localisation was reported for each image-set. The readers results were combined and the diagnostic performance for each image set was determined. Sensitivity was also calculated for the different quartiles of PTA weight distribution. RESULTS: The median adenoma weight was 315 mg. No statistically significant differences in diagnostic performance between arterial and venous based image sets were found. The net effect of adding [N] was to increase specificity. Sestamibi SPECT significantly increased the overall diagnostic accuracy for arterial- and venous-based image sets, p = 0.0008 and p = 0.001, respectively. [A + N + S] was found to have the highest diagnostic performance with 86.5% sensitivity and 94.9% overall accuracy. [A + N + S] was particularly advantageous for locating PTA in the lower weight quartiles. CONCLUSIONS: Native CT-phase and dual time point Sestamibi SPECT increase specificity and sensitivity, respectively. These, in combination with a single contrast-enhanced CT-phase is the most optimal examination protocol for preoperative localisation of PTA using SPECT/CT.

Multiphase Iodine Contrast-Enhanced SPECT/CT Outperforms Nonenhanced SPECT/CT for Preoperative Localization of Small Parathyroid Adenomas.

PURPOSE: The aim of this study was to assess the value of intravenously contrast-enhanced CT in conjunction with Tc-MIBI SPECT for preoperative localization of parathyroid adenoma. METHODS: One hundred ninety-two patients with primary hyperparathyroidism were enrolled in the study between May 2015 and May 2017. The patients underwent a preoperative "one-stop shop" examination with Tc-MIBI SPECT/CT by using dual time-point (10 and 90 minutes) protocol and both nonenhanced CT and contrast-enhanced CT acquisition in the arterial and venous phase, 35 and 75 seconds, respectively, after contrast medium injection start. For 149 patients, the imaging results could be correlated to those at surgery and histopathology. RESULTS: The median adenoma weight was 330 mg. The addition of contrast-enhanced CT increased the sensitivity from 81.1% to 89.9% (P = 0.003). The specificity of nonenhanced SPECT/CT was similar to contrast-enhanced CT (96.1% vs 97.9%; P = 0.077). For patients with uniglandular disease (n = 140, 94.0%), the sensitivity increased from 86.4% to 93.6% (P = 0.021) and the specificity from 96.2% to 97.9% (P = 0.118) by adding contrast-enhanced CT. In patients with multiglandular disease (n = 9, 6.0%), adding contrast-enhanced CT improved detection sensitivity from 42.1% to 63.2%. However, these patients were few and significance was not reached (P = 0.125). CONCLUSIONS: In this cohort, with generally small parathyroid adenomas, the sensitivity in preoperative localization was greatly improved by adding contrast-enhanced CT to Tc-MIBI SPECT/CT.

Comparison of acquisition protocols for ventilation/perfusion SPECT-a Monte Carlo study.

One of the most commonly used imaging techniques for diagnosing pulmonary embolism (PE) is ventilation/perfusion (V/P) scintigraphy. The aim of this study was to evaluate the performance of the currently used imaging protocols for V/P single photon emission computed tomography (V/P SPECT) at two nuclear medicine department sites and to investigate the effect of altering important protocol parameters. The Monte Carlo technique was used to simulate 4D digital phantoms with perfusion defects. Six imaging protocols were included in the study and a total of 72 digital patients were simulated. Six dually trained radiologists/nuclear medicine physicians reviewed the images and reported all perfusion mismatch findings. The radiologists also visually graded the image quality. No statistically significant differences in diagnostic performance were found between the studied protocols, but visual grading analysis pointed out one protocol as significantly superior to four of the other protocols. Considering the study results, we have decided to harmonize our clinical protocols for imaging patients with suspected PE. The administered Technegas and macro aggregated albumin activities have been altered, a low energy all purpose collimator is used instead of a low energy high resolution collimator and the acquisition times have been lowered.

Ten-year-old children with a history of bronchopulmonary dysplasia have regional abnormalities in ventilation perfusion matching.

AIM: The ratio of ventilation to blood flow is an important determinant for regional gas exchange in the lung and hypoxemia is one of the clinical hallmarks in infants with bronchopulmonary dysplasia (BPD). We have previously demonstrated ventilation/perfusion ratio (V/Q) abnormalities in infants with BPD at 36 weeks postconceptional age. The status of V/Q matching in older children with a history of BPD in infancy is unknown. In this study, we examined if 10-year-old children with a history of BPD had V/Q impairments. METHODS: Three-dimensional V/Q-scintigraphy (SPECT) was performed in 26 children. RESULTS: In the BPD group, lung volume with mismatch, (V>Q) was larger compared to areas with reverse mismatch (Q>V), 26.2% and 11.8%, respectively, implying that perfusion defects contribute more than ventilation defects in the V/Q mismatch. Also, the mean fractional distribution of V and Q to V/Q in children with BPD was reduced compared to healthy children, 31% and 51% compared to 64% and 89%, respectively (P < 0.01). CONCLUSION: At 10 years of age children with a history of BPD had ventilation/perfusion abnormalities, with prominent perfusion defects. These V/Q abnormalities suggest the presence of residual alveolar-capillary impairment.

18F FDG-PET/CT evaluation of histological response after neoadjuvant treatment in patients with cancer of the esophagus or gastroesophageal junction.

BACKGROUND: In most parts of the world, curatively intended treatment for esophageal cancer includes neoadjuvant therapy, either with chemoradiotherapy or chemotherapy alone, followed by esophagectomy. Currently 18F-FDG positron emission tomography/computed tomography (PET/CT) is used for preoperative disease staging, but is not well established in the evaluation of neoadjuvant treatment. PURPOSE: To evaluate changes in PET parameters in relation to the histological primary tumor response in the surgical specimen in patients randomized to neoadjuvant chemoradiotherapy or chemotherapy. MATERIAL AND METHODS: Patients were randomized between either neoadjuvant chemotherapy or chemoradiotherapy followed by esophagectomy.18F-FDG PET/CT exams were conducted at baseline and following neoadjuvant treatment. Standardized uptake ratio (SUR) values were measured in the primary tumor and compared as regards histological responders and non-responders as well as different treatment arms. RESULTS: Seventy-nine patients were enrolled and 51 were available for analysis. A significant rate of SUR reduction was observed ( P = 0.02) in the primary tumor in histological responders compared to non-responders. Changes in SUR were significantly greater in responders following chemoradiotherapy ( P = 0.02), but not following chemotherapy alone ( P = 0.49). There was no statistically significant difference in SUR in patients with a complete histological response compared to those with a subtotal response. CONCLUSION: Our results are similar to those of previous studies and show that changes in the rate of SUR can be used reliably to differentiate histological responders from non-responders after neoadjuvant treatment with either chemoradiotherapy or chemotherapy. Limitations of current PET technology are likely to restrict the possibility of accurately ruling out limited residual disease.

Lung Ventilation/Perfusion Single Photon Emission Computed Tomography (SPECT) in Infants and Children with Nonembolic Chronic Pulmonary Disorders.

Single photon emission computed tomography (SPECT) provides high contrast three dimensional images of the regional distribution of a radiotracer. SPECT is a widely used technique in pulmonary investigations of the ventilation (V) and perfusion (Q) in the adult patient, mainly in the diagnosis of pulmonary embolism. However, safety concerns among practitioners due to radiation exposure and the use of macroaggregate albumin for the perfusion scan have historically precluded the use of SPECT in pediatric patients with nonembolic pulmonary disorders. Additionally, patient cooperation at ventilation tracer administration and image artifacts from patient movements due the long acquisition times, have further limited the application of SPECT in pediatric patients. With the introduction of technegas aerosol for ventilation studies and the use of high sensitive multihead gamma cameras, both the total amount of administered activity and acquisition time have drastically been reduced allowing the application of SPECT in pediatric patients. Modern hybrid gamma camera/computed tomography systems (SPECT/CT) also brings the possibility of adding a fully diagnostic CT to the SPECT images, incrementing the clinical value of the investigation. Besides pulmonary embolism, there is now some clinical evidence that lung SPECT has diagnostic value in several pulmonary pathologies causing V/Q mismatching, which are specific to the pediatric age group. In this work, we will exemplify and briefly discuss some of these applications based on the literature and our routine clinical experience. Consideration to the risks and safety aspects associated to performing pediatric V/Q SPECT are also discussed.

Lung Scintigraphy in the Assessment of Aerosol Deposition and Clearance.

Environmental and occupational exposure to particulate aerosols is known to have negative health effects. However little is known about how these aerosols trigger the development of pathophysiological mechanisms in the body or the fate of ultrafine particles in the lungs after inhalation. The development of aerosols of different origin that can be labeled to a large variety with radionuclides compatible with clinical gamma camera systems opens the possibility of using lung scintigraphy imaging to study these causalities in detail. Lung scintigraphy (planar or SPECT) allows regional mapping of the deposition of the aerosol in the lungs and the dynamic assessment of particle clearance and translocation from the healthy and affected human lungs. In this paper, we will review the unique features of lung scintigraphy applied to aerosol clearance studies in humans.

Hallmarks in prostate cancer imaging with Ga68-PSMA-11-PET/CT with reference to detection limits and quantitative properties.

BACKGROUND: Gallium-68-labeled prostate-specific antigen positron emission tomography/computed tomography imaging (Ga68-PSMA-11-PET/CT) has emerged as a potential gold standard for prostate cancer (PCa) diagnosis. However, the imaging limitations of this technique at the early state of PCa recurrence/metastatic spread are still not well characterized. The aim of this study was to determine the quantitative properties and the fundamental imaging limits of Ga68-PSMA-11-PET/CT in localizing small PCa cell deposits. METHODS: The human PCa LNCaP cells (PSMA expressing) were grown and collected as single cell suspension or as 3D-spheroids at different cell numbers and incubated with Ga68-PSMA-11. Thereafter, human HCT116 cells (PSMA negative) were added to a total cell number of 2 × 105 cells per tube. The tubes were then pelleted and the supernatant aspirated. A whole-body PET/CT scanner with a clinical routine protocol was used for imaging the pellets inside of a cylindrical water phantom with increasing amounts of background activity. The actual activity bound to the cells was also measured in an automatic gamma counter. Imaging detection limits and activity recovery coefficients as a function of LNCaP cell number were obtained. The effect of Ga68-PSMA-11 mass concentration on cell binding was also investigated in samples of LnCaP cells incubated with increasing concentrations of radioligand. RESULTS: A total of 1 × 104 LNCaP cells mixed in a pellet of 2 × 105 cells were required to reach a 50% detection probability with Ga68-PSMA-11-PET/CT without background. With a background level of 1 kBq/ml, between 4 × 105 and 1 × 106 cells are required. The radioligand equilibrium dissociation constant was 27.05 nM, indicating high binding affinity. Hence, the specific activity of the radioligand has a profound effect on image quantification. CONCLUSIONS: Ga68-PSMA-11-PET detects a small number of LNCaP cells even when they are mixed in a population of non-PSMA expressing cells and in the presence of background. The obtained image detection limits and characteristic quantification properties of Ga68-PSMA-11-PET/CT are essential hallmarks for the individualization of patient management. The use of the standardized uptake value for Ga68-PSMA-11-PET/CT image quantification should be precluded.

Diagnostic accuracy of 11C-methionine PET in detecting neuropathologically confirmed recurrent brain tumor after radiation therapy.

OBJECTIVE: This study aims to determine the diagnostic test accuracy (DTA) of 11C-methionine (MET) PET in the discrimination between recurrent tumor and radiation-induced injury in neuropathologically confirmed cases. METHODS: A retrospective cohort of 30 patients with previously irradiated intracranial tumors (23 gliomas, 6 metastases, and 1 meningioma) was included. All patients underwent a preoperative MET PET and postoperative neuropathological analysis. Maximum and mean standardized uptake values (SUV) were obtained in the lesion, in the contralateral mirror region, and in the contralateral frontal cortex. Lesion-to-background SUV ratios (SUR mirror and SUR cortex) were then calculated. The Mann-Whitney U test was used to evaluate differences in SUV ratios between confirmed recurrent tumor and radiation injury. DTA was determined through receiver operating characteristic (ROC) analysis. RESULTS: Twenty-one patients had recurrent tumor and nine had radiation injury. The area under the ROC curve (AUC) was 0.89 for SURmaxmirror and 0.88 for SURmaxcortex. The mean (SD) of SURmaxmirror was 2.37 (0.58) in tumor recurrence and 1.57 (0.40) in radiation necrosis (P ≤ 0.001). The corresponding values for SURmaxcortex were 2.13 (0.50) and 1.45 (0.37) (P = 0.001). Clinically relevant cutoffs were SURmaxmirror ≥ 1.99 giving a specificity of 100% for tumor recurrence with a sensitivity of 76% and SURmaxcortex ≥ 1.58 giving a sensitivity and specificity of 90 and 78%, respectively. CONCLUSIONS: Based on neuropathologically confirmed cases, the DTA of SURmaxmirror and SURmaxcortex from 11C-methionine PET was high when discriminating recurrent tumor from radiation injury.

SPECT/CT's Advantage for Preoperative Localization of Small Parathyroid Adenomas in Primary Hyperparathyroidism.

PURPOSES: The aims of this study were to assess the performance of Tc-sestamibi SPECT/CT, with diagnostic CT quality, compared with SPECT alone for preoperative localization of parathyroid adenomas and to assess the influence of adenoma weight on the correct adenoma lateralization with SPECT/CT and with SPECT alone. METHODS: Two hundred forty-nine consecutive patients, biochemically diagnosed with primary hyperparathyroidism, were examined with a combined SPECT/CT scanner. Subsequently, 200 patients with confirmed histopathology and biochemical cure after parathyroidectomy were included in this study (16 with multiglandular disease). For each patient, the SPECT-alone data were analyzed first. Thereafter, the CT information was added, and a new evaluation was performed with the combined data. In addition, for each patient, the diagnostic confidence with each method was graded on a scale based on the presence of different image features. The preoperative diagnostic findings were then compared with the surgical and histopathologic reports. RESULTS: The distribution of adenoma weights showed a peak at 210 mg, with a median at 338 mg. The sensitivity and specificity (multiglandular disease included) for correct classification of adenomas were significantly higher for SPECT/CT, 83% and 96%, respectively, than for SPECT alone, 80% and 93% (P < 0.01). Below 210 mg, the differences between SPECT/CT and SPECT alone in accurate adenoma lateralization were more prominent. Sixty-seven percent of all adenomas were graded with the highest confidence score with SPECT/CT compared with 53% with SPECT. CONCLUSIONS: SPECT/CT yields fewer false-positive findings than SPECT alone. The advantage of SPECT/CT over SPECT alone was most apparent for correct lateralization of small adenomas (<210 mg).

Predictive value of [18F]-fluoride PET for monitoring bone remodeling in patients with orthopedic conditions treated with a Taylor spatial frame.

PURPOSE: The Taylor Spatial Frame (TSF) is used to correct orthopedic conditions such as correction osteotomies in delayed fracture healing and pseudarthrosis. Long-term TSF-treatments are common and may lead to complications. Current conventional radiological methods are often unsatisfactory for therapy monitoring. Hence, an imaging technique capable of quantifying bone healing progression would be advantageous. METHODS: A cohort of 24 patients with different orthopedic conditions, pseudarthrosis (n = 10), deformities subjected to correction osteotomy (n = 9), and fracture (n = 5) underwent dynamic [18F]-fluoride (Na18F) PET/CT at 8 weeks and 4 months, respectively, after application of a TSF. Parametric images, corresponding to the net transport rate of [18F]-fluoride from plasma to bone, K i were calculated. The ratio of the maximum K i at PET scan 2 and 1 ([Formula: see text]) as well as the ratio of the maximum Standard Uptake Value at PET scan 2 and 1 ([Formula: see text]) were calculated for each individual. Different treatment end-points were scored, and the overall treatment outcome score was compared with the osteoblastic activity progression as scored with [Formula: see text] or [Formula: see text]. RESULTS: [Formula: see text] and [Formula: see text] were not correlated within each orthopedic group (p > 0.1 for all groups), nor for the pooled population (p = 0.12). The distribution of [Formula: see text] was found significantly different among the different orthopedic groups (p = 0.0046) -also for [Formula: see text] (p = 0.022). The positive and negative treatment predictive values for [Formula: see text] were 66.7 % and 77.8 %, respectively. Corresponding values for [Formula: see text] were 25 % and 33.3 % CONCLUSIONS: The [Formula: see text] obtained from dynamic [18F]-fluoride-PET imaging is a promising predictive factor to evaluate changes in bone healing in response to TSF treatment.

18F-FDG PET/CT Diagnosis of Bronchopulmonary Carcinoids Versus Pulmonary Hamartomas.

PURPOSE: Radiological characterization of pulmonary tumors may be difficult and invasive. Needle biopsy may produce false-negative results. 18F-FDG PET/CT is an established noninvasive procedure for lung tumor characterization and staging. This study was aimed at differentiating bronchopulmonary carcinoids from hamartomas and typical from atypical bronchopulmonary carcinoids by means of 18F-FDG PET/CT. PATIENTS AND METHODS: In a retrospective analysis of 118 patients, with surgically resected pulmonary carcinoid tumors and hamartomas, 87 of those selected had also undergone 18F-FDG PET/CT preoperatively and constituted the study population. To better assess the tracer accumulation, especially in small lesions, the 18F-FDG uptake (SUV) in the tumors was corrected for partial volume effect by applying recovery coefficients corresponding to the respective various specific tumor volumes, as extrapolated from those obtained from experiments in a NEMA phantom. RESULTS: The SUVmax was higher in the pulmonary carcinoids (mean, 3.9) than in the hamartomas (mean, 1.4; P ≤ 0.00001) and higher in the subgroup of peripheral carcinoids than in hamartomas (P ≤ 0.00001). The SUVmax was similar for the atypical and typical carcinoids, 5.0 and 3.8, respectively, because of the large variation in the data (P = 0.11). CONCLUSIONS: Using PET measurements of the 18F-FDG uptake (SUVmax) in the tumors, corrected for partial volume effects, it was possible to differentiate the carcinoids from the hamartomas, but the clinically more aggressive atypical carcinoids could not be differentiated from the typical carcinoids.

Repeatability of the Maximum Standard Uptake Value (SUVmax) in FDG PET.

OBJECTIVE: SUVmax is often calculated at FDG PET examinations in systematic studies as well as at clinical examinations. Since SUVmax represents a very small portion of a lesion it may be questioned how statistically reliable the figure is. This was studied by assessing the repeatability of SUVmax between two FDG acquisitions acquired immediately upon each other in patients with chest lesions. METHODS: In 100 clinical patients with a known chest lesion, two identical 3 min PET registrations (PET1 and PET2, respectively) were initiated within 224±31 sec of each other. The difference in SUVmax between the lesion for the two PET scans (ΔSUVmax) was calculated and the uncertainty expressed as the coefficient of variation, CV (%). The correlation between ΔSUVmax and the lowest SUVmax from PET1 or PET2, the approximate metabolic lesion volume, the time from FDG injection to PET1 and the time between PET1 and PET2, respectively, was also assessed. RESULTS: In 56 patients SUVmax increased at the second acquisition and in 44 patients it decreased. Mean of SUVmax was 7.8±6.1 and 7.8±6.2 for PET1 and PET2, respectively. The mean percentage difference was 0.9±7.8. The difference was not significant (p=0.20). CV gave an uncertainty of 4.3% between the two measurements which is a strong indicator of equivalence. There was no correlation between ΔSUVmax and any of the assessed four parameters. The difference between the acquisitions, 0.9%, was much lower compared to the 3 previous published similar, but more restricted studies where the difference was 2.5-8.2%. CONCLUSION: From camera and computational perspectives, SUVmax is a stable parameter Conflict of interest:None declared.

Bronchopulmonary dysplasia: clinical grading in relation to ventilation/perfusion mismatch measured by single photon emission computed tomography.

Bronchopulmonary dysplasia (BPD) is a significant cause of morbidity in the preterm population. Clinical severity grading based on the need for supplemental oxygen and/or need for positive airway pressure at 36 weeks postmenstrual age does not yield reproducible predictive values for later pulmonary morbidity. Single photon emission computed tomography (SPECT) was used to measure the distribution of lung ventilation (V) and perfusion (Q) in 30 BPD preterm infants at a median age of 37 weeks postmenstrual age. The V and Q were traced with 5 MBq Technegas and Technetium-labeled albumin macro aggregates, respectively, and the V/Q match-mismatch was used to quantify the extent of lung function impairment. The latter was then compared with the clinical severity grading at 36 weeks, and time spent on mechanical ventilation, continuous positive airway pressure (CPAP) and supplemental oxygen. Of those with mild and moderate BPD 3/9 and 3/11 patients, respectively, showed significant V/Q mismatches. By contrast, 4/10 patients with severe BPD showed a satisfactory V/Q matching distribution. An unsatisfactory V/Q match was not correlated with time spent on supplemental oxygen or CPAP, but was significantly negatively correlated with time spent on mechanical ventilation. SPECT provides unique additional information about regional lung function. The results suggest that the current clinical severity grading can be improved and/or complemented with SPECT.

Comparison of Gallium-68 and Fluorine-18 imaging characteristics in positron emission tomography.

This review article compares PET imaging performance with Gallium-68 ((68)Ga) and Fluorine-18 ((18)F). The literature on this topic is scarce; hence in order to complete the published data, Monte Carlo calculations, as well as phantom measurements, were carried out. The qualitative and quantitative differences between (68)Ga and (18)F imaging were evaluated in terms of spatial resolution, sensitivity, contrast and activity recovery coefficients for both human PET systems and small animal PET scanners. The clinical and pre-clinical implications of these differences are discussed.

The pulmonary deposition and retention of indium-111 labeled ultrafine carbon particles in healthy individuals.

CONTEXT: Particulate air pollution, for example, from ultrafine (UF) particles, has negative health effects. However, there is still limited knowledge regarding the fate of inhaled particles in the human body. OBJECTIVES: To describe the normal lung deposition and 1 week particle retention of indium-111 labeled UF carbon particles in healthy subjects. Additionally, the possibility to extend the follow-up period to 4 weeks was also investigated for one of the subjects. RESULTS: The cumulative pulmonary particle clearance 1 week post-administration, corrected for activity leaching and mucocilliary transport of activity deposited in the central airways, was 4.3 ± 8.5% (average ± standard deviation at group level), with marginal translocation of particles from lungs to blood, 0.3%. There was no observable elimination of particles from the body via urine. Seven days after exposure, the cumulated activity leaching was 3% (group level), which indicates a stable bonding between the particles and Indium-111. The volunteer followed for a total of 4 weeks, showed a cumulative decrease of activity retention in the lungs of 10.5%. After correction for activity leaching and clearance from central airway deposition, the estimated particle clearance was about 2%. CONCLUSIONS: No evidence for particle translocation from the lungs could be proven 7 days after exposure. It is possible to follow-up Indium-111 labeled UF carbon particles at least 1 month post-administration without increasing the administered activity.

A revision of the organ radiation doses from 2-fluoro-2-deoxy-D-glucose with reference to tumour presence.

Absorbed radiation doses to major human organs after intravenous bolus administration of 2-[(18)F]fluoro-2-deoxy-d-glucose (FDG) were reviewed. Absorbed doses were calculated using the medical internal radiation dose (MIRD) formalism from experimental activity-time curves. Thirty patients (22 with macroscopic lung tumour and 8 without observable disease) were investigated using a state-of-the-art combined positron emission tomography/computer tomography system (Siemens Biograph 64). Each patient underwent a series of 10 consecutive whole-body PET scans during the first 60-min post-FDG administration. Differences were observed between organ radiation doses in this work and those reported in International Commission for Radiation Protection 106 (21 % in effective dose). The presence of tumour did not affect the FDG biodistribution. Large inter-individual variations in organ-absorbed doses were observed. This in combination with the lack of a model for bladder voiding suitable for all patients suggests the need for a more precise estimate of normal-organ radiation doses. This will be beneficial in optimising FDG administration in clinical routine.