Pulmonary Vein Stenosis as a Pitfall of Ventilation/Perfusion SPECT/CT for Pulmonary Embolism.

ABSTRACT: A 58-year-old man with progressive dyspnea and recurrent extensive left-sided pleural effusion underwent pulmonary ventilation/perfusion SPECT/CT, which showed a pronounced mismatched perfusion deficit of the entire, normally ventilated left lung. As unilateral perfusion deficits of an entire lobe are generally not due to pulmonary embolism, further CT angiography and cardiac MRI were conducted. These examinations revealed high-grade left pulmonary vein stenosis (PVS) caused by pulmonary vein isolation performed for atrial fibrillation 3 and 4 years earlier. Thus, in addition to, for example, neoplastic processes or pulmonary congenital vascular abnormalities, PVS must be considered as a differential diagnosis and possible pitfall in ventilation/perfusion SPECT/CT in dyspneic patients with prior pulmonary vein isolation.

Research on the method of controlling the 99mTc-Technegas inhaled during 1-day pulmonary ventilation/perfusion imaging.

OBJECTIVE: Our purpose was to establish a simple and feasible method for monitoring and controlling the Tc-Technegas inhaled to improve the success ratio of imaging and ensure the imaging quality. MATERIALS AND METHODS: The relationship between the success ratio and the pulmonary ventilation counting rate (VCR) of 113 cases, the activity of perfusion imaging agents injected and the pulmonary perfusion counting rate (PCR) of another 114 cases were analysed retrospectively. And combined with the relationship between the surface radioactivity monitoring value and the SPECT probe counting rate of a pulmonary model, the effective range of the VCR and the surface radioactivity monitoring value were determined. Two hundred fifty cases with Tc-Technegas inhaled monitored and controlled were used to verify the reliability and practicability of this method. RESULTS: The VCR of the ventilation/perfusion imaging with deep venous thrombosis imaging and the ventilation/perfusion imaging without deep venous thrombosis imaging was in 1.0-3.0 kct/s and 1.0-2.0 kct/s when the monitoring values of handheld radiation monitor was within the range of 60-170 µSv/h and 60-110 µSv/h, respectively. The success ratio of the V/Q-Only increased from 48.9% (43/88) of the control group to 80.8% (122/151) of the experimental group. The VCR in the two groups was examined by the non-parametric Mann-Whitney U test (P < 0.001), which indicated that there was a significant difference between the experimental group and the control group. CONCLUSION: The external monitoring method established in this study was of great significance in improving the success ratio of 1-day pulmonary ventilation/perfusion imaging and ensuring the image quality.

Renal Safety of Intra-Arterial Treatment after Acute Ischemic Stroke with Multimodal CT Imaging selection.

BACKGROUND: Multimodal computed tomography imaging is used to identify eligible patients for intra-arterial treatment. A concern with this method is the multiple use of iodinated contrast material which presents a possible risk of renal toxicity. We compared the safety of intra-arterial treatment versus intravenous treatment during acute ischemic stroke treatment with a focus on renal safety. METHODS: Adult acute ischemic stroke patients who underwent a baseline Multimodal computed tomography, then intra-arterial treatment and/or intravenous treatment were identified. Primary outcomes were acute kidney injury and changes in serum creatinine at 24-72 hours (Δ serum creatinine). RESULTS: A total of 184 patients received intra-arterial treatment, while 68 received intravenous treatment. There were no differences in mean serum creatinine in the 24-72-hour time period, 24-hour urine volume, or rates of acute kidney injury, dialysis, or mortality. Univariate regression analysis identified diabetes mellitus, operation duration and times of embolectomy as predictors of creatinine increase while the multiple regression model identified diabetes mellitus as the only significant predictor. CONCLUSIONS: There were no significant differences in renal safety between the intra-arterial treatment and intravenous treatment groups. Diabetes mellitus may be a predictor of acute kidney injury. The use of Multimodal computed tomography imaging in the selection of patients who could benefit from endovascular therapy is safe.

DNA double-strand breaks in blood lymphocytes induced by two-day 99mTc-MIBI myocardial perfusion scintigraphy.

OBJECTIVES: To investigate DNA double-strand breaks (DSBs) in blood lymphocytes induced by two-day 99mTc-MIBI myocardial perfusion scintigraphy (MPS) using y-H2AX immunofluorescence microscopy and to correlate the results with 99mTc activity in blood samples. METHODS: Eleven patients who underwent two-day MPS were included. DSB blood sampling was performed before and 5min, 1h and 24h after the first and second radiotracer injections. 99mTc activity was measured in each blood sample. For immunofluorescence microscopy, distinct foci representing DSBs were quantified in lymphocytes after staining for the phosphorylated histone variant y-H2AX. RESULTS: The 99mTc-MIBI activity measured on days one and two was similar (254±25 and 258±27 MBq; p=0.594). Compared with baseline DSB foci (0.09±0.05/cell), a significant increase was found at 5min (0.19±0.04/cell) and 1h (0.18±0.04/cell) after the first injection and at 5min and 1h after the second injection (0.21±0.03 and 0.19±0.04/cell, respectively; p=0.003 for both). At 24h after the first and second injections, the number of DSB foci had returned to baseline (0.06±0.02 and 0.12±0.05/cell, respectively). 99mTc activity levels in peripheral blood samples correlated well with DSB counts (r=0.451). CONCLUSIONS: DSB counts reflect 99mTc-MIBI activity after injection for two-day MPS, and might allow individual monitoring of biological effects of cardiac nuclear imaging. KEY POINTS: • Myocardial perfusion scintigraphy using 99mTc induces time-dependent double-strand breaks (DSBs) • γ-H2AX immunofluorescence microscopy shows DSB as an early response to radiotracer injection • Activity measurements of 99mTc correlate well with detected DSB • DSB foci induced by 99mTc return to baseline 24h after radiotracer injection.

Risk of early-onset breast cancer among women exposed to thoracic computed tomography in pregnancy or early postpartum.

Essentials Tests for pulmonary embolism expose women to low-dose radiation. 5859 pregnancies had a thoracic computed tomography (T-CT) vs. 1.3 million who did not. The adjusted hazard ratio for breast cancer was 1.17 (95% confidence interval 0.80-1.70). The long-term risk of breast cancer among women who had a T-CT remains unknown. SUMMARY: Background The risk of breast cancer may be higher with direct exposure to ionizing radiation from thoracic computed tomography (CT) during pregnancy or the postpartum. We evaluated the short-term risk of maternal breast cancer after exposure to thoracic CT during these periods. Methods We completed a retrospective population-based cohort study of all deliveries between 1995 and 2014 using universal healthcare databases in the province of Ontario, Canada. The main exposure was thoracic CT in pregnancy or ≤ 42 days postpartum. The passive exposure was ventilation-perfusion scintigraphy (VQ) scan in pregnancy or ≤ 42 days postpartum. Each was compared to pregnancies unexposed to thoracic CT or VQ scan. The primary study outcome was newly diagnosed breast cancer starting 366 days post-index delivery date. Results A total of 5859 pregnancies were exposed to thoracic CT, 4075 to VQ scan and 1 292 059 to neither. Starting from 1 year after the index delivery, the median duration of follow-up was 5.9, 7.3 and 11.1 years, respectively. A total of 10 129 women were diagnosed with breast cancer, of whom 9039 (89.2%) were aged ≤ 50 years. There were 27 new cases of breast cancer (7.1 per 10 000 person-years) following thoracic CT vs. 10 080 (7.0 per 10 000 person-years) among the unexposed, an adjusted hazard ratio (HR) of 1.17 (95% confidence interval [CI], 0.80-1.70). Following VQ scan exposure, the incidence rate of breast cancer was 7.0 per 10 000 person-years, an adjusted HR of 1.23 (95% CI 0.81-1.87), compared with the unexposed cohort. Conclusion Exposure to thoracic CT during pregnancy or the postpartum was not associated with an increased short-term risk of maternal breast cancer. The long-term risk should be studied.

Effects of Radiation Exposure on the Cost-Effectiveness of CT Angiography and Perfusion Imaging in Aneurysmal Subarachnoid Hemorrhage.

BACKGROUND AND PURPOSE: CT angiography and perfusion imaging is an important prognostic tool in the management of patients with aneurysmal subarachnoid hemorrhage. The purpose of this study was to perform a cost-effectiveness analysis of advanced imaging in patients with SAH, incorporating the risks of radiation exposure from CT angiography and CT perfusion imaging. MATERIALS AND METHODS: The risks of radiation-induced brain cancer and cataracts were incorporated into our established decision model comparing the cost-effectiveness of CT angiography and CT perfusion imaging and transcranial Doppler sonography in SAH. Cancer risk was calculated by using National Cancer Institute methodology. The remaining input probabilities were based on literature data and a cohort at our institution. Outcomes were expected quality-adjusted life years gained, costs, and incremental cost-effectiveness ratios. One-way, 2-way, and probabilistic sensitivity analyses were performed. RESULTS: CT angiography and CT perfusion imaging were the dominant strategies, resulting in both better health outcomes and lower costs, even when incorporating brain cancer and cataract risks. Our results remained robust in 2-way sensitivity analyses varying the prolonged latency period up to 30 years, with either brain cancer risk up to 50 times higher than the upper 95% CI limit or the probability of cataracts from 0 to 1. Results were consistent for scenarios that considered either symptomatic or asymptomatic patients with SAH. Probabilistic sensitivity analysis confirmed our findings over a broad range of selected input parameters. CONCLUSIONS: While risks of radiation exposure represent an important consideration, CT angiography and CT perfusion imaging remained the preferred imaging compared with transcranial Doppler sonography in both asymptomatic and symptomatic patients with SAH, with improved health outcomes and lower health care costs, even when modeling a significantly higher risk and shorter latency period for both cataract and brain cancer than that currently known.

[Effects of Lung Ventilation Perfusion Imaging Examination on Pregnant Outcomes of Rabbits.]

OBJECTIVES: To examine the pregnancy outcomes of rabbits being subjected to pulmonary ventilation perfusion imaging examinations. METHODS: Pregnant rabbits were randomly divided into two groups: control group and experimental (lung ventilation-perfusion scintigraphy) group.The pregnancy outcomes were measured using indicators of miscarriage,premature birth,and stillbirth,as well as malformations and developmental abnormalities of offspring over a three-month period. RESULTS: No significant differences in miscarriage,premature birth,and stillbirth were found between the two groups.No obvious deformity appearances in the offspring were observed.The two groups showed no statistically significant differences in fetal progeny-intrauterine growth and developmental indicators measured by body mass,head circumference,abdominal circumference and length. CONCLUSIONS: Lung ventilation-perfusion scintigraphy examination has no effects on pregnant outcomes measured by miscarriage,premature birth,stillbirth,fetal teratogenicity and fetal growth.

Radiation dose reduction in perfusion CT imaging of the brain: A review of the literature.

Perfusion CT (PCT) of the brain is widely used in the settings of acute ischemic stroke and vasospasm monitoring. The high radiation dose associated with PCT is a central topic and has been a focus of interest for many researchers. Many studies have examined the effect of radiation dose reduction in PCT using different approaches. Reduction of tube current and tube voltage can be efficient and lead to a remarkable reduction of effective radiation dose while preserving acceptable image quality. The use of novel noise reduction techniques such as iterative reconstruction or spatiotemporal smoothing can produce sufficient image quality from low-dose perfusion protocols. Reduction of sampling frequency of perfusion images has only little potential to reduce radiation dose. In the present article we aimed to summarize the available data on radiation dose reduction in PCT imaging of the brain.

Evaluation of the preventive effect of dexpanthenol in radiation injury by lung perfusion scintigraphy: a preclinical experimental model of radiation injury.

AIM: The aim of this study was to show the preventative effects of dexpanthenol in radiation injuries caused by radiotherapy (RT) through the use of lung perfusion scintigraphy in the pre-RT and post-RT periods. MATERIALS AND METHODS: Six male New Zealand rabbits (5-6 months of age and ∼2.5-3 kg in weight) were the used in this study. The animals were subjected to Tc-macroaggregated albumin lung perfusion scintigraphy in the pre-RT and post-RT (i.e. 2 weeks after treatment) periods. The scintigraphies were performed with the same dose by the same staff and the methodology used the same acquisition parameters. The rabbits were divided into two groups: group I (administered RT only) and group II (also administered intramuscular 500 mg dexpanthenol injections for 14 consecutive days after RT). Quantification was performed to compare the groups and the quantification variables were compared using a paired samples t-test, with P value less than 0.05 considered to be statistically significant. Histopathological analysis was also carried out. RESULTS: The post-RT scintigraphies indicated a decrease in the counts in both lungs, suggesting early post-RT injury. The difference between the counts obtained from both lungs in groups I and II was significantly different and favoured group II. Histopathological results confirmed the scintigraphy results. CONCLUSION: It is possible to estimate post-RT changes in the early period (in contrast to previous data) by lung perfusion scintigraphy. Dexpanthenol may also reduce the effects of RT to a degree. Although this is the first study to report the preventive effects of dexpanthenol on RT injuries, further studies are warranted in this area.

Perfusion scintigraphy versus 256-slice CT angiography in pregnant patients suspected of pulmonary embolism: comparison of radiation risks.

UNLABELLED: One aim of the current study was to determine normalized dose data for maternal radiosensitive organs and embryo/fetus from 256-slice CT pulmonary angiography (CTPA) performed on pregnant patients suspected of having pulmonary embolism. A second aim was to provide reliable maternal and fetal doses and associated radiation cancer risk estimates from 256-slice CTPA and lung perfusion scintigraphy (LPS) for comparison. METHODS: Mathematic anthropomorphic phantoms were generated to simulate the average woman at early pregnancy and at the third, sixth, and ninth months of gestation. In each phantom, 0-3 additional 1.5-cm-thick fat tissue layers were added to derive 4 phantoms representing pregnant women with different body sizes. Monte Carlo methods were used to simulate low-dose 256-slice CTPA exposures on each of the 16 generated phantoms. Normalized organ and embryo/fetal dose data were derived for exposures at 80, 100, and 120 kV. Maternal effective dose and embryo/fetal dose from 256-slice CTPA and associated lifetime attributable risks of radiation cancer were determined for different body sizes and gestational stages and compared with corresponding data from LPS. RESULTS: For an average-sized pregnant patient at the first trimester, the 256-slice CTPA exposure resulted in a maternal effective dose of 1 mSv and an embryo/fetal dose of 0.05 mGy. However, maternal effective dose considerably increased with body size, whereas embryo/fetal dose increased with both body size and gestational stage. Compared with LPS, low-dose CTPA to an average-sized pregnant patient resulted in a 30% higher maternal effective dose but a 3.4-6 times lower embryo/fetal dose. Nevertheless, LPS was associated with less aggregated radiation risk for an average-sized pregnant patient, with the difference from CTPA being increased further for larger patients. CONCLUSION: Compared with CTPA performed with a modern wide-area CT scanner, LPS remains comparatively more dose-efficient.

Safety of ventilation/perfusion single photon emission computed tomography for pulmonary embolism diagnosis.

PURPOSE: The aim of this management outcome study was to assess the safety of ventilation/perfusion single photon emission computed tomography (V/Q SPECT) for the diagnosis of pulmonary embolism (PE) using for interpretation the criteria proposed in the European Association of Nuclear Medicine (EANM) guidelines for V/Q scintigraphy. METHODS: A total of 393 patients with clinically suspected PE referred to the Nuclear Medicine Department of Brest University Hospital from April 2011 to March 2013, with either a high clinical probability or a low or intermediate clinical probability but positive D-dimer, were retrospectively analysed. V/Q SPECT were interpreted by the attending nuclear medicine physician using a diagnostic cut-off of one segmental or two subsegmental mismatches. The final diagnostic conclusion was established by the physician responsible for patient care, based on clinical symptoms, laboratory test, V/Q SPECT and other imaging procedures performed. Patients in whom PE was deemed absent were not treated with anticoagulants and were followed up for 3 months. RESULTS: Of the 393 patients, the prevalence of PE was 28 %. V/Q SPECT was positive for PE in 110 patients (28 %) and negative in 283 patients (72 %). Of the 110 patients with a positive V/Q SPECT, 78 (71 %) had at least one additional imaging test (computed tomography pulmonary angiography or ultrasound) and the diagnosis of PE was eventually excluded in one patient. Of the 283 patients with a negative V/Q SPECT, 74 (26 %) patients had another test. The diagnosis of PE was finally retained in one patient and excluded in 282 patients. The 3-month thromboembolic risk in the patients not treated with anticoagulants was 1/262: 0.38 % (95 % confidence interval 0.07-2.13). CONCLUSION: A diagnostic management including V/Q SPECT interpreted with a diagnostic cut-off of "one segmental or two subsegmental mismatches" appears safe to exclude PE.

Optimizing the ventilation-perfusion lung scan for image quality and radiation exposure.

UNLABELLED: Our purpose was to compare the performance of an initial ventilation-perfusion (V/Q) scan protocol with that of a data-driven modified protocol to improve diagnostic quality without increasing radiation dose to the patient. METHODS: The initial V/Q scan protocol consisted of a ventilation scan after inhalation of (99m)Tc-diethylenetriaminepentaacetic acid (DTPA) aerosol for 5 min followed by a (99m)Tc-macroaggregated albumin perfusion scan. Interim analysis after 34 scans under an initial protocol included calculations of ventilation efficiency, perfusion efficiency, and perfusion-to-ventilation counting rate ratio (Q:V). Ventilation efficiency was defined as ventilation counting rate divided by ventilation dose, perfusion efficiency as perfusion counting rate divided by perfusion dose, and Q:V as perfusion counting rate divided by ventilation counting rate. From these data, the protocol was modified to improve the Q:V ratio and was applied to 60 patients. Results from the 94 scans were tabulated, and a comparison of ventilation efficiency, perfusion efficiency, and Q:V between the 2 protocols was statistically analyzed. RESULTS: The initial protocol returned a mean ventilation efficiency of 7.8% (SD, 4.6%; range, 1.4%-19%), mean perfusion efficiency of 100% (SD, 31%; range, 39%-160%), and mean Q:V of 2.4 (SD, 1.9; range, 0.51-9.0). All 3 parameters displayed a wide range. Fifty-four percent of these cases demonstrated an unacceptable Q:V (≤2) indicating that the perfusion dose did not overwhelm the ventilation dose. To improve Q:V, options included decreasing ventilation dose, increasing perfusion dose, or performing the ventilation scan with a much higher dose after the perfusion scan. To minimize radiation, the protocol was modified to decrease the ventilation from 5 min to 2.5 min. The modified protocol yielded a mean ventilation efficiency of 5.1% (SD, 1.8; range, 2.0-11), mean perfusion efficiency of 120% (SD, 27%; range, 65%-170%), and mean Q:V of 3.6 (SD, 1.7; range, 1.2-12). Differences between protocols were statistically significant for ventilation efficiency, perfusion efficiency, and Q:V (P < 0.02). Less than 8% of cases under the modified protocol exhibited an unacceptable Q:V. CONCLUSION: The initial V/Q scan protocol was successfully modified to improve image quality with less radiation. By decreasing the ventilation time by half, the percentage of studies with an unacceptable Q:V decreased from 54% to 8%. This analysis may help others to optimize their V/Q protocols.

Pulmonary embolism: role of ventilation-perfusion scintigraphy.

The evaluation for pulmonary embolism in the emergency setting has many challenges. Patients often present with symptoms that are nonspecific. Emergency Department physicians utilize their own subjective judgment or objective clinical algorithms, such as the Wells Score to assess the likelihood of the patient having PE. Other techniques, such as D-dimer assays and Doppler ultrasound leg studies for deep venous thrombosis are very useful, as well. Ventilation-perfusion lung scans and computed tomography pulmonary angiography are both available in most institutions. However, factors such as sensitivity or specificity, overnight availability, radiation exposure, and comfort with interpretation criteria play a role in deciding which procedure should be used. Relative merits of both the procedures will be discussed.

Assessment of the kidneys: magnetic resonance angiography, perfusion and diffusion.

Renal magnetic resonance (MR) imaging has undergone major improvements in the past several years. This review focuses on the technical basics and clinical applications of MR angiography (MRA) with the goal of enabling readers to acquire high-resolution, high quality renal artery MRA. The current role of contrast agents and their safe use in patients with renal impairment is discussed. In addition, an overview of promising techniques on the horizon for renal MR is provided. The clinical value and specific applications of renal MR are critically discussed.

Xenon-enhanced cerebral blood flow at 28% xenon provides uniquely safe access to quantitative, clinically useful cerebral blood flow information: a multicenter study.

BACKGROUND AND PURPOSE: Xe-CT measures CBF and can be used to make clinical treatment decisions. Availability has been limited, in part due to safety concerns. Due to improvements in CT technology, the concentration of inhaled xenon gas has been decreased from 32% to 28%. To our knowledge, no data exist regarding the safety profile of this concentration. We sought to better determine the safety profile of this lower concentration through a multicenter evaluation of adverse events reported by all centers currently performing xenon/CT studies in the US. MATERIALS AND METHODS: Patients were prospectively recruited at 7 centers to obtain safety and efficacy information. All studies were performed to answer a clinical question. All centers used the same xenon delivery system. CT imaging was used during a 4.3-minute inhalation of 28% xenon gas. Vital signs were monitored on all patients throughout each procedure. Occurrence and severity of adverse events were recorded by the principal investigator at each site. RESULTS: At 7 centers, 2003 studies were performed, 1486 (74.2%) in nonventilated patients. The most common indications were occlusive vascular disease and ischemic stroke; 93% of studies were considered clinically useful. Thirty-nine studies (1.9%) caused respiratory suppression of >20 seconds, all of which resolved spontaneously. Shorter respiratory pauses occurred in 119 (5.9%), and hyperventilation, in 34 (1.7%). There were 53 additional adverse events (2.9%), 7 of which were classified as severe. No adverse event resulted in any persistent neurologic change or other sequelae. CONCLUSIONS: Xe-CT CBF can be performed safely, with a very low risk of adverse events and, to date, no risk of permanent morbidity or sequelae. On the basis of the importance of the clinical information gained, Xe-CT should be made widely available.