Comparison of 81mKrypton and 99mTc-Technegas for ventilation single-photon emission computed tomography in severe chronic obstructive pulmonary disease.

INTRODUCTION: Ventilation and perfusion single-photon emission computed tomography combined with computed tomography (SPECT/CT) is a powerful tool to assess the state of the lungs in chronic obstructive pulmonary disease (COPD). 81mKrypton is a gaseous ventilation tracer and distributes similarly to air, but is not widely available and relatively expensive. 99mTc-Technegas is cheaper and has wider availability, but is an aerosol, which may deposit in hot spots as the severity of COPD increases. In this study, 81mKrypton and 99mTc-Technegas were compared quantitatively in patients with severe COPD. METHODS: The penetration ratio, the heterogeneity index (with and without band filtering for relevant clinical sizes) and hot spot appearance were assessed in eleven patients with severe COPD that underwent simultaneous dual-isotope ventilation SPECT/CT with both 99mTc-Technegas and 81mKrypton. RESULTS: Significant differences were found in the penetration ratio for the medium energy general purpose (MEGP) collimators, but not for the low energy general purpose (LEGP) collimators. The difference in the overall and the band filtered heterogeneity index was significant in most cases. All patients suffered from 99mTc-Technegas hot spots in at least one lung. Comparison of MEGP 81mKrypton and LEGP Technegas scans revealed similar results as the comparison for the MEGP collimators. CONCLUSION: Caution should be taken when replacing 81mKrypton with 99mTc-Technegas as a ventilation tracer in patients with severe COPD as there are significant differences in the distribution of the tracers over the lungs. Furthermore, this patient group is prone to 99mTc-Technegas hot spots and might need additional scanning if hot spots severely hamper image interpretation.

Non-ECG-gated CT pulmonary angiography and the prediction of right ventricular dysfunction in patients suspected of pulmonary embolism.

PURPOSE: Right ventricular dysfunction (RVD) is an important prognostic factor of 30-day mortality in patients with acute pulmonary embolism (PE). The aim of our study was to evaluate whether non-electrocardiogram (ECG)-gated cardiovascular parameters attained during computed tomography pulmonary angiography (CTPA) could predict RVD in patients suspected of PE using ECG-gated cardiac CT angiography as reference. METHODS: Consecutive patients suspected of PE were referred to a ventilation/perfusion single-photon emission tomography (V/Q-SPECT) as first-line imaging procedure. Patients had a V/Q-SPECT/CT, a CTPA and an ECG-gated cardiac CT angiography performed the same day. RESULTS: A total of 71 patients were available for analysis. Seventeen patients (24%) had RVD. The non-ECG-gated dimensions of left and right ventricle and the major vessels were correlated with ECG-gated cardiac dimensions. The size of the pulmonary trunk could identify patients with RVD: AUC (0·67, 95% confidence intervals (CIs) 0·52-0·82) as seen in the ROC curve (P<0·05). With a cut-off value of the pulmonary trunk of 29 mm, the sensitivity and specificity were 70·6% and 55·5%, respectively. The positive predictive and negative predictive values for detection of RVD were 59·1% and 85·7%, respectively. CONCLUSION: In the present study, we demonstrated correlation between ECG-gated cardiac dimensions and non-ECG-gated cardiovascular parameters, however with only moderate diagnostic accuracies. We demonstrated that the dimension of the pulmonary trunk might be of value in detection of patients with RVD. We suggest further studies on the potential value of non-ECG-gated cardiac dimensions in patients suspected of PE.

[SPECT combined with CT angiography yield better diagnostic accuracy of pulmonary embolism--secondary publication]. / SPECT kombineret med CT-angiografi giver bedre diagnostik af lungeemboli--sekundaerpublikation.

The aim of our study was to perform a prospective study that compared the diagnostic ability of V/Q single photon emission computer tomography (V/Q-SPECT), V/Q-SPECT combined with low-dose computed tomography (CT) and pulmonary multidetector computed tomography(MDCT)-angiography in patients suspected of having pulmonary embolism (PE) using a dedicated combined SPECT/MDCT-scanner. V/Q-SPECT in combination with low-dose CT had a sensitivity of 97% and a specificity of 100%. MDCT angiography had a sensitivity of 68% and a specificity of 100%. We conclude that V/Q-SPECT in combination with low-dose CT without contrast has an excellent diagnostic performance and should be considered the first-line imaging technique in the work-up of PE in most cases.

Comparison of V/Q SPECT and planar V/Q lung scintigraphy in diagnosing acute pulmonary embolism.

PURPOSE: Planar ventilation/perfusion (V/Q) scintigraphy is currently the standard method for the diagnosis of pulmonary embolism (PE) in most nuclear medicine centers. However, recent studies have shown a superior sensitivity and specificity when applying V/Q single photon emission computed tomography (SPECT) in diagnosing PE. This study evaluated the diagnostic performance of three-dimensional V/Q SPECT in comparison with planar V/Q scintigraphy. MATERIALS AND METHODS: Consecutive patients suspected of acute PE from June 2006 to February 2008 were referred to the Department of Nuclear Medicine at Frederiksberg Hospital, Denmark to a V/Q SPECT, as the first-line imaging procedure. Patients with positive D-dimer (>0.5 mg/l) or after clinical assessment with a Wells score of more than 2 were included and had a V/Q SPECT, low-dose CT, planar V/Q scintigraphy, and pulmonary multidetector computer tomography angiography performed the same day. Ventilation studies were performed using Kr. Patient follow-up was at least 6 months. RESULTS: A total of 36 patient studies were available for analysis, of which 11 (31%) had PE. V/Q SPECT had a sensitivity of 100% and a specificity of 87%. Planar V/Q scintigraphy had a sensitivity of 64% and a specificity of 72%. CONCLUSION: We conclude that V/Q SPECT has a superior diagnostic performance compared with planar V/Q scintigraphy and should be preferred when diagnosing PE.

Detection of pulmonary embolism with combined ventilation-perfusion SPECT and low-dose CT: head-to-head comparison with multidetector CT angiography.

UNLABELLED: The diagnosis of pulmonary embolism (PE) is usually established by a combination of clinical assessment, D-dimer testing, and imaging with either pulmonary ventilation-perfusion (V/Q) scintigraphy or pulmonary multidetector CT (MDCT) angiography. Both V/Q SPECT and MDCT angiography seem to have high diagnostic accuracy. However, only limited data directly comparing these 2 modalities are available. Hybrid gamma-camera/MDCT systems have been introduced and allow simultaneous 3-dimensional lung V/Q SPECT and MDCT angiography, suitable for diagnosing PE. The aim of our study was to compare, in a prospective design, the diagnostic ability of V/Q SPECT, V/Q SPECT combined with low-dose CT, and pulmonary MDCT angiography obtained simultaneously using a combined SPECT/MDCT scanner in patients suspected of having PE. METHODS: Consecutive patients from June 2006 to February 2008 suspected of having acute PE were referred to the Department of Nuclear Medicine at Rigshospitalet or Frederiksberg Hospital, Denmark, for V/Q SPECT as a first-line imaging procedure. The number of eligible patients was 196. Patients with positive D-dimer results (>0.5 mmol/mL) or a clinical assessment with a Wells score greater than 2 were included and underwent V/Q SPECT, low-dose CT, and pulmonary MDCT angiography in a single session. Patient follow-up was 6 mo. RESULTS: A total of 81 simultaneous studies were available for analysis, of which 38% were from patients with PE. V/Q SPECT had a sensitivity of 97% and a specificity of 88%. When low-dose CT was added, the sensitivity was still 97% and the specificity increased to 100%. Perfusion SPECT with low-dose CT had a sensitivity of 93% and a specificity of 51%. MDCT angiography alone had a sensitivity of 68% and a specificity of 100%. CONCLUSION: We conclude that V/Q SPECT in combination with low-dose CT without contrast enhancement has an excellent diagnostic performance and should therefore probably be considered first-line imaging in the work-up of PE in most cases.

[Gastroduodenal intussusception causing gastric retention]. / Duodenal invagination som årsag til ventrikelretention.

A case of gastroduodenal intussusception caused by a duodenal lipoma is presented. The condition was characterized by severe upper gastrointestinal retention, epigastric pain and weight loss. The mass was diagnosed by CT scan. The diagnosis was confirmed by operation. The patient was treated successfully by manually reducing the intussusception and resection of the lipoma. Histopathology confirmed the mass to be a pedunculated submucosal lipoma. The patient had an uneventful recovery.