肺灌注/通气显像与肺动脉造影诊断肺动脉栓塞的对比研究

目的评价核素肺通气/灌注(V/Q)显像在肺动脉栓塞(PE)诊断中的价值。方法临床疑有PE患者30例,男女各15例,平均年龄(38.2±13.9)岁。均行胸部X线片检查、核素V/Q显像和肺动脉造影。11例患者在行肺灌注显像时,选择双侧足背静脉注射肺灌注显像剂,同时完成双下肢静脉显像。结果30例患者中22例V/Q显像示不相匹配的肺叶、肺段或多发亚肺段的放射性分布稀疏或缺损,提示为PE;但肺动脉造影证实22例中20例为PE。8例患者的V/Q显像为相匹配的肺叶、肺段或多发亚肺段的稀疏或缺损,提示不是PE,与肺动脉造影结果一致。核素V/Q显像诊断PE的灵敏度为100%（20/20例）,特异性为80.0%（8/10例）,准确性为93.3%（28/30例）。X线胸片和核素下肢静脉显像有助于PE的正确诊断。结论多数PE患者通过核素肺V/Q显像结合X线胸片可以作出明确诊断,少数肺V/Q显像与临床表现不符的患者需行肺动脉造影。     

肺灌注显像结合X线胸片诊断急性肺栓塞

目的探讨肺灌注显像／x线胸片检查（Q／X）替代肺灌注／通气显像（Q／V）用于急性肺栓塞诊断的可行性。方法72例疑诊急性肺栓塞，且肺灌注显像显示至少有一个肺段灌注缺损的患者，24h内行x线胸片检查和肺通气显像，比较Q／X和QIV的诊断符合率和准确性。结果Q／x与Q／V结果的符合率为84．7％，Q／x对Q／V的阳性预测值为83．7％，阴性预测值为87．0％。在该组病例中，Q／X诊断急性肺栓塞的灵敏度为94．9％，特异性为63．6％，准确性为80．6％；而Q／V则分别为94．9％，78．8％和87．5％。5例慢性阻塞性肺部疾病（COPD）Q／X均显示不匹配，而Q／v均显示匹配，两者结果不同。结论对于多数疑诊急性肺栓塞患者，Q／X可以替代Q／v用于诊断，但对于COPD患者应选择Q／V。     

放射性核素肺显像与螺旋CT诊断急性肺栓塞的对比研究

目的 比较肺通气／灌注（V／Q）显像与多层螺旋CT肺动脉造影（CTPA）在诊断急性肺动脉血栓栓塞症（PTE）方面的临床价值。方法 前瞻性分析2005年10月～2006年5月共51例临床疑诊急性PTE患者的肺灌注显像，其中18例行肺通气显像，并与CTPA对比。以汇总所有临床资料、各实验室检查及影像学检查后讨论得出的最终诊断作为“标准”。结果 最终24位患者被诊断为PTE占47．1％（24／51例），V／Q显像与CTPA的灵敏度分别为95．8％（23／24例）和95．8％（23／24例），特异性分别为88．9％（24／27例）和92．6％（25／27例），准确性分别为92．2％（47／51例）和94．1％（48／51例）。在定性诊断方面，2种影像学检查结果差异无统计学意义（χ^2=0．14，P=0．71），两者定性诊断符合率为86．3％（44／51例），Kappa值为0．73。24例PTE患者中，CTPA显示为“完全阻塞”的肺动脉血管所对应的44个肺段中，肺灌注显像显示为“放射性稀疏、缺损”的肺段数为32个（72．7％）；CTPA显示为“部分充盈缺损”的肺动脉血管所对应的266个肺段中，肺灌注显像显示为“放射性稀疏、缺损”的肺段数为155个（58．3％），显示为“亚肺段放射性稀疏、缺损”的肺段数为9个（3．4％）。结论 V／Q显像与CTPA在PTE定性诊断方面符合率高，一致性好，但在定位方面存在差异；两者为互补关系。     

肺通气/灌注显像对急性肺血栓栓塞症患者的诊断价值

目的 评价放射性核素肺通气／灌注（V／Q）显像在急性肺血栓栓塞症（PTE）诊断中的价值及国人肺动脉血栓栓塞后肺血流灌注受损情况和受累肺段、肺叶的分布特点。方法 采用前瞻性描述性研究方法，将明确诊断为PTE的519例患者分为大面积、次大面积PTE组（249例）和非大面积（不含次大面积）PTE组（270例）。对519例急性PTE患者均进行了肺V／Q显像，其中有773例次与CT肺动脉造影（CTPA）结果进行了对比分析。结果 在治疗前行肺V／Q显像和CTPA的PTE患者中，PTE的总检出率分别为93．3％和89．3％（P〉0．05）；急性大面积和次大面积PTE组的检出率分别为86．9％和100％（P〈0．001）；急性非大面积PTE组的检出率分别为98．2％和77．5％（P〈0．001）。肺V／Q显像示病变分布的特点为：右肺多于左肺，下叶多于上叶，背段多于前段。肺V／Q显像与CTPA的符合率比较：肺高于肺叶，肺叶高于肺段，溶栓组高于抗凝组。结论 肺V／Q显像在急性PTE的诊断中具有重要的作用和独特的价值，与CTPA联合应用，可起到决定性的诊断作用。PTE患者肺内血栓的分布特点符合“浓度守衡定律”。     

肺通气/灌注显像对肺栓塞疗效的评价

目的 探讨肺通气／灌注（V／Q）显像在观察肺栓塞（PE）溶栓和抗凝治疗效果中的价值。方法 对65例抗凝和溶栓治疗的PE患者，治疗前后分别给予^99Tc^m气体37-74MBq和^99Tc^m-聚合白蛋白（MAA）148—185MBq后行8个体位V／Q显像；并在治疗后不同时间多次重复V／Q显像。结 果44例PE患者296个受损肺段，单纯抗凝治疗1年半内，V／Q显像显示106个肺段恢复正常（35．8％），69个受损肺段改善（23．3％），121个肺段无改善（40．9％）。21例PE患者165个受损肺段，溶栓结合抗凝治疗后V／Q显像示有85个肺段恢复正常（51．5％），有29个肺段改善（17．6％），有51个肺段无改善（30．9％）。其中在PE发病7d内治疗效果最佳，单纯抗凝治疗7d与14d疗效之间比较及溶栓结合抗凝治疗7d与14d疗效之间比较，差异均有统计学意义（χ^2=8．79和56．31，P〈0．05和〈0．01）。结论 V／Q显像能较好地评价PE抗凝和溶栓治疗效果。     

肺通气/灌注显像诊断不典型亚肺段肺栓塞

目的评价核索肺通气／灌注（V／Q）显像对不典型亚肺段肺栓塞（PE）的诊断价值。方法患者141例，男58例，女83例，年龄（65．67±11．29）岁，其中下肢静脉病变史者14例，糖尿病、高脂血症史者45例，63例近期内行有创性诊断和治疗，另19例均无上述病史或诊疗史。所有患者行常规盼^99Tc^m-MAA和^99Tc^m气体显像后进行1—24个月的抗凝治疗，于治疗后再行肺灌注显像。将抗凝治疗前后肺灌注显像进行对比分析，根据肺内放射性分布的变化判断治疗效果，再结合临床资料及其他影像检查综合判断不典型PE的诊断。结果141例患者肺灌注显像均显示某个肺野内不呈肺段或亚肺段分布的片状或小斑片状放射性分布稀疏区。肺通气显像示肺野内放射性分布基本均匀，未见放射性分布稀疏区。治疗后118例肺灌注显像显示双肺内放射性分布不同程度的增多或均匀。按肺野内放射性分布改善情况标准评价：抗凝治疗后恢复正常35例，显效49例，有效34例。总有效率为83．69％（118／141）。另23例肺内放射性分布无明显变化，视为无效。结论V／Q显像是诊断不典型亚肺段PE的首选方法。     

肺灌注/通气显像与肺动脉造影诊断肺栓塞的对比分析

目的：评价肺灌注／通气显像诊断肿栓塞的价值。方法：回顾性分析45例疑肺栓塞患者的肺核素显像结果，并与肺动脉造影检查对照。结果：肺动脉造影诊断为肺栓塞的患者26例，有180个肺动脉支为充盈缺损，其肺灌注显像示167个节段呈完全肺段性或亚肺段缺损，符合率为92．7％。肺动脉造影显示为86个肺动脉支为部分充盈缺损，肺灌注显像有63个肺段或亚肺段缺损，符合率为73．2％（P＜0．01）。肺核素显像对肺栓塞诊断的灵敏度为92．3％，特异性为84．2％，阳性预测值和阴性预测值均为88．9％。26例肺动脉造影诊断为肺栓塞的患者，有23例行肺通气显像，通气／灌注均不匹配。结论：肺灌注／通气显像对肺栓塞诊断具有重要的临床价值。     

肺通气/灌注显像与HCTPA诊断肺动脉栓塞的价值

目的　评价核素肺通气 灌注(V Q)显像、螺旋CT肺动脉造影(HCTPA)及血浆D 二聚体在诊断肺动脉血栓中的作用。方法　临床疑为肺动脉栓塞(PE)患者4 2例,男2 6例,女16例,平均年龄( 4 9 18±16 5 6 )岁,均行核素肺V Q显像、HCTPA及血浆D 二聚体测定。其中32例患者在行肺灌注显像时,选择双足背静脉注射肺灌注显像剂,同时完成双下肢静脉显像。结果　4 2例患者中34例经临床诊断为PE ,肺V Q显像诊断PE的灵敏度、准确性和阳性预测值分别为94 12 %、90 4 8%和94 12 % ,HCTPA分别为85 2 9%、83 33%和93 5 5 % ,D 二聚体分别为5 2 94 %、5 7 14 %和90 0 0 %。32例行下肢深静脉显像的PE患者中2 0例有下肢静脉血栓。结论　肺V Q显像无创、安全、简便,诊断PE的灵敏度、准确性高。核素肺显像诊断亚肺段水平PE的能力明显高于HCTPA。     

急性肺动脉栓塞14例诊断与临床分析

目的：探讨急性肺动脉栓塞的临床．特点，提高对本病的诊断水平。方法：对14例急性肺动脉栓塞患者临床表现进行回顾性分析。结论：PE患者都有发病的诱因。临床症状缺乏特异性；动脉血气分析、心电图检查是PE的初选诊断方法。由于肺接受双重血液供应，APE时X线胸片检查敏感性及特异性均较低，早期病变不明显。X线片正常，不能排除诊断。CT扫描可代替肺通气扫描，综合肺灌注显像进行分析，可大大提高特异性，作为诊断PE的依据。     

肺灌注显像结合Wells评分及D-二聚体检查对急性肺血栓栓塞症的诊断价值

目的评价肺灌注显像结合Wells评分及D-二聚体检查对急性肺血栓栓塞症（APE）的诊断价值。方法选择2006年1月至2008年12月连续121例疑诊APE的初诊患者,所有患者均进行Wells评分、D-二聚体检查、胸部X线检查及核素肺灌注显像。分别计算肺灌注显像结合x线胸片（Q／X显像）、Q／X显像结合Wells评分或（和）D-二聚体检查用于诊断APE的灵敏度、特异性、阳性预测值和阴性预测值。结果全部121例患者中,41．3％（50／121）的患者最终诊断为APE;58．7％（71／121）最终排除了APE。Q／X显像示APE阳性者49例（40．5％）。Q／X显像的诊断灵敏度、特异性、阳性预测值、阴性预测值分别为86．O％（43／50）、91．5％（65／71）、87．8％（43／49）和90．3％（65／72）。Q／x显像对于Wells评分〉4且D-二聚体阳性（≥0．5mg／L）的患者,其APE阳性预测值为100．0％（29／29）;Q／X显像对Wells评分≤4且D-二聚体阴性（〈0．5mg／L）的患者,其APE阴性预测值亦为100．0％（41／41）。结论Q／X显像结合Wells评分及D-二聚体检查可以有效提高Q／X显像诊断APE的阳性预测值和阴性预测值,从而更准确地诊断APE。     

The added value of spiral computed tomographic angiography after lung scintigraphy for the diagnosis of pulmonary embolism

OBJECTIVES: The objectives of this study were to evaluate the added clinical value of spiral computed tomographic angiography (CTA) after ventilation-perfusion lung scintigraphy (V/Q) for the management of patients with suspected pulmonary embolism (PE). METHODS: Of 987 patients who had V/Q during 2001, 64 patients (6%) had CTA performed for further evaluation. V/Q and CTA findings were retrospectively analyzed by 2 clinicians who were blinded to the patients' outcome. Patient management was determined based on clinical and V/Q data and was reassessed after the addition of CTA data. RESULTS: CTA was performed in 2 patients with normal V/Q, 16 patients with low probability, 28 patients with intermediate, 4 patients with high probability, and 14 patients with nonconclusive V/Q. Three patients (19%) with low probability, 9 (32%) with intermediate probability, 4 (29%) with nonconclusive, and 4 (100%) with high probability V/Q had PE diagnosed by CTA. CTA findings changed the management in 2 patients (13%) with low probability, 15 (54%) with intermediate probability, and 4 (29%) with nonconclusive V/Q. CONCLUSION: In our institution, V/Q remains the main imaging modality for evaluation of patients with clinically suspected PE. CTA was performed after V/Q in 6% of patients. Patients with intermediate probability and those with nonconclusive V/Q, and to a much lesser extent, patients with low probability V/Q could benefit from the addition of CTA after V/Q. In patients with normal V/Q and those with high-probability V/Q, the addition of CTA does not seem to influence patient management.     

Ventilation-perfusion lung scanning and spiral computed tomography of the lungs: Competing or complementary modalities?

The recently developed technique of spiral computed tomographic angiography (CTA) is being used for the detection of pulmonary emboli (PE), and several studies have assessed its accuracy using pulmonary angiography as the gold standard. CTA shows a high level of accuracy in the detection of pulmonary emboli in segmental or larger central vessels. The specificity is high enough to eliminate the requirement for angiography if a positive CTA result is found. The main factor limiting the sensitivity of CTA is the frequency of peripheral emboli in the vessels outside the central chest field covered by CTA. The incidence of such peripheral emboli varies in different reports from 0% to 36%, and their significance remains arguable. Interpretative criteria for V/Q-lung scintigraphy have been refined as a result of the lessons learned from the MOPED study. Using these modified criteria, and taking into account the prior probability of PE based on the presence or absence of clinical risk factors, treatment decisions can be reasonably made in patients in the following categories: those with normal lung scans, those with high probability scans and high prior probability of PE, and those with low probability scans and low clinical suspicion. Patients with intermediate probability or indeterminate scans, and those in whom the scan results conflict with the clinical expectation, will need further tests. Ultrasound examination of the leg veins, if positive, will select a further subgroup of patients for active treatment. Patients with a negative or inconclusive ultrasound result, who previously have been candidates for pulmonary angiography, can now go on to CTA. The advantages in specificity which CTA offers will make it an important part of the diagnostic workup for selected patients, but in view of its increased cost and high radiation dose compared with V/Q scintigraphy, the argument that CTA should completely replace lung scintigraphy is currently unsupportable.     

Downstream Imaging Utilization After MR Angiography Versus CT Angiography for the Initial Evaluation of Pulmonary Embolism

ObjectiveTo compare the proportion of emergency department (ED) patients who undergo subsequent chest CT or MR within 1 year of an initially negative scan for pulmonary embolism (PE).MethodsThis single-center, retrospective, observational study examined the use of chest CT or MR for ED patients with MR angiography (MRA) negative for PE during April 2008 to March 2013. We compared the 1-year scan utilization for these cases to an age- and sex-matched cohort of patients who underwent CT angiography (CTA). We also calculated time to first follow-up scan and mean radiation dose in each arm. Trained data abstractors used a standardized protocol and electronic case report form to gather all outcomes of interest. Results are reported as means or proportions with their associated confidence intervals (CIs).ResultsIn all, 717 ED patients (430 MRAs and 287 CTAs) were included. At 1 year, the proportion undergoing subsequent imaging (MRA 16.7%, CTA 15.3%; difference = 1.4%, 95% CI 4.05%-6.86%) and time to first follow-up scan (difference = 13 days, 95% CI −22.69-48.7) did not differ between arms. Mean radiation dose per patient at 1 year was significantly higher in the CTA arm (9.82 mSv; 95% CI 9.12-10.53) compared with 2.92 mSv (95% CI 1.86-3.98) with MRA. Those with an index MRA were more likely to undergo subsequent MRAs (odds ratio 3.68; 95% CI 1.22-11.12) than those with an index CTA. However, in both arms, the majority (85%) of subsequent scans were CTAs.ConclusionsWhen comparing patients initially undergoing MRA versus CTA for the evaluation of PE, there was no difference in downstream chest CT or MR use at 1 year.     

Ventilation-perfusion lung scan for the detection of pulmonary involvement in Takayasu's arteritis.

The aim of study was to analyse ventilation and perfusion (V/Q) lung scan findings in a series of Italian patients with Takayasu's arteritis. Eighteen consecutive patients underwent V/Q lung planar scintigraphy and single-photon emission tomography (SPET). Before perfusion scan acquisition was started, a first-pass study with (99m)Tc-macroaggregates of albumin was performed to assess the right ventricular ejection fraction (RVEF). All patients had normal chest X-rays and were symptom free at the time of the investigation. They also underwent echocardiography to evaluate pulmonary artery pressure and in 13 patients respiratory function tests were performed. In four patients, perfusion lung scan was repeated after 1 year. In 10/18 patients (55.5%), 43 unmatched lobar, segmental or subsegmental perfusion defects were found on planar images; ventilation scintigraphy was normal in all cases. On SPET images, 55 defects were found; no defects were found with SPET in the remaining patients who had normal planar images. All patients had normal RVEF and 5/13 patients had mild restrictive-obstructive lung disease. The pulmonary artery pressure was increased in two patients with perfusion defects. In the four patients who had repeat scintigraphy, all defects remained unchanged. The prevalence of lung perfusion abnormalities observed in Italian patients with Takayasu's arteritis is within the range of values reported in other countries, and V/Q planar scintigraphy is sufficient for the screening of patients.     

Ventilation-perfusion lung scan for the detection of pulmonary involvement in Takayasu's arteritis

The aim of study was to analyse ventilation and perfusion (V/Q) lung scan findings in a series of Italian patients with Takayasu's arteritis. Eighteen consecutive patients underwent V/Q lung planar scintigraphy and single-photon emission tomography (SPET). Before perfusion scan acquisition was started, a first-pass study with ^99mTc-macroaggregates of albumin was performed to assess the right ventricular ejection fraction (RVEF). All patients had normal chest X-rays and were symptom free at the time of the investigation. They also underwent echocardiography to evaluate pulmonary artery pressure and in 13 patients respiratory function tests were performed. In four patients, perfusion lung scan was repeated after 1 year. In 10/18 patients (55.5%), 43 unmatched lobar, segmental or subsegmental perfusion defects were found on planar images; ventilation scintigraphy was normal in all cases. On SPET images, 55 defects were found; no defects were found with SPET in the remaining patients who had normal planar images. All patients had normal RVEF and 5/13 patients had mild restrictive-obstructive lung disease. The pulmonary artery pressure was increased in two patients with perfusion defects. In the four patients who had repeat scintigraphy, all defects remained unchanged. The prevalence of lung perfusion abnormalities observed in Italian patients with Takayasu's arteritis is within the range of values reported in other countries, and V/Q planar scintigraphy is sufficient for the screening of patients.     

Comparison of lung scintigraphy and CT angiography in the diagnosis of pulmonary embolism

In our institution, as in others, pulmonary angiography is not used in the diagnosis of pulmonary embolism because of its perceived risks. We compared the results on lung scintigraphy and computed tomography angiography (CTA) in 116 consecutive patients with suspected pulmonary embolism. In 14 patients with normal lung scans 13 (93%) were also normal with CTA. In the 73 patients with low probability lung scans only five (7%) demonstrated pulmonary embolism with CTA. In 12 patients with high probability lung scans 11 (92%) demonstrated pulmonary embolism on CTA. However, in the 17 patients with intermediate probability lung scans, 10 (58.8%) showed embolism with CTA. We conclude that wherever practicable lung scans should be performed in all patients due to its relatively low radiation burden and that CTA be performed in patients with intermediate probability scans due to the high incidence of pulmonary embolism. Patients with either a normal scan or high probability scan should be treated appropriately. In patients with low probability scans CTA should be performed in those with a high clinical suspicion of thromboembolism.     

Gadolinium-enhanced pulmonary magnetic resonance angiography in the diagnosis of acute pulmonary embolism: a prospective study on 48 patients

OBJECTIVE: Gadolinium-enhanced pulmonary magnetic resonance angiography (MRA) can be an option in patients with a history of previous adverse reaction to iodinated contrast material and renal insufficiency. Radiation is also avoided. The aim of this study is to prospectively compare the diagnostic value of MRA with that of a diagnostic strategy, taking into account catheter angiography, computed tomography angiography (CTA), and lung scintigraphy [ventilation-perfusion (VQ)]. MATERIAL AND METHODS: Magnetic resonance angiography was done in 48 patients with clinically suspected pulmonary embolism (PE) using fast gradient echo coronal acquisition with gadolinium. Interpretation was done with native coronal images and multiplanar maximum intensity projection reconstructions. Results were compared to catheter angiography (n=15), CTA (n=34), VQ (n=45), as well as 6-12 months clinical follow-ups, according to a sequenced reference tree. RESULTS: The final diagnosis of PE was retained in 11 patients (23%). There were two false negatives and no false positive results with MRA. Computed tomography angiography resulted in no false negatives or false positives. Magnetic resonance angiography had a sensitivity of 82% and a specificity of 100%. CONCLUSION: In our study, pulmonary MRA had a sensitivity of 82% and a specificity of 100% for the diagnosis of PE, with slightly less sensitivity than CTA. In the diagnostic algorithm of PE, pulmonary MRA should be considered as an alternative to CTA when iodine contrast injection or radiation is a significant matter.     

Incremental diagnostic quality gain of CTA over V/Q scan in the assessment of pulmonary embolism by means of a Wells score Bayesian model: results from the ACDC collaboration

Objective

Our objective was to evaluate the diagnostic value of computed tomography angiography (CTA) and ventilation perfusion (V/Q) scan in the assessment of pulmonary embolism (PE) by means of a Bayesian statistical model.

Methods

Wells criteria defined pretest probability. Sensitivity and specificity of CTA and V/Q scan for PE were derived from pooled meta-analysis data. Likelihood ratios calculated for CTA and V/Q were inserted in the nomogram. Absolute (ADG) and relative diagnostic gains (RDG) were analyzed comparing post- and pretest probability. Comparative gain difference was calculated for CTA ADG over V/Q scan integrating ANOVA p value set at 0.05.

Results

The sensitivity for CT was 86.0% (95% CI: 80.2%, 92.1%) and specificity of 93.7% (95% CI: 91.1%, 96.3%). The V/Q scan yielded a sensitivity of 96% (95% CI: 95%, 97%) and a specificity of 97% (95% CI: 96%, 98%). Bayes nomogram results for CTA were low risk and yielded a posttest probability of 71.1%, an ADG of 56.1%, and an RDG of 374%, moderate-risk posttest probability was 85.1%, an ADG of 56.1%, and an RDG of 193.4%, and high-risk posttest probability was 95.2%, an ADG of 36.2%, and an RDG of 61.35%. The comparative gain difference for low-risk population was 46.1%; in moderate-risk 41.6%; and in high-risk a 22.1% superiority. ANOVA analysis for LR+ and LR? showed no significant difference (p = 0.8745, p = 0.9841 respectively).

Conclusions

This Bayesian model demonstrated a superiority of CTA when compared to V/Q scan for the diagnosis of pulmonary embolism. Low-risk patients are recognized to have a superior overall comparative gain favoring CTA.

     

Comprehensive assessment of lung CT attenuation alteration at perfusion defects of acute pulmonary thromboembolism with breath-hold SPECT-CT fusion images

Regional computed tomography attenuation (CTA) alteration at perfusion defects in acute pulmonary thromboembolism (PTE) was comprehensively assessed using deep-inspiratory breath-hold SPECT-CT fusion images. Subjects were 14 acute and 9 chronic PTE patients and 13 control subjects. Regional perfusion, CTA, and intravascular clots were correlated on deep-inspiratory breath-hold SPECT-unenhanced/angiographic CT fusion images. Fusion images visualized hypo-CTA in 57% of the acute PTE patients, which preferentially occurred at extensively and severely decreased perfusion areas caused by central clots. CTA at 35 defects of acute PTE was significantly decreased compared with that of normal lungs (P<0.001), but the degree was less compared with chronic PTE (P<0.0001). Fusion images also revealed variable relationships of clots and regional perfusion/CTA in the distal lungs of each central clot. Fusion images provide important information about the actual effects of intravascular clots on peripheral perfusion/CTA and indicate that lung CTA can be decreased at perfusion defects in acute PTE.     

Improving the diagnostic performance of lung scintigraphy in suspected pulmonary embolic disease

AIM: to determine the effectiveness of a new imaging algorithm in the investigation of suspected pulmonary embolism (PE). MATERIALS AND METHODS: A new imaging algorithm for suspected PE was introduced following the installation of a multisection computed tomography (CT) machine at our institution. Before its installation, patients with suspected PE were evaluated with ventilation/perfusion (V/Q) scintigraphy. Subsequently, patients were triaged according to chest radiography (CR) and respiratory history to either lung scintigraphy or CT pulmonary angiography (CTPA). Patients with a normal CR and no history of lung disease were evaluated using perfusion (Q) scintigraphy [ventilation (V) scintigraphy was no longer performed]. Patients with an abnormal CR, asthma or chronic lung disease were evaluated using CTPA. All V/Q images in a continuous 3-year period before the introduction of the new imaging algorithm and all Q images performed in a 3-year period after its introduction were retrospectively reviewed. Imaging reports were categorized into normal, non-diagnostic (low or intermediate probability) or high probability for PE. Patients in the later group who subsequently underwent CTPA, were also reviewed. RESULTS: After the policy change the percentage of normal scintigrams significantly increased (39 to 60%; p<0.001). There was a non-significant increase in the percentage of high probability scintigrams (15 to 18%; p=0.716). Overall the diagnostic yield of lung scintigraphy improved significantly (54 to 78%; p<0.001). CONCLUSION: the diagnostic performance of lung scintigraphy can be improved by careful triage of patients to either Q scintigraphy or CTPA based on clinical history and CR findings. Q scintigraphy remains a valuable diagnostic test in the investigation of suspected PE in carefully selected patients.