Sixty-four–slice multidetector computed tomography: the future of ED cardiac care

Demands for medical imaging and workforce Size: A nationwide population-based Study, 2000-2020

PURPOSE

The aim of this study was to investigate associations between workforce and workload among radiologists in Taiwan.

MATERIALS AND METHODS

Data for the period 2000-2020 describing the demand for imaging services and radiologists have been obtained from databases and statistical reports of the Ministry of Health and Welfare. The future demand for radiologists was based on Taiwanese people aged 40 and over.

RESULTS

The workforce of Taiwan's radiologists has increased by 6 % annually over the past 20 years (from 450 to 993), performing 2125, 3202 and 3620 monthly examinations (mainly conventional radiography and CT) in medical centers, regional hospitals and district hospitals. Between 2000 and 2020, the use of CT and MRI increased by more than 3.5 times. Demand for interventional radiology also increased by 1.77 times, 2.25 times, and 5 times, respectively. To maintain this volume of services in 2040, at least 1168 radiologists are needed, about 1.18 times more in 2020.

CONCLUSION

Taiwan has 2.4 to 2.9 times fewer radiologists than the United States and 3 times fewer than Europe, while the annual workload is approximately 2 to 3.4 times greater than that of the United States and 1.4 to 2.5 times greater than that of the United Kingdom. This report may serve as a reference for policy makers who address the challenges of the growing workload among radiologists in countries of similar situations.

Desempenho Diagnóstico da Angiotomografia Computadorizada e da Avaliação Seriada de Troponina Cardíaca Sensível em Pacientes com Dor Torácica e Risco Intermediário para Eventos Cardiovasculares

Fundamento

A angiotomografia coronária (ATC) tem sido usada para avaliação de dor torácica principalmente em pacientes de baixo risco, e poucos dados existem com pacientes em risco intermediário.

Objetivo

Avaliar o desempenho de medidas seriadas de troponinas sensíveis e de ATC em pacientes de risco intermediário.

Métodos

Um total de 100 pacientes com dor torácica, TIMI score 3 ou 4 e troponina negativa foram prospectivamente incluídos. Todos os pacientes foram submetidos à ATC, e aqueles com obstruções ≥ 50% foram encaminhados à cineangiocoronariografia. Pacientes com lesões < 50% recebiam alta hospitalar, receberam alta e foram contatados 30 dias depois por telefonema para avaliação dos desfechos clínicos. Os desfechos foram hospitalização, morte, e infarto agudo do miocárdio em 30 dias. A comparação entre os métodos foi realizada pelo teste de concordância kappa. O desempenho das medidas de troponina e da ATC na detecção de lesões coronárias significativas e desfechos clínicos foi calculado. Os resultados foram considerados estatisticamente significativos quando p <0,05.

Resultados

Estenose coronária ≥ 50% na ATC foi encontrada em 38% dos pacientes e lesões coronárias significativas na angiografia coronária foram encontradas em 31 pacientes. Dois eventos clínicos foram observados. A análise de concordância Kappa mostrou baixa concordância entre as medidas de troponina e ATC na detecção de lesões coronárias significativas (kappa = 0,022, p = 0,78). O desempenho da ATC para detectar lesões coronárias significativas na angiografia coronária ou para prever eventos clínicos em 30 dias foi melhor que as medidas de troponina sensível (acurácia de 91% versus 60%).

Conclusão

ATC teve melhor desempenho que as medidas seriadas de troponina na detecção de doença coronariana significativa em pacientes com dor torácica e risco intermediário para eventos cardiovasculares.

The effects of changes in utilization and technological advancements of cross-sectional imaging on radiologist workload

RATIONALE AND OBJECTIVES

To examine the effect of changes in utilization and advances in cross-sectional imaging on radiologists' workload.

MATERIALS AND METHODS

All computed tomography (CT) and magnetic resonance imaging (MRI) examinations performed at a single institution between 1999 and 2010 were identified and associated with the total number of images for each examination. Annual trends in institutional numbers of interpreted examinations and images were translated to changes in daily workload for the individual radiologist by normalizing to the number of dedicated daily CT and MRI work assignments, assuming a 255-day/8-hour work day schedule. Temporal changes in institutional and individual workload were assessed by Sen's slope analysis (Q = median slope) and Mann-Kendall test (Z = Z statistic).

RESULTS

From 1999 to 2010, a total of 1,517,149 cross-sectional imaging studies (CT = 994,471; MRI = 522,678) comprising 539,210,581 images (CT = 339,830,947; MRI = 199,379,634) were evaluated at our institution. Total annual cross-sectional studies steadily increased from 84,409 in 1999 to 147,336 in 2010, representing a twofold increase in workload (Q = 6465/year, Z = 4.2, P < .0001). Concomitantly, the number of annual departmental cross-sectional images interpreted increased from 9,294,140 in 1990 to 94,271,551 in 2010, representing a 10-fold increase (Q = 8707876/year, Z = 4.5, P < .0001). Adjusting for staffing changes, the number of images requiring interpretation per minute of every workday per staff radiologist increased from 2.9 in 1999 to 16.1 in 2010 (Q = 1.7/year, Z = 4.3, P < .0001).

CONCLUSIONS

Imaging volumes have grown at a disproportionate rate to imaging utilization increases at our institution. The average radiologist interpreting CT or MRI examinations must now interpret one image every 3-4 seconds in an 8-hour workday to meet workload demands.

Electrocardiographic changes in patients with type A acute aortic dissection. Incidence, patterns and underlying mechanisms in 159 cases

BACKGROUND

Not only symptoms but electrocardiographic (ECG) changes mimicking acute coronary syndrome as well have been known to develop in acute aortic dissection (AAD). However, detailed information is lacking.

OBJECTIVE

We sought to evaluate incidence, patterns, and underlying mechanisms for acute ECG changes in type A AAD.

METHODS

Retrospective study in a single tertiary care hospital. A total of 159 cases (mean age 65.1±14.8 years, male/female=67/92) that presented within 12 h from the onset were included. Shift of the ST segment ≥0.1 mV or changes of the T wave were considered acute ECG changes.

RESULTS

Acute and chronic ECG changes were observed in 49.7% and 36.5% cases, respectively. ECG was normal only in 27.0% cases. ST elevation was observed in 8.2% cases and was closely related to direct coronary involvement. ST depression and T wave changes were observed in 34.0% and 21.4% cases, respectively. Cases with ST depression or T wave changes had higher incidence of shock (65.2% vs. 28.8%, p<0.001) and cardiac tamponade (51.2% vs. 15.0%, p<0.001) compared with those without changes.

CONCLUSION

Acute ECG changes were common in type A AAD. Physicians taking care of patients with chest pain and acute ECG changes should consider the possibility of AAD before performing thrombolysis or percutaneous catheter intervention.

Quantitative assessment of image quality in 64-slice-computed tomography of coronary arteries in subjects undergoing screening for coronary artery disease

Accurate and consistent visualization of the entire coronary system with high-grade imaging quality is crucial for routine applications of multi-detector-computed tomography (MDCT) coronary angiography. To determine the imaging quality of 64-slice-MDCT coronary angiography, we respectively explored the quantitative parameters of imaging quality in 105 consecutive subjects (71 men, 34 women; aged 58.66 +/- 10.62 years) who underwent 64-slice-MDCT coronary angiography to screen for coronary disease. The interobserver agreement for semi-quantitative image quality, visible length, signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) of the coronary arteries was good. The SNR and CNR of the proximal segments of the coronary arteries were superior to that of the distal segments of coronary arteries (p < 0.001). The visible length of the stenosed right coronary artery was significantly shorter than that of the non-stenosed right coronary artery (p = 0.03). The SNR and CNR of the stenosed and non-stenosed coronary arteries revealed no significant difference (p > 0.05). Body weight and body mass index were inversely related to the SNR and CNR of the aorta (p < 0.001). In conclusion, 64-slice-MDCT coronary angiography can provide excellent imaging quality of coronary arteries in subjects undergoing screening for coronary disease, although the SNR and CNR were relatively low at the distal segments of coronary arteries.

Coronary computerized tomography angiography for rapid discharge of low-risk patients with cocaine-associated chest pain

BACKGROUND

Most patients presenting to emergency departments (EDs) with cocaine-associated chest pain are admitted for at least 12 hours and receive a "rule out acute coronary syndrome" protocol, often with noninvasive testing prior to discharge. In patients without cocaine use, coronary computerized tomography angiography (CTA) has been shown to be useful for identifying a group of patients at low risk for cardiac events who can be safely discharged. It is unclear whether a coronary CTA strategy would be efficacious in cocaine-associated chest pain, as coronary vasospasm may account for some of the ischemia. We studied whether a negative coronary CTA in patients with cocaine-associated chest pain could identify a subset safe for discharge.

METHODS

We prospectively evaluated the safety of coronary CTA for low-risk patients who presented to the ED with cocaineassociated chest pain (self-reported or positive urine test). Consecutive patients received either immediate coronary CTA in the ED (without serial markers) or underwent coronary CTA after a brief observation period with serial cardiac marker measurements. Patients with negative coronary CTA (maximal stenosis less than 50%) were discharged. The main outcome was 30-day cardiovascular death or myocardial infarction.

RESULTS

A total of 59 patients with cocaine-associated chest pain were evaluated. Patients had a mean age of 45.6 +/- 6.6 yrs and were 86% black, 66% male. Seventy-nine percent had a normal or nonspecific ECG and 85% had a TIMI score <2. Twenty patients received coronary CTA immediately in the ED, 18 of whom were discharged following CTA (90%). Thirty-nine received coronary CTA after a brief observation period, with 37 discharged home following CTA (95%). Six patients had coronary stenosis >or=50%. During the 30-day follow-up period, no patients died of a cardiovascular event (0%; 95% CI, 0-6.1%) and no patient sustained a nonfatal myocardial infarction (0%; 95% CI, 0-6.1%).

CONCLUSIONS

Although cocaine-associated myocardial ischemia can result from coronary vasoconstriction, patients with cocaine associated chest pain, a non-ischemic ECG, and a TIMI risk score <2 may be safely discharged from the ED after a negative coronary CTA with a low risk of 30-day adverse events.

CT evaluation of congenital heart disease in adults

OBJECTIVE

The purpose of this article is to describe the spectrum of imaging findings of congenital heart disease in adults.

CONCLUSION

Continued advances in CT have facilitated evaluation of two important patient populations: adults with surgically palliated congenital heart disease and adults with previously undiagnosed congenital heart disease.

Comparison of image quality and arterial enhancement with a dedicated coronary CTA protocol versus a triple rule-out coronary CTA protocol

RATIONALE AND OBJECTIVES

To compare the image quality of dedicated coronary computed tomography angiography (cCTA) to that of triple rule-out (TRO) CTA designed to evaluate the coronary arteries, thoracic aorta, and pulmonary arteries.

MATERIALS AND METHODS

Consecutive cCTA examinations performed by a single radiologist over 1 year were reviewed. Biphasic injection protocols were employed: 70 mL of optiray-350 followed by 40 mL of saline injected at 5.5 mL/second for dedicated cCTA; 70 mL of optiray-350 followed by 25 mL of the contrast diluted with 25 mL of saline injected at 5.0 mL/second for TRO-CTA. Two independent cardiovascular radiologists reviewed the coronary vessels in each case and rated diagnostic image quality on a 5 point scale (1, suboptimal; 3, adequate; 5, excellent). Vascular enhancement was measured in the coronary arteries, aorta, and pulmonary arteries.

RESULTS

There was excellent interobserver agreement between the cardiovascular radiologists (kappa = 0.91). Coronary image quality score were similar among 260 dedicated cCTA studies and 168 TRO-CTA studies (mean: 3.8-3.9. P > .18). At least one coronary segment demonstrated suboptimal image quality in 8% of examinations, including 18 dedicated cCTA studies and 16 TRO studies (P = .94). Enhancement was greater in the distal thoracic aorta of TRO patients (336 vs. 311 Hounsfield units; P = .01); no other significant differences in enhancement were identified in the aorta and coronary arteries of dedicated cCTA and TRO studies. Vascular enhancement was adequate for diagnostic evaluation of the pulmonary arteries in all TRO studies.

CONCLUSIONS

A TRO-CTA protocol using 95 mL of contrast can provide comparable coronary image quality and coronary vascular enhancement as compared to dedicated cCTA with 70 mL of contrast.

Development of variable pitch factor scanning for multislice computed tomography

RATIONALE AND OBJECTIVES

The latest multislice computed tomography (MSCT) scanners permit the chest and abdomen to be scanned continuously. However, conventionally, it has been necessary to perform scanning twice using different pitch factors for the cardiac and abdominal regions. We have developed a new scanning technique known as variable pitch factor scanning, in which the table speed is changed during scanning to obtain continuous images from the heart to the abdomen in a single scan, and have evaluated its physical characteristics.

MATERIALS AND METHODS

A bead phantom, a comb phantom, and a gold wire placed at an angle were scanned using a 64-row MSCT scanner. The variation in the spatial resolution and continuity of images in the body axis direction because of changes in the pitch factor were evaluated.

RESULTS

Because reconstruction taking the cone angle into consideration was employed, the spatial resolution in the body axis direction was unchanged and the continuity of images in the body axis direction was maintained at a certain level even when the pitch factor was changed.

CONCLUSION

Variable pitch factor scanning is a useful technique for obtaining continuous images from the heart to the abdomen in a single scan.

Actual financial comparison of four strategies to evaluate patients with potential acute coronary syndromes

OBJECTIVES

Small studies have shown that a negative computed tomography coronary angiogram (CTA) in low-risk chest pain patients predicts a low rate of 30-day adverse events. The authors hypothesized that an immediate CTA strategy would be as effective but less costly than alternative strategies for evaluation of patients with potential acute coronary syndrome (ACS).

METHODS

The authors retrospectively compared four strategies for evaluation of patients after initial physician determination that the patient required admission and testing to rule out ACS. Patients were frequency-matched by age, race, gender, thrombolysis in myocardial infarction (TIMI) score, and initial electrocardiogram (ECG). The four groups were immediate CTA in the emergency department (ED) without serial markers (n = 98); clinical decision unit/observation unit (CDU) with biomarkers and CTA (n = 102); CDU evaluation with serial cardiac biomarkers and stress testing (n = 154); and usual care, defined as admission with serial biomarkers and hospitalist-directed evaluation (n = 289). The main outcomes were actual cost of care (facility direct and indirect fixed, facility variable direct labor and supply costs), length of stay (LOS), diagnosis of coronary artery disease (CAD), and safety (30-day death or myocardial infarction [MII).

RESULTS

Patients in each group were of similar age (mean +/- standard deviation [SD] 46 +/- 9 years), race (62% African American), and gender (57% female) and had similar TIMI scores (100% between 0-2). Comparing immediate CTA versus CDU CTA versus CDU stress versus usual care, median costs were less ($1,240 vs. 2,318 vs. 4,024 vs. 2,913; p < 0.01), and LOS was shorter (8.1 hr vs. 20.9 hr vs. 26.2 hr vs. 30.2 hr; p < 0.01). Diagnosis of CAD was similar (5.1% vs. 5.9% vs. 5.8% vs. 6.6%; p = 0.95), but fewer patients had 30-day death/MI (0% vs. 0% vs. 0.7% vs. 3.1%; p = 0.04) or 30-day readmission (0% vs. 3.2% vs. 2.3% vs. 12.2%; p < 0.01).

CONCLUSIONS

Compared to the other strategies, immediate CTA was as safe, identified as many patients with CAD, had the lowest cost, had the shortest LOS, and allowed discharge for the majority of patients. Larger prospective studies should confirm safety before immediate CTA replaces other strategies to rule out possible ACS.

Initial evaluation of coronary images from 320-detector row computed tomography

PURPOSE

To evaluate image quality and contrast opacification from coronary images acquired from 320-detector row computed tomography (CT). Patient dose is estimated for prospective and retrospective ECG-gating; initial correlation between 320-slice CT and coronary catheterization is illustrated.

METHODS

Retrospective image evaluation from forty consecutive patients included subjective assessment of image quality and contrast opacification (80 ml iopamidol 370 mg I/ml followed by 40 ml saline). Region of interest opacification measurements at the ostium and at 2.5 mm diameter were used to determine the gradient of contrast opacification (defined as the proximal minus distal HU measurements) in coronary arteries imaged in a single heartbeat. Estimated effective dose was compared for prospective versus retrospective ECG-gating, two body mass index categories (30 kg/m(2) cutoff), and single versus two heartbeat acquisition. When available, CT findings were correlated with those from coronary catheterization.

RESULTS

Over 89% of arterial segments (15 segment model) had excellent image quality. The most common reason for image degradation was cardiac motion. One segment in one patient was considered unevaluable. Contrast opacification was almost universally considered excellent. The mean Hounsfield units (HU) was greater than 350; the coronary contrast opacification gradient was 30-50 HU. Patient doses were greater for retrospective ECG-gating, larger patients, and those imaged with two heartbeats. For the most common (n=25) protocol (120 kV, 400 mA, prospective ECG-gating, 60-100% phase window, 16 cm craniocaudal coverage, single heartbeat), the mean dose was 6.8+/-1.4 mSv. All CT findings were confirmed in the four patients who underwent coronary catheterization.

CONCLUSION

Initial 320-detector row coronary CT images have consistently excellent quality and iodinated contrast opacification. These patients were scanned with conservative protocols with respect to iodine load, prospective ECG-gating phase window, and craniocaudal coverage. Future work will focus on lowering contrast and radiation dose while maintaining image quality.

Clinical utility of cardiac computed tomography

Technological advances have made cardiac computed tomography (CT) an important player in cardiac imaging. Cardiac CT has become a powerful tool in the armamentarium of cardiac risk stratification assessment of intermediate-risk patients, bypass grafts, stents, and anomalous coronary arteries. With advancement in accuracy and reliability, cardiac CT is becoming mainstream in everyday clinical cardiology. It is up to the clinician to use the technology effectively and appropriately. It is certain that cardiac CT technology will continue to improve.