Can the unenhanced phase be eliminated from dual-phase CT angiography for chest pain? Implications for diagnostic accuracy in acute aortic intramural hematoma

Expert Panel on Vascular Imaging and Interventional Radiology, Ripley B, Scheidt MJ, Aghayev A, Kim CY, Hedgire SS, Ahmed O, Ahmad S, Clough RE, DeMartino RR, Ferencik M, Hughes GC, Klitzke AK, Steenburg SD, Thomas R, Wells BJ, Wolf SJ, Pinchot JW, Majdalany BS. ACR Appropriateness Criteria® Thoracic Aortic Aneurysm or Dissection-Treatment Planning and Follow-Up: 2024 Update

Diseases of the thoracic aorta include two broad categories: aneurysmal dilation involving all three layers of the intact aortic wall, and acute aortic syndromes, wherein at least one layer of the aortic wall is disrupted, such as in aortic dissection. These diseases carry a variable risk of subsequent aortic rupture, which is associated with high morbidity and mortality. Imaging is critical in the diagnosis, surveillance, and treatment of this constellation of diseases. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision process support the systematic analysis of the medical literature from peer reviewed journals. Established methodology principles such as Grading of Recommendations Assessment, Development, and Evaluation or GRADE are adapted to evaluate the evidence. The RAND/UCLA Appropriateness Method User Manual provides the methodology to determine the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where peer reviewed literature is lacking or equivocal, experts may be the primary evidentiary source available to formulate a recommendation.

ACR Appropriateness Criteria® Suspected Acute Aortic Syndrome

Acute aortic syndrome (AAS) includes the entities of acute aortic dissection, intramural hematoma, and penetrating atherosclerotic ulcer. AAS typically presents with sudden onset of severe, tearing, anterior, or interscapular back pain. Symptoms may be dominated by malperfusion syndrome, due to obstruction of the lumen of the aorta and/or a side branch when the intimal and medial layers are separated. Timely diagnosis of AAS is crucial to permit prompt management; for example, early mortality rates are reported to be 1% to 2% per hour after the onset of symptoms for untreated ascending aortic dissection. The appropriateness assigned to each imaging procedure was based on the ability to obtain key information that is used to plan open surgical, endovascular, or medical therapy. This includes, but is not limited to, confirming the presence of AAS; classification; characterization of entry and reentry sites; false lumen patency; and branch vessel compromise. Using this approach, CT, CTA, and MRA are all considered usually appropriate in the initial evaluation of AAS if those procedures include intravenous contrast administration. Ultrasound is also considered usually appropriate if the acquisition is via a transesophageal approach. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision include an extensive analysis of current medical literature from peer reviewed journals and the application of well-established methodologies (RAND/UCLA Appropriateness Method and Grading of Recommendations Assessment, Development, and Evaluation or GRADE) to rate the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where evidence is lacking or equivocal, expert opinion may supplement the available evidence to recommend imaging or treatment.

"Dark-blood" dual-energy computed tomography angiography for thoracic aortic wall imaging

OBJECTIVES

To assess the capability of a newly developed material decomposition method from contrast-enhanced dual-energy CT images, aiming to better visualize the aortic wall and aortic intramural hematoma (IMH), compared with true non-contrast (TNC) CT.

MATERIALS AND METHODS

Twenty-two patients (11 women; mean age, 61 ± 20 years) with acute chest pain underwent 25 dual-layer non-contrast and contrast-enhanced CT. CT-angiography images were retrospectively processed using two-material decomposition analysis, where we defined the first material as the content of a region of interest placed in the ascending aorta for each patient, and the second material as water. Two independent radiologists assessed the images from the second material termed "dark-blood" images and the TNC images regarding contrast-to-noise ratio (CNR) between the wall and the lumen, diagnostic quality regarding the presence of aortic wall thickening, and the inner/outer vessel wall conspicuity.

RESULTS

Diagnostic quality scores in normal aortic segments were 0.9 ± 0.3 and 2.7 ± 0.6 (p < 0.001) and wall conspicuity scores were 0.7 ± 0.5 and 1.8 ± 0.3 (p < 0.001) on TNC and dark-blood images, respectively. In aortic segments with IMH, diagnostic quality scores were 1.7 ± 0.5 and 2.4 ± 0.6 (p < 0.001) and wall conspicuity scores were 0.7 ± 0.7 and 1.8 ± 0.3 (p < 0.001) on TNC and dark-blood images, respectively. In normal aortic segments, CNRs were 0.3 ± 0.2 and 2.8 ± 0.9 on TNC and dark-blood images, respectively (p < 0.001). In aortic segments with IMH, CNRs were 0.3 ± 0.2 and 4.0 ± 1.0 on TNC and dark-blood images, respectively (p < 0.001).

CONCLUSIONS

Compared with true non-contrast CT, dark-blood material decomposition maps enhance quantitative and qualitative image quality for the assessment of normal aortic wall and IMH.

KEY POINTS

• Current dual-energy CT-angiography provides virtual non-contrast and bright-blood images. • Dark-blood images represent a new way to assess the vascular wall structure with dual-energy CT and can improve the lumen-to-wall contrast compared with true non-contrast CT. • This dual-energy CT material decomposition method is likely to improve contrast resolution in other applications as well, taking advantage of the high spatial resolution of CT.

Atrial fibrillation, an epiphenomenon of acute Stanford type-A aortic dissection with suspected intimo-intimal intussusception

Supraventricular arrhythmias can sometimes be "only" epiphenomena appearing during acute hypoxia, pneumonia, pulmonary embolism, and thrombosis. Indeed, atrial fibrillation is not rare in acute aortic dissection as it is estimated in about one half of patients and may be secondary to a perfusion deficit of the sinoatrial node artery.

Multislice spiral CT angiography for evaluation of acute aortic syndrome

OBJECTIVE

To discuss the diagnostic value of multislice CT angiography (MSCTA) in acute aortic syndrome (AAS).

MATERIALS AND METHODS

The clinical and imaging data of 36 cases diagnosed as AAS by MSCTA were collected. The manifestations of the MSCTA images were reviewed retrospectively, and the average x-ray dose was calculated.

RESULTS

Among 36 AAS cases, 16 cases had aortic dissection (AD), 8 cases had penetrating atherosclerotic ulcer (PAU), 7 cases had intramural hematoma (IMH), and 5 cases had unstable thoracic aneurysm (UTA). Of 16 cases with AD, type A and type B accounted for 43.7% (7/16) and 56.3% (9/16), respectively. Of 7 cases with IMH, type A and type B accounted for 42.9% (3/7) and 57.1% (4/7), respectively.

CONCLUSION

In spite of the x-ray radiation, MSCTA proves to be a rapid and noninvasive imaging technique for the diagnosis of AAS.

Acute aorta, overview of acute CT findings and endovascular treatment options

Acute aortic pathologies include acute aortic syndrome (aortic dissection, intramural hematoma, penetrating aortic ulcer), impending rupture, aortic aneurysm rupture and aortic trauma. Acute aortic syndrome, aortic aneurysm rupture and aortic trauma are life-threatening conditions requiring prompt diagnosis and treatment. The basic imaging modality for "acute aorta" is CT angiography with typical findings for these aortic pathologies. Based on the CT, it is possible to classify aortic diseases and anatomical classifications are essential for the planning of treatment. Currently, endovascular treatment is the method of choice for acute diseases of the descending thoracic aorta and is increasingly indicated for patients with ruptured abdominal aortic aneurysms.

Angiotensin II Type 1 Receptor Gene A1166C Polymorphism Was Not Associated With Acute Coronary Syndrome in an Iranian Population

Background

There are very limited data for Iranian populations on the predisposing genetic factors for acute coronary syndrome (ACS).

Objectives

The objective of the present study was to investigate the association of the angiotensin II type 1 receptor (AT1R) gene polymorphism and ACS in an Iranian population.

Patients and Methods

This cross-sectional study was conducted among 263 subjects (97 men and 166 women). Patients (n = 128) aged 30 - 80 years with chest pain were recruited from the emergency department of Ghaem Hospital (Mashhad, Iran). A 12-lead electrocardiograph plus creatine kinase MB (CK-MB) levels were used as the basis for the diagnosis of myocardial ischemia. The control group was selected from age-matched healthy subjects (n = 135). Non-enzymatic kits were used for extraction of DNA from blood samples. Polymerase chain reaction (PCR) was performed to amplify the DNA fragments. For restriction fragment length polymorphism (RFLP) determination, the DdeI enzyme was used to digest the amplified DNA fragments. Statistical analyses were performed using SPSS version 13.0.

Results

There was no statistical difference in the genotype frequency of patients and healthy subjects with regard to age and gender (P > 0.05).

Conclusions

The AT1R A1166C polymorphism appeared not to be associated with the presence of ACS in the population studied.

[Pre- and postoperative imaging of type B aortic dissection]

Type B aortic dissections are serious diseases with a 60 to 80 % 5-year survival rate. Although typically managed with a medical treatment, surgery may be necessary in the acute/subacute or the chronic phase if significant complications are encountered. For these patients, CT angiography is the first-line imaging modality, used for indicating and preparing the surgical procedure as well as for follow-up. Physicians in charge of these patients should be familiar with the key reading points. Visceral malperfusion is the most common acute complication, while aneurysmal dilatation of the false lumen is the most common chronic complication, with surgical management generally indicated when the axial diameter of the aorta exceeds 55mm. Endovascular treatment tends to replace open surgery: it requires precise measurements and identification of the entry tear (contribution of 4D-MRA).