Dual-source dual-energy CT: dose reduction after endovascular abdominal aortic aneurysm repair

Assessing the diagnostic accuracy of artificial intelligence in post-endovascular aneurysm repair endoleak detection using dual-energy computed tomography angiography

Purpose

The aim of this study was to evaluate the diagnostic accuracy of an artificial intelligence (AI) tool in detecting endoleaks in patients undergoing endovascular aneurysm repair (EVAR) using dual-energy computed tomography angiography (CTA).

Material and methods

The study involved 95 patients who underwent EVAR and subsequent CTA follow-up. Dualenergy scans were performed, and images were reconstructed as linearly blended (LB) and 40 keV virtual monoenergetic (VMI) images. The AI tool PRAEVAorta®2 was used to assess arterial phase images for endoleaks. Two experienced readers independently evaluated the same images, and their consensus served as the reference standard. Key metrics, including accuracy, precision, recall, F1 score, and area under the receiver operating characteristic (ROC) curve (AUC), were calculated.

Results

The final analysis included 94 patients. The AI tool demonstrated an accuracy of 78.7%, precision of 67.6%, recall of 10 71.9%, F1 score of 69.7%, and an AUC of 0.77 using LB images. However, the tool failed to process 40 keV VMI images correctly, limiting further analysis of these datasets.

Conclusions

The AI tool showed moderate diagnostic accuracy in detecting endoleaks using LB images but failed to achieve the reliability needed for clinical use due to the significant number of misdiagnoses.

Review of Clinical Applications of Dual-Energy CT in Patients after Endovascular Aortic Repair

Abdominal aortic aneurysms (AAAs) are a significant cause of mortality in developed countries. Endovascular aneurysm repair (EVAR) is currently the leading treatment method for AAAs. Due to the high sensitivity and specificity of post-EVAR complication detection, CT angiography (CTA) is the reference method for imaging surveillance in patients after EVAR. Many studies have shown the advantages of dual-energy CT (DECT) over standard polyenergetic CTA in vascular applications. In this article, the authors briefly discuss the technical principles and summarize the current body of literature regarding dual-energy computed tomography angiography (DECTA) in patients after EVAR. The authors point out the most useful applications of DECTA in this group of patients and its advantages over conventional CTA. To conduct this review, a search was performed using the PubMed, Google Scholar, and Web of Science databases.

Improved Detection of Endoleaks in Virtual Monoenergetic Images in Dual-Energy CT Angiography Following EVAR

OBJECTIVES

The objective of this prospective study was to evaluate the virtual monoenergetic images (VMI) and virtual noncontrast (VNC) phase in the detection of endoleaks after endovascular abdominal aortic repair (EVAR). The potential dose reduction of abbreviated examination protocols was calculated.

MATERIALS AND METHODS

Ninety-seven patients after the EVAR procedure were enrolled in this study. An initial single-source noncontrast acquisition was followed by two dual-energy acquisitions (arterial and 60 s delayed). Fast-kVp switching scanner was used. VNC images were reconstructed from the delayed phase. First examination session (reference) included a full triphasic study protocol consisting of true noncontrast (TNC) images and two postcontrast phases, the latter ones presented as classical polyenergetic reconstructions. Reading sessions II and III were performed by two independent and blinded readers evaluating VMIs in abbreviated protocols-biphasic (VNC + arterial, delayed phase), monophasic (VNC + delayed phase). The diagnostic accuracy of sessions II and III was calculated.

RESULTS

The calculated sensitivity of the biphasic protocol with the use of VMIs in endoleak detection was 100%, with a statistically significant increase in the number of endoleaks detected in comparison with the reference study. The monophasic protocol showed 83.33% sensitivity. The use of abbreviated examination protocols led to a decrease in the mean effective dose (ED) of 23.28% (biphasic protocol) and 61.37% (monophasic protocol).

CONCLUSION

The use of VMIs increases the number of endoleaks diagnosed with a possible radiation reduction by up to ¼ (biphasic protocol). Further reduction to a monophasic protocol leads to over 60% dose reduction but with a decrease in diagnostic accuracy.

Photon-Counting Detector CT Angiography for Endoleak Detection After Endovascular Aortic Repair: Triphasic CT With True Noncontrast Versus Biphasic CT With Virtual Noniodine Imaging

OBJECTIVES

The aim of this study was to compare image quality and endoleak detection after endovascular abdominal aortic aneurysm repair between a triphasic computed tomography (CT) with true noncontrast (TNC) and a biphasic CT with virtual noniodine (VNI) images on photon-counting detector CT (PCD-CT).

MATERIALS AND METHODS

Adult patients after endovascular abdominal aortic aneurysm repair who received a triphasic examination (TNC, arterial, venous phase) on a PCD-CT between August 2021 and July 2022 were retrospectively included. Endoleak detection was evaluated by 2 blinded radiologists on 2 different readout sets (triphasic CT with TNC-arterial-venous vs biphasic CT with VNI-arterial-venous). Virtual noniodine images were reconstructed from the venous phase. The radiologic report with additional confirmation by an expert reader served as reference standard for endoleak presence. Sensitivity, specificity, and interreader agreement (Krippendorf α) were calculated. Image noise was assessed subjectively in patients using a 5-point scale and objectively calculating the noise power spectrum in a phantom.

RESULTS

One hundred ten patients (7 women; age, 76 ± 8 years) with 41 endoleaks were included. Endoleak detection was comparable between both readout sets with a sensitivity and specificity of 0.95/0.84 (TNC) versus 0.95/0.86 (VNI) for reader 1 and 0.88/0.98 (TNC) versus 0.88/0.94 (VNI) for reader 2. Interreader agreement for endoleak detection was substantial (TNC: 0.716, VNI: 0.756). Subjective image noise was comparable between TNC and VNI (4; IQR [4, 5] vs 4; IQR [4, 5], P = 0.44). In the phantom, noise power spectrum peak spatial frequency was similar between TNC and VNI (both f peak = 0.16 mm -1 ). Objective image noise was higher in TNC (12.7 HU) as compared with VNI (11.5 HU).

CONCLUSIONS

Endoleak detection and image quality were comparable using VNI images in biphasic CT as compared with TNC images in triphasic CT offering the possibility to reduce scan phases and radiation exposure.

Vascular Applications of Dual-Energy Computed Tomography

Dual- or multi-energy CT imaging provides several advantages over conventional CT in the context of vascular imaging. Specific advantages include the use of low-energy virtual monoenergetic images (VMIs) to boost iodine attenuation to salvage suboptimal enhanced studies, perform low-contrast material dose studies, and increase conspicuity of small vessels and lesions. Alternatively, high-energy VMIs reduce artifacts caused by some metals, endoprosthesis, calcium blooming, and beam hardening. Virtual non-contrast (VNC) images reduce radiation dose by eliminating the need for a true non-contrast acquisition in multiphasic CT studies. Iodine maps can be used to evaluate perfusion of tissues and lesions.

Quality of virtual-non-contrast phases derived from arterial and delayed phases of fast-kVp switching dual-energy CT in patients after endovascular aortic repair

Objective of this study is: to analyze CT numbers in arteries and endoleaks in true non-contrast (TNC) and virtual non-contrast phases derived from arterial (VNCa) and delayed (VNCd) phases of dual-energy CT (DECT) in patients after endovascular aneurysm repair (EVAR); to assess the impact of image noise on subjective image quality parameters and the degree of subtraction of calcifications; to calculate effective dose (ED) reduction following replacement of TNC with VNC. The study included 97 patients after EVAR procedure. An initial single-energy TNC acquisition was followed by two DECT acquisitions. CT numbers of TNC, VNCa, VNCd were analyzed statistically. VNCd images were assessed qualitatively. The mean densities in endoleaks were 46.19 HU in TNC, 51.24 HU in VNCa, 42.24 HU in VNCd. The differences between them were statistically significant (p < 0.05). The mean signal-to-noise ratio (SNR) measured in the aorta and endoleaks was highest in VNCa, lowest in TNC images. No correlation between image noise, the results of qualitative analysis of VNCd, and the degree of subtraction of calcifications was found. Omitting TNC led to mean 6.54 ± 1.63 (SD) mSv (23.28% of total examination) ED reduction. VNC images have a higher SNR compared to TNC images with significant differences in the CT numbers between the TNC and VNC reconstructions. Image noise has no impact on the subjective image quality and the degree of subtraction of calcifications in VNCd images. The findings show a high diagnostic value of VNC images and suggest that VNCd images are optimal in the assessment of endoleaks with possible substantial ED reduction.

Can Low-Iodine, Low-Radiation-Dose CT Aortogram Reliably Detect Endoleak after Endovascular Aneurysm Repair of the Aorta?

OBJECTIVE

Double-low CT aortography (DLCTA) is increasingly used in follow-up studies of aortic aneurysm after endovascular aneurysm repair (EVAR). However, whether DLCTA can reliably detect the presence of endoleak is not clear.

METHODS

From February 2014 to October 2019, patients who received EVAR, underwent CT surveillance, and had at least one standard CTA protocol (120 kVp, 400 mg I/kg) and one DLCTA (70-80 kVp, 200 mg I/kg) were included. The integrated findings of the standard CTA and sequential change were considered as the reference standard for the presence of endoleak.

RESULTS

In all, 36 patients received TEVAR and 24 patients received EVAR; 62 standard CTA and 167 DLCTA results were analyzed. There were 2 type I (3.3%) and 12 type II (20.0%) endoleaks in 14 patients (23.3%). The performance of DLCTA in the diagnosis of endoleak reached 100% accuracy compared to that of standard CTA in case of the correction of CT findings by an expert second reading. Compared to the standard CTA, DLCTA scan reduced the radiation dose by 71% and the iodine dose by 50%.

CONCLUSIONS

DLCTA with 70-80 kVp and 200 mg I/kg can reliably detect the presence of endoleak after TEVAR/EVAR.

Structured reporting of computed tomography in the polytrauma patient assessment: a Delphi consensus proposal

OBJECTIVES

To develop a structured reporting (SR) template for whole-body CT examinations of polytrauma patients, based on the consensus of a panel of emergency radiology experts from the Italian Society of Medical and Interventional Radiology.

METHODS

A multi-round Delphi method was used to quantify inter-panelist agreement for all SR sections. Internal consistency for each section and quality analysis in terms of average inter-item correlation were evaluated by means of the Cronbach's alpha (Cα) correlation coefficient.

RESULTS

The final SR form included 118 items (6 in the "Patient Clinical Data" section, 4 in the "Clinical Evaluation" section, 9 in the "Imaging Protocol" section, and 99 in the "Report" section). The experts' overall mean score and sum of scores were 4.77 (range 1-5) and 257.56 (range 206-270) in the first Delphi round, and 4.96 (range 4-5) and 208.44 (range 200-210) in the second round, respectively. In the second Delphi round, the experts' overall mean score was higher than in the first round, and standard deviation was lower (3.11 in the second round vs 19.71 in the first round), reflecting a higher expert agreement in the second round. Moreover, Cα was higher in the second round than in the first round (0.97 vs 0.87).

CONCLUSIONS

Our SR template for whole-body CT examinations of polytrauma patients is based on a strong agreement among panel experts in emergency radiology and could improve communication between radiologists and the trauma team.

Dual-Energy CT applications in urinary tract cancers: an update

Urothelial tumours are the fourth most common cancer in the world and account for the majority of tumours involving the bladder. The symptom that often leads to diagnosis is the presence of haematuria. Diagnosis is made by cystoscopy, which is currently the gold standard in bladder cancer. Computed tomography (CT) performed with pre- and post-contrastographic phases is essential in order to assess the loco-regional and distant extension of disease. The diagnosis and staging of upper tract urothelial cancer (UTUC) are best done with computed tomography urography and flexible ureteroscopy (URS). In the acquisition protocol of this type of tumour, a urographic phase is mandatory, which allows for an accurate diagnostic assessment of the renal pelvis, ureter and bladder, especially in papillary forms. The use of multiple acquisition phases, especially in this type of patient who will have to perform follow-up CTs, leads to the problem of overexposure to ionising radiation, as well as the frequent administration of iodinated contrast medium. For this reason, in recent year, the focus has been put on advanced technologies such as dual-energy CT (DECT), that is a method that can offer some advantages for both radiologist and patient, in the diagnosis of cancer and, in particular, urinary tract disease.

Dual Energy CT Physics-A Primer for the Emergency Radiologist

Dual energy CT (DECT) refers to the acquisition of CT images at two energy spectra and can provide information about tissue composition beyond that obtainable by conventional CT. The attenuation of a photon beam varies depends on the atomic number and density of the attenuating material and the energy of the incoming photon beam. This differential attenuation of the beam at varying energy levels forms the basis of DECT imaging and enables separation of materials with different atomic numbers but similar CT attenuation. DECT can be used to detect and quantify materials like iodine, calcium, or uric acid. Several post-processing techniques are available to generate virtual non-contrast images, iodine maps, virtual mono-chromatic images, Mixed or weighted images and material specific images. Although initially the concept of dual energy CT was introduced in 1970, it is only over the past two decades that it has been extensively used in clinical practice owing to advances in CT hardware and post-processing capabilities. There are numerous applications of DECT in Emergency radiology including stroke imaging to differentiate intracranial hemorrhage and contrast staining, diagnosis of pulmonary embolism, characterization of incidentally detected renal and adrenal lesions, to reduce beam and metal hardening artifacts, in identification of uric acid renal stones and in the diagnosis of gout. This review article aims to provide the emergency radiologist with an overview of the physics and basic principles of dual energy CT. In addition, we discuss the types of DECT acquisition and post processing techniques including newer advances such as photon-counting CT followed by a brief discussion on the applications of DECT in Emergency radiology.

Virtual Non-Contrast Reconstructions of Photon-Counting Detector CT Angiography Datasets as Substitutes for True Non-Contrast Acquisitions in Patients after EVAR-Performance of a Novel Calcium-Preserving Reconstruction Algorithm

The purpose of this study was to evaluate virtual-non contrast reconstructions of Photon-Counting Detector (PCD) CT-angiography datasets using a novel calcium-preserving algorithm (VNCPC) vs. the standard algorithm (VNCConv) for their potential to replace unenhanced acquisitions (TNC) in patients after endovascular aneurysm repair (EVAR). 20 EVAR patients who had undergone CTA (unenhanced and arterial phase) on a novel PCD-CT were included. VNCConv- and VNCPC-series were derived from CTA-datasets and intraluminal signal and noise compared. Three readers evaluated image quality, contrast removal, and removal of calcifications/stent parts and assessed all VNC-series for their suitability to replace TNC-series. Image noise was higher in VNC- than in TNC-series (18.6 ± 5.3 HU, 16.7 ± 7.1 HU, and 14.9 ± 7.1 HU for VNCConv-, VNCPC-, and TNC-series, p = 0.006). Subjective image quality was substantially higher in VNCPC- than VNCConv-series (4.2 ± 0.9 vs. 2.5 ± 0.6; p < 0.001). Aortic contrast removal was complete in all VNC-series. Unlike in VNCConv-reconstructions, only minuscule parts of stents or calcifications were erroneously subtracted in VNCPC-reconstructions. Readers considered 95% of VNCPC-series fully or mostly suited to replace TNC-series; for VNCConv-reconstructions, however, only 75% were considered mostly (and none fully) suited for TNC-replacement. VNCPC-reconstructions of PCD-CT-angiography datasets have excellent image quality with complete contrast removal and only minimal erroneous subtractions of stent parts/calcifications. They could replace TNC-series in almost all cases.

When to perform vertebroplasty? A retrospective analysis from a single center and a review of the literature

BACKGROUND AND AIM

To establish an optimal timing for vertebroplasty in order to obtain a clinically important pain reduction and improving quality of live in patients with osteoporotic or traumatic vertebral fractures.

METHODS

This study includes 22 vertebroplasty procedures performed from October 2018 to July 2020 in 21 patients with traumatic or osteoporotic vertebral fractures (19 female, two men; age between 53 and 89 years). All treatments were executed under fluoroscopic guidance using 11 or 13 G needle through transpedicular or costovertebral unilateral approach. Each patient underwent conscious sedation, continuously monitored by an anesthesiologist. Preoperative MRI images, obtained by 3T or 1.5T MRI scanner, always showed bone marrow edema. The VAS scale and Roland Morris disability questionnaire (RMdq) were administered to patients before and after the treatment to evaluate pain and life quality.

RESULTS

7 patients were treated in the first month after the injury, one was treated twice; 8 patients in the second month, 6 in the third. We observed a reduction of: 5.5 points in the vas scale, 10.3 in the RMdq in the first month; 5.6 points vas, 11.6 points RMdq in the second month; 4 points vas and 9.75 points RMdq in the third month.

CONCLUSIONS

This study demostrated that, in our preliminary experience, vertebroplasty has the best outcome if performed at 2 months from injury.

The role of interventional radiology in hepatic and renal hemorrhage embolization: single center experience and literature review

Background and aim:

Intraabdominal hemorrhage secondary to liver and kidney injury is a major cause of morbidity and mortality. Endovascular arterial embolization is an established interventional radiology technique used to treat active bleeding, and its role in managing abdominal hemorrhages is growing, given the increasing trend for conservative treatment. Our study aims to retrospectively evaluate the technical and clinical results and the possible complications of arterial embolization procedures performed in emergency, in post-traumatic, iatrogenic, and pathological hepatic and renal bleedings.

Methods:

We performed a ten-year, single-center retrospective survey (from January 2010 to December 2019) of all patients treated in emergency by intra-arterial embolization of liver and kidney bleeding. Preliminary CT angiography studies were evaluated, as well as the angiographic findings. Materials used, procedural data, and clinical outcomes, including complications, were recorded.

Results:

The diagnostic angiography showed a single source of bleeding in 20 cases (66.7%), two bleeding vessels in 4 cases (13.3%), and multiple hemorrhagic sources in 6 cases (20%). All bleeding sources were successfully embolized; in 12 patients (40%), complete embolization was achieved with coils and 18 patients (60%) with hemostatic sponges. In one case, a second embolization procedure was performed for the persistence of hemodynamic instability. No major post-procedural complications were recorded. The mean procedure duration was 65.1 minutes.

Conclusions:

Based on our experience and literature data, the treatment of endovascular embolization in acute abdominal bleeding of hepatic and renal origin represents the treatment of choice, as it can provide complete therapeutic success in hemodynamically stable patients. (www.actabiomedica.it)

Gene expression changes and DNA damage after ex vivo exposure of peripheral blood cells to various CT photon spectra

Dual-energy CT provides enhanced diagnostic power with similar or even reduced radiation dose as compared to single-energy CT. Its principle is based on the distinct physical properties of low and high energetic photons, which, however, may also affect the biological effectiveness and hence the extent of CT-induced cellular damage. Therefore, a comparative analysis of biological effectiveness of dual- and single-energy CT scans with focus on early gene regulation and frequency of radiation-induced DNA double strand breaks (DSBs) was performed. Blood samples from three healthy individuals were irradiated ex vivo with single-energy (80 kV and 150 kV) and dual-energy tube voltages (80 kV/Sn150kV) employing a modern dual source CT scanner resulting in Volume Computed Tomography Dose Index (CTDIvol) of 15.79-18.26 mGy and dose length product (DLP) of 606.7-613.8 mGy*cm. Non-irradiated samples served as a control. Differential gene expression in peripheral blood mononuclear cells was analyzed 6 h after irradiation using whole transcriptome sequencing. DSB frequency was studied by 53BP1 + γH2AX co-immunostaining and microscopic evaluation of their focal accumulation at DSBs. Neither the analysis of gene expression nor DSB frequency provided any evidence for significantly increased biological effectiveness of dual-energy CT in comparison to samples irradiated with particular single-energy CT spectra. Relative to control, irradiated samples were characterized by a significantly higher rate of DSBs (p < 0.001) and the shared upregulation of five genes, AEN, BAX, DDB2, FDXR and EDA2R, which have already been suggested as radiation-induced biomarkers in previous studies. Despite steadily decreasing doses, CT diagnostics remain a genotoxic stressor with impact on gene regulation and DNA integrity. However, no evidence was found that varying X-ray spectra of CT impact the extent of cellular damage.

Large Bowel Ischemia/Infarction: How to Recognize It and Make Differential Diagnosis? A Review

Ischemic colitis represents the most frequent form of intestinal ischemia occurring when there is an acute impairment or chronic reduction in the colonic blood supply, resulting in mucosal ulceration, inflammation, hemorrhage and ischemic necrosis of variable severity. The clinical presentation is variable and nonspecific, so it is often misdiagnosed. The most common etiology is hypoperfusion, almost always associated with generalized atherosclerotic disease. The severity ranges from localized and transient ischemia to transmural necrosis of the bowel wall, becoming a surgical emergency, with significant associated morbidity and mortality. The diagnosis is based on clinical, laboratory suspicion and radiological, endoscopic and histopathological findings. Among the radiological tests, enhanced-CT is the diagnostic investigation of choice. It allows us to make the diagnosis in an appropriate clinical setting, and to define the entity of the ischemia. MR may be adopted in the follow-up in patients with iodine allergy or renal dysfunctions, or younger patients who should avoid radiological exposure. In the majority of cases, supportive therapy is the only required treatment. In this article we review the pathophysiology and the imaging findings of ischemic colitis.

Evaluating the Image Quality of Monoenergetic Images From Dual-Energy Computed Tomography With Low-Concentration and Low-Flow-Rate Contrast Media for the Arterials Supply to the Nipple-Areola Complex in Breast Cancer Compared With Conventional Computed Tomography Angiography

Objective

The objective of this study was to evaluate the image quality of monoenergetic images (MEIs (+)) acquired from dual-energy computed tomography with low-concentration and low-flow-rate contrast media for the arterial supply to the nipple-areola complex (NAC) in breast cancer compared with conventional computed tomography angiography (CTA).

Methods

We enrolled 25 patients (MEI (+)₃₀₀ group, 300 mg/mL and 2.5 mL/s of contrast media) and 23 patients (CTA₃₇₀ group, 370 mg/mL and 3.5 mL/s of contrast media) for assessing NAC blood supply angiography. The image quality of the 2 groups was evaluated objectively and subjectively.

Results

The 40 keV MEI (+)₃₀₀ demonstrated higher attenuation and contrast-to-noise ratio than CTA₃₇₀ group (P < 0.001). The subjective image quality and visualization of the arteries were comparable between 2 groups.

Conclusions

The 40 keV MEI (+)₃₀₀ acquired from dual-energy computed tomography can achieve comparable image quality of arterial supply to NAC with low-concentration and low-flow-rate contrast media in breast cancer compared with CTA₃₇₀.

Dual energy CT in clinical routine: how it works and how it adds value

Dual energy computed tomography (DECT), also known as spectral CT, refers to advanced CT technology that separately acquires high and low energy X-ray data to enable material characterization applications for substances that exhibit different energy-dependent x-ray absorption behavior. DECT supports a variety of post-processing applications that add value in routine clinical CT imaging, including material selective and virtual non-contrast images using two- and three-material decomposition algorithms, virtual monoenergetic imaging, and other material characterization techniques. Following a review of acquisition and post-processing techniques, we present a case-based approach to highlight the added value of DECT in common clinical scenarios. These scenarios include improved lesion detection, improved lesion characterization, improved ease of interpretation, improved prognostication, inherently more robust imaging protocols to account for unexpected pathology or suboptimal contrast opacification, length of stay reduction, reduced utilization by avoiding unnecessary follow-up examinations, and radiation dose reduction. A brief discussion of post-processing workflow approaches, challenges, and solutions is also included.

Best Practice Guidelines: Imaging Surveillance After Endovascular Aneurysm Repair

OBJECTIVE. Abdominal aortic aneurysm is a significant cause of morbidity and mortality in the United States. Endovascular aneurysm repair (EVAR) is the preferred treatment modality. Surveillance imaging after EVAR detects potential complications. The most common complication is endoleak, which can predispose the aorta to rupture. This article provides a comprehensive and evidence-based review regarding surveillance imaging after EVAR to help readers understand current societal guidelines, guide institutional protocols, and provide a framework to facilitate safe, cost-effective, and clinically relevant imaging of patients after EVAR. CONCLUSION. Lifelong surveillance is necessary for patients who have undergone EVAR. Triple-phase CT angiography (CTA) within 30 days after EVAR is necessary to triage patients appropriately and guide future imaging. Patients without endoleak on initial CTA can be monitored with annual duplex ultrasound. Patients with type I or type III endoleaks should be referred for intervention. Patients with type II and type V endoleaks should be referred for intervention only if the sac diameter grows by more than 1 cm. MR angiography should be used primarily as a problem-solving modality or in patients with contraindications to contrast media or radiation. Strong consideration should be given to more frequent surveillance in patients who have undergone EVAR who have aneurysms with a hostile neck anatomy compared with those patients with favorable neck anatomy.

Vascular computed tomography angiography technique and indications

Non-invasive cross-sectional imaging techniques play a crucial role in the assessment of the vascular disease processes. Computed tomography angiography (CTA) is an imaging method of choice for a wide range of vascular diseases that span across different vascular territories. A diagnostic quality CTA requires a robust imaging protocol tailored according to the physiologic state and vascular area of interest. This review article is aimed to provide an overview of the technical considerations and clinical applications of CTA.

Percutaneous needle biopsy of retroperitoneal lesions: technical developments

Percutaneous Needle Biopsy (PNB) is the insertion of a needle into a suspected lesion or an organ with the aim to obtain cells or tissue for diagnosis. It’s a relatively non-invasive procedure and is performed by radiologist under guidance of imaging techniques such as ultrasound (US), computed tomography (CT), fluoroscopy, magnetic resonance imaging (MRI), and positron emission tomography CT (PET-CT). The choice of imaging technique depends on the evaluation of the target lesion and patient compliance. PNB includes two categories: fine-needle aspiration biopsy (FNAB) that is the use of a thin needle (18-25 gauge) to extract cells for cytological evaluation; and core needle biopsy (CNB) that is the use of a larger needle (9-20 gauge) to extract a piece of tissue for histological evaluation. The indications for biopsy are the characterization of nature (benign or malignant) of a lesion, diagnosis and staging of tumor, and biological or immunohistochemical/genetic analisys on tissue. Success of PNB is the procurement of sufficient material to characterize lesions and to guide the patient outcome. Major complications are rare. PNB became a useful technique in diagnosis and study of retroperitoneal lesions, because of a more suitable access to specific intra-abdominal structures, lowering the risk of injury of interposed structures (such as bowel, great vessels). (www.actabiomedica.it)

Magnetic resonance enterography (MRE) and ultrasonography (US) in the study of the small bowel in Crohn's disease: state of the art and review of the literature

Crohn’s disease (CD) is a chronic idiopathic disease and its diagnosis is based on a combination of clinical symptoms, laboratory tests and imaging data. There isn’t a diagnostic gold standard: the ileocolonoscopy with mucosal biopsies represents the standard for luminal disease, while cross-sectional imaging such as Ultrasound (US), Computed Tomography (CT) or Magnetic Resonance Imaging (MRI) can show transmural alterations and extraintestinal manifestations. CD is usually diagnosed in the young age and after baseline diagnosis, the patients have to undergo to variable follow-up depending on remission or active disease. The aim of our review is to compare Magnetic Resonance Enterography (MRE) to Ultrasonography (US) in the follow-up of CD. (www.actabiomedica.it)

Internal hernias: a difficult diagnostic challenge. Review of CT signs and clinical findings

Although internal hernias are uncommon, they must be beared in mind in the differential diagnosis in cases of intestinal obstruction, especially in patients with no history of previous surgery or trauma. Because of the high possibility of strangulation and ischemia of the affected loops, internal hernias represent a potentially life-threatening condition and surgical emergency that needs to be quickly recognized and managed promptly. Imaging plays a leading role in the diagnosis and in particular multidetector computed tomography (MDCT), with its thin-section and high-resolution multiplanar reformatted (MPR) images, represents the first line image technique in these patients. The purpose of the present paper is to illustrate the characteristic anatomic location, the clinical findings and the CT appearance associated with main types of internal hernia, including paraduodenal, foramen of Winslow, pericecal, sigmoid-mesocolon- and trans-mesenteric-related, transomental, supravesical and pelvic hernias. (www.actabiomedica.it)

Radiation-induced brain cavernomas in elderly: review of the literature and a rare case report

Radiation-induced brain cavernomas have been mainly reported in children who underwent radiotherapy for medulloblastoma, leukemia, or low-grade glioma. Otherwise, the “de novo” appearance of a cavernoma in an elderly long-survivor patient after resection and radiotherapy of a glioblastoma is a rare event. We report the case of a 62-year-old female patient who underwent surgical resection of a right temporal glioblastoma, followed by radiation therapy of the operative field and surrounding brain and concomitant adjuvant temozolomide. Four years after the operation, a follow-up Magnetic Resonance revealed a good tumor control and a small round lesion at the superior surface of the right cerebellar hemisphere, close to the margins of the previous irradiation field. The radiological items were consistent with a cavernous angioma. Because of the small size of the malformation and the absence of related symptoms, no treatment was performed. The patient died for tumor progression 86 months after the initial operation, with unchanged cerebellar cavernoma. The occurrence of a cavernous angioma in an elderly patient after radiotherapy for brain glioblastoma is an exceptional event; the distribution of radiotherapy-induced cavernous malformations reported in current literature is presented and the mechanism of their formation is discussed. (www.actabiomedica.it)

Diagnostic value/performance of radiological liver imaging during chemoterapy for gastrointestinal malignancy: a critical review

This article reviews the main toxic effect, complications and relative imaging findings of the liver that may appear during the oncologic follow up among patients affected by gastrointestinal malignancy. Awareness of the causative chemotherapeutic agent and regimens, pathophysiology and relative characteristic imaging findings of hepatic injuries is critical in order to obtain an accurate diagnosis especially when these parenchymal lesions are focal. An accurate synergic radiological diagnosis with Computed Tomography (CT) and Magnetic Resonance (MR) techniques may induce a potential termination of ineffective/toxic chemotherapy during early phases of treatment, changing the therapeutic plan in order to avoid first unnecessary liver biopsy and then invasive treatment as hepatic resection if not required.

Contemporary imaging methods for the follow-up after endovascular abdominal aneurysm repair: a review

Abdominal aortic aneurysm (AAA) is defined as a localized enlargement of the aortic cross-section where the diameter is greater than 3 cm or more than 50% larger than the diameter in a normal segment. The most important complication of AAA is rupture, which, if untreated, results in mortality rates of up to 90%. Conventional open surgical repair is associated with significant 30-day mortality. Endovascular aneurysm repair (EVAR) is a significantly less invasive procedure; it is related to a lower early mortality rate and a lower number of perioperative complications. Although EVAR is a minimally invasive technique, lifelong follow-up imaging is necessary due to possible late complications including endoleak, recurrent aneurysm formation, graft infection, migration, kinking and thrombosis. The total rate of complications after EVAR is estimated at approximately 30%, and the rate of complications that require intervention is 2–3%. Early detection and progression analysis of such situations is crucial for proper intervention.

Role of dual energy CT to improve diagnosis of non-traumatic abdominal vascular emergencies

Computed tomography angiography (CTA) is the modality of choice to evaluate abdominal vascular emergencies (AVE). CTA protocols are often complex and require acquisition of multiple phases to enable a variety of diagnosis such as acute bleeding, pseudoaneurysms, bowel ischemia, and dissection. With single energy CT (SECT), differentiating between calcium, coagulated blood, and contrast agents can be challenging based on their attenuation, especially when in small quantity or present as a mixture. With dual-energy CT (DECT), virtual monoenergetic (VM) and material decomposition (MD) image reconstructions enable more robust tissue characterization, improve contrast-enhancement, and reduce beam hardening artifacts. This article will demonstrate how radiologists can utilize DECT for various clinical scenarios in assessment of non-traumatic AVE.

Dual energy CT angiography: pros and cons of dual-energy metal artifact reduction algorithm in patients after endovascular aortic repair

PURPOSE

To evaluate the value of metal artifact reduction (MAR) post-processing and iodine MD images in fast kV-switching dual-energy computed tomography (DECT) in patients after endovascular aortic repair (EVAR).

MATERIALS AND METHODS

Twenty-four consecutive EVAR patients (age 76 ± 9 years, 7/24 (29%) with coils, 9/24 (37.5%) with 10 endoleaks) who underwent DECT angiography were included in this HIPAA-compliant, IRB-approved retrospective study. Monochromatic reconstructions included 55, 60, 65, 70, and 75 keV with and without MAR and iodine MD images. Near field, far field, and vessel artifacts were assessed subjectively (1 = none; 5 = severe) and objectively by measuring noise and contrast-to-noise ratio. Visibility of endoleak was evaluated (1 = optimal; 5 = not visible).

RESULTS

MAR objectively decreased artifacts from EVAR stents in the near field (60.7 ± 25.4 HU vs. 70.1 ± 34.2; p = .002) and subjectively increased near field (3.2 ± 0.9 vs. 2.8 ± 0.6; p < .001), far field (2.2 ± 0.6 vs. 1.6 ± 0.6; p < .001), and vessel (3.1 ± 1.1 vs. 2.5 ± 0.9; p < .001) artifacts. Near-field artifacts from coils were reduced by the MAR objectively (72.4 ± 24.8 vs. 182.7 ± 57.3 HU; p < .001) and subjectively (4.5 ± 0.5 vs. 4.9 ± 0.4; p = .02). CNR of standard reconstructions was optimal at 60 keV (38.3 ± 16.8). Reconstructions without MAR and iodine MD images provided improved endoleak visualization in 6/10 (60%) of cases (median 1 for both) compared to MAR (median 3) (p < 0.001). However, MAR improved visualization in 1/10 (10%) cases due to endoleak location adjacent to a coil.

CONCLUSION

DECT with MAR reduced artifacts from coils and improved endoleak visualization in 1/10 (10%) cases due to location adjacent to a coil. However, MAR impaired endoleak visualization in 6/10 (60%) cases and should be reviewed combined with 60 keV standard reconstructions and iodine MD images.

Comparison of Radiation Exposure Associated With Intraoperative Cone-Beam Computed Tomography and Follow-up Multidetector Computed Tomography Angiography for Evaluating Endovascular Aneurysm Repairs

Purpose: To compare the radiation exposure associated with intraoperative contrast-enhanced cone-beam computed tomography (ceCBCT) acquisitions to standard 3-phase multidetector computed tomography (MDCT) angiography used for assessing technical success after endovascular aortic repair (EVAR). Methods: Effective doses (EDs) were calculated for 66 EVAR patients (mean age 71 years; 61 men) with a mean 27.7-kg/m2 body mass index (range 17–49) who had both intraoperative ceCBCT and postoperative 3-phase MDCT angiography between November 2012 and April 2015. In addition, EDs were directly determined using thermoluminescent dosimeters (TLDs) embedded in anthropomorphic phantoms with body mass indexes of 22 and 30 kg/m2. Effective doses were calculated by summing doses recorded by all TLDs corresponding to a specific tissue type before applying the International Commission on Radiological Protection (ICRP) 60 and 103 weighting factors. EDs were compared with each other for both imaging modalities as well as to TLD measurements. Results: Average EDs of the patient collective were 4.9±1.1 mSv for ceCBCT, 2.6±1.2 mSv for single-phase MDCT (46% decrease, covering solely the area of the implanted endograft), and 13.6±5.5 mSv for comprehensive 3-phase MDCT examinations (178% increase, anatomical coverage from the aortic arch to femoral artery bifurcation). EDs determined in phantom measurements ranged from 3.1 to 4.5 mSv for ceCBCT, amounting to 2.6 mSv for a single MDCT phase (15% to 40% decrease) using ICRP 60 conversion factors. Applying ICRP 103 factors resulted in higher values for ceCBCT and slightly lower ones for MDCT. Conclusion: ceCBCT offers the chance for immediate intraoperative revisions of endograft-related problems. Requiring only a single-phase acquisition, ceCBCT is associated with a considerable reduction in ED (50%–75%) compared to standard 3-phase MDCT angiography after EVAR. On the other hand, MDCT has a larger field of view and is associated with less radiation exposure for a single phase (reduction of 20%–60%) if only the stented region is covered; however, MDCT angiography also uses larger amounts of contrast.

Follow-up of endovascular aortic aneurysm repair: Preliminary validation of digital tomosynthesis and contrast enhanced ultrasound in detection of medium- to long-term complications

AIM: To validate the feasibility of digital tomosynthesis of the abdomen (DTA) combined with contrast enhanced ultrasound (CEUS) in assessing complications after endovascular aortic aneurysm repair (EVAR) by using computed tomography angiography (CTA) as the gold standard.

METHODS: For this prospective study we enrolled 163 patients (123 men; mean age, 65.7 years) referred for CTA for EVAR follow-up. CTA, DTA and CEUS were performed at 1 and 12 mo in all patients, with a maximum time interval of 2 d.

RESULTS: Among 163 patients 33 presented complications at CTA. DTA and CTA correlated for the presence of complications in 32/33 (96.96%) patients and for the absence of complications in 127/130 (97.69%) patients; the sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) and accuracy of DTA were 97%, 98%, 91%, 99%, and 98%, respectively. CEUS and CTA correlated for the presence of complications in 19/33 (57.57%) patients and for the absence of complications in 129/130 (99.23%) patients; the sensitivity, specificity, PPV, NPV and accuracy of CEUS were 58%, 99%, 95%, 90%, and 91%, respectively. Sensitivity, specificity and accuracy of combining DTA and CEUS together in detecting EVAR complications were 77%, 98% and 95%, respectively.

CONCLUSION: Combining DTA and CEUS in EVAR follow-up has the potential to limit the use of CTA only in doubtful cases.

High-pitch, low-voltage and low-iodine-concentration CT angiography of aorta: assessment of image quality and radiation dose with iterative reconstruction

Objective

To assess the image quality of aorta obtained by dual-source computed tomography angiography (DSCTA), performed with high pitch, low tube voltage, and low iodine concentration contrast medium (CM) with images reconstructed using iterative reconstruction (IR).

Methods

One hundred patients randomly allocated to receive one of two types of CM underwent DSCTA with the electrocardiogram-triggered Flash protocol. In the low-iodine group, 50 patients received CM containing 270 mg I/mL and were scanned at low tube voltage (100 kVp). In the high-iodine CM group, 50 patients received CM containing 370 mg I/mL and were scanned at the tube voltage (120 kVp). The filtered back projection (FBP) algorithm was used for reconstruction in both groups. In addition, the IR algorithm was used in the low-iodine group. Image quality of the aorta was analyzed subjectively by a 3-point grading scale and objectively by measuring the CT attenuation in terms of the signal- and contrast-to-noise ratios (SNR and CNR, respectively). Radiation and CM doses were compared.

Results

The CT attenuation, subjective image quality assessment, SNR, and CNR of various aortic regions of interest did not differ significantly between two groups. In the low-iodine group, images reconstructed by FBP and IR demonstrated significant differences in image noise, SNR, and CNR (p<0.05). The low-iodine group resulted in 34.3% less radiation (4.4 ± 0.5 mSv) than the high-iodine group (6.7 ± 0.6 mSv), and 27.3% less iodine weight (20.36 ± 2.65 g) than the high-iodine group (28 ± 1.98 g). Observers exhibited excellent agreement on the aortic image quality scores (κ = 0.904).

Conclusions

CT images of aorta could be obtained within 2 s by using a DSCT Flash protocol with low tube voltage, IR, and low-iodine-concentration CM. Appropriate contrast enhancement was achieved while maintaining good image quality and decreasing the radiation and iodine doses.