Computed tomography angiography versus digital subtraction angiography in vascular mapping for planning of microsurgical reconstruction of the mandible

Spectral computed tomography with inorganic nanomaterials: State-of-the-art

Recently, spectral computed tomography (CT) technology has received great interest in the field of radiology. Spectral CT imaging utilizes the distinct, energy-dependent X-ray absorption properties of substances in order to provide additional imaging information. Dual-energy CT and multi-energy CT (Spectral CT) are capable of constructing monochromatic energy images, material separation images, energy spectrum curves, constructing effective atomic number maps, and more. However, poor contrast, due to neighboring X-ray attenuation of organs and tissues, is still a challenge to spectral CT. Hence, contrast agents (CAs) are applied for better differentiation of a given region of interest (ROI). Currently, many different kinds of inorganic nanoparticulate CAs for spectral CT have been developed due to the limitations of clinical iodine (I)-based contrast media, leading to the conclusion that inorganic nanomedicine applied to spectral CT will be a powerful collaboration both in basic research and in clinics. In this review, the underlying principles and types of spectral CT techniques are discussed, and some evolving clinical diagnosis applications of spectral CT techniques are introduced. In particular, recent developments in inorganic CAs used for spectral CT are summarized. Finally, the challenges and future developments of inorganic nanomedicine in spectral CT are briefly discussed.

Facial Arterial Variations in Asians: A Study on Computed Tomographic Angiography

BACKGROUND

A consensus on facial artery anatomy has not been established due to the discrepancies in previous studies.

OBJECTIVES

The authors sought to assess the branches, course, and location of the facial artery in Asians by utilizing computed tomographic angiography.

METHODS

The computed tomographic angiography images of 300 facial arteries from 150 Asian patients were evaluated. The FA was classified as follows: type 1, facial artery terminates superior labial or inferior labial artery; type 2, facial artery terminates lateral nasal or inferior alar artery; type 3, facial artery terminates medial canthal artery; or type 4, facial artery is divided into duplex branches with dominant medial canthal artery laterally. The relationship between nasolabial fold and FA was evaluated, and the distances from anatomical landmarks to FA were measured to position the course.

RESULTS

Seventy (23.3%), 163 (54.3%), 49 (16.3%), and the other 18 arteries (6.0%) were classified as type 1, 2, 3, and 4, respectively. A total 72.3% of facial arteries were located medially to the nasolabial fold, and only 14.7% of arteries were lateral to the nasolabial fold. The vertical distance between the facial artery and the inner canthus or the midpoint of the inferior orbital rim decreased from type 1 to type 4 facial artery (P < 0.0001). The 4 types did not significantly differ in distance between the mandibular angle (P = 0.1226) or oral commissure (P = 0.1030) and the facial artery at inferior of mandible.

CONCLUSIONS

Detailed findings of the facial artery will provide a valuable reference for filler injection in cosmetic procedures and flap design in reconstructive surgery.

Current Radiographic Iodinated Contrast Agents

Millions of radiologic examinations requiring the use of iodinated contrast are performed yearly in North America. Triiodobenzoic acid, the contrast agent molecule currently in use, is a benzene ring covalently bonded to the 3 iodine atoms. Iodinated contrast media can be divided in 4 categories: ionic monomers, ionic dimers, nonionic monomer, and nonionic dimers. Currently, second- and third-generation nonionic low-osmolar and iso-osmolar contrast media are used in clinical practice. The search for a safer and more effective iodinated contrast agents remains an ongoing challenge and important research topic.

Dose reduction potential of iterative reconstruction algorithms in neck CTA-a simulation study

OBJECTIVES

This study aimed to determine the degree of radiation dose reduction in neck CT angiography (CTA) achievable with Sinogram-affirmed iterative reconstruction (SAFIRE) algorithms.

METHODS

10 consecutive patients scheduled for neck CTA were included in this study. CTA images of the external carotid arteries either were reconstructed with filtered back projection (FBP) at full radiation dose level or underwent simulated dose reduction by proprietary reconstruction software. The dose-reduced images were reconstructed using either SAFIRE 3 or SAFIRE 5 and compared with full-dose FBP images in terms of vessel definition. 5 observers performed a total of 3000 pairwise comparisons.

RESULTS

SAFIRE allowed substantial radiation dose reductions in neck CTA while maintaining vessel definition. The possible levels of radiation dose reduction ranged from approximately 34 to approximately 90% and depended on the SAFIRE algorithm strength and the size of the vessel of interest. In general, larger vessels permitted higher degrees of radiation dose reduction, especially with higher SAFIRE strength levels. With small vessels, the superiority of SAFIRE 5 over SAFIRE 3 was lost.

CONCLUSIONS

Neck CTA can be performed with substantially less radiation dose when SAFIRE is applied. The exact degree of radiation dose reduction should be adapted to the clinical question, in particular to the smallest vessel needing excellent definition.

In Vivo Monitoring of Microcirculation in Burn Healing Process with Optical Microangiography

Objective: Optical microangiography (OMAG)-based optical coherence tomography is a noninvasive technique capable of imaging functional microvasculature innervating scanned tissue volume. In this study, we utilize OMAG to investigate dynamic changes of microcirculation during the healing process of a burn. Approach: A soft-contact superficial burn injury was induced on a mouse ear with 1 μL 70°C hot water. Microangiograms were generated by using OMAG before and after the burn. Results: Vessel recruitment and remodeling were observed in the healing process. Burn injury reached to the worst extent within the first 24 h and had no expansion thereafter. The interrupted microcirculation in the mouse ear was progressively recovered in the consequent postburn days and completely healed on postburn day 7. Innovation: OMAG provides a novel way for noninvasive visualization and quantification of vasculature changes over time after burn injuries. The high resolution achieved by the imaging system reveals microvascular details down to capillary level. Conclusion: Our results demonstrated that OMAG has great potential to improve the understanding of microcirculatory responses to burns and thus benefit the development of effective therapeutics.

[Locoregional solutions for groin defects : Coverage after vascular surgery]

INTRODUCTION

Vascular surgery through a groin incision may be associated with severe wound healing disorders in this sensitive area. There are many options to reconstruct the defect surgically. The choice of surgical reconstruction depends mainly on the individual status of vasculature, which is most often compromised in these patients. There are random pattern flaps, as well as perforator, pedicled flaps or microvascular flaps to choose from.

AIM

We give an overview of plastic surgical solutions for groin defects, with a special focus on complex wounds after vascular surgical complications. We discuss advantages and disadvantages of different flaps with two case reports and also show alternatives.

PATIENTS AND METHODS

We demonstrate in two cases how the reconstruction of the groin defect was planned, taking into account the vascular status, and why we chose an innovative and seldom-used option in each case.

RESULTS

The selected flaps, a pedicled fasciocutaneous ALT propeller flap and a perforator-based, pedicled abdominal advancement flap reconstructed the defects successfully.

DISCUSSION

The surgical therapy for the reconstruction of groin defects should be chosen according to the individual vascular status to ensure safe and reliable blood supply. To guarantee the best possible reconstruction and avoid postoperative healing disorders and infections, less common flaps should also be considered.

Extracranial internal carotid artery: anatomical variations in asymptomatic patients

The anatomical variations of internal carotid artery (ICA) are mostly asymptomatic, thus being disregarded and only incidentally diagnosed, with very few symptomatic patients. The awareness of these anomalies is crucial to solve the differential with other neck lesions, preventing accidental injuries during neck surgery. Therefore, the aim of our study is to estimate the prevalence of ICA anomalies, using magnetic resonance angiography (MRA) and computed tomography angiography (CTA). 253 patients underwent head and neck MRA and CTA examinations, with multiplanar and volumetric reformations. For each set of images, the following items were investigated: origin, development, course, persistence of embryonic vessels and anomalous origin of collateral branches. In our series, ICA arose from the bifurcation of the common carotid artery at the level of: C4 in 303 hemi-necks (59.9 %); C3 in 98 hemi-necks (19.3 %); C5 in 57 hemi-necks (11.3 %); C2 in 48 hemi-necks (9.5 %). ICA kinking and/or coiling was found in 105 hemi-necks, and location variation of ICA (reversed-type) in two hemi-necks. In just one case the origin of the ascending pharyngeal artery was from ICA (0.2 %), while an anomalous persistence of the proatlantal artery was noticed in three cases (0.6 %). CTA and MRA showed similar accuracy in detecting ICA anomalies.

Whole body magnetic resonance angiography and computed tomography angiography in the vascular mapping of head and neck: an intraindividual comparison

Introduction

The aim of the study was to compare the detectability of neck vessels with contrast enhanced magnetic resonance angiography (MRA) in the setting of a whole-body MRA and multislice computed tomography angiography (CTA) for preoperative vascular mapping of head and neck.

Methods

In 20 patients MRA was performed prior to microvascular reconstruction of the mandible with osteomyocutaneous flaps. CTA of the neck served as the method of reference.

1.5 T contrast enhanced magnetic resonance angiograms were acquired to visualize the vascular structures of the neck in the setting of a whole-body MRA examination. 64-slice spiral computed tomography was performed with a dual-phase protocol, using the arterial phase images for 3D CTA reconstruction. Maximum intensity projection was employed to visualize MRA and CTA data. To retrieve differences in the detectability of vessel branches between MRA and CTA, a McNemar test was performed.

Results

All angiograms were of diagnostic quality. There were no statistically significant differences between MRA and CTA for the detection of branches of the external carotid artery that are relevant host vessels for microsurgery (p = 0.118). CTA was superior to MRA if all the external carotid artery branches were included (p < 0.001).

Conclusions

MRA is a reliable alternative to CTA in vascular mapping of the cervical vasculature for planning of microvascular reconstruction of the mandible. In the setting of whole-body MRA it could serve as a radiation free one-stop-shop tool for preoperative assessment of the arterial system, potentially covering both, the donor and host site in one single examination.

Role of computed tomography angiography in the diagnosis of vascular stenosis in head and neck microvascular free flap reconstruction

The aim of this study was to evaluate the role of computed tomography angiography (CTA) in the diagnosis of vascular stenosis at the vascular pedicle of head and neck microvascular free flaps. A prospective study was done of 65 consecutive patients (49 male, 16 female; mean age 55 years) who had undergone head and neck microvascular free flap reconstruction. All patients underwent 64-slice CTA of the carotid artery. Post-processing with volume rendering reconstruction of CTA images was done. There was excellent inter-observer agreement (weighted kappa=0.82, 95% confidence interval (CI) 0.74-0.93) in grading of the degree of vascular stenosis. The true sensitivity of CTA for diagnosis of stenosis of the vascular pedicle to the flap was 63% (95% CI 63-100%). Patients with failed flaps showed complete occlusion (n=2) on CTA and underwent a replacement flap procedure. Patients with failing flaps showed severe stenosis (n=6) of the vascular pedicle on CTA and underwent revision surgery. There was no change in the degree of stenosis on follow-up CTA for patients with moderate stenosis (n=9). CTA is a reliable, non-invasive, high-quality imaging tool for the diagnosis and grading of vascular stenosis of the vascular pedicle of head and neck microvascular free flaps.

Tracking dynamic microvascular changes during healing after complete biopsy punch on the mouse pinna using optical microangiography

Optical microangiography (OMAG) and Doppler optical microangiography (DOMAG) are two non-invasive techniques capable of determining the tissue microstructural content, microvasculature angiography, and blood flow velocity and direction. These techniques were used to visualize the acute and chronic microvascular and tissue responses upon an injury in vivo. A tissue wound was induced using a 0.5 mm biopsy punch on a mouse pinna. The changes in the microangiography, blood flow velocity and direction were quantified for the acute (<30 min) wound response and the changes in the tissue structure and microangiography were determined for the chronic wound response (30 min–60 days). The initial wound triggered recruitment of peripheral capillaries, as well as redirection of main arterial and venous blood flow within 3 min. The complex vascular networks and new vessel formation were quantified during the chronic response using fractal dimension. The highest rate of wound closure occurred between days 8 and 22. The vessel tortuosity increased during this time suggesting angiogenesis. Taken together, these data signify that OMAG has the capability to track acute and chronic changes in blood flow, microangiography and structure during wound healing. The use of OMAG has great potential to improve our understanding of vascular and tissue responses to injury in order to develop more effective therapeutics.

Analysis of the dynamic relationships between the lingual artery and lingual markers in patients with obstructive sleep apnea

PURPOSE

To determine the relationships between the lingual artery and the lingual markers in tongue resting and extended positions in patients with obstructive sleep apnea-hypopnea syndrome (OSAHS) for the clinical application of functional tongue surgery.

METHOD

Computed tomography angiography (CTA) of the lingual artery was performed on 30 OSAHS patients using a 16-slice spiral CT scanner. The anatomical relationships between the lingual artery and the lingual markers were analyzed with the tongue in resting and extended positions using the CTA images.

RESULTS

The course of the lingual artery resembled the configuration of the Big Dipper constellation when the tongue was in a resting position. When the tongue was in a full-extended position, the majority of the lingual artery moved forward and upward with the hyoid and formed a "√" fashion. The positions of the tip of the greater horn of the hyoid changed with the tongue positions. While the relationship between the main lingual artery and the tip of the greater horn of the hyoid, as well as the distances between bilateral lingual arteries, remained constant in both tongue positions.

CONCLUSIONS

In conditions of dynamic tongue movement, the tip of the great horn of the hyoid and the lingual midline are constant anatomical markers to indicate the course of the lingual artery.

Computed tomography and magnetic resonance angiography in the evaluation of aberrant origin of the external carotid artery branches

Aim of our study was to evaluate the prevalence of aberrant origin of the branches of the external carotid artery (ECA) in 97 patients by computed tomography (CTA) and magnetic resonance angiography (MRA) and to compare the accuracy of these two techniques in the visualization of the ECA system. All patients underwent CTA and MRA examination of the head and neck. Multiplanar and volumetric reformations were obtained in all cases. For each set of images, the presence of aberrant origin of the branches of the external carotid artery was investigated. MRA and CTA images of each patient were compared to define their information content. Anatomical anomalies were found in 88 heminecks, with a prevalence of 53.3%. In the 61 patients in whom the CTA was performed before the MRA, the latter method showed only 92% of abnormalities detected at the first examination; in the 36 patients in whom MRA was performed first, CTA identified all of the anomalies highlighted by the former, adding 12 new. Knowledge of the anomalies of origin of the ECA branches is essential for the head and neck surgeon; the high prevalence of anomalies found in our series as in the previous studies indicates the opportunity to perform a CTA or a MRA of the head and neck before any surgical or interventional procedure. CTA is the method of choice in the evaluation of anomalies of origin of the branches of the ECA and in the definition of their course.

Thyrolingual trunk arising from the common carotid artery identified by three-dimensional computed tomography angiography

It is well-known that the branches of the external carotid artery (ECA) can show anatomical variation, but it is extremely rare that thyrolingual trunk originates from common carotid artery (CCA). Here we report a case of the thyrolingual trunk arising from the CCA on the right side in a 73-year-old female as revealed by three-dimensional computed tomography angiography for vascular mapping of the carotid vessels before head and neck microsurgical reconstruction. The thyrolingual trunk arose from the anterior surface of the right CCA, with an origin 14.5 mm (difference between the carotid bifurcation and upper border of the origin 12.7 mm) below the carotid bifurcation. The inner diameter of origin of the thyrolingual trunk was 3.5 mm, and the angle between the thyrolingual trunk and the CCA was 130°. After a 10.2-mm course, the thyrolingual trunk divided into the superior thyroid artery (STA) and lingual artery (LA). The inner diameters of the origins of the STA and LA were 1.7 and 1.9 mm, respectively, and the angle between the branches was 94°. It is important to recognize this anatomic variation of the branches of the ECA before the microsurgical reconstruction or super-selective intra-arterial chemotherapy for head and neck cancer.

Whole-body magnetic resonance angiography for presurgical planning of free-flap head and neck reconstruction

OBJECTIVES

Aim of the study was to evaluate if a whole-body magnetic resonance angiography (MRA) protocol meets the requirements to evaluate the donor and host site target vessels for planning of microvascular head and neck reconstructions.

PATIENTS AND METHODS

In 20 patients, scheduled for reconstruction of the mandible with fibular free flaps, contrast-enhanced whole-body MRA was performed prior to surgery. 32-Channel 1.5-T MR angiograms were acquired using a 2-step contrast (gadobutrol) injection scheme to visualize the arterial vasculature from head to feet. Maximum intensity projection and multiplanar reconstruction technique was employed to visualize MRA data. For image evaluation the arterial tree was divided into 51 segments. The presence of artefacts impairing diagnostic quality was noted. Evaluable segments were assessed regarding the presence of stenoses >50% diameter reduction, occlusions or aneurysms.

RESULTS

No adverse reactions or complications occurred. Of 1020 vessel segments 1003 (98.3%) were evaluable. 36 stenoses >50%, 50 occlusions and one aneurysm were observed. In 21 of 40 lower limbs relevant atherosclerotic changes were depicted.

CONCLUSION

Whole-body MRA proved to be a suitable three-dimensional, noninvasive, nonionising modality for preoperative evaluation of the entire arterial vasculature.

Computerized tomographic angiography for preoperative assessment of the superficial temporal artery for external carotid artery to internal carotid artery bypass: Case illustration

INTRODUCTION

While catheter angiography has traditionally been used to assess the caliber and course of the superficial temporal artery prior to its use as a conduit for external carotid artery to internal carotid artery (EC-IC) bypass, computed tomographic angiography (CTA) has become increasingly used in the diagnostic assessment of cerebral vasculature. We demonstrate the application of CTA for evaluation of the superficial temporal artery as a vascular conduit for EC-IC bypass.

CASE PRESENTATION

A female in the fourth decade of life presented with the chief complaint of headache. CTA of the Circle of Willis revealed an unruptured fusiform aneurysm of the M1 segment of the right middle cerebral artery (MCA). We performed CTA for the preoperative assessment of the STA for a putative EC-IC bypass procedure, and correlated this to conventional external carotid angiography. Reformatted CTA provided excellent surface visualization of the STA and its course in relationship to the cranial and zygomatic surfaces, and correlated well with findings on the conventional angiogram.

CONCLUSION

CTA may eventually prove sufficient for use in assessing the STA in preparation for EC-IC bypass.

Fast noise reduction in computed tomography for improved 3-D visualization

Computed tomography (CT) has a trend towards higher resolution and higher noise. This development has increased the interest in anisotropic smoothing techniques for CT, which aim to reduce noise while preserving structures of interest. However, existing smoothing techniques are slow, which makes clinical application difficult. Furthermore, the published methods have limitations with respect to preserving small details in CT data. This paper presents a widely applicable speed optimized framework for anisotropic smoothing techniques. A second contribution of this paper is an extension to an existing smoothing technique aimed at better preserving small structures of interest in CT data. Based on second-order image structure, the method first determines an importance map, which indicates potentially relevant structures that should be preserved. Subsequently an anisotropic diffusion process is started. The diffused data is used in most parts of the images, while structures with significant second-order information are preserved. The method is qualitatively evaluated against an anisotropic diffusion method without structure preservation in an observer study to assess the improvement of 3-D visualizations of CT series and quantitatively by determining the reduction of the difference between low and high dose CT scans of in vitro carotid plaques.

Value of automatic bone subtraction in cranial CT angiography: comparison of bone-subtracted vs. standard CT angiography in 100 patients

Non-contrast-enhanced cranial computed tomography (NECT) and CT angiography (CTA) are the most frequently used modalities in the triage of patients with acute ischemic and hemorrhagic stroke. CTA bone removal can improve the delineation of vasculature closely adjacent to bony structures, which is sometimes limited in standard CTA. The aim of this study was the evaluation of the clinical benefit of bone subtraction (BS) regarding delineation of cerebral vasculature, reading time and depiction of vascular pathologies compared to standard CTA without BS. A total of 100 patients who underwent NECT and supraaortic CTA on a 64-slice CT system were retrospectively included in the study. Bone removal was performed by subtraction of the NECT data from the CTA data using a dedicated workstation. Standard and BS CTA of each patient was reviewed for delineation of cerebral vasculature (grading scale from 1 = "excellent delineation" to 10 = "hardly any delineation"), reading time and depiction of vascular pathologies (standardized catalog) by two blinded readers. For BS data sets, the quality of BS was rated by a combination of the criteria complete bone removal, depiction of vascular structures and sufficient quality for diagnostic evaluation. The use of BS significantly reduced reading time from 4.60 min to 3.49 min (p<0.001). Performing BS, the quality of vascular delineation of the cerebral arteries, cerebral veins and cavernous segment of the ICA increased significantly as compared to standard CTA (1.70 vs. 2.70; 2.60 vs. 4.12; 2.35 vs. 4.40, all p<0.001). Consensus reading showed 41 pathologies in 35 patients. Diagnosis was missed or wrong overall in 15 cases, with 3 missed aneurysms (CTA: 2 vs. BS: 1), 8 wrong stenotic findings (CTA: 3 vs. BS: 5) and 4 missed partial thromboses (CTA: 2 vs. BS: 2). Performing BS in supraaortic CTA for the evaluation of cerebral vasculature reduces reading time and improves delineation of vessels. Diagnostic accuracy in general is not improved by BS, as the diagnostic accuracy of stenotic vessel alterations is reduced by potential truncation artifacts, but the detection rate of cerebral aneurysms slightly increases.

Clinical evaluation of bone-subtraction CT angiography (BSCTA) in head and neck imaging

Fifty-one patients were examined with bone subtraction CT angiography (BSCTA). Data were acquired on 4-and 64-slice spiral CT systems. The post-processing method is based on fully automatic registration of non-enhanced and contrast-enhanced CT data and subsequent selective bone removal. Vascular structures and brain tissue are retained with the original CTA noise level. Image quality and delineation of the pathologic process were assessed and artifacts introduced by the bone removal process recorded. The bone subtraction algorithm worked successfully in all examinations. The processing time was 6 min on average. Image quality was rated excellent in 20 (39%), good in 26 (51%) and acceptable in 5 (10%) patients. Ophthalmic arteries were visible in 12 (24%) patients bilaterally, in 13 (25%) patients unilaterally and in 26 (51%) patients at least at the origin. BSCTA improved visualization of the infraclinoid ICA and the vertebral arteries. The depiction of stenosis of the extracranial ICA and supraclinoid aneurysms was not significantly improved. In patients with suspicion of sinus thrombosis, BSCTA and conventional CTA yielded similar results. To conclude, BSCTA improves the visualization of vessels with close contact to bone and can improve the diagnostic accuracy and therapy planning of infraclinoid aneurysms.