Optical probing of ultrafast laser-induced solid-to-overdense-plasma transitions.

Understanding the solid target dynamics resulting from the interaction with an ultrashort laser pulse is a challenging fundamental multi-physics problem involving atomic and solid-state physics, plasma physics, and laser physics. Knowledge of the initial interplay of the underlying processes is essential to many applications ranging from low-power laser regimes like laser-induced ablation to high-power laser regimes like laser-driven ion acceleration. Accessing the properties of the so-called pre-plasma formed as the laser pulse's rising edge ionizes the target is complicated from the theoretical and experimental point of view, and many aspects of this laser-induced transition from solid to overdense plasma over picosecond timescales are still open questions. On the one hand, laser-driven ion acceleration requires precise control of the pre-plasma because the efficiency of the acceleration process crucially depends on the target properties at the arrival of the relativistic intensity peak of the pulse. On the other hand, efficient laser ablation requires, for example, preventing the so-called "plasma shielding". By capturing the dynamics of the initial stage of the interaction, we report on a detailed visualization of the pre-plasma formation and evolution. Nanometer-thin diamond-like carbon foils are shown to transition from solid to plasma during the laser rising edge with intensities < 1016 W/cm². Single-shot near-infrared probe transmission measurements evidence sub-picosecond dynamics of an expanding plasma with densities above 1023 cm-3 (about 100 times the critical plasma density). The complementarity of a solid-state interaction model and kinetic plasma description provides deep insight into the interplay of initial ionization, collisions, and expansion.

Middle meningeal artery pseudoaneurysm and pterygoid plexus fistula following percutaneous radiofrequency rhizotomy: illustrative case.

BACKGROUND: Percutaneous treatment for trigeminal neuralgia is a safe and effective therapeutic methodology and can be accomplished in the form of balloon compression, glycerol rhizotomy, and radiofrequency thermocoagulation. These procedures are generally well tolerated and demonstrate minimal associated morbidity. Moreover, vascular complications of these procedures are exceedingly rare. OBSERVATIONS: We present the case of a 64-year-old female with prior microvascular decompression and balloon rhizotomy who presented after symptom recurrence and underwent a second balloon rhizotomy at our institution. Soon thereafter, she presented with pulsatile tinnitus and a right preauricular bruit on physical examination. Subsequent imaging revealed a middle meningeal artery (MMA) to pterygoid plexus fistula and an MMA pseudoaneurysm. Coil and Onxy embolization were used to manage the pseudoaneurysm and fistula. LESSONS: This case illustrates the potential for MMA pseudoaneurysm formation as a complication of percutaneous trigeminal balloon rhizotomy, which has not been seen in the literature. Concurrent MMA-pterygoid plexus fistula is also a rarity demonstrated in this case.

Cervical extradural arteriovenous fistula with radiculopathy managed endovascularly.

Background: Extradural arteriovenous fistulas (AVFs) of the cervical spine are extremely rare, and typically manifest as slowly progressive myelopathy caused by mass effect. This is a unique case of extradural AVF of the cervical spine manifesting with purely radicular symptoms and treated endovascularly with coil and liquid embolization. Case Description: A 55-year-old woman presented with neck pain and right upper extremity radiculopathy persisting for 9 months. Imaging studies demonstrated an AVF spanning from C4-C6 with extension into the C5-C6 foramen supplied primarily from the deep cervical branch of the costocervical trunk. The patient underwent successful coil and liquid (Onyx) embolization. Six-week postoperatively, the patient's symptoms completely resolved and magnetic resonance imaging and angiographic imaging confirmed complete obliteration of the fistula. Conclusion: While extradural AVFs typically present with myelopathic symptoms, they may present with solely radicular symptoms and can be successfully treated endovascularly.

A pictorial review of imaging findings associated with upper cervical trauma.

The diagnosis of cervical spine injury in the emergency department remains a critical skill of emergency room physicians as well as radiologists. Such diagnoses are often associated with high morbidity and mortality unless readily identified and treated appropriately. Both computed tomography (CT) and magnetic resonance imaging (MRI) often are crucial in the workup of spinal injury and play a key role in arriving at a diagnosis. Unfortunately, missed cervical spine injuries are not necessarily uncommon and often precede detrimental neurologic sequalae. With the increase in whole-body imaging ordered from the emergency department, it is critical for radiologists to be acutely aware of key imaging features associated with upper cervical trauma, possible mimics, and radiographic clues suggesting potential high-risk patient populations. This pictorial review will cover key imaging features from several different imaging modalities associated with upper cervical spine trauma, explore patient epidemiology, mechanism, and presentation, as well as identify confounding radiographic signs to aid in confident and accurate diagnoses.

Radiology Resident Education - Keys to Successful Workstation Learning: A Resident Perspective.

Medical education can be overwhelming for radiology residents, particularly when during the first year. Although there is no one single formula or set of resources for success as a resident, a universal and often overlooked educational experience is the readout at the workstation with the attending. Getting the most out of this key interaction requires forethought and engagement from both the attending and the resident. The aim of this article is to discuss helpful tips in maximizing this educational experience from the resident's perspective.

Radiology resident education - Keys to successful workstation teaching.

Resident education is a complex process that requires many inputs from both the learner and the educator. As teaching faculty, many radiologists rely on two main methods to impart knowledge to their residents; namely didactic/case-based lectures and workstation teaching. The traditional lecture format is well known to both the learner and the educator, as this has been the primary platform that has been used almost universally. In addition, there are a multitude of excellent recorded and live lectures that faculty members can access from national society meetings that can be used as an example of how to give an effective well-organized lecture. Workstation teaching, on the other hand, is instead a more individualistic endeavor that is quite heterogeneous across institutions. In addition, there is very little in the literature that describes effective strategies that can be used to optimize the educational experience for the resident. This discussion will focus on pre-readout, readout, and post-readout strategies that educators can use at the workstation. Implementation of these techniques can be extremely helpful in accelerating resident progression through their training.

Radiology of Abnormal Globe Contour.

The orbits are easily identified on routine computed tomography (CT) and magnetic resonance imaging (MRI) imaging of the head and neck. Although there are many structures within the orbits, the overall structure of the globe is the most noticeable and can be an important source for pathology. In particular, many disease processes alter globe morphology and it is imperative that the radiologist be aware of not only the most common, but uncommon etiologies as well. This article provides an image-rich review of the wide range of emergent and non-emergent pathology that can result in altered globe contour.

Emergency radiologic approach to sinus disease.

Sinus disease is commonly encountered, especially in the acute care setting. Imaging can support a diagnosis of sinusitis, help identify an etiology, and delineate intracranial and extracranial complications. Suspicion of complicated rhinosinusitis is an indication for contrast-enhanced computed tomography or magnetic resonance imaging. It is important for radiologists to be familiar with patient risk factors that predispose to uncommon but aggressive forms of sinus disease such as invasive fungal sinusitis. Lastly, many conditions, ranging from benign to malignant, can mimic rhinosinusitis clinically and on imaging. Radiologists can help by recognizing these entities and facilitating appropriate referral and follow-up. This article reviews the breadth of sinus disease commonly encountered in the emergency setting, potential complications, and mimics.

Imaging of the Primary Visual Pathway based on Visual Deficits.

Vision loss can occur due to a variety of etiologies along the primary visual pathway. Understanding the anatomic organization of the visual pathway, which spans the globe to the occipital cortex, can help tailor neuroimaging to identify the cause of visual dysfunction. In this review, relevant anatomy and optimization of computed tomography and magnetic resonance imaging techniques will be described. This will be followed by a discussion of imaging findings related to pathologies at each functional anatomic level.

Facial swelling for the emergency radiologist-typical and atypical causes.

There are a wide variety of inflammatory, infectious, and cystic lesions which may lead patients to seek acute care for facial swelling. Computed tomography (CT) has become the mainstay for imaging in the urgent/emergent setting. However, magnetic resonance imaging (MRI) can also serve as a powerful problem solving tool in the modern era. As volume continues to increase, a wide variety of facial pathology will be encountered by the emergency radiologist. Recognition of both common and uncommon pathology will assist in diagnosis and value-based care. This article serves as an image-rich review of the many causes of facial swelling with an emphasis on key imaging findings and possible complications.

Post-operative complications of craniotomy and craniectomy.

Craniotomy and craniectomy are widely performed emergent neurosurgical procedures and are the prescribed treatment for a variety of conditions from trauma to cancer. It is vital for the emergency radiologist to be aware of expected neuroimaging findings in post-craniotomy and craniectomy patients in order to avoid false positives. It is just as necessary to be familiar with postsurgical complications in these patients to avoid delay in lifesaving treatment. This article will review the commonly encountered normal and abnormal findings in post-craniotomy and craniectomy patients. The expected postoperative CT and MRI appearance of these procedures are discussed, followed by complications. These include hemorrhage, tension pneumocephalus, wound/soft tissue infection, bone flap infection and extradural abscesses. Complications specifically related to craniectomies include extracranial herniation, external brain tamponade, paradoxical herniation, and trephine syndrome.

Review of the Major and Minor Salivary Glands, Part 1: Anatomy, Infectious, and Inflammatory Processes.

The major and minor salivary glands of the head and neck are important structures that contribute to many of the normal physiologic processes of the aerodigestive tract. The major salivary glands are routinely included within the field of view of standard neuroimaging, and although easily identifiable, salivary pathology is relatively rare and often easy to overlook. Knowledge of the normal and abnormal imaging appearance of the salivary glands is critical for forming useful differential diagnoses, as well as initiating proper clinical workup for what are often incidental findings. The purpose of this review is to provide a succinct image-rich article illustrating relevant anatomy and pathology of the salivary glands via an extensive review of the primary literature. In Part 1, we review anatomy as well as provide an in-depth discussion of the various infectious and inflammatory processes that can affect the salivary glands.

Review of the Major and Minor Salivary Glands, Part 2: Neoplasms and Tumor-like Lesions.

The salivary glands are small structures in the head and neck, but can give rise to a wide variety of benign and malignant pathology. When this occurs, patients may present with palpable swelling, although it is quite common that they are asymptomatic and a salivary gland mass was discovered as an incidental finding on imaging performed for another reason. It is, therefore, critical that radiologists pay careful attention to the salivary glands and have working knowledge of the key differentiating features of the most common neoplastic and nonneoplastic etiologies of salivary gland masses. The purpose of this review is to provide a succinct image-rich article illustrating the various causes of salivary gland masses via an extensive review of the primary literature. In Part 2, we discuss neoplasms and tumor-like lesions of the salivary glands with a key emphasis on specific imaging features of the most common pathologic entities.

Brain tumour post-treatment imaging and treatment-related complications.

PURPOSE: The imaging of primary and metastatic brain tumours is very complex and relies heavily on advanced magnetic resonance imaging (MRI). Utilisation of these advanced imaging techniques is essential in helping clinicians determine tumour response after initiation of treatment. Many options are currently available to treat brain tumours, and each can significantly alter the brain tumour appearance on post-treatment imaging. In addition, there are several common and uncommon treatment-related complications that are important to identify on standard post-treatment imaging. METHODS: This article provides a review of the various post-treatment-related imaging appearances of brain neoplasms, including a discussion of advanced MR imaging techniques available and treatment response criteria most commonly used in clinical practice. This article also provides a review of the multitude of treatment-related complications that can be identified on routine post-treatment imaging, with an emphasis on radiation-induced, chemotherapy-induced, and post-surgical entities. Although radiological evaluation of brain tumours after treatment can be quite challenging, knowledge of the various imaging techniques available can help the radiologist distinguish treatment response from tumour progression and has the potential to save patients from inappropriate alterations in treatment. In addition, knowledge of common post-treatment-related complications that can be identified on imaging can help the radiologist play a key role in preventing significant patient morbidity/mortality. TEACHING POINTS: • Contrast enhancement does not reliably define tumour extent in many low-grade or infiltrative gliomas. • Focal regions of elevated cerebral blood volume (rCBV) on dynamic susceptibility contrast (DSC) perfusion-weighted imaging are suggestive of tumour growth/recurrence. • Brain tumour treatment response criteria rely on both imaging and clinical parameters. • Chemotherapeutic agents can potentiate many forms of radiation-induced injury. • Ipilimumab-induced hypophysitis results in transient diffuse enlargement of the pituitary gland.

Hemorrhagic and non-hemorrhagic causes of signal loss on susceptibility-weighted imaging.

Susceptibility-weighted imaging (SWI) plays a key role in an emergency setting. SWI takes the intrinsic properties of materials being scanned and creates a visual representation of their effects on the magnetic field, thereby differentiating a number of pathologies. Magnetic resonance imaging (MRI) is now more often used, especially when computed tomography (CT) is inconclusive or even negative. Often, clinicians prefer to obtain an MRI first. This article will review the various hemorrhagic and non-hemorrhagic causes of low signal on SWI. There will be a focus on the distribution patterns of low signal on SWI in pathologies such as diffuse axonal injury, cerebral amyloid angiopathy, and cerebral fat embolism. It is important to recognize these patterns of susceptibility, as the radiologist may be the first to give an accurate diagnosis and therefore, directly impact clinical management.

Intracavity stretcher for chirped-pulse amplification in high-power laser systems.

We present pulse stretching with an intracavity Offner-type pulse stretcher applied to a high-energy, short-pulse laser system. The compact intracavity design, offering a tunable stretching factor, allows the pulses to be stretched to several nanoseconds and, at the same time, to be amplified to 100 µJ. The stretched pulses have been further amplified with the high-power laser system Polaris and have been recompressed to durations as short as 102 fs, reaching peak powers of 100 TW. Furthermore, the temporal intensity contrast is investigated and compared to the formerly used stretcher setup.

54 J pulses with 18 nm bandwidth from a diode-pumped chirped-pulse amplification laser system.

We report on results from the fully diode-pumped chirped-pulse amplification laser system Polaris. Pulses were amplified to a maximum energy of 54.2 J before compression. These pulses have a full width at half-maximum spectral bandwidth of 18 nm centered at 1033 nm and are generated at a repetition rate of 0.02 Hz. To the best of our knowledge, these are the most energetic broadband laser pulses generated by a diode-pumped laser system so far. Due to the limited size of our vacuum compressor, only attenuated pulses could be compressed to a duration of 98 fs containing an energy of 16.7 J, which leads to a peak power of 170 TW. These pulses could be focused to a peak intensity of 1.3×1021 W/cm2. Having an ultra-high temporal contrast of 1012 with respect to amplified spontaneous emission these laser pulses are well suited for high-intensity laser-matter experiments.

High contrast, 86 fs, 35 mJ pulses from a diode-pumped, Yb:glass, double-chirped-pulse amplification laser system.

We demonstrate the generation of 86 fs, 35 mJ, high-contrast laser pulses at 1030 nm with a repetition rate of 1 Hz from a diode-pumped double chirped-pulse amplification setup. The pulses exhibit a spectral bandwidth exceeding 27 nm full width at half-maximum. This could be achieved by using a laser architecture comprising two stages of chirped pulse amplification with a cross-polarized wave generation filter in between, by applying spectral shaping and by increasing the spectral hard-clip of the second stretcher. These are, to the best of our knowledge, the shortest pulses at the mJ level with ultra-high contrast generated with a diode-pumped front end at 1030 nm.

Pulmonary artery angiosarcoma on 18F-FDG PET/CT masquerading as pulmonary embolism.

A 53-year old woman suspicious for having pulmonary embolism on enhanced chest CT was proven to have metabolically active tumor in her pulmonary arteries on F-FDG PET/CT. Through biopsy and surgery, this turned out to be a pulmonary artery angiosarcoma. This case demonstrates that PET/CT is very useful in differentiating an aggressive malignant tumor from a bland pulmonary embolus in the pulmonary vasculature.