Alida A. Postma

Dual-Energy CT of the Brain and Intracranial Vessels

OBJECTIVE The purpose of this review is to summarize the principles and applications of dual-energy CT in evaluation of the brain and the intracranial blood vessels. CONCLUSION One major advantage of dual-energy CT is the capability of material differentiation. In general, this property can be applied to bone removal in CT angiography for easier and faster postprocessing. In neuroradiology, material decomposition allows detection of hemorrhage on contrast-enhanced CT scans and facilitates the search for the underlying pathologic mechanism of hematomas. The combination of low radiation dose and advantageous spectral information (blood vs contrast) from these datasets justifies broad clinical implementation of dual-energy CT in neuroradiology.

Dual-Energy CT: What the Neuroradiologist Should Know

Because of the different attenuations of tissues at different energy levels, dual-energy CT offers tissue differentiation and characterization, reduction of artifacts, and remodeling of contrast-to-noise ratio (CNR) and signal-to-noise ratio (SNR), hereby creating new opportunities and insights in CT imaging. The applications for dual-energy imaging in neuroradiology are various and still expanding. Automated bone removal is used in CT angiography and CT venography of the intracranial vessels. Monoenergetic reconstructions can be used in patients with or without metal implants in the brain and spine to reduce artifacts, improve CNR and SNR, or to improve iodine conspicuity. Differentiation of iodine and hemorrhage is used in high-density lesions, after intra-arterial recanalization in stroke patients or after administration of contrast media. Detection of underlying (vascular and non-vascular) pathology and spot sign can be used in patients presenting with (acute) intracranial hemorrhage.

Posterior reversible encephalopathy syndrome in paediatric leukaemia

This report describes four patients with acute lymphoblastic leukaemia, suffering from posterior reversible encephalopathy syndrome during the induction period of treatment. A review of the literature on posterior reversible encephalopathy syndrome in paediatric leukaemia is given. The exact mechanism of posterior reversible encephalopathy syndrome is not clear and seems to be multifactorial. Hypertension is likely to play a major role in the development but could be also secondary. All patients in this case series presented after introduction of the new induction protocol for acute lymphoblastic leukaemia. Treatment of hypertension is likely to have a favourable role and posterior reversible encephalopathy syndrome is most often reversible. It is important to consider this diagnosis during the induction phase of leukaemia treatment in the presence of neurological symptoms. The incidence of PRES in the induction scheme should be investigated, in order to optimize the ALL treatment.

The clinical spectrum of Blake’s pouch cyst: report of six illustrative cases

IntroductionAlthough Blake’s pouch cyst (BPC) is frequently mentioned in the spectrum of posterior fossa cysts and cystlike malformations since its first description in 1996, its natural history, clinical presentation, specific imaging characteristics, optimal treatment, and outcome are relatively unknown. Consequently, BPC may still be underdiagnosed. We therefore report six cases ranging from a fatal hydrocephalus in a young boy, over an increasing head circumference with or without impaired neurological development in two infants, to a decompensating hydrocephalus at an advanced age.DiscussionWe focus on their radiological uniformity, which should help making the correct diagnosis, and widely variable clinical presentation, which includes adult cases as well. Differentiating BPC from other posterior fossa cysts and cystlike malformations and recognizing the accompanying hydrocephalus are essentially noncommunicating, not only have important implications on clinical management but also on genetic counseling, which is unnecessary in case of BPC. In our experience, endoscopic third ventriculostomy is a safe and effective treatment option, avoiding the risks and added morbidity of open surgery, as well as many shunt-related problems.

Intraobserver and Interobserver Agreement in Volumetric Assessment of Glioblastoma Multiforme Resection

BACKGROUND:The role of extent of tumor resection in improving outcome for patients with glioblastoma multiforme (GBM) is still under debate. OBJECTIVE:To analyze intraobserver and interobserver agreement of manual segmentation as a method for volumetric assessment of GBM resection. METHODS:Three observers performed volumetric assessment of preoperative tumor volume (PreTV) and postoperative tumor volume (PostTV) by manual segmentation on contrast-enhanced T1-weighted MRI data sets of 8 patients. Measurements were repeated after a minimum interval of 2 weeks. Intraobserver and interobserver agreement for PreTV, PostTV, and residual tumor volume (RTV) percentage were expressed in intraclass correlation coefficients (ICCs). RESULTS:Intraobserver agreement is high for PreTV (ICC = 0.99), PostTV (ICC = 0.73-0.94), and RTV (ICC = 0.89-0.94). Interobserver agreement is high for PreTV (ICC = 0.97), but low for PostTV (ICC = 0.54) and RTV (ICC = 0.52). CONCLUSION:Postoperative assessment of GBM volume seems to offer high intraobserver agreement, but low interobserver agreement. Using absolute RTV values to relate extent of tumor resection with survival may be unreliable. More research is needed before this method can be used as a valid end point for clinical studies. Computer-assisted tumor volume calculation may increase interobserver agreement in the future.

Diagnostic radiation exposure in children with spinal dysraphism: an estimation of the cumulative effective dose in a cohort of 135 children from The Netherlands

Objective Based on the assumption that children with spinal dysraphism are exposed to a large amount of ionising radiation for diagnostic purposes, our objective was to estimate this exposure, expressed in cumulative effective dose. Design Retrospective cohort study. Settings The Netherlands. Patients 135 patients with spinal dysraphism and under 18 years of age treated at our institution between 1991 and 2010. Results A total of 5874 radiological procedures were assessed of which 2916 (49.6%) involved ionising radiation. Mean cumulative effective dose of a child with spinal dysraphism during childhood was 23 mSv, while the individual cumulative effective dose ranged from 0.1 to 103 mSv. Although direct radiography accounted for 81.7% of examinations, the largest contributors to the cumulative effective dose were fluoroscopic examinations (40.4% of total cumulative effective dose). Conclusions Exposure to ionising radiation and associated cancer risk were lower than expected. Nevertheless, the use of ionising radiation should always be justified and the medical benefits should outweigh the risk of health detriment, especially in children.

Does a Change in Bone Mineral Density Occur in the Mandible of Gottingen Minipigs After Irradiation in Correlation With Radiation Dose and Implant Surgery

PURPOSE To date, studies have not agreed on the effects of irradiation on bone mineral density. The aim of our study was to investigate the changes in mandibular bone mineral density after irradiation at various doses with and without surgery. MATERIALS AND METHODS We implemented a descriptive animal experiment. The sample included 16 female Göttingen Minipigs, randomly assigned to 4 groups and irradiated with equivalent doses of 0, 25, 50, and 70 Gy to the mandibular region. At 3 months after irradiation, the mandibular left premolars and molars were removed, and dental implants were placed. Computed tomography scans were taken before and 6 months after irradiation. The measured bone density was related to a bone phantom to calculate the bone mineral density quotient (BMDQ). The outcome variable was the BMDQ. Other study variables were the radiation dose and surgery. Descriptive and univariate analyses were computed, and significance was set at P ≤ .05. RESULTS In the left hemimandible, compared with the control group, a significant decrease in BMDQ was observed: 0.01 at 0 Gy, -0.01 at 25 Gy, -0.06 at 50 Gy, and -0.11 at 70 Gy (P = .023). The right hemimandible compared with the control group also showed a significant decrease in BMDQ: -0.02 at 0 Gy, -0.08 at 25 Gy, -0.09 at 50 Gy, and -0.11 at 70 Gy (P = .007). CONCLUSIONS The present study used a large animal model to simulate the tissue reactions induced by various radiation doses in the mandible. We found a significant decrease in the BMDQ after irradiation, but no significant correlation could be found between the irradiation dose and a decrease in the BMDQ.

Vasospasm is a significant factor in cyclosporine-induced neurotoxicity : Case report

BackgroundThe aetiology of central nervous system lesions observed in cerebral cyclosporine neurotoxicity remains controversial.Case presentationWe report a 48-year-old woman with a non-severe aplastic anaemia who presented with stroke-like episodes while on cyclosporine treatment.Transcranial Doppler ultrasound revealed severely elevated flow velocities in several cerebral vessels, consistent with vasospasm. Immediately after reducing the cyclosporine dose, the stroke-like episodes disappeared. Only after cyclosporine withdrawal the transcranial Doppler ultrasound abnormalities fully resolved.ConclusionsThis case demonstrates a significant role of vasospasm in the pathway of cyclosporine-induced neurotoxicity. Transcranial Doppler ultrasound is an effective tool for the diagnosis and follow-up of cyclosporine-induced vasospasm.

Dual-Energy CT in Head and Neck Imaging

Purpose of ReviewTo explain the technique of Dual-energy CT (DECT) and highlight its applications and advantages in head and neck radiology.Recent FindingsUsing DECT, additional datasets can be created next to conventional images. In head and neck radiology, three material decomposition algorithms can be used for improved lesion detection and delineation of the tumor. Iodine concentration measurements can aid in differentiating malignant from nonmalignant lymph nodes and benign posttreatment changes from tumor recurrence. Virtual non-calcium images can be used for detection of bone marrow edema. Virtual mono-energetic imaging can be useful for improved iodine conspicuity at lower keV and for reduction of metallic artifacts and increase in signal-to-noise ratio at higher keV.SummaryDECT and its additional reconstructions can play an important role in head and neck cancer patients, from initial diagnosis and staging, to therapy planning, evaluation of treatment response and follow-up. Moreover, it can be helpful in imaging of infections and inflammation and parathyroid imaging as supplementary reconstructions can be obtained at lower or equal radiation dose compared with conventional single energy scanning.

Teaching NeuroImages: Duret hemorrhage due to bilateral subdural hematomas causing internuclear ophthalmoplegia

Rob P.W. Rouhl, MD, PhD Alida A. Postma, MD, PhD A 67-year-old man with a clinical history of atrial fibrillation and oral anticoagulant use presented with headache and vomiting, rapidly deteriorating to coma in a few hours. CT showed bilateral subdural hematomas with transtentorial herniation and brainstem compression (figure). Decompressive burr holes were made bilaterally. Postoperative recovery was unremarkable except for a left-sided anterior internuclear ophthalmoplegia (paralysis of adduction of the left eye on right lateral gaze with preserved convergence). Subsequent MRI showed a focal lesion at the central part of the mesencephalon interpreted as a Duret hemorrhage (shown in the figure). Generally, a Duret hemorrhage is considered a serious, often fatal, complication of brain herniation,1 however, subtle neurologic deficits, such as internuclear ophthalmoplegia, may be its only sign.