Blindness : An Uncommon Presentation of Colloid Cysts = العمى : عرض إستثنائي لتكيسات غروانية

Correlation Between Imaging and Pathologic Tumor Delineation for Non-colorectal Hepatic Metastases

To investigate the use of diffusion-weighted (DW) imaging for differentiating benign lesions from malignant pleural disease (MPD) and to retrospectively assess dynamic contrast material-enhanced (DCE) magnetic resonance (MR) imaging acquisitions to find out whether combining these measurements with DW imaging could improve the diagnostic value of DW imaging. This study was approved by the local ethics committee, and all patients provided written informed consent. Thirty-one consecutive patients with pleural abnormalities suspicious for MPD underwent whole-body positron emission tomography (PET)/computed tomography (CT) and thorax MR examinations. Diagnostic thoracoscopy with histopathologic analysis of pleural biopsies served as the reference standard. First-line evaluation of each suspicious lesion was performed by using the apparent diffusion coefficient (ADC) calculated from the DW image, and the optimal cutoff value was found by using receiver operating characteristic curve analysis. Afterward, DCE MR imaging data were used to improve the diagnosis in the range of ADCs where DW imaging results were equivocal. Sensitivity, specificity, and accuracy of PET/CT for diagnosis of MPD were 100%, 35.3%, and 64.5%. The optimal ADC threshold to differentiate benign lesions from MPD with DW MR imaging was 1.52 × 10(-3) mm(2)/sec, with sensitivity, specificity, and accuracy of 71.4%, 100%, and 87.1%, respectively. This result could be improved to 92.8%, 94.1%, and 93.5%, respectively, when DCE MR imaging data were included in those cases where ADC was between 1.52 and 2.00 × 10(-3) mm(2)/sec. A total of 20 patients had disease diagnosed correctly, nine had disease diagnosed incorrectly, and two cases were undetermined with PET/CT. DW imaging helped stage disease correctly in 27 patients and incorrectly in four. The undetermined cases at PET/CT were correctly diagnosed at MR imaging. DW imaging is a promising tool for differentiating MPD from benign lesions, with high accuracy, and supplementation with DCE MR imaging seems to further improve sensitivity.

An 18-year-old woman, with a 5-month history of intermittent acute headaches, was admitted to her local hospital owing to drowsiness and confusion. Her mother described a feeling of heaviness in the head when leaning forward, and dizziness, followed by short and intense headaches, sometimes accompanied by vomiting and blurred vision. The symptoms were typically transient and disappeared suddenly after a few minutes. No focal neurological deficits were noted. The brain computed tomography (CT) scan showed an acute obstructive biventricular hydrocephalus and a spherical isodense lesion in the anterior third ventricle (Fig, 1A, white arrow). During the transfer of the patient to our clinic, her level of consciousness declined acutely. She was intubated and sedated. Upon arrival, magnetic resonance imaging (MRI) T2-weighted axial images (Fig, 1B) confirmed the obstruction of both interventricular foramina by an approximately 1cm hyperintense colloid cyst (black arrow) of the roof of the third ventricle. The lesion appeared hypointense on the T1-weighted images and did not contrast enhance. The very thin third ventricle (white arrowheads) highlighted the strictly biventricular nature of the hydrocephalus. Periventricular hypodensity on CT and hyperintensity on T2 MRI demonstrated cerebrospinal fluid (CSF) resorption from the increased hydrostatic pressure. The patient underwent an urgent, minimally invasive endoscopic surgery. There was complete and immediate postoperative recovery, with a normal neurological examination. The operative endoscopic view from the right lateral ventricle (Fig, 1D) shows the colloid cyst (*) obstructing the right interventricular foramen. The septum pellucidum (SP), the right fornix (Fx), the choroid plexus (CP) and the right thalamus (Th) are also visible. Only a narrow window remains for the CSF flow (black curved arrow). The wall of the cyst was fenestrated, and the viscous and heterogeneous contents were aspirated, allowing the cyst to collapse and the restoration of CSF circulation. T2-weighted axial MRI at 2 months follow-up (Fig, 1C) shows the collapsed cyst and resolution of hydrocephalus, with permeable Monro foramina. Colloid cysts are benign tumors, most often asymptomatic, representing around 1% of all intracranial neoplasms. They are usually discovered between 35 and 60 years of age. Although benign, their localization is ominous because they can potentially cause obstruction of both foramina of Monro1 and acute biventricular hydrocephalus. Their shape and relative rigidity can cause positional “ball-valve” gravity- and pressure-dependent foraminal closure leading to flow obstruction, causing headache. An increase in the intensity or frequency of symptoms is believed to be a signal of impeding acute foraminal closure. Coma, by complete obstruction of CSF pathways, is rare but leaves little time for life-saving surgery. Sudden death is exceptional and can occur spontaneously2 or after a lumbar puncture by immediate and fatal tonsillar herniation.3 Although colloid cysts are usually hyperdense on brain CT, they can sometimes be isodense to the brain, as in this case. If the isodense cyst is also small, it can be missed on CT scanning, but usually appears on MRI. Understanding the pathophysiology of colloid cysts is essential to identify and treat them in a timely way and to avoid hazardous diagnostic examinations, such as lumbar taps. All authors were involved in patient management. F.L., A.L. and E.S. contributed to the conception and design of the study; F.L. and A.L. contributed to the acquisition and analysis of data; F.L., A.L., J.F.Z.-J. and E.S. contributed to drafting the text and preparing the figure. Nothing to report.

A case of bilateral occipital lobe infarcts following Indian tree viper bite.

INTRODUCTION Oblique lumbar interbody fusion (OLIF) is a minimally-invasive technique that relies on a sufficient corridor anterior to the psoas and posterior to vascular structures.This intraoperative corridor is evaluated on preoperative computed tomography (CT) and/or magnetic resonance (MR) imaging to guide patient selection.Previous cadaveric studies and preoperative MR imaging analysis have examined this corridor to determine corridor variations along right- and left-sided approaches and among patient characteristics.This is the first study that directly evaluates the true intraoperative corridor in the lateral decubitus position based on intraoperative 3D imaging. METHODS We performed a retrospective evaluation identifying patients > 18 yr old who had undergone an OLIF via a left-sided approach at 2 tertiary care centers from 2016 to 2018. Patients with scoliosis greater than 20 degrees, transitional anatomy, and psoas abnormalities were excluded.We recorded demographics and the intraoperative corridor defined by the distance between the left lateral border of the aorta or iliac vessels and anteromedial border of the psoas from L1-L2 through L4-5 disc spaces.This corridor was measured on supine, preoperative MR axial imaging and subsequent intraoperative 3D cone beam CT acquired in the right lateral decubitus position. RESULTS A total of 33 patients, 15 of whom were female, were included in this study.The average age was 65.4 and body mass index (BMI) was 31 kg/m2.There was a statistically significant increase (P < .05) in the intraoperative corridor from supine to lateral decubitus positioning at all levels.The greatest increase in corridor size was noted at L1-2 (3.1 cm) and least at L4-5 (2.1 cm).There was no statistically significant difference between age, BMI, or gender in the preoperative versus intraoperative corridor. CONCLUSION This is the first study to provide objective evidence to support that lateral decubitus positioning increases the intraoperative corridor for anterior to the psoas techniques.This information should increase confidence with an anterior to the psoas approach if there is adequate corridor size on supine preoperative imaging evaluation.

To compare diagnostic accuracy of T2-weighted magnetic resonance (MR) imaging with that of multiparametric (MP) MR imaging combining T2-weighted imaging with diffusion-weighted (DW) MR imaging, dynamic contrast material-enhanced (DCE) MR imaging, or both in the detection of locally recurrent prostate cancer (PCa) after radiation therapy (RT). This retrospective HIPAA-compliant study was approved by the institutional review board; informed consent was waived. Fifty-three men (median age, 70 years) suspected of having post-RT recurrence of PCa underwent MP MR imaging, including DW and DCE sequences, within 6 months after biopsy. Two readers independently evaluated the likelihood of PCa with a five-point scale for T2-weighted imaging alone, T2-weighted imaging with DW imaging, T2-weighted imaging with DCE imaging, and T2-weighted imaging with DW and DCE imaging, with at least a 4-week interval between evaluations. Areas under the receiver operating characteristic curve (AUC) were calculated. Interreader agreement was assessed, and quantitative parameters (apparent diffusion coefficient [ADC], volume transfer constant [K(trans)], and rate constant [k(ep)]) were assessed at sextant- and patient-based levels with generalized estimating equations and the Wilcoxon rank sum test, respectively. At biopsy, recurrence was present in 35 (66%) of 53 patients. In detection of recurrent PCa, T2-weighted imaging with DW imaging yielded higher AUCs (reader 1, 0.79-0.86; reader 2, 0.75-0.81) than T2-weighted imaging alone (reader 1, 0.63-0.67; reader 2, 0.46-0.49 [P ≤ .014 for all]). DCE sequences did not contribute significant incremental value to T2-weighted imaging with DW imaging (reader 1, P > .99; reader 2, P = .35). Interreader agreement was higher for combinations of MP MR imaging than for T2-weighted imaging alone (κ = 0.34-0.63 vs κ = 0.17-0.20). Medians of quantitative parameters differed significantly (P < .0001 to P = .0233) between benign tissue and PCa (ADC, 1.64 × 10(-3) mm(2)/sec vs 1.13 × 10(-3) mm(2)/sec; K(trans), 0.16 min(-1) vs 0.33 min(-1); k(ep), 0.36 min(-1) vs 0.62 min(-1)). MP MR imaging has greater accuracy in the detection of recurrent PCa after RT than T2-weighted imaging alone, with no additional benefit if DCE is added to T2-weighted imaging and DW imaging.

In the last few years there has been rapid progress in the application of nuclear magnetic resonance clinical imaging as a diagnostic aid (Partain et al, 1983; Steiner, 1983; Worthington, 1983). Records kept by the operators of NMR imaging equipment indicate that about 1800 individuals have now been examined without incident within the United Kingdom. In view of this progress, an advisory group (Appendix) appointed by the National Radiological Protection Board recommends some modifications to the original advice given in 1981 (NRPB, 1981). The principal modifications are that: (1) It is no longer considered necessary to exclude volunteers with a history of epilepsy or cardiac disease. (2) It is not obligatory that a registered medical practitioner trained in resuscitation techniques be present during an exposure. (3) Higher limits are recommended for rates of change of magnetic flux density when the period of change is less than 10 ms. (4) The radiofrequency limit of 15 MHz has been removed. Theoretical considerations indicate that the interaction of an applied magnetic field with the intrinsic magnetic moments of protons and electrons within a molecule could alter its rate of chemical reaction (McLauchlan, 1981). Chemical reactions involving radical pair intermediates are expected to be sensitive to magnetic fields for this reason and a number of enzyme reactions that might be expected to be affected have been identified (A. Cass, personal communication). However, there is no experimental confirmation of these theoretical possibilities at present.

The purpose of this study was to evaluate the use of gadolinium and barium-enhanced magnetic resonance (MR) imaging in detecting intestinal and extraintestinal Crohn's disease and compare MRI with contrast-enhanced helical computed tomography (CT). Twenty-six patients with Crohn's disease underwent imaging examinations, including gadolinium-enhanced, fat suppressed fast multiplanar spoiled gradient-recalled (FMPSPGR) MR imaging with oral 2% barium sulfate and rectal water and with helical CT using i.v. and positive (13) or negative (13) intestinal contrast material. MR images and CT scans were reviewed separately by two radiologists for bowel wall thickness and enhancement, presence of abscess, phlegmon, and fistula. MR images and CT scans were then compared side by side. Surgical, endoscopic, and histopathologic findings and results of barium studies were reviewed to determine the location and severity of involvement of intestinal Crohn's disease. Depiction of mural thickening and/or enhancement was superior on the MR images, which showed 55 (85%) and 52 (80%) of 65 abnormal bowel segments for the two observers, compared with helical CT, which showed 39 (60%) and 42 (65%; P < 0.001, P < 0.05) of bowel segments affected by Crohn's disease. Segments of bowel with moderate or marked mural thickening were depicted equally on MR imaging and helical CT. In mildly diseased segments of bowel, with only slight thickening and enhancement, MR imaging depicted 22 (79%) and 19 (68%) of 28 segments, compared with helical CT, which depicted 9 (32%; P < 0.01), and 13 (46%; P > 0.05) of 28 segments. In the side-by side comparison, MR imaging was preferred over helical CT for depicting normal bowel wall (MR 71%, CT 4%, equal 25%; P < 0.001), mural thickening (MR 41%, CT 11% equal 48%; P < 0.01), mural enhancement (MR 89%, equal 11%; P < 0.001), and overall GI tract evaluation (MR 52%, CT 10%, equal 38%; P < 0.001). Gadolinium-enhanced MR imaging with oral dilute barium sulfate and rectal water depicts intestinal and extraintestinal changes of Crohn's disease and shows promise as a clinically useful tool.

Diffusion-weighted imaging provides a novel contrast mechanism in magnetic resonance (MR) imaging and has a high sensitivity in the detection of changes in the local biologic environment. A significant advantage of diffusion-weighted MR imaging over conventional contrast material-enhanced MR imaging is its high sensitivity to change in the microscopic cellular environment without the need for intravenous contrast material injection. Approaches to the assessment of diffusion-weighted breast imaging findings include assessment of these data alone and interpretation of the data in conjunction with T2-weighted imaging findings. In addition, the analysis of apparent diffusion coefficient (ADC) value can be undertaken either in isolation or in combination with diffusion-weighted and T2-weighted imaging. Most previous studies have evaluated ADC value alone; however, overlap in the ADC values of malignant and benign disease has been observed. This overlap may be partly due to selection of b value, which can influence the concomitant effect of perfusion and emphasize the contribution of multicomponent model influences. The simultaneous assessment of diffusion-weighted and T2-weighted imaging data and ADC value has the potential to improve specificity. In addition, the use of diffusion-weighted imaging in a standard breast MR imaging protocol may heighten sensitivity and thereby improve diagnostic accuracy. Standardization of diffusion-weighted imaging parameters is needed to allow comparison of multicenter studies and assessment of the clinical utility of diffusion-weighted imaging and ADC values in breast evaluation.

To determine retrospectively whether unenhanced computed tomographic (CT) images of the brain have added value in distinguishing tumefactive demyelinating lesions (TDLs) from primary glioma or central nervous system (CNS) lymphoma, compared with conventional contrast material-enhanced magnetic resonance (MR) images only. This study was approved by the institutional review board, and informed consent was waived. Unenhanced CT and MR images in 15 patients with TDLs (seven women, eight men; mean age, 42 years; range, 27-57 years) and 48 patients with primary brain tumor (27 women, 21 men; mean age, 48 years; range, 19-70 years; 10 lymphomas, 38 gliomas) were retrospectively reviewed. The CT attenuation of regions that were enhanced or unenhanced at MR imaging was visually categorized into three grades, and CT attenuation values were determined quantitatively. The diagnostic accuracy of MR imaging for differentiating TDLs from tumors was compared with that of MR imaging plus CT. The following MR imaging features were found more frequently in patients with TDL than in those with brain tumor: incomplete rim enhancement, mixed T2-weighted iso- and hyperintensity of enhanced regions, absence of a mass effect, and absence of cortical involvement (all P values < .05). CT hypoattenuation of MR enhanced regions was observed in 14 (93%) of 15 patients with TDL but in only two (4%) of 48 patients with tumor. The CT attenuation of MR enhanced regions was significantly lower for patients with TDL than for those with tumor (P < .001). The diagnostic accuracy of CT plus MR imaging was significantly higher than that of MR imaging alone (97% vs 73.0%, respectively; P < .001), and the diagnostic accuracy of CT was significantly higher than that of unenhanced T1-weighted MR imaging (95% vs 63%, P < .001). Unenhanced CT plus MR imaging was more accurate for distinguishing TDLs from glioma or CNS lymphoma than contrast-enhanced MR imaging alone.

Magnetic resonance (MR) imaging is used with increasing frequency to evaluate the neonatal brain because it can provide important diagnostic and prognostic information that is needed for optimal treatment and appropriate counseling. Special care must be taken in preparing encephalopathic neonates for an MR study, transporting them from the intensive care unit, monitoring their vital signs, and optimizing MR sequences and protocols. Moreover, to accurately interpret the findings, specific knowledge is needed about the normal MR imaging appearances of the physiologic processes of myelination, cell migration, and sulcation, as well as patterns of injury, in the neonatal brain at various stages of gestational development. Hypoxic-ischemic injury, the most common cause of neonatal encephalopathy, has characteristic appearances that depend on the severity and duration of the insult as well as the stage of brain development. Diffusion-weighted MR imaging and MR spectroscopy depict abnormalities earlier than do conventional MR imaging sequences. However, diffusion-weighted imaging, if performed in the first 24 hours after the insult, might lead to underestimation of the extent of injury. When the MR findings are atypical, the differential diagnosis of neonatal encephalopathy also should include congenital and metabolic disorders and infectious diseases. Despite recent advances in the MR imaging-based characterization of these conditions, the clinical history must be borne in mind to achieve an accurate diagnosis.

Habib Zaidi, PhD This is an exciting time for molecular imaging because molecular medicine is expected to lead to a revolutionary paradigm shift in health care. While the nuclear medicine community is witnessing a revolution in the practice of this specialty with the introduction of dual-modality positron emission tomography (PET) and computed tomography (CT), many groups in academic and corporate settings are focusing their efforts on the development of promising multimodality imaging technologies that will combine magnetic resonance (MR) imaging and PET components in a single gantry. One such preclinical system is described by Judenhofer et al (1) in this issue of Radiology, and different design trends have been reported in the literature (2–8). Similar design concepts are also being investigated for combined single photon emission CT (SPECT) and MR imaging instrumentation (9). The recent interest in simultaneous PET/MR imaging is not the consequence of controversies surrounding the role and clinical benefits of PET/CT (10,11) but will likely be the subject of similar critique and debates. The development of PET/MR imaging has been motivated by various factors and has several important incentives (12). First, MR imaging is used to obtain anatomic and structural images with submillimeter spatial resolution that offers better soft-tissue contrast sensitivity than that offered by CT. MR imaging has excellent contrast between white and gray matter and allows for functional imaging in brain studies, and, more importantly, it can be used to assess flow, diffusion, perfusion, and cardiac motion in one examination (13). In addition, MR imaging can be combined with MR spectroscopy to measure the regional biochemical content and to assess the metabolic status or the presence of neoplasia and other diseases in specific tissue areas. Finally, MR imaging does not involve the use of ionizing radiation; thus, it can be used without restrictions in serial studies, for pediatric studies, and in many other situations where radiation exposure is a concern. PET imaging is used to record the regional distribution of radiolabeled tracers; however, unlike MR spectroscopy, it cannot be used to distinguish the specific molecular species to which the radionuclide is attached, and, unlike MR imaging, it provides little anatomic information. While many technical problems have recently been solved, there are still several important challenges to the implementation and operation of a PET/MR imaging system that must be overcome. In comparison with x-ray CT, MR imaging typically is more costly, involves longer examination times, and produces anatomic images from which it is more difficult or at least not as straightforward to derive attenuation maps for photon correction of the emission data (14). The latter issue was not described by Judenhofer et al (1), as it has received only limited attention in the scientific literature and few investigators have addressed the problem of the use of segmented MR data to construct an attenuation map for attenuation correction purposes with PET (15). However, interest in PET/MR imaging has been the driving force behind many worthwhile research efforts recently undertaken by different research groups. The major difficulty lies in the fact that the MR signal or tissue intensity level is not directly related to electronic attenuation, which renders conversion of MR images to attenuation maps less obvious when compared with CT. It is worth emphasizing that the optimal transmission scanning technique for PET/CT (ie, CT versus radionuclide sources) is still an open issue that remains to be addressed (16). This is not an issue for PET/MR imaging because of the limited space available, and thus, placement of external Published online 10.1148/radiol.2443070092

Preoperative rotational assessment of the distal femur with CT may cause femoral component malrotation in TKA

A Case of Cerebral Venous Thrombosis in a 77-Year-Old White Man

Object. The aim of this study was to assess the diagnostic yield of imaging tests performed in patients in whom the cause of subarachnoid hemorrhage (SAH) had not been demonstrated on initial angiography. Methods. By reviewing medical records of 806 patients with SAH who had been admitted during a 6.5-year period, the authors identified 86 in whom initial transfemoral catheter angiography failed to reveal the cause of SAH. Clinical and radiological data were analyzed to determine the diagnostic yield of subsequent catheter angiography, computerized tomography (CT) angiography, magnetic resonance (MR) angiography, and MR imaging of the brain and spine for various subtypes of SAH (bleeding not visualized on CT studies [CT-negative SAH], perimesencephalic SAH, and nonperimesencephalic SAH). Of 41 patients with nonperimesencephalic SAH, 36, 32, and 21 underwent repeated catheter angiography, CT angiography, and MR angiography, respectively; brain MR imaging was performed in 23 patients (18 with Gd and 15 with susceptibility contrast sequences), and spine MR imaging in 17. Of 36 patients with perimesencephalic SAH, 31, 23, and 17 underwent repeated catheter angiography, CT angiography, and MR angiography, respectively; brain MR imaging was performed in 18 patients (17 with Gd and 11 with susceptibility contrast sequences), and spine MR imaging in 14. Of nine patients with SAH not visualized on CT scanning, three, one, and six underwent repeated catheter angiography, CT angiography, and MR angiography, respectively; brain MR imaging was performed in eight patients (five with Gd and three with susceptibility contrast sequences), and spine MR imaging in seven. The cause of SAH could be determined in only four patients, all with nonperimesencephalic SAH. The only test that yielded a diagnosis was catheter angiography (three aneurysms on the second and one on the third angiography, all surgically secured). Diffusion-weighted MR imaging demonstrated small, deep infarcts in five patients. Conclusions. Repeated catheter angiography remains the most sensitive test to determine the cause of SAH that is not demonstrated on initial angiography, particularly in the subtype of nonperimes-encephalic SAH. Newer, noninvasive imaging techniques provide little diagnostic yield.