Spiral head CT in the evaluation of acute intracranial pathology: a pictorial essay

Comparison of physical image qualities and artifact indices for head computed tomography in the axial and helical scan modes

This study aimed to validate the clinically demonstrated equivalency of the axial and helical scan modes (AS and HS, respectively) for head computed tomography (CT) using physical image quality measures and artifact indices (AIs). Two 64-row multi-detector row CT systems (CT-A and CT-B) were used for comparing AS and HSs with detector rows of 64 and 32. The modulation transfer function (MTF), noise power spectrum (NPS), and slice sensitivity profile were measured using a CT dose index corresponding to clinical use. The system performance function (SPF) was calculated as MTF²/NPS. The AI of streak artifacts in the skull base was measured using an image obtained of a head phantom, while the AI of motion artifacts was measured from images obtained during the head phantom was in motion. For CT-A, the 50%MTFs were 7% to 9% higher in the HS than the AS, and the higher MTFs of HS associated NPS increases. For CT-B, the MTFs and NPSs were almost equivalent between the AS and HS, respectively. Consequently, the SPFs of AS and HS were nearly identical for both CT systems. For both CT systems, the skull base AI did not differ significantly between AS and HS, while the motion AIs of HS were significantly better than of AS. The superior motion AI in the HS indicated the effectiveness of HS on moving patients.

Continuous Versus Sequential Acquisition Head Computed Tomography: A Phantom and Clinical Image Quality Comparative Study

OBJECTIVE

Sequential computed tomography (CT) technique remains the most common protocol for CT evaluation of the head despite nearly universal adoption of continuous technique for all other body parts. This may be attributable to the belief by radiologists that this technique is superior to helical scanning uniquely for this indication. This study attempts to clarify the issue.

METHODS

A phantom evaluation and a prospective randomized clinical image quality trial were performed comparing sequential and helical technique using the most current generation 128-row detector CT scanner.

RESULTS

Phantom evaluation demonstrated equivalence between the 2 techniques for low-contrast resolution and line pair spatial discrimination. Continuous scanning provided the highest contrast-to-noise ratio. There was no significant difference between the 2 techniques regarding image quality except for cortical visualization at the cerebral hemispheres, which was subtly but significantly superior for sequential technique.

CONCLUSIONS

Head CT image quality for sequential and continuous techniques are virtually equivalent.

Reevaluating the Utility of Maxillary Sinus Opacification as a Screening Tool for Facial Bone Fracture a Decade After Its Original Analysis

In 1997, Lambert and colleagues demonstrated that the absence of sinus fluid on head CT essentially excludes a fracture involving the sinus walls. Our purpose is to reevaluate this association utilizing the current standard of imaging technology. With improved image resolution, we aim to reassess whether the sensitivity and specificity of the “clear sinus sign” are improved or worsened. Furthermore, the current standard of care is to obtain a CT of the facial bones along with a head CT when facial trauma is suspected, so we also analyzed the association of the "clear sinus sign" with nasal bone and mandible fractures. We identified 629 facial bone CT scans performed on adult patients in the emergency department between July 2012 and May 2013. They were retrospectively analyzed by three reviewers for the presence of facial bone fracture and/or fluid opacification of at least one paranasal sinus (as defined by either complete sinus opacification or an air-fluid level - circumferential mucosal thickening was considered the absence of fluid). We found that sinus opacification was 98.8% specific for facial bone fracture but only 44.7% sensitive. However, for complex facial fractures, such as zygomaticomaxillary complex, orbital, and sinus fractures, the lack of sinus fluid is significantly more sensitive at 91%. Therefore, our results for complex facial fractures are congruent with those of the previous studies conducted by Lambert, et al. and Lewandowski, et al. However, we also demonstrate that sinus opacification is not specific for nasal bone or mandibular fractures.  

Skull fractures in pediatric patients on computerized tomogram: comparison between routing bone window images and 3D volume-rendered images

Skull fracture is a common finding following head trauma. It has a prognostic significance and its presence points to severe trauma. Additionally, there is a greater possibility of detecting associated small underlying extra-axial hematomas and subtle injuries to the brain parenchyma. In pediatric patients, the presence of multiple open sutures often makes fracture evaluation challenging. In our experience, 3D volume (3DV)-rendered CT images complement routine axial bone window (RBW) images in detection and characterization of fractures. This is a multi-reader, multi-case, paired retrospective study to compare the sensitivity and specificity of RBW and 3DV images in detection of calvarial fractures in pediatric patients. A total of 60 cases (22 with fractures and 38 without) were analyzed. Two experienced neuroradiologists and a radiology trainee were the readers of the study. For all readers, the sensitivity was not statistically different between the RBW and the 3DV interpretations. For each reader, there was a statistically significant difference in the interpretation times between the RBW and the 3DV viewing formats. A greater number of sutural diastasis was identified on 3DV. We propose that 3DV images should be part of routine head trauma imaging, especially in the pediatric age group. It requires minimal post-processing time and no additional radiation. Furthermore, 3DV images help in reducing the interpretation time and also enhance the ability of the radiologist to characterize the calvarial fractures.

A new preoperative radiological assessment in LeFort I surgery: anterior nasal spine-sphenoidal rostrum

OBJECTIVE

The aim of this study is to assess the distance between the anterior nasal spine and the sphenoidal rostrum related to the LeFort I surgery in a Turkish population sample.

MATERIAL AND METHODS

We retrospectively reviewed multidetector computerized tomography (MDCT) scans of 209 patients (134 males and 75 females). The images were obtained on a 64-MDCT scanner. The imaging parameters were 0.5 × 64 mm slice thickness, 0.5/0.3 mm increment, 120 kV, 250 mAs, 0.5 sn rotation time, 0.641 pitch, and 512 matrix. The distance between the anterior nasal spine and the sphenoidal rostrum was assessed with the Vitrea 2 software program.

RESULTS

The study group consisted of 134 male (mean age 57.90 ± 5.86) and 75 female (mean age 54.84 ± 4.31) patients. The distance between the anterior nasal spine and the sphenoidal rostrum was ranging between 40.4 and 70.9 mm (average 58.3 ± 5.9) in males and 45.0 and 63.2 mm in (average 55.2 ± 4.3) females. In addition, no statistically significant differences were found between genders.

CONCLUSION

The results of the current study showed that after 40 mm proceeding of the ball end nasal osteotome, the surgeons must be aware of penetrating the sphenoidal rostrum.

Prevalence of idiopathic cuneate gyrus herniation based on emergency room CT examinations

Idiopathic brain herniation caused by a focal dural defect can be confused for a mass or post-traumatic herniation. The prevalence of idiopathic brain herniation has never been described. We sought to ascertain the prevalence of idiopathic cuneate gyrus herniation in a general emergency room (ER) population on computed tomography (CT) imaging. The purpose of this study is to elucidate cuneate gyrus herniation and differentiate it from other pathologic conditions such as mass or traumatic herniation and to provide its anatomical prevalence in an ER population. Consecutive emergency room CT scans of the brain were evaluated prospectively for cuneate gyrus herniation over a 1 year period by a neuroradiologist. Of 1,500 brain CT scans evaluated, 11 patients demonstrated idiopathic cuneus gyrus herniation. The prevalence was 0.73 %. CT manifestations are normal brain tissue herniating into the superior cerebellar cistern. Idiopathic brain herniation can be mistaken for a pathologic process. We found the prevalence of one such idiopathic brain herniation, involving the cuneus gyrus, to be exceedingly rare. CT imaging demonstrates normal brain tissue herniating beyond the dural boundary.

Role of noncontrast head CT in the assessment of vascular abnormalities in the emergency room

Noncontrast CT of the head is a widely used noninvasive investigation for a variety of acute and chronic neurological conditions. Since CT head without contrast is usually the first and often the only investigation in the emergency room for many neurological symptoms, it is imperative to detect subtle vascular changes, which in many patients can be life-saving. The vascular abnormalities may present with increased density and/or size of the vessels, filling defects, and be associated with parenchymal and bony changes. In this article, we present examples of several vascular pathologies which can be identified on the noncontrast CT of the head, and learn imaging and interpretation techniques to help recognize what often are nebulous changes. While some of the findings are diagnostic by themselves and others subtle, any suspicious abnormality should be followed with dedicated vascular imaging such as CT/MR angiogram, venogram, or catheter angiogram for confirmation and better characterization.