Cranial bone marrow in children: assessment of normal development with MR imaging

Radiomics model and deep learning model based on T1WI image for acute lymphoblastic leukemia identification

AIM

This study aimed to develop highly precise radiomics and deep learning models to accurately detect acute lymphoblastic leukemia (ALL) using a T1WI image.

MATERIALS AND METHODS

A total of 604 brain magnetic resonance data of ALL group and normal children (NC) group. Two radiologists independently retrieved radiomics features after manually delineating the area of interest along the clivus at the median sagittal position of T1WI. According to the 9:1 ratio, all samples were randomly divided into the training cohort and the testing cohort. support vector machine was then used to classify the radiomics model using the features that had a correlation coefficient of greater than 0.99 in the training cohort. The Efficientnet-B3 network model received the training set images to create a deep learning model. The sensitivity, specificity, and area under the ROC curve were calculated in order to evaluate the diagnostic efficacy of the different models after the validation of two aforementioned models in the testing cohort.

RESULTS

The deep learning model had a higher AUC value of 0.981 than the radiomics model's value of 0.962 in the testing cohort. Delong's test showed no statistical difference between the two models (P>0.05). The accuracy/sensitivity/specificity/negative predictive value/positive predictive value achieved 0.9180/0.9565/0.8947/0.9714/0.8462 for the radiomics model and 0.9344/0.8696/0.9737/0.9250/0.9524 for deep learning model.

CONCLUSIONS

The deep learning and radiomics models showed high AUC values in the training and test cohorts. They also exhibited good diagnostic efficacy for predicting ALL.

High-resolution three-dimensional micro-computed tomography assessment of micro-architectural patterns in non-adults with cribra orbitalia: Correlation between macro- and micro-scale bone features

Skeletal porous lesions such as cribra orbitalia (CO) have long been of interest to bioanthropologists worldwide, mainly due to their high prevalence in osteological material. Previous studies considered CO as an external morphological manifestation, and therefore, research has mainly focused on visible (macroscopic) CO patterns. However, the understanding of CO-induced micro-scale bone changes is still scarce. Therefore, we performed high-resolution micro-computed tomography imaging to investigate three-dimensional CO-induced micro-architectural patterns in non-adults, with a particular focus on the correlation between macroscopic and micro-architectural orbital features. Cortical and trabecular micro-architectural changes in the orbital roof were analyzed in non-adults younger than 15 years, using orbital roof samples with and without macroscopic traces of CO (n = 28). A widely accepted five-grade macroscopic CO scoring system was applied to analyze CO severity. Areas affected with CO (area 1) and areas without macroscopic CO traces (area 2) were analyzed separately. The conducted high-resolution analysis showed that cortical and trabecular micro-architecture varied with CO presence, lesion severity (CO grade), and the analyzed area. Inter-grade comparisons suggested that most of the analyzed micro-architectural parameters were not significantly different between adjacent CO grades. Based on the micro-architectural evaluation of areas 1 and 2, the porous lesions were much more extensive than revealed by gross examination. In addition, micro-architectural differences were particularly pronounced in younger non-adults. In summary, our pilot study suggests that the macroscopic examination of CO reflects only the tip of the iceberg, as the micro-architectural changes seem to be much larger than macroscopically identified. RESEARCH HIGHLIGHTS: Cribra orbitalia (CO) represents orbital porous lesions. A high-resolution microscopic assessment of CO-induced changes in non-adults was done by micro-computed tomography. The microarchitecture was affected by CO presence, CO grade, area, and age.

MRI Diagnosis of Clival Cancer and Sixth Nerve Palsy

BACKGROUND

Imaging diagnosis of clival cancer may be difficult, in part because of normal variation in marrow signal with aging. Identifying whether clival cancer has damaged the sixth cranial nerve is a further challenge because minimal clival abnormalities could impinge on the nerve, which travels very close to the clivus.

METHODS

Two neuroradiologists, who were unaware of previous imaging and clinical diagnoses, reviewed MRI studies of 25 patients with cancer but no clival involvement and no sixth nerve palsy, 24 patients with clival cancer but without sixth nerve palsy, and 31 patients with clival cancer and sixth nerve palsy. The radiologists were tasked with determining whether there was clival cancer, whether there was a sixth nerve palsy and its laterality, and with indicating the pulse sequences used to make those determinations.

RESULTS

Both neuroradiologists correctly identified all 25 cases with a normal clivus. In about half of those cases, they depended on finding a homogeneously bright marrow signal; in the remaining cases, they excluded cancer by determining that the clivus was not expanded and that there were no focal signal abnormalities. Both neuroradiologists correctly identified clival cancer in 54 (98%) of the 55 cases with and without sixth nerve palsy. In doing so, they relied mostly on clival expansion but also on focal signal abnormalities. Both neuroradiologists were at least 80% correct in identifying a sixth nerve palsy, but they often incorrectly identified a palsy in patients who did not have one. When there was a one-sided signal abnormality or the clivus was expanded in one direction, both neuroradiologists were accurate in identifying the side of the sixth nerve palsy.

CONCLUSION

Current MRI pulse sequences allow accurate differentiation of a normal from a cancerous clivus. When the marrow signal is not homogeneously bright in adults, cancer can be diagnosed on the basis of clival expansion or focal signal abnormalities. MRI is less accurate in predicting the presence of a sixth nerve palsy. However, the side of a unilateral palsy can be predicted when the clivus is clearly expanded in one direction or there is a focal signal abnormality on one side.

Magnetic resonance imaging study of normal cranial bone marrow conversion at high altitude

BACKGROUND

To use conventional magnetic resonance imaging (MRI) and diffusion-weighted imaging (DWI) to investigate the effects of long-term hypoxia on cranial bone marrow conversion in healthy people at high altitudes.

METHODS

A total of 1,130 individuals were selected from altitudinal areas of 2,000-3,000, 3,100-4,000, and >4,100 m. Each altitude range was divided into 5 age groups: 0-5, 6-14, 15-29, 30-49, and ≥50 years. Firstly, cranial bone marrow typing of the participants in each altitude range was performed on sagittal T1-weighted images (T1WI) according to the average diploe thickness and signal intensity of the normal skull, and the relationship between bone marrow conversion and age was analyzed. Secondly, the apparent diffusion coefficient (ADC) values of the frontal bone, parietal bone, occipital bone, and temporal bone were measured in the DWI post-processing workstation and statistical methods were used to analyze whether different altitudinal gradients and long-term hypoxic environment had any effect on cranial bone marrow conversion.

RESULTS

There was a positive correlation between bone marrow type and age in the healthy populations at all 3 levels of altitude (P<0.05). The average thickness of the cranial diploe also positively correlated with age (P<0.05); in the age ranges of 30-49 and ≥50 years, the ADC values of the occipital and temporal bone marrow positively correlated with increasing altitude (P<0.05).

CONCLUSIONS

The cranial bone marrow of normal people at high altitudes changes from Type I to Type IV with increasing age and under the influence of long-term chronic hypoxia. The bone marrow of the occipital and temporal bones of healthy people aged 30-49 and ≥50 years showed erythromedularization during the process of Type III and IV bone marrow conversion.

A biological approach to adult sex differences in skeletal indicators of childhood stress

OBJECTIVES

In previous work examining the etiology of cribra orbitalia (CO) and porotic hyperostosis (PH) in a contemporary juvenile mortality sample, we noted that males had higher odds of having CO lesions than females. Here, we examine potential reasons for this pattern in greater detail. Four non-mutually exclusive mechanisms could explain the observed sex differences: (1) sex-biased mortality; (2) sexual dimorphism in immune responses; (3) sexual dimorphism in bone turnover; or (4) sexual dimorphism in marrow conversion.

SUBJECTS AND METHODS

The sample consists of postmortem computed tomography scans and autopsy reports, field reports, and limited medical records of 488 individuals from New Mexico (203 females; 285 males) aged between 0.5 and 15 years. We used Kaplan-Meier survival analysis, predicted probabilities, and odds ratios to test each mechanism.

RESULTS

Males do not have lower survival probabilities than females, and we find no indications of sex differences in immune response. Overall, males have a higher probability of having CO or PH lesions than females.

CONCLUSIONS

All results indicate that lesion formation in juveniles is influenced by some combination of sex differences in the pace of red-yellow conversion of the bone marrow and bone turnover. The preponderance of males with CO and PH likely speaks to the potential for heightened osteoblastic activity in males. We find no support for the hypotheses that sex biases in mortality or immune responses impacted lesion frequency in this sample. Sex differences in biological processes experienced by children may affect lesion formation and lesion expression in later life.

Agreement on grading of normal clivus using magnetic resonance imaging among radiologists

Purpose

The present study was aimed to evaluate the agreement on grading normal clivus on MRI among radiologists.

Methods

A retrospective study included patients who underwent MRI brain during January 1, 2015 to October 31, 2019. Two hundred forty-four patients who had no marrow pathology on MRI were included and divided into 8 age groups by decades. Three radiologists independently reviewed the signal intensity of clivus in mid sagittal T1-weighted image. The signal intensity was classified into three grades (Grade I-III). Fleiss’ kappa coefficients (k) were calculated to assess interrater agreement.

Results

Of 244 patients, there were 123 (50.4%) males and 121 (49.6%) females. Age ranged from 1 to 79 years old. Clivus Grade II was more frequently reported (> 50%) by radiologists. The agreement (kappa) among all three radiologists on evaluation of clivus irrespective of the grading equals to 0.67 (95%CI: 0.60–0.74). In stratified analyses by the grade of clivus, the kappa values for Grade I to III and were 0.73, 0.62, and 0.69 respectively.

Conclusion

Interrater agreement of MRI evaluation of normal clivus among radiologists was good. The visual grading criteria to classify the clivus is sufficient to distinguish the marrow maturation. However, the consensus reading should be made whenever normal clivus Grade II is read.

Imaging Spectrum of Calvarial Abnormalities

Calvarial abnormalities are usually discovered incidentally on radiologic studies or less commonly manifest with symptoms. This narrative review describes the imaging spectrum of the abnormal calvaria. The extent, multiplicity, and other imaging features of calvarial abnormalities can be combined with the clinical information to establish a final diagnosis or at least narrow the differential considerations. Prior trauma (congenital depression, leptomeningeal cysts, posttraumatic osteolysis), surgical intervention (flap osteonecrosis and burr holes), infection, and inflammatory processes (sarcoidosis) can result in focal bone loss, which may also be seen with idiopathic disorders without (bilateral parietal thinning and Gorham disease) or with (Parry-Romberg syndrome) atrophy of the overlying soft tissues. Anatomic variants (arachnoid granulations, venous lakes, parietal foramina) and certain congenital lesions (epidermoid and dermoid cysts, atretic encephalocele, sinus pericranii, and aplasia cutis congenita) manifest as solitary lytic lesions. Other congenital entities (lacunar skull and dysplasia) display a diffuse pattern of skull involvement. Several benign and malignant primary bone tumors involve the calvaria and manifest as lytic, sclerotic, mixed lytic and sclerotic, or thinning lesions, whereas multifocal disease is mainly due to hematologic or secondary malignancies. Metabolic disorders such as rickets, hyperparathyroidism, renal osteodystrophy, acromegaly, and Paget disease involve the calvaria in a more diffuse pattern. Online supplemental material is available for this article. ^©RSNA, 2021.

Preliminary analysis of interaction of the fat fraction in the sacroiliac joint among sex, age, and body mass index in a normal Chinese population

Objective

Iterative decomposition of water and fat with echo asymmetry and least-squares estimation-iron quantification (IDEAL-IQ) is a noninvasive and objective method used to quantitatively measure fat content. Although this technique has been used in the entire abdomen, IDEAL-IQ findings in the sacroiliac joint (SIJ) have rarely been reported. This preclinical study was performed to quantify the amount of fat in the SIJ in healthy volunteers by IDEAL-IQ.

Methods

From April to November 2017, 60 healthy volunteers with low back pain were included in this retrospective study. The participants were allocated into groups by age (15–30, 31–50, and ≥51 years), sex (male and female), and body mass index (BMI) (<18.5, 18.5–23.9, and ≥24.0 kg/m²). The iliac-side (Fi) and sacral-side (Fs) fat fractions were obtained in all groups. Two- and three-factor multivariate analyses were performed to analyze the effects of sex, age, and BMI on the Fi and Fs.

Results

The interaction among sex, age, and BMI had no statistically significant effect on the dependent variable. Both Fi and Fs were significantly influenced by age. Fs was significantly influenced by sex.

Conclusion

The IDEAL-IQ sequence can be used to quantitatively assess the SIJ fat content in healthy volunteers.

Correlation between fat signal ratio on T1-weighted MRI in the lower vertebral bodies and age, comparing 1.5-T and 3-T scanners

Background

The hypothesis was that the fat-dependent T1 signal intensity in vertebral bodies increases with age due to red-yellow marrow conversion.

Purpose

To analyze the increasing fatty conversion of red bone marrow with age.

Material and Methods

A continuous sample of 524 patients (age range 2–96 years) with normal lumbar spine MRIs (T11–L5) was retrospectively selected in order to get a representative sample from our 1.5-T and 3-T MRI units (Siemens, Erlangen, Germany). Four radiologists read the images independently. Absolute T1 signal intensities were measured in the lower vertebral bodies and standardized by dividing their value by the signal of the subcutaneous fat on lumbar and sacral level.

Results

The standardized T1 signal correlated significantly with patients’ age at the 1.5-T unit, with the best correlation demonstrated by thoracic vertebra T11, followed by lumbar vertebra L1, with correlation coefficients (R) of 0.64 (95% CI 0.53–0.72, P < 0.0001) and 0.49 (95% CI 0.38–0.59, P < 0.0001), respectively. For women and men, the R values were similar in thoracic vertebra T11 at 0.62 (95% CI 0.49–0.72) and 0.64 (95% CI 0.44–0.77), respectively. The vertebral signal correlated significantly better with age in the 1.5-T compared to the 3-T unit on all vertebral levels: the best R value of the 3-T unit was only 0.20 (95% CI 0.09–0.30, P < 0.0001). Our study showed an average increase of the relative T1 signal in T11 of 10% per decade.

Conclusion

T1 fat signal ratio increases with age in the vertebral bodies, which could help estimating the age of a person. Best age correlation was found when measuring T1 signal in T11, standardized by the sacral subcutaneous fat signal and using a 1.5-T MRI.

Skull Base Tumors and Tumor-Like Lesions: A Pictorial Review

A number of tumors and tumor-like non-neoplastic lesions with different cell types on histology occur in the skull base. A wide variety in disease and lesion appearance often complicates the process of radiological diagnosis. The main role of radiographic imaging is the detection and characterization of skull base lesions, with evaluation of the extent of invasion or preservation of adjacent critical organs. Evaluation of the skull base anatomy and surgical planning by using image guidance are also important for surgeons. Computed tomography (CT) and magnetic resonance (MR) imaging are the preferred modalities for the evaluation of skull base lesions. CT and MR are used for lesion detection, tissue characterization and assessment of neurovascular and bone involvement by the lesions. Both modalities provide useful information, one sometimes of greater value than the other. T1-weighted MR imaging is useful in detecting skull base lesions, typically surrounded by abundant fatty bone marrow. T2-weighted MR imaging is generally useful for tumor tissue characterization. CT surpasses MR imaging in evaluating intratumoral calcification and bone destruction or hyperostosis. To date, imaging features have been well-reported in individual skull base tumors; however, correct diagnosis by imaging alone still presents a challenge. Knowledge of clinical issues and awareness of variants of skull base tumors are of help in making a diagnosis. The purpose of this article is to review pertinent clinical issues, typical imaging appearances and certain imaging variations of common skull base lesions.

Role of diffusion-weighted imaging for detecting bone marrow infiltration in skull in children with acute lymphoblastic leukemia

PURPOSE

We aimed to determine whether diffusion-weighted imaging (DWI) with apparent diffusion coefficient (ADC) measurement can detect skull bone marrow infiltration in newly diagnosed acute lymphoblastic leukemia (ALL) children before therapy and normalization in complete remission after treatment.

METHODS

Fifty-one newly diagnosed acute lymphoblastic leukemia (ALL) patients and 30 healthy age-matched subjects were included. Cranial magnetic resonance imaging (MRI) scans were reviewed, and skull marrow ADC values were compared before treatment and in complete remission after therapy.

RESULTS

Skull marrow infiltration, manifested with abnormal DWI signals, was present in 37 patients (72.5%) before treatment. Of these, 23 (62.2%) showed scattered signal abnormalities and 14 (37.8%) showed a uniform abnormal signal pattern. Compared with the control group, ADC was significantly decreased in patients with ALL. DWI signal intensity and ADC normalized in patients with complete remission.

CONCLUSION

DWI is a useful and noninvasive tool for detecting skull infiltration in ALL children before treatment and normalization at complete remission after therapy, and it is superior to conventional MRI in terms of conspicuity of these lesions. DWI could be used as an MRI biomarker for evaluation of treatment in ALL children.

A new theory on the pathogenesis of acquired cholesteatoma: Mucosal traction

OBJECTIVES/HYPOTHESIS

Although the migration of its squamous outer surface of the tympanic membrane has been well characterized, there is a paucity of data available concerning the migratory behavior of its medial mucosal surface. Existing theories of primary acquired cholesteatoma pathogenesis do not adequately explain the observed characteristics of the disease. We propose a new hypothesis, based upon a conjecture that mucosal membrane interactions are the driving force in cholesteatoma.

STUDY DESIGN

A retrospective chart review and a prospective observational cohort study in rats.

METHODS

After developing the new theory, it was tested through both clinical and experimental observations. To evaluate whether impairment of middle ear mucociliary migration would influence cholesteatoma formation, a retrospective chart review evaluating cholesteatoma occurrence in a sizable population of patients with either primary ciliary dyskinesia (PCD) or cystic fibrosis (CF) was performed. To study mucosal migration on the medial aspect of the tympanic membrane, ink tattoos were monitored over time in a rat model.

RESULTS

No cholesteatomas were identified in either PCD patients (470) or in CF patients (1,910). In the rat model, mucosa of the posterior pars tensa migrated toward the posterior superior quadrant, whereas the mucosa of the anterior pars tensa migrated radially toward the annulus.

CONCLUSION

Mucosal coupling with traction generated by interaction of migrating opposing surfaces provides the first comprehensive theory that explains the observed characteristics of primary acquired cholesteatoma. The somewhat counterintuitive hypothesis that cholesteatoma is fundamentally a mucosal disease has numerous therapeutic implications.

Gender and age groups interactions in the quantification of bone marrow fat content in lumbar spine using 3T MR spectroscopy: a multivariate analysis of covariance (Mancova)

INTRODUCTION

There is an age-related conversion of red to yellow bone marrow in the axial skeleton, with a gender-related difference less well established. Our purpose was to clarify the variability of bone marrow fat fraction (FF) in the lumbar spine due to the interaction of gender and age groups.

METHODS

44 healthy volunteers (20 males, 30-65 years old and 24 females, 30-69 years old) underwent 3T magnetic resonance spectroscopy (MRS) and conventional MRI examination of the lumbar spine; single-voxel spectrum was acquired for each vertebral body (VB). After controlling body mass index (BMI), a two-way between-groups multivariate analysis of covariance (MANCOVA) assessed the gender and age group differences in FF quantification for each lumbar VB.

RESULTS

There was a significant interaction between gender and age group, p=.017, with a large effect size (partial η(2)=.330). However the interaction explained only 33% of the observed variance. Main effects were not statistically significant. BMI was non-significantly related to FF quantification.

CONCLUSIONS

Young males showed a high FF content, which declined in the 4th decade, then increased the next 3 decades to reach a FF content just below the initial FF means. Females' FF were low in the 3rd decade, depicted an accelerated increase in the 4th decade, then a gradual increase the next 3 decades to reach a FF content similar to males' values. Our findings suggest that quantification of bone marrow FF using MRS might be used as a surrogate biomarker of bone marrow activity in clinical settings.

Magnetic resonance imaging of the clivus and its age-related changes in the bone marrow

Background

The clivus is a bone region between dorsum cella and foramen magnum. It can be evaluated very clearly in routine brain magnetic resonance imaging (MRI) dueto its central location.

Objectives

Quantitative and qualitative evaluation of the clivus and its changes according to age in a group of healthy people.

Patients and Methods

The transition of clival bone marrow to fatty marrow by the increasein age is examined by MRI in 105 men and 105 women who had no clival and bone marrow pathology on MRI. The clivus/pons, clivus/CSF intensity values and clival bone marrow imaging patterns according to age groups were prospectively evaluated using a 1.5 Tesla MR device.

Results

When age groups were individually compared, there were meaningful statistical differences both in men and women in terms of clivus/CSF and clivus/pons intensity ratios (both Ps < 0.05). Clivus/pons and clivus/CSF intensity ratios were found to be increased with age in all cases. The distribution of age groups according to stages in all individuals was statistically meaningful (P < 0.05). When the appearance patterns of both genders in every ten-fold age were examined, stage III bone marrow was observed more in elder ages.

Conclusions

As a result, besides the fact that standard ranges determined for clivus/CSF, clivus/pons intensity ratios according to age may be used in the assessment of potential pathological cases involving bone marrow; they can also be leading in the diagnosis of bone marrow diseases when taken into consideration together with clinical and laboratory data.

Role of MRI in paediatric musculoskeletal conditions

The aim of this review is to discuss the indications and use of MR imaging (MRI) in the paediatric musculoskeletal system. After briefly reviewing basic technical considerations the MRI appearance of the most relevant congenital, inflammatory, infectious, ischemic, and posttraumatic skeletal conditions, as well as benign and malignant bone and soft tissue tumours that are typical for the paediatric age group will be presented.

Tumor-biology and current treatment of skull-base chordomas

Chordomas are rare, slow growing tumors of the axial skeleton, which derive from the remnants of the fetal notochord. They can be encountered anywhere along the axial skeleton, most commonly in the sacral area, skull base and less commonly in the spine. Chordomas have a benign histopathology but exhibit malignant clinical behavior with invasive, destructive and metastatic potential. Genetic and molecular pathology studies on oncogenesis of chordomas are very limited and there is little known on mechanisms governing the disease. Chordomas most commonly present with headaches and diplopia and can be readily diagnosed by current neuroradiological methods. There are 3 pathological subtypes of chordomas: classic, chondroid and dedifferentiated chordomas. Differential diagnosis from chondrosarcomas by radiology or pathology may at times be difficult. Skull base chordomas are very challenging to treat. Clinically there are at least two subsets of chordoma patients with distinct behaviors: some with a benign course and another group with an aggressive and rapidly progressive disease. There is no standard treatment for chordomas. Surgical resection and high dose radiation treatment are the mainstays of current treatment. Nevertheless, a significant percentage of skull base chordomas recur despite treatment. The outcome is dictated primarily by the intrinsic biology of the tumor and treatment seems only to have a secondary impact. To date we only have a limited understanding this biology; however better understanding is likely to improve treatment outcome. Hereby we present a review of the current knowledge and experience on the tumor biology, diagnosis and treatment of chordomas.

Age, gender, and skeletal variation in bone marrow composition: a preliminary study at 3.0 Tesla

PURPOSE

To evaluate the efficacy of MR Spectroscopy (MRS) at 3.0 Tesla for the assessment of normal bone marrow composition and assess the variation in terms of age, gender, and skeletal site.

MATERIALS AND METHODS

A total of 16 normal subjects (aged between eight and 57 years) were investigated on a 3.0 Tesla GE Signa system. To investigate axial and peripheral skeleton differences, non-water-suppressed spectra were acquired from single voxels in the calcaneus and lumbar spine. In addition, spectra were acquired at multiple vertebral bodies to assess variation within the lumbar spine. Data was also correlated with bone mineral density (BMD) measured in six subjects using dual-energy X-ray absorptiometry (DXA).

RESULTS

Fat content was an order of magnitude greater in the heel compared to the spine. An age-related increase was demonstrated in the spine with values greater in men compared to female subjects. Significant trends in vertebral bodies within the same subjects were also shown, with fat content increasing L5 > L1. Population coefficient of variation (CV) was greater for fat fraction (FF) compared to BMD.

CONCLUSION

Significant normal variations of marrow composition have been demonstrated, which provide important data for the future interpretation of patient investigations.

Occipitalization of the atlas in children. Morphologic classification, associations, and clinical relevance

BACKGROUND

Occipitalization is defined as a congenital fusion of the atlas to the base of the occiput. We are not aware of any previous studies addressing the morphologic patterns of occipitalization or the implications of occipitalization in children. We present data on what we believe is the largest reported series of children with occipitalization studied with computed tomography and/or magnetic resonance imaging, and we provide a description of their clinical characteristics.

METHODS

We retrospectively reviewed all cases of occipitalization in children included in our spine database. Patient charts and imaging studies were reviewed. A new morphologic classification of occipitalization was developed from the two-dimensional sagittal and coronal reformatted computed tomographic reconstructions and/or magnetic resonance images. The classification includes four patterns according to the anatomic site of occipitalization (Zones 1, 2, and 3 and a combination of those zones), and it was applied to this group of patients. Imaging studies were also reviewed for evidence of cervical instability and for other anomalies of the craniovertebral junction.

RESULTS

Thirty patients with occipitalization were identified. There were twenty-four boys and six girls with a mean age of 6.5 years. The morphologic categorization was Zone 1 (a fused anterior arch) in six patients, Zone 2 (fused lateral masses) in five, Zone 3 (a fused posterior arch) in four, and a combination of fused zones in fifteen. Seventeen patients (57%) had atlantoaxial instability, and eight of them had an associated C2-C3 fusion. Eleven patients (37%) had spinal canal encroachment, and five of them had clinical findings of myelopathy. The highest prevalence of spinal canal encroachment (63%) was noted in patients with occipitalization in Zone 2.

CONCLUSIONS

Occipitalization is associated with abnormalities that lead to narrowing of the space available for the spinal cord or brainstem. The risk of atlantoaxial instability developing is particularly high when there is an associated congenital C2-C3 fusion. Two-dimensional sagittal and coronal reformatted computed tomographic reconstructions and/or magnetic resonance images can help to establish the diagnosis and permit categorization of occipitalization in three zones, each of which may have a different prognostic implication.

[Skull base tumors]

Modern imaging techniques have great importance in the diagnosis and therapy of skull-base pathologies. Many of these lesions, especially in relation to their specific location, can be evaluated using CT and MR imaging. Tumors commonly found in the anterior skull base include carcinoma, rhabdomyosarcoma, esthesioneuroblastoma and meningioma. In the central cranial fossa, nasopharyngeal carcinoma, metastases, meningioma, pituitary adenoma and neurinoma have to be considered. The most common neoplasms of the posterior skull base, including the CP angle, are neurinoma, meningioma, nasopharyngeal carcinoma, chordoma and paraganglioma. One major task of imaging is the evaluation of the exact tumor extent as well as its relationship to the neighboring neurovascular structures. The purpose of this review is to recapitulate the most important anatomical landmarks of the skull base. The typical imaging findings of the most common tumors involving the skull base are also presented.

MRI evaluation of cranial bone marrow signal intensity and thickness in chronic anemia

BACKGROUND AND PURPOSE

The aim is to assess the magnetic resonance imaging (MRI) findings for cranial bone marrow (CBM) signal intensity and thickness in patients with chronic anemia and compared these with findings in healthy subjects. We also investigated the relationships between CBM changes and age, type of anemia (hemolytic versus non-hemolytic), and severity of anemia.

METHODS

We quantitatively evaluated CBM signal intensity and thickness on images from 40 patients with chronic anemia (20 with congenital hemolytic anemia (HA) and 20 with acquired anemia) and compared these to findings in 28 healthy subjects. The intensity of CBM relative to scalp, white matter (WM), gray matter (GM), and muscle intensity was also investigated in patients and subjects in the control group. The sensitivity and specificity of CBM hypointense to GM and CBM hypointense to WM as markers of anemia were evaluated. Relationships between age and CBM thickness/intensity, and between anemia severity (hemoglobin (Hb) level) and CBM thickness/intensity were evaluated.

RESULTS

Cranial bone marrow signal intensity was lower in the chronic anemia patients than in the controls (P<0.001). In the control group, CBM intensity was higher than GM intensity, whereas the opposite was true in the patient group. The finding of CBM hypointense to GM was 85% sensitive and 67% specific as a marker of anemia. The corresponding statistics for CBM hypointense to WM were 90 and 46%. The patients had thicker CBM than the controls (temporal, P<0.05; parietal, P<0.005). The subgroup with hemolytic anemia had thicker parietal CBM than the subgroup with non-hemolytic anemia (NHA) (P<0.05) and exhibited thicker temporal and parietal CBM than the controls (temporal, P<0.05; parietal, P<0.001). The CBM thicknesses in the non-hemolytic anemia subgroup were similar to control values (P>0.05 for both). There were no correlations between age and CBM intensity or thickness, or between anemia severity and CBM intensity or thickness.

CONCLUSION

Patients with chronic anemia exhibit lower CBM signal intensity on MRI than healthy subjects. Patients with hemolytic anemia have thicker CBM than patients with non-hemolytic anemia or healthy individuals. Decreased CBM intensity may indicate that the patient has anemia, and increased CBM thickness may specifically point to hemolytic anemia. These MRI findings may signal the need for further evaluation for the clinician.

Imaging of neoplasms of the paranasal sinuses

The assessment of sinonasal malignancies requires a multidisciplinary team approach.Advances in pretherapeutic imaging have significantly contributed to the managementof sinonasal tumors. CT and MR imaging play complementary roles in the assess-mentand staging of these malignancies by determining the presence or absence of exten-sionof disease into the skull base and its foramina, the orbit, and the intracranial compartment.

MRI of the marrow in the paediatric skeleton

Magnetic resonance imaging (MRI) has greatly advanced evaluation of marrow diseases of the paediatric skeleton. As with many other aspects of paediatric radiology it is important to recognize the normal variations in the appearance of the marrow that occur in the growing child. These normal variations need to be differentiated from diseases and conditions that affect the marrow. This review describes the normal changes that occur in children with age, and the appearances of the pathological changes seen in infection, infiltration, haematological disorders, transplantation and radiation therapy.

The development of sphenoid sinus in Asian children

OBJECTIVES

(1) To study the developmental changes of sphenoid sinus in Asian children and (2) to test the hypothesis that the sphenoid sinus may be developing slower in Asian, by comparing the growth patterns between Asian and Caucasian children.

MATERIALS AND METHODS

Review of MR imaging of the skull of 220 Asian children less than 15 years of age in a tertiary hospital. The results were compared to a representative Caucasian study by Szolar et al. [Surg. Radiol. Anat., 16 (1994) 193].

RESULTS

Grade 1 sphenoid was present in all children less than 6 months old. Conversion from marrow to fat of the sphenoid sinus (Grade 2) began at 7 months and was present in patients up to 6 years old. Signs of pneumatization (Grade 3) of the sphenoid sinus were first noted in patients at 10 months old. Almost 100% pneumatization was seen in all the children after 6 years old except for one child with Grade 1 sphenoid at 11 years old. Compared to Caucasian children, there was a significantly higher proportion of Grade 3 cases in Asian children from 0 to 4 years of age (P = 0.05). No difference in the distribution of cases was noted from 4 to 8 years (P = 0.466) and 8-15 years (P = 1.00).

CONCLUSION

The developmental changes of the sphenoid sinus in Asian children were determined and found to be similar when compared to Caucasian children. The findings did not support the hypothesis that the Asian sphenoid sinus is developing slower compared to that of the Caucasians.

Comparison of qualitative and quantitative analyses of age-related changes in clivus bone marrow on MR imaging

Magnetic resonance (MR) imaging is capable of detecting a wide spectrum of diseases involving clivus bone marrow. To evaluate any pathology in this region, the normal MR signal intensity patterns according to age should be known. Assessment of clivus bone marrow is usually and more efficiently made visually (qualitatively) on routine MR imaging. To compare the qualitative and quantitative analyses of age-related changes in clivus bone marrow on MR imaging, midsagittal T1-weighted MR images of the clivus bone marrow were prospectively evaluated in 201 subjects. MR signal intensity patterns of clivus bone marrow were qualitatively graded from I to III according to the proportions of low and high signal intensity areas within the clivus (Grade I: predominantly hypointense, Grade III: predominantly hyperintense). Signal intensity measurements were also made from the clivus, pons, and the cerebrospinal fluid within the fourth ventricle. Grade I pattern was observed in 92% of the subjects in the first decade, whereas Grade III pattern was not seen in this decade; Grade I pattern was absent in all but one of the subjects over the age of 50. Mean values of clivus/pons and clivus/CSF signal intensity measurements gradually increased with age in both males and females. Comparison of these ratios in each gender showed statistically significant higher values for males (P < 0.05). Comparison of the qualitative and quantitative results showed that calculated mean values of intensity ratios for each grade were different from each other; however, there was an overlap of the ranges of signal intensity ratios for Grades II and III. Visual evaluation of the clivus bone marrow MR signal is validated with the quantitative assessment results. Statistically significant higher intensity ratios in males may reflect a difference between gender in the bone mineral content under the influence of sex hormones.

Imaging of neoplasms of the paranasal sinuses

The assessment of sinonasal malignancies requires a multidisciplinary team approach. Advances in pretherapeutic imaging have significantly contributed to the management of sinonasal tumors. CT and MR imaging play complementary roles in the assessment and staging of these malignancies by determining the presence or absence of extension of disease into the skull base and its foramina, the orbit, and the intracranial compartment.

Magnetic resonance imaging of clival marrow in patients with anorexia nervosa

Hematological abnormalities, commonly associated with anorexia nervosa (AN) patients, are thought to be the results of serous atrophy in the bone marrow. Magnetic resonance imaging (MRI) has been utilized to ascertain T1 and T2 prolongation of marrow intensity in the lumbar spine, pelvis and proximal femora. The results correlate well with the severity of hematological abnormalities, and body mass index. More importantly, the propensity for peripheral marrow involvement of T2 prolongation contrasts with the axial involvement in other marrow disorders. MRI undertaken in patients with AN to exclude hypothalamic tumor showed that the clival marrow was equivalent to the peripheral marrow. The signal pattern of clival marrow on sagittal T1 weighted MR images was evaluated in four teenage female patients with AN complicated by hematological abnormalities. Although the clival marrow intensity should be uniformly high in teenagers, three patients, two with pancytopenia and one with leukopenia and anemia, exhibited homogeneous low intensity. One patient who had leukopenia only and the highest body mass index, showed inhomogeneous low intensity. The signal changes returned to normal in all patients but one, who died before examination after 6-11 months, at which time the others had almost recovered their original weight and normal hemogram. T1 prolongation in the clival marrow represents bone marrow dysfunction and the inhomogeneity of the signal change may imply relative preservation of hematopoiesis and body fat composition. Lack of knowledge of this phenomenon may lead to diagnostic confusion with other marrow disorders on cranial MRI.

Assessment of normal clivus related to age with magnetic resonance imaging

The signal intensity pattern cf normal clivus bone marrow related to age was studied on T1-weighted sagittal plain magnetic resonance images. Bone marrow in the clivus had a uniformly low signal intensity (grade 1) in 100% of the patients at 0-5 years and 96% of patients in the first decade (0-9 years). In the second decade there was a sharp decrease in the number of patients (43%) showing grade 1 clivus. Patients having mixed clivus signal intensity (grade 2) were mostly seen in the second decade (28.5%). Uniform high signal intensity (grade 3) was not observed under the age of 10. Grade 3 clivus pattern increased with age from the second decade, while grades 1 and 2 clivus bone marrow showed a marked decrease.

MRI "road-map" of normal age-related bone marrow. I. Cranial bone and spine

We retrospectively reviewed 733 cranial and 250 spinal T1-weighted MR images of patients younger than 24 years to evaluate the bone marrow changes. The signal intensity of the bone marrow on short-TR/TE images was compared with that of fat and normal muscles in the contiguous region and graded. The signal intensity of all anatomic segments was as low as that of muscle, or inferior, in all patients younger than 3 months because of hematopoietic tissue and probably greater amounts of trabecular bone. The first anatomic segments of cranial bone to become hyperintense were the zygomatic bone and mandibular symphysis, followed by the presphenoid bone, basisphenoid, basiocciput, calvaria, and the petrous apex. After 3 years of age, most patients demonstrated pneumatization of the sphenoid sinus. We describe the most interesting changes in the developing spine, which occur in the first 2 years of life. The morphology of the vertebral bodies was evaluated. The variability of the signal and the morphology of the disks were also evaluated. Regional patterns of bone marrow signal intensity and age-related differences should not be misinterpreted as a pathologic condition.

The calvarium

The calvarium is a crucial structure that can manifest a great deal of pathology. The plain film remains the main imaging modality, although CT and MRI are becoming increasingly important. We discuss its anatomy, normal variants, congenital and developmental anomalies, hematologic disease, idiopathic disorders, neoplasms, metabolic disease, trauma, and the postoperative skull. Whenever possible, we emphasize CT and MRI.

Imaging the sphenoid bone and basiocciput: anatomic considerations

The sphenoid bone is a complex structure with an intricate embryologic origin. It is centrally located within the skull base and articulates with almost every structure in the skull and face. The sphenoid bone contains multiple foramina and fissures accommodating numerous vessels and nerves. This report reviews the embryology of the sphenoid bone and its normal postnatal changes, and describes the normal anatomy of the sphenoid bone and its numerous foramina and fissures. Computed tomography (CT) and magnetic resonance (MR) are used to illustrate developmental changes and normal anatomy.

Iron deposition in cranial bone marrow with sickle cell disease: MR assessment using a fat suppression technique

Thirteen patients with sickle cell disease (SCD) undergoing transfusion therapy and 8 control patients were examined by magnetic resonance imaging to discriminate bone marrow change due to iron deposition from hematologic marrow hyperplasia. Using T1-weighted spin echo images, only two subjects showed extremely low signal intensity marrow compatible with iron deposition. However, using T2-weighted fast spin echo images with fat suppression, cranial bone marrow in SCD patients with transfusion therapy showed considerably lower signal than that of controls. The main cause of marrow signal decrease in SCD patients with transfusion therapy was considered to be iron deposition due to repeated transfusion therapy rather than red marrow hyperplasia.

Variability in the enhancement of the normal central skull base in children

We studied the signal and enhancement characteristics of the central skull base prospectively in 40 children aged 13 days to 8 years, on a 1.5 T MRI system. Identical standard short TR/TE spin echo sequences in the sagittal plane were performed before and after intravenous gadolinium-DTPA. The sequences used for comparison were filmed at identical window and level settings. Three independent observers assessed (1) the intensity of contrast enhancement of the basisphenoid, basiocciput and presphenoid, (2) the signal intensity of the spheno-occipital synchondrosis, (3) the degree of pneumatization of the sphenoid sinus and (4) the uniformity of signal intensity reflecting fatty replacement of the marrow of the basisphenoid, basiocciput and presphenoid. In 16% and 28% respectively of cases there was no enhancement of the basisphenoid and basiocciput after gadolinium administration; in 42% and 44% there was mild enhancement, and moderate or intense enhancement was observed in 42% and 28% of cases. Even when there was irregular fatty replacement, residual hemopoietic clements could enhance intensely. When skull base neoplasms are being investigated, the normal signal irregularity and enhancement of the central skull base in children must not be confused with pathologic invasion of the marrow.

Normal childhood developmental patterns in skull bone marrow by MR imaging

To establish the normal developmental pattern of skull bone marrow in children by MR imaging, sagittal T1-weighted MR skull images of 324 normal children (newborn to 18 years) were reviewed. Bone marrow intensity was assigned four gradations as compared with that of muscle and fat on the same image. Bone marrow became isointense with fat (yellow marrow) at a mean age +/- S.E.M. (in years) of 8.5 +/- 0.24 in sphenoid, 9.1 +/- 0.29 in mandible, 9.3 +/- 0.28 in hard palate, 9.7 +/- 0.26 in frontal, 11.0 +/- 0.26 in squamous occiput, 11.5 +/- 0.28 in parietal, and 11.9 +/- 0.24 in basiocciput. There is a strong correlation between age and marrow intensity by Spearman analysis (p < 0.001): hard palate 0.64, mandible 0.61, parietal 0.42, sphenoid 0.70, cervical spine 0.50, basi-occiput 0.58 and occiput 0.52. Two consistent overall patterns of red-yellow marrow conversion were observed. Bone marrow became isointense with fat prior to pneumatization of the paranasal sinuses. Marrow conversion in the bones of the face occurred before those of the calvarium in a specific pattern. There was no significant sex difference in the pattern or rate of marrow conversion. These normative data are necessary to evaluate the immature skull by MR imaging in disease states.

Paranasal sinuses in pediatric patients by MRI: normal development and preliminary findings in disease

A two-part study using medium field strength magnetic resonance imaging (MRI) was designed to describe the normal paranasal sinus development and to provide preliminary criteria for clinical sinus disease. In part I of the study the paranasal sinuses were retrospectively evaluated in 80 infants and children aged 0-17 years undergoing brain MRI for indications both unrelated and related to sinus disease. We developed MRI criteria for independent grading of paranasal sinus development and 'anatomical' sinus disease, i.e., disease as seen by the radiologist. We quantified the variability in extent of sinus pneumatization (a measure of sinus development) in infants and young children. Part II of the study was a double-blind prospective study in 21 patients to correlate 'anatomical' disease with 'clinical' sinus disease. In this limited preliminary study, clinical sinus disease was only seen in the patients with moderate or severe anatomical disease (sensitivity 100%; specificity 100%).

Magnetic resonance imaging contrast agents: theory and application to the central nervous system

The theoretical aspects of magnetic resonance (MR) imaging contrast agents are reviewed, and their current applications to the central nervous system (CNS) and their future applications are discussed. Profound differences exist between contrast agents used for MR imaging and computerized tomography (CT). In MR imaging, the contrast agents are not imaged directly but rather act on adjacent protons to shorten T1 and T2 relaxation times. This in turn results in signal intensity changes. The lanthanide metal, gadolinium, in the form of gadopentetate dimeglumine, has been found to be both safe and efficacious as the only currently approved contrast agent for MR imaging. Magnetic resonance imaging revolutionized the detection and treatment of disease affecting the brain and spine. Initially, it was thought that signal characteristics on MR imaging would allow differentiation of specific pathology. It was soon found that MR studies were able to detect more abnormalities but were less able to characterize them. The recent development of contrast agents for MR imaging has allowed this modality to surpass CT for the evaluation of most CNS lesions. At present, contrast-enhanced MR imaging is generally accepted as the study of choice for evaluating acoustic neurinomas, pituitary lesions, meningeal disease, primary and secondary brain tumors, active multiple sclerosis, intradural spinal neoplasms, intramedullary spinal disease, and postoperative states in both the spine and brain. Even when contrast-enhanced CT can detect the same abnormalities, evaluation of the lesions in multiple planes on MR imaging can sometimes yield invaluable information, especially prior to surgery. Future developments of contrast material for MR imaging include non-gadolinium compounds, intrathecal contrast media, cerebral blood flow and volume evaluation, and, possibly, antibody-labeled contrast agents.

MR imaging of the calvarium: pictorial essay

Magnetic resonance is unique in its ability to directly image the bone marrow. Thus, primary or secondary processes involving the bone marrow of the calvarium can be well visualized. In cases of superficial lesions, magnetic resonance demonstrates calvarial and bone marrow invasion. This is particularly important in cases where surgical preservation of the inner table in contemplated. Both erosion and involvement of the calvarium by intracranial processes can also be well visualized. Because of the ability of magnetic resonance to image in multiple orthogonal planes, it is particularly useful for precise delineation of the extent of lesions. Its ability to also image in oblique planes may aid in better demonstration of pathology. Use of both T1 and T2 weighted imaging sequences may also be of help in determination of the tissue type.