Skull base: pseudolesion or true lesion?

The skull base is a complex anatomical structure. Therefore, radiologists often use “side-to-side” comparison for detection of abnormalities. This approach is compromised by the high frequency of anatomical variations involving the skull base and the common presence of flow-related artifacts within vessels at the skull base that might mimic true lesions. The spectrum of “pseudolesions” ranging from different anatomical variations, such as unusual arachnoid granulations, asymmetric pneumatization and/or appearance of neurovascular foramina, to flow-related artifacts will be discussed in this review article, and tips for their distinction from a true lesion in a similar location will be given.     

Sequential tibial and peroneal intraneural ganglia arising from the superior tibiofibular joint

We present a patient who developed a peroneal intraneural ganglion and an adventitial cyst following the incomplete treatment of a tibial intraneural ganglion. These separate cysts all originated from the superior tibiofibular joint and dissected along their respective articular branches. A logical mechanistic explanation for these coexisting cysts is provided, which highlights the shared pathogenesis—its joint-related nature—rather than a multifocal de novo process. These observations would not only be consistent with, but would extend previous evidence in support of, the unifying articular (synovial) theory.     

Magnetic resonance imaging of surgically confirmed anterior cruciate ligament graft disruption

Objective To evaluate previously described primary and secondary MRI signs of disruption to anterior cruciate ligament (ACL) grafts in surgically proven cases. Materials and methods We retrospectively analyzed MR images of 48 patients (mean age 29 years) with clinically suspected ACL graft disruption. All patients had surgical confirmation of the MRI findings. The reviewers analyzed the cases blinded to the surgical results and assessed each of the primary and secondary MRI signs of graft disruption individually. Subsequently, a final impression of the graft integrity based on a comprehensive assessment of all of the primary and secondary findings was made. Results Utilizing a comprehensive assessment of previously described primary and secondary MR findings of ACL graft disruption, the blinded reviewers were able to identify correctly full-thickness graft tears with test accuracy of 85%, sensitivity of 72%, and specificity of 100%. Individual assessment of the primary finding of graft fiber discontinuity had sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of 72%, 100%, 100%, 77% and 85%, respectively, for full-thickness tears. Other individual primary and secondary findings were less reliable; however, the primary findings of marked segmental thinning of the graft and markedly abnormal graft orientation, and the secondary findings of bone contusions in the lateral compartment and large joint effusion, had high specificity and positive predictive value. Of the four missed cases, two had associated arthrofibrosis. Conclusion The comprehensive assessment of previously described primary and secondary MRI findings of ACL graft disruption has high test specificity and moderately high test accuracy. The presence of graft fiber discontinuity is the most reliable primary or secondary finding when assessed individually. Marked segmental thinning of the graft and abnormal fiber orientation, and the presence of bone contusions in the lateral compartment and large joint effusion, are less reliable overall but are highly suggestive of full-thickness graft tear when present.     

Percutaneous Cryoablation and Vertebroplasty: A Case Report

A 70-year-old man with a painful vertebral metastasis was treated with combined percutaneous cryoablation and vertebroplasty therapy (CVT) in one session. The patient was suffering from diffuse visceral metastasized cholangiocarcinoma. After several weeks of back pain, magnetic resonance imaging documented a single L2 bone metastasis. In consultation with the oncologists, palliative combined CVT was administered with the aim of obtaining pain relief and bone stabilization. In our experience this combined treatment is safe and effective for immediate pain relief in painful bone metastases when other standard palliative treatments have failed.     

A technique for arthroscopic fasciotomy for the chronic exertional tibialis anterior compartment syndrome

Chronic exertional anterior compartment syndrome (CECS) is a condition that causes pain over the front of the shin bone that usually occurs in physically active people, especially runners. It may require sometimes an immediate fasciotomy. A longitudinal incision just over the fibula has used as surgical treatment bad cosmetic appearance. Although nowadays mini surgical incisions are preferred. The aim of this study to evaluate a simple fasciotomy technique with a minimal incision by using arthroscope. Nine legs of six patients that diagnosed as CECS has underwent fasciotomy operation with a 1 cm incision. Complaints had disappeared after operation. The mean follow-up time is 2 years. The results were good all of the patients and they never experienced exertional pain episodes. The arthroscopic assisted mini incisional fasciotomy technique has advantage such as early rehabilitation and good cosmetic appearance.     

Differentiating normal hyaline cartilage from post-surgical repair tissue using fast gradient echo imaging in delayed gadolinium-enhanced MRI (dGEMRIC) at 3 Tesla

The purpose was to evaluate the relative glycosaminoglycan (GAG) content of repair tissue in patients after microfracturing (MFX) and matrix-associated autologous chondrocyte transplantation (MACT) of the knee joint with a dGEMRIC technique based on a newly developed short 3D-GRE sequence with two flip angle excitation pulses. Twenty patients treated with MFX or MACT (ten in each group) were enrolled. For comparability, patients from each group were matched by age (MFX: 37.1 ± 16.3 years; MACT: 37.4 ± 8.2 years) and postoperative interval (MFX: 33.0 ± 17.3 months; MACT: 32.0 ± 17.2 months). The Δ relaxation rate (ΔR1) for repair tissue and normal hyaline cartilage and the relative ΔR1 were calculated, and mean values were compared between both groups using an analysis of variance. The mean ΔR1 for MFX was 1.07 ± 0.34 versus 0.32 ± 0.20 at the intact control site, and for MACT, 1.90 ± 0.49 compared to 0.87 ± 0.44, which resulted in a relative ΔR1 of 3.39 for MFX and 2.18 for MACT. The difference between the cartilage repair groups was statistically significant. The new dGEMRIC technique based on dual flip angle excitation pulses showed higher GAG content in patients after MACT compared to MFX at the same postoperative interval and allowed reducing the data acquisition time to 4 min.     

Magnetic resonance imaging of the normal pituitary gland using ultrashort TE (UTE) pulse sequences (REV 1.0)

Introduction The purpose of this study was to examine the normal pituitary gland in male subjects with ultrashort echo time (TE) pulse sequences, describe its appearance and measure its signal intensity before and after contrast enhancement. Methods Eleven male volunteers (mean age 57.1 years; range 36–81 years) were examined with a fat-suppressed ultrashort TE (= 0.08 ms) pulse sequence. The studies were repeated after the administration of intravenous gadodiamide. The MR scans were examined for gland morphology and signal intensity before and after enhancement. Endocrinological evaluation included baseline pituitary function tests and a glucagon stimulatory test to assess pituitary cortisol and growth hormone reserve. Results High signal intensity was observed in the anterior pituitary relative to the brain in nine of the 11 subjects. These regions involved the whole of the anterior pituitary in three subjects, were localised to one side in two examples and were seen inferiorly in three subjects. Signal intensities relative to the brain increased with age, with a peak around the sixth or seventh decade and decreasing thereafter. Overall, the pituitary function tests were considered to be within normal limits and did not correlate with pituitary gland signal intensity. Conclusion The anterior pituitary shows increased signal intensity in normal subjects when examined with T₁-weighted ultrashort TE pulse sequences. The cause of this increased intensity is unknown, but fibrosis and iron deposition are possible candidates. The variation in signal intensity with age followed the temporal pattern of iron content observed at post mortem. No relationship with endocrine status was observed.     

Prone positioning improves distribution of pulmonary perfusion: noninvasive magnetic resonance imaging study in healthy humans

The purpose of this study was to evaluate the effects of prone positioning on pulmonary perfusion using flow-sensitive alternating inversion recovery (FAIR), a noninvasive magnetic resonance imaging technique that requires no contrast medium. Seven healthy volunteers were studied in the supine and prone positions under three respiratory conditions: normal breathing of room air, unassisted breathing of 45% O₂, and controlled mechanical ventilation (CMV) with positive end-expiratory pressure. Signal intensities (SIs) were obtained from ventral, middle, and dorsal regions on sagittal lung images and dependent/nondependent SI ratios were calculated to evaluate pulmonary perfusion distribution. In the supine position, SIs increased significantly from the ventral to dorsal region under all three respiratory conditions and prone positioning inverted the perfusion distribution under all conditions. Right lung SI ratios were 2.34 ± 0.29, 2.74 ± 0.66, and 2.42 ± 0.73 in the supine position and 1.68 ± 0.48, 1.78 ± 0.36, and 1.92 ± 0.21 in prone for room air, 45% O₂, and CMV, respectively. The difference between supine and prone positions was statistically significant. The left lung showed a similar pattern and the difference was significant only under CMV. No difference was observed between the different respiratory conditions in both lungs. This study demonstrated that the distribution of pulmonary perfusion was more uniform in prone than in the supine position.     

Imaging of sacral tumours

All components of the sacrum (bone, cartilage, bone marrow, meninges, nerves, notochord remnants, etc.) can give rise to benign or malignant tumours. Bone metastases and intraosseous sites of haematological malignancies, lymphoma and multiple myeloma are the most frequent aetiologies, while primary bone tumours and meningeal or nerve tumours are less common. Some histological types have a predilection for the sacrum, especially chordoma and giant cell tumour. Clinical signs are usually minor, and sacral tumours are often discovered in the context of nerve root or pelvic organ compression. The roles of conventional radiology, CT and MRI are described and compared with the histological features of the main tumours. The impact of imaging on treatment decisions and follow-up is also reviewed.     

Effects of anesthetic agents on cellular <Superscript>123</Superscript>I-MIBG transport and in vivo <Superscript>123</Superscript>I-MIBG biodistribution

Objectives Small animal imaging with meta-iodobenzylguanidine (MIBG) allows characterization of animal models, optimization of tumor treatment strategies, and monitoring of gene expression. Anesthetic agents, however, can affect norepinephrine (NE) transport and systemic sympathetic activity. We thus elucidated the effects of anesthetic agents on MIBG transport and biodistribution. Methods SK-N-SH neuroblastoma and PC-12 pheochromocytoma cells were measured for ¹²³I-MIBG uptake after treatment with ketamine (Ke), xylazine (Xy), Ke/Xy, or pentobarbital (Pb). NE transporters were assessed by Western blots. Normal ICR mice and PC-12 tumor-bearing mice were injected with ¹²³I-MIBG 10 min after anesthesia with Ke/Xy, Ke, Xy, or Pb. Plasma NE levels and MIBG biodistribution were assessed. Results Cellular ¹²³I-MIBG uptake was dose-dependently inhibited by Ke and Xy but not by Pb. Treatment for 2 h with 300 μM Ke, Xy, and Ke/Xy decreased uptake to 46.0 ± 1.6, 24.8 ± 1.5, and 18.3 ± 1.6% of controls. This effect was completely reversed by fresh media, and there was no change in NE transporter levels. In contrast, mice anesthetized with Ke/Xy showed no decrease of MIBG uptake in target organs. Instead, uptakes and organ-to-blood ratios were increased in the heart, lung, liver, and adrenals. Plasma NE was notably reduced in the animals with corresponding decreases in blood MIBG, which partly contributed to the increase in target organ uptake. Conclusion In spite of their inhibitory effect at the transporter level, Ke/Xy anesthesia is a satisfactory method for MIBG imaging that allows favorable target tissue uptake and contrast by reducing circulating NE and MIBG. Bong-Ho Ko and Jin-Young Paik equally contributed to this work. This work was supported by the Korea Research Foundation Grant KRF-2005-202-E00116. Presented in part at the fifth Annual Meeting of the Society for Molecular Imaging, Hawaii, August 30–September 2, 2006.