18F-FDG imaging: pitfalls and artifacts

18F-FDG PET is emerging as a useful tool in the staging and restaging of many malignant neoplasms, such as lymphoma, lung cancer, colorectal cancer, head and neck cancer, breast cancer, and melanoma. To accurately interpret 18F-FDG findings one must be familiar with the normal physiologic distribution of the tracer, frequently encountered physiologic variants, and benign pathologic causes of 18F-FDG uptake that can be confused with a malignant neoplasm. The objectives of this article are to (a) describe the mechanism of 18F-FDG uptake, (b) list the patient preparation and pertinent patient history before 18F-FDG imaging, (c) describe the whole-body physiologic distribution of 18F-FDG, (d) list and discuss normal physiologic variants, and (e) list and discuss benign pathologic causes of 18F-FDG uptake.     

Normal anatomy, variants and pitfalls on shoulder MRI

MR imaging of the shoulder is widely used for assessment of impingement and instability-related clinical conditions. The following review article demonstrates the normal anatomy, variations and classical pitfalls. In addition to classical pitfalls (sublabral hole, sublabral recess, Buford complex) the authors focus on a number of normal, bony, cartilaginous, ligamentous and tendinous structures that can simulate disease at the shoulder. In addition, ways to distinguish these pitfalls from true shoulder abnormalities are shown.     

Normal variants, artefacts and interpretative pitfalls in PET imaging with 18-fluoro-2-deoxyglucose and carbon-11 methionine.

Interpretation of studies from all imaging modalities requires a knowledge of the possible pitfalls that may occur due to normal variation, artefacts and processes which may mimic pathology. The applications and use of not only 18-fluoro-2-deoxyglucose but also l-[methyl-(11)C] methionine positron emission tomography (PET) are widening and it is timely that the currently recognised interpretative pitfalls are reviewed as the number of dedicated PET scanners and coincidence gamma cameras increases.     

Artifacts, normal variants, and imaging pitfalls of musculoskeletal magnetic resonance imaging

This article is an early attempt to catalogue some of the many artifacts, normal variants, and imaging pitfalls that the authors have seen in musculoskeletal MRI. The study of such phenomena is potentially very rewarding and may help to prevent some cases of misdiagnosis with MRI.     

Thoracic aortic dissection: pitfalls and artifacts in MR imaging

Results of 53 thoracic magnetic resonance (MR) imaging examinations were reviewed to determine the prevalence and severity of artifacts and pitfalls that may occur in the evaluation of acute aortic dissection. Grade 1 artifacts and pitfalls were mimics of aortic dissection on individual images but could be demonstrated not to represent a dissection when other images from the same sequence were evaluated. Grade 2 artifacts and pitfalls required the use of images from other planes or sequences to distinguish them from a dissection. Grade 3 artifacts and pitfalls could not be distinguished from a dissection without the use of other imaging modalities. Of the 53 cases examined, 34 (64%) had artifacts or pitfalls of grade 1 or higher, 10 (19%) had artifacts or pitfalls of grade 2 or higher, and one case (2%) had grade 3 artifacts or pitfalls. Sixteen cases had more than one artifact or pitfall. Pitfalls and artifacts that mimic aortic dissection occur in a significant percentage of thoracic MR imaging examinations. An awareness of their existence, knowledge of normal anatomy, the use of axial images in all cases with the addition of images in other planes as needed, rotation of phase and frequency gradients as needed, and clinical correlation may avert misinterpretation in nearly all cases.     

CT of the lumbar spine: normal variants and pitfalls

Benign variants in the appearance of the lumbar spine on CT may be confused with significant lesions. Here such benign processes and their distinguishing features are illustrated.     

Doppler artifacts and pitfalls

With increasing technologic advances in ultrasound, its applications have continued to grow for the detection of pathology and physiology. To avoid misinterpretation of results, however, the Doppler US practitioner must understand the factors that produce a Doppler signal, whether vascular, motion, or artifact. Color or power Doppler artifacts can be verified by their atypical spectral waveform. Some artifacts, such as aliasing (for rapid detection of stenoses or arteriovenous fistulae) and the twinkle artifact (for identification of renal calculi and verification of other stones or crystals), are extremely useful diagnostically. Careful attention to the technical parameters of frequency, gain, filter and scale is required to correctly identify vascular patency or thrombosis, especially in slow-flowing vessels.     

Normal variants, artefacts and interpretative pitfalls in PET imaging with 18-fluoro-2-deoxyglucose and carbon-11 methionine

Interpretation of studies from all imaging modalities requires a knowledge of the possible pitfalls that may occur due to normal variation, artefacts and processes which may mimic pathology. The applications and use of not only 18-fluoro-2-deoxyglucose but also l-[methyl-¹¹C] methionine positron emission tomography (PET) are widening and it is timely that the currently recognised interpretative pitfalls are reviewed as the number of dedicated PET scanners and coincidence gamma cameras increases.     

MR imaging of the normal shoulder: variants and pitfalls.

In 30 volunteers with normal shoulders, the following conclusions were made with regard to normal anatomic features at magnetic resonance (MR) imaging: (a) The supraspinatus tendon has low signal intensity, except for a 1-cm area with intermediate signal intensity in the region of the "critical zone." (b) The deltoid tendon attachment on the inferior surface of the acromion may simulate a subacromial spur if not imaged in continuity. (c) Fluid in the long head of the biceps tendon sheath is normal if not completely surrounding the tendon. (d) The anterolateral branch of the anterior humeral circumflex vessels in the proximal bicipital groove adjacent to the biceps tendon mimics fluid in the tendon sheath. (e) Continuity or obliteration of the subacromial-subdeltoid bursal fat plane is an unreliable diagnostic sign since the fat plane is often focally absent. (f) Fluid is not detected in subacromial-subdeltoid bursae. (g) Undercutting of the anterior glenoid labrum by hyaline cartilage or a closely apposed middle glenohumeral ligament may simulate an anterior labral tear.     

Sonography of the neonatal spine: part 1, Normal anatomy, imaging pitfalls, and variations that may simulate disorders

OBJECTIVE: Our objective is to discuss neonatal spine sonography with emphasis on imaging pitfalls and normal variants that may simulate disease and to distinguish them from true spinal disorders. CONCLUSION: Sonography of the neonatal spine is now accepted as a highly sensitive, readily available screening study that can be used to evaluate various anomalies of the lumbar spine in most infants younger than 4 months.     

Lumbar spine, sport and actual treatment.

Low back pains are very frequent in athletes by microtraumatisms and sudden efforts. The prolapse of the nucleus pulposus is created. After the failure of correct medical treatment, some new technics give good results: chemonucleolysis, trans-cutaneous nucleotomy, microdiscectomy. These techniques permit a faster and more active return to effort. The choice must be perfect: clinical examination and imagery manage this advance.     

Whole-body PET/CT: spectrum of physiological variants, artifacts and interpretative pitfalls in cancer patients

Accurate diagnosis and staging in oncology is essential in the evaluation of cancer for optimal patient outcome. Conventional imaging techniques, such as computed tomography (CT), rely basically on morphological changes for tumour detection. Clinical experience, however, shows that morphological criteria may be misleading and may not always allow differentiation between benign and malignant lesions. Positron emission tomography (PET) with [F]fluorodeoxyglucose (FDG) is rapidly gaining a critical role in the clinical evaluation of patients with cancer. However, PET lacks anatomical landmarks for topographic orientation, and identification of abnormal glucose metabolic activity in regions close to organs with variable physiological FDG uptake can be difficult. To overcome these difficulties, a combined PET/CT scanner that acquires both functional (PET) and CT images has been recently developed. Proper interpretation of PET (and PET/CT) images requires a thorough understanding of the normal physiological distribution of FDG in the body, along with a knowledge of frequently encountered physiological variations in FDG distribution, and recognition of non-malignant causes of FDG uptake that can be confused with a malignant neoplasm. In addition, because of the utilization of the CT transmission information for the correction of the attenuation of the PET emission data (and for the reconstruction of the PET images), some artifacts may be generated. As a consequence, CT based attenuation correction of PET images may result in erroneous PET/CT interpretations. The aim of this extensively illustrated paper is to demonstrate several potential pitfalls encountered during the interpretation of PET/CT images so that radiologists can avoid false positive diagnoses and recognize inherently non-specific findings on PET/CT images obtained for oncological diagnosis.     

Lumbar spine: postoperative MR imaging with Gd-DTPA

Thirty patients with failed back surgery syndrome were studied to evaluate the effectiveness of magnetic resonance (MR) imaging with gadolinium-diethylenetriaminepentaacetic acid/dimeglumine (Gd-DTPA) in differentiating postoperative epidural fibrosis (scar) from recurrent disk herniation. Pre- and postcontrast MR images were interpreted without access to other diagnostic, surgical, or pathologic findings. Seventeen patients had surgical and pathologic correlation of the MR findings at 19 disk levels. The precontrast studies had a sensitivity, specificity, and accuracy of 100%, 71%, and 89%, respectively. The enhanced MR studies correctly depicted the character of abnormal epidural soft tissue in 17 patients at all 19 levels. Scar showed heterogeneous enhancement on the early T1-weighted spin-echo images obtained within 10 minutes after contrast material administration. Herniated disk did not show significant enhancement on the early studies but showed variable degrees of enhancement on delayed images in nine of 12 cases. Other criteria were found to be less useful than the pattern of enhancement. Results indicate that precontrast and early postcontrast T1-weighted spin-echo studies are highly accurate in separating epidural fibrosis from herniated disk.     

Lumbar spine: postoperative assessment with surface-coil MR imaging

A prospective study of 15 patients who were scheduled to undergo various types of lumbar spine surgery was undertaken to assess the postoperative changes observable with magnetic resonance (MR) imaging. Patients underwent imaging preoperatively, immediately postoperatively (1-10 days), and late postoperatively (2-6 months). A retrospective review of MR images obtained in 62 patients who had undergone lumbar surgery but still had low back pain was also conducted. Epidural soft-tissue change and mass effect mimicking preoperative findings were present in nine of 13 patients who underwent laminectomy and diskectomy. Mass effect improved in appearance by the late postoperative period in eight of nine patients. T2-weighted sagittal images were best in demonstrating the site of anulus disruption immediately after diskectomy, which was seen in 11 of 13 patients, and the rent resolved on the late images in eight of ten cases. Sites of foraminotomy were seen as a loss of the normal foraminal fat signal. Extensive soft-tissue changes present in the immediate postoperative period severely limit the usefulness of MR imaging in that period for evaluating persistent symptoms. The exception may be hemorrhage, as its distinctive signal on T1-weighted images makes its identification possible.     

儿童脊柱正常MRI与胎儿脊柱骨发育

目的 :探讨胎儿椎体和椎间盘的组织学结构以及儿童脊柱的正常X线和MRI表现。方法 :44周胎儿X线平片 1例 ;儿童脊柱正常椎体MRI 13例 ;胎儿脊柱标本 2 6例 ,全部标本经固定、水冲洗、分批脱水、火棉胶包埋后制成脊柱标本整体切片 ,HE染色。结果 :44周胎儿脊柱每个椎体前面X线表现均有“V”字形凹陷。 13例儿童脊柱正常椎体MRI ,共分析了110个椎体的信号变化 ,其T1WI和T2 WI表现 :44 %的椎体前面“V”形凹陷呈高信号 ,63 %的椎体后面“V”形凹陷 ;16.4%的椎体前后面均凹陷 ;47%的椎体中心有雪花样高信号 ;13例中有 9例各椎体内均有双层低信号生长线。 2 6例胎儿脊柱椎体的组织学结构 :① 12周和 15周胎儿 ,椎体软骨内血管数量较多 ;②胎儿椎体前、后面中部凹陷 ,以膜内成骨形成“V”字形骨皮 ,不同病例椎体前面或后面均可见凹陷 ,出现率 9.6%～ 2 7.1% ,有 2例在椎体前面“V”字骨皮内形成松质骨小梁 ,并有骨髓形成 ;③椎体骨化中心有红髓和血管 :椎体后面“V”字骨皮内的大静脉窦与骨化中心静脉窦相通 ;④椎间盘 :只见于 12周的胎儿椎间盘内有血管 ,2例紧贴椎间盘的软骨椎体内见无细胞区 ,且部分髓核物突入椎体软骨内。结论 :4～ 11岁儿童脊柱正常椎体MRI表现仍然相应的保持着胎儿脊柱骨发育的组织学特点