Phase errors in multi-shot echo planar imaging

Field inhomogeneity related phase errors in multi-shot echo planar imaging (EPI) are directly visualized and analyzed in the spatial frequency domain data or ‘k-space’. The echo time shift (ETS) technique incrementally moves the position of the echo train and improves the phase error function by redistributing phase discontinuities away from the center of k-space.     

Technical errors in MR arthrography

This article discusses potential technical problems of MR arthrography. It starts with contraindications, followed by problems relating to injection technique, contrast material and MR imaging technique. For some of the aspects discussed, there is only little published evidence. Therefore, the article is based on the personal experience of the author and on local standards of procedures. Such standards, as well as medico-legal considerations, may vary from country to country. Contraindications for MR arthrography include pre-existing infection, reflex sympathetic dystrophy and possibly bleeding disorders, avascular necrosis and known allergy to contrast media. Errors in injection technique may lead to extra-articular collection of contrast agent or to contrast agent leaking from the joint space, which may cause diagnostic difficulties. Incorrect concentrations of contrast material influence image quality and may also lead to non-diagnostic examinations. Errors relating to MR imaging include delays between injection and imaging and inadequate choice of sequences. Potential solutions to the various possible errors are presented.     

Role of technetium-99m planar bone scanning in the evaluation of low back pain

The records of 1018 patients with low back pain in a tertiary spine referral practice were reviewed. One hundred thirty-nine out of 1018 (13.6%) underwent technetium-99m planar bone scanning as part of their investigation. Seventy-three out of 139 scans (52%) showed increased uptake in some area, but only 27 out of 139 (19.4%) showed increased uptake specifically in the low back. Scans consistently yielded no findings with reference to the back when the prescan diagnosis was spinal stenosis, lumbar pain syndrome, herniated nucleus pulposus, or postlaminectomy syndrome. Some scans gave positive findings in patients with a diagnosis of degenerative disc disease, pseudarthrosis, spondylolisthesis, fracture, infection, metabolic disorder, or tumor. Positive scans were generally obtained early after presentation (within 3 months) and negative scans obtained later (after 6 months), suggesting that clinical suspicion is still the main indication for early scanning. Planar bone scanning was helpful in both diagnosis and therapeutic decisionmaking in many conditions.     

Technical aspects of ct scanning

The advent of computed tomography (CT) has initiated a technological revolution which continues to the present time. A brief review of basic principles of CT scanning is presented, and the evolution of modern CT scanner systems is traced. Some early indications of future trends are also presented.     

Linearity and accuracy errors in bone densitometry

This investigation was undertaken to quantify accuracy errors and identify possible linearity errors in dual energy X-ray absorptiometry (DXA) of bone, based on studies of commercially available bone densitometers for planar densitometry. The following was found in a combination of in vitro phantom studies and in vivo investigations of human volunteers: (1) Pronounced differences between the instruments when measuring vertebral size and contours of the projected bone regions. (2) Falsely low bone mineral content (BMC in terms of g) in cases of low nominal bone mass, due to the fact that edge regions were omitted by the calculation software of some devices. (3) An increase in the projected bone area secondary to an increase in nominal bone mass with some instruments. (4) Clinically and statistically significant errors of accuracy of BMC and to a lesser extent bone mineral density (BMD). (5) Substantial linearity errors with some osteodensitometers for BMC, a phenomenon that reduces the usefulness of this parameter. It is concluded that DXA devices are affected by a combination of accuracy errors and linearity errors, some more than others, and that linearity errors influence their ability to monitor change in BMC and to a lesser extent in BMD, making system intercomparison difficult.     

Recent advances in bone marrow scanning

Interest in bone marrow scanning has been renewed as the result of the development of radiopharmaceuticals for evaluating specific aspects of bone marrow anatomy, physiology and pathology. This article provides a brief review of bone marrow structure, blood flow and function essential to the understanding of basic principles of bone marrow radionuclide imaging. The prospects and limitations of imaging haematopoietic bone marrow in man using indium 111 chloride, technetium-99m (^99mTc)-labelled microcolloid or^99mTc-labelled monoclonal antigranulocytic and antimyelocytic antibodies are discussed in more detail. The technical aspects of bone marrow scintigraphy are presented. Results of more recent studies evaluating bone marrow scanning in circulatory, inflammatory and in systemic haematological disorders are summarized. Special attention is paid to the concept of bone marrow micrometastases and its implications for the follow-up of patients with malignant tumours. Recent results suggest that immunoscintigraphy of bone marrow may provide a novel and sensitive approach for establishing the presence and extent of bone marrow infiltration.     

Recent advances in bone marrow scanning

Interest in bone marrow scanning has been renewed as the result of the development of radiopharmaceuticals for evaluating specific aspects of bone marrow anatomy, physiology and pathology. This article provides a brief review of bone marrow structure, blood flow and function essential to the understanding of basic principles of bone marrow radionuclide imaging. The prospects and limitations of imaging haematopoietic bone marrow in man using indium 111 chloride, technetium-99m (99mTc)-labelled microcolloid or 99mTc-labelled monoclonal antigranulocytic and antimyelocytic antibodies are discussed in more detail. The technical aspects of bone marrow scintigraphy are presented. Results of more recent studies evaluating bone marrow scanning in circulatory, inflammatory and in systemic haematological disorders are summarized. Special attention is paid to the concept of bone marrow micrometastases and its implications for the follow-up of patients with malignant tumours. Recent results suggest that immunoscintigraphy of bone marrow may provide a novel and sensitive approach for establishing the presence and extent of bone marrow infiltration.     

Postprandial blush in multiphase bone scanning

The presence of transient soft-tissue activity in the left side and the lower midportion of the abdomen on the early phases of the multiphase bone scan represents postprandial physiologic hyperemia of the small intestine. The bowel uptake was present in all 33 patients ingesting food between 15 min and 3.5 hr before scanning. In those patients who had not eaten within 4 hr of the study, only 25% demonstrated bowel activity. The observation of bowel uptake is important in differentiating a physiologic phenomenon from pathologic accumulations of activity. Pathology should be ruled out when bowel activity is not located in the usual left flank and lower mid-abdomen, or is present in a fasting individual.     

Polyphosphate bone scanning of non-malignant bone disease in children.

The advent of 99mTechnetium phosphate bone scanning radiopharmaceuticals has opened new methods of investigation of pediatric bone diseases. In axial skeleton pain, suspected osteomyelitis, evaluation of vascular integrity and suspected but undetected fractures, the bone scan has proved to be a highly complementary study to the radiologic examination.     

Diphosphonate bone scanning agents--current concepts

The bone scan is generally recognized to be an extremely powerful investigational tool in the evaluation of patients with skeletal disease. Currently 99mTc-methylene diphosphonate is the most widely used bone scanning agent, but recently several new diphosphonate compounds have been introduced which appear to have relatively higher skeletal affinity, leading to greater absolute uptake of tracer by bone. While the resulting improved contrast between bone and background soft-tissue may provide more pleasing scan images, it is not clear that increased bone uptake of tracer is equally desirable for identification of disease. Nevertheless, to date, no significant difference in lesion detection has been found in any comparative study of diphosphonate compounds. In this review the clinical studies evaluating diphosphonate bone scanning agents are summarized and the properties required of an ideal bone scanning agent in both benign and malignant disease discussed.     

Clinical uses of bone scanning

The skeleton is a frequent site of metastatic disease. Radiographic examination is not sufficiently reliable in early detection since an abnormality is unlikely to be observed until more than 50% of the bone material has been lost. Therefore, skeletal scanning represents a viable technique for demonstration of dynamic response of bone to tumor invasion. This technique provides a more sensitive method for detection of early skeletal metastatic disease. Technetium 99m labeled methylenediphosphonate seems to be the best technetium 99m labeled agent for skeletal images, although ethyline hydroxydiphosphonate may be equally good. The toxicity of the compounds is low and repetitive studies can be done for continued clinical evaluation of the patient without significant risk.This paper was supported by PHS Research Grants No. 1-R10-CA 12252 and 5-R10-CA12478 from the National Cancer Institute, by PHS Center Grant No. 1-P01-CA 14043 from the National Cancer Institute, by the Friends of the Radiation Therapy Center, and by the Alperin Foundation     

Radioisotope bone scanning in pulmonary alveolar microlithiasis

A 30-year-old woman was examined for a history of exertional breathlessness, swelling of her feet, and a mild dry cough of 4 to 5 months' duration. Her symptoms developed during the last month of her pregnancy, with gradually increasing dyspnea, swelling of the feet, and reduced urinary output. There was no history of expectoration, hemoptysis, chest pain, or tuberculosis. General physical examination showed no evidence of clubbing of the nails or lymphadenopathy. Chest auscultation revealed a few end-inspiratory crepitations at both lung bases. Bronchial alveolar lavage showed calcium particles, whereas results of the transbronchial lung biopsy were consistent with alveolar microlithiasis.     

Quantitative radionuclide scanning in metabolic bone disease

A simple method of quantifying skeletal uptake of 99Tcm-methylene diphosphonate, using a rectilinear scanner and a simultaneously image standard, is described. The pattern of quantified uptake in ten regions of the skeleton, the sacro-iliac joints and kidneys in 57 controls and 54 patients with various metabolic bone disease is presented. This method distinguishes patients with primary hyperparathyroidism and osteomalacia from controls with a sensitivity adequate for clinical purposes. In primary hyperparathyroidism the increased skull uptake of tracer correlated well with levels of serum alkaline phosphatase, plasma parathyroid hormone, urinary hydroxyproline excretion and the degree of intracortical resorption in the metacarpal bones. The skull uptake in oestoporosis was normal or moderately elevated and correlated well with bone mass density measurements of the radius. Patients with osteomalacia also showed the greatest increase in tracer uptake in the skull. Patients with thyrotoxicosis differed from most other patients by showing moderately increased uptake in shafts of long bones. We propose our method of quantitative bone uptake as a useful noninvasive test to detect metabolic bone disease and to monitor responses to therapy of bone disease.     

The role of bone scanning in osteomalacia

The presence of eight "metabolic features" was assessed on the bone scintigrams of ten patients with osteomalacia. In all of these bone images, sufficient features were present to strongly suggest a metabolic disorder. There scintiphotos were included in a controlled blind study using 30 normal bone scans and 20 scans of metastatic disease. Nine of the ten metabolic bone images were correctly identified by two independent observers. Skeletal uptake of radiotracer, expressed as bone-to-soft tissue ratio, was significantly higher in the osteomalacic patients than in a group of 80 controls.     

Radionuclide bone scanning in giant cell tumor

Radionuclide bone scan findings are described and correlated with pathology in 23 patients with giant cell tumor (GCT) of the bone. The degree of radionuclide activity was markedly increased in 20 (87%), minimally increased in three (13%), and decreased in none of the patients. Of the 23 patients with increased radioactivity, the pattern was diffuse in 11 (48%) and doughnut in 12 (52%). Extended patterns of radioactivity were present in 19 of 22 patients; however, none were associated with true tumor extension. Bone scanning did not aid in the detection of GCT, was nonspecific, and did not differentiate benign from malignant GCT. Although radioactivity extended beyond the radiographic abnormality in the majority of patients, this was most likely secondary to other bony abnormalities or local and/or regional hyperemia, and caution should be taken in ascribing this extension to either tumor or metastasis.