The role of single photon emission computed tomography in bone imaging.

Single photon emission computed tomography (SPECT) of the bone is the second most frequently performed SPECT examination in routine nuclear medicine practice, with cardiac SPECT being the most frequent. Compared with planar scintigraphy, SPECT increases image contrast and improves lesion detection and localization. Studies have documented the unique diagnostic information provided by SPECT, particularly for avascular necrosis of the femoral head, in patients with back pain, for the differential diagnosis between malignant and benign spinal lesions, in the detection of metastatic cancer in the spine, for the diagnosis of temporomandibular joint internal derangement, and for the evaluation of acute and chronic knee pain. Although less rigorously documented, SPECT is being increasingly used in all types of situations that demand more precise anatomic localization of abnormal tracer uptake. The effectiveness of bone SPECT increases with the selection of the proper collimator, which allows one to acquire adequate counts and minimize the patient-to-detector distance. Low-energy, ultrahigh-resolution or high-resolution collimation is preferred over all-purpose collimators. Multihead gamma cameras can increase the counts obtained or shorten acquisition time, making SPECT acquisitions more practical in busy departments and also increasing image quality compared with single-head cameras. Iterative reconstruction, with the use of ordered subsets estimation maximization, provides better quality images than classical filtered back projection algorithms. Three-dimensional image analysis often aids lesion localization.

Life-threatening hemorrhage of an unanticipated superficial circumflex iliac artery origin imaged with Tc-99m-labeled erythrocytes.

The authors report, for the first time, the nuclear medicine diagnosis of extraperitoneal bleeding that originated from the superficial circumflex iliac artery and review the critical role of dynamic nuclear imaging techniques in the localization of sites of nonenteric hemorrhage. Dynamic imaging techniques using Tc-99m-labeled erythrocytes played a critical role in the localization of an extraperitoneal bleeding site near the entrance site of a Jackson-Pratt drain. Localization of the site remained undiagnosed before nuclear imaging despite two exploratory laparotomies and diagnostic angiography.

Measurement of distal forearm bone mineral density: can different forearm segments be used interchangeably ?

Many different forearm sites have been used for the measurement of bone mineral density (BMD) and prediction of risk of future fracture among community dwelling populations. In populations where bone densitometry of peripheral sites may be the most cost effective and practical means of measuring BMD, such as the nursing home population, knowing the characteristics of forearm BMD measures would be beneficial. The purpose of this study was to assess the relationship of four common commercially available measures to each other and to estimate the inter- and intrarater reliability of the measures in a sample of nursing home residents as a first step toward identifying appropriate forearm measurement sites. These sites were the distal radius, the distal ulna, a composite of the distal radius and distal ulna, and the ultra distal radius. BMD measurements on 48 nursing home patients were obtained using single X-ray absorptiometry. Inter- and intrarater reliability was excellent at all four sites (interclass correlation coefficients > 0. 85). Moderate to high correlations (0.84-0.91) between the distal radius and ultra distal radius sites of the forearm suggest that these measures may be interchangeable. Although not directly assessed here, differences in bone composition among forearm sites may partially explain moderate rather than high correlations between sites and may affect the ability of each site to predict future fractures. Thus, different forearm sites may be used interchangeably for diagnostic purposes; however, the prognostic value of each site remains unknown.

Dual-isotope protocol for indium-111 capromab pendetide monoclonal antibody imaging.

OBJECTIVE: A dual-isotope imaging protocol using 99mTc-labeled red blood cells with 111In capromab pendetide monoclonal antibody imaging for detective and localizing nodal metastasis in prostate cancer is described. METHODS: This protocol involves a single SPECT acquisition that is less time consuming and more comfortable for the patient than the currently recommended method, which requires two separate SPECT acquisitions performed on different days. RESULTS: Forty patients were studied with the dual-isotope protocol. Preliminary data suggest increased accuracy compared with the single-isotope technique. CONCLUSION: The dual-isotope technique assures the precise image registration needed for accurate comparison of blood pool and pelvic lymph node activity that is required for confident and accurate image interpretation.

Effects of the attenuation map used in the Chang algorithm on quantitative SPECT results.

OBJECTIVE: This study examined the effects on SPECT quantitation caused by erroneous size and position of the attenuation map and inaccurate pixel size used in the Chang algorithm. METHODS: Projection data of a three-dimensional head phantom were simulated with a uniform attenuation coefficient of 0.15/cm for the inside of the phantom. Images were reconstructed using the filtered backprojection algorithm without attenuation compensation and the Chang algorithm with different attenuation maps. Quantitative comparison then was performed between the reconstructed images and the phantom. RESULTS: The pixel values obtained for noisy data by using the first-order Chang algorithm with an accurate attenuation map were less than 10% different from the true values and the left-right asymmetry was under 5%. Small errors in the geometric parameters of the attenuation map, however, caused considerable quantitative inaccuracy in the reconstructed image. For example, a 0.64-cm error in the size of the map caused 10% deviation from the true value and a 0.64-cm shift of the position of the map towards the left produced 10% left-right pixel value asymmetry. CONCLUSION: The accuracy of the Chang algorithm critically depends on the geometric parameters. For a uniform attenuator with symmetric geometry, such as the human brain, a true left-right symmetry in the pixel value can be altered significantly by a small error in the geometric parameters, while symmetry can be maintained with no attenuation compensation.

Reflex sympathetic dystrophy: diagnostic controversies.

Reflex sympathetic dystrophy, (RSD) is a complex physiologic response of the body to an external stimulus resulting in sympathetically mediated, usually nonanatomic pain, which is out of proportion to the inciting event or expected healing response. This complex entity has been the focus of much investigation, leading however to somewhat confusing and conflicting results and theories about the etiology and pathophysiology. There is even significant conflict about what characteristics define the clinical entity called RSD, and if these characteristics vary with the specific site of involvement. We have examined the current literature regarding these fundamental conflicts, and in addition we have evaluated the current controversies surrounding the role of Three Phase Radionuclide Bone Imaging (TPBI) for diagnosis, prognosis, and patient management. These controversies include the role of scintigraphy, the various criteria for scintigraphic diagnosis, and the reported variations in sensitivity and specificity of TPBI in RSD. We have examined several factors that may have affected these results, and potentially underestimated the value of scintigraphy in the diagnosis of RSD. In addition to the heterogeneous patient populations used to establish the diagnosis by different subspecialty physicians, these factors include duration of patient's symptoms, age of the patient population evaluated, location of the disease, and the varying scintigraphic scan interpretation criteria used.

Technical considerations for optimal orthopedic imaging.

Over the past 25 years bone scintigraphy has played an essential role in most Nuclear Medicine departments, accounting for 25% to 60% of the patient volumes. No longer is every bone scan ordered as part of a metastatic workup. Today radionuclide bone imaging (RNBI) is included in most orthopedic diagnostic pathways. It is necessary to optimize the bone scan procedure to be sensitive, to carefully localize abnormal uptake for diagnosis, to correlate the bone scans, plain radiographs, computed tomographic (CT) scans, and magnetic resonance (MR) scans that accompany the patient, and to be precise in reporting a final impression. This can be done through meticulous attention to the image acquisition so that it encompasses not only equipment specifications and acquisition parameters, but also patient history, preparation, imaging protocols, positioning, and image correlation. The importance of these considerations, the rationale to explain them, and suggested guidelines for their implementation will be discussed in this article.

Comparison of parathyroid imaging with technetium-99m-pertechnetate/sestamibi subtraction, double-phase technetium-99m-sestamibi and technetium-99m-sestamibi SPECT.

UNLABELLED: The ability of 99mTc-pertechnetate/sestamibi subtraction, double-phase 99mTc-sestamibi and 99mTc-sestamibi SPECT imaging to localize abnormal parathyroid tissue was compared. METHODS: Fifty-five consecutive patients had parathyroid imaging before surgery for hyperparathyroidism. Imaging consisted of 99mTc-pertechnetate pinhole images of the neck followed by 99mTc-sestamibi pinhole images of the neck and parallel-hole images of the neck and chest (early images). Within 2.5-4.0 hr later pinhole images of the neck, parallel-hole and SPECT images of the neck and chest were obtained (late images). Nodular foci of increased sestamibi activity were considered abnormal. RESULTS: The sensitivity for abnormal parathyroid glands by visual comparison of early images and pertechnetate images was 72%-75%, late images and pertechnetate images was 73%-78% and double-phase (early and late) sestamibi images was 62%-65%; computer subtraction of pertechnetate from early images was 71%-74%; and SPECT imaging was 79%. The sensitivity for parathyroid adenomas was 89%-98%, while the sensitivity for hyperplastic parathyroid glands was only 47%-58%. CONCLUSION: Late imaging, computer subtraction and SPECT may not be necessary since they provided only marginal improvements on visual comparison of early sestamibi with pertechnetate images. Double-phase sestamibi imaging was less sensitive, so baseline thyroid imaging with pertechnetate is recommended.

Scrotal pathology as the cause for hip pain. Diagnostic findings on bone scintigraphy.

Scrotal scintigraphy has become a relatively uncommon examination in many nuclear medicine departments. However, scrotal perfusion is visualized during three-phase bone imaging of the pelvis and hips. The authors present a compilation of three cases of hip pain secondary to unsuspected scrotal pathology documented on routine three-phase bone scintigraphy, discussing this topic for the first time in the literature. A short review of the pathophysiology of referred hip pain, differential diagnosis, and imaging alternatives emphasize the unique contribution of nuclear imaging.

Morphine augmentation increases gallbladder visualization in patients pretreated with cholecystokinin.

UNLABELLED: The purpose of this study was to determine if a combination of cholecystokinin (CCK) pretreatment followed by morphine augmentation improved the detection of cystic duct patency compared with CCK pretreatment only. METHODS: One hundred fifty-five patients with suspected acute cholecystitis had scintigraphy performed with 185-481 MBq (5-13 mCi) 99mTc-mebrofenin adjusted to the patients' total bilirubin levels. All patients were pretreated with 0.02 microgram/kg sincalide injected intravenously over 3-5 min. Sequential imaging was performed until gallbladder activity was identified or up to 90 min postinjection of mebrofenin. If no gallbladder was identified, a second dose of mebrofenin was given as necessary to have tracer in the biliary system. Then, 0.04 mg/kg intravenous morphine sulfate was administered, followed by imaging for up to 30 min or until gallbladder visualization. RESULTS: Twenty-eight percent (43/155) of the patients pretreated with CCK had nonvisualization of the gallbladder at 90 min postinjection of radiotracer. After intravenous morphine, the gallbladder was identified in 42% (18/43) of these patients (p = 0.0001). CONCLUSION: Hepatobiliary imaging with CCK pretreatment and imaging for 90 min was insufficient to identify all patent cystic ducts. Morphine augmentation significantly increased the frequency of gallbladder visualization in patients pretreated with CCK.