Maria B. Tomas

Diagnosing spinal osteomyelitis: a comparison of bone and Ga-67 scintigraphy and magnetic resonance imaging.

Purpose The objective of this investigation was to compare the accuracies of bone and Ga-67 scintigraphy and magnetic resonance imaging (MRI) for diagnosing spinal osteomyelitis and to determine the optimal radionuclide approach to this disorder. Methods Twenty-two patients, with 24 sites of possible spinal osteomyelitis, who underwent three-phase bone scintigraphy with SPECT, Ga-67 scintigraphy with SPECT, and MRI with and without contrast were included in this retrospective review. Bone scans were interpreted as three-phase studies, delayed planar images alone, delayed planar plus SPECT, and SPECT alone (to identify uptake patterns). Sequential bone/ Ga-67 images were interpreted as planar and as SPECT studies. Planar and SPECT Ga-67 images were also interpreted alone. Precontrast MRI studies were used to identify osteomyelitis, whereas postcontrast images were used to identify soft tissue infection. Results Eleven sites of spinal osteomyelitis were identified. Tracer uptake in two contiguous vertebrae, as noted on SPECT, was the most accurate bone scan criterion for detecting spinal osteomyelitis (71%). SPECT bone/Ga-67 was significantly more accurate (92%) than both planar bone/Ga-67 (75%) and bone SPECT (P = 0.15 and P = 0.2, respectively). SPECT Ga-67 was as accurate as SPECT bone/Ga-67 and as sensitive as MRI (91%); the radionuclide study was slightly but not significantly more specific (92% vs. 77%) than MRI. Of 11 sites of extraosseous infection, 10 were identified on MRI, 9 on SPECT Ga-67, 7 on planar Ga-67, and none on bone scintigraphy. Conclusions Spinal osteomyelitis and accompanying soft tissue infection can be diagnosed accurately with a single radionuclide procedure: SPECT Ga-67. This procedure can be used as a reliable alternative when MRI cannot be performed and as an adjunct in patients in whom the diagnosis is uncertain.

Preoperative parathyroid scintigraphic lesion localization: accuracy of various types of readings.

PURPOSEnTo retrospectively compare the accuracy of various parathyroid scintigraphy readings for single-gland disease (SGD) and multigland disease (MGD) in patients with primary hyperparathyroidism, with histologic analysis as the reference standard.nnnMATERIALS AND METHODSnInstitutional review board approval was obtained for this HIPAA-compliant study. Records of 462 patients with primary hyperparathyroidism who underwent preoperative imaging with a technetium 99m ((99m)Tc) sestamibi and (99m)TcO4- protocol that consisted of early and late pinhole (99m)Tc sestamibi, pinhole thyroid imaging, image subtraction, and single photon emission computed tomography (SPECT) were retrospectively reviewed. An experienced nuclear medicine physician without knowledge of other test results or of the final diagnoses graded images on a scale from 0 (definitely normal) to 4 (definitely abnormal). Early pinhole (99m)Tc sestamibi images, late pinhole (99m)Tc sestamibi images, subtraction images, SPECT images, early and late pinhole (99m)Tc sestamibi images, all planar images, and all images--including SPECT images--were read in seven sessions. Receiver operating characteristic curves were generated for each session and were used to calculate sensitivity, specificity, and accuracy.nnnRESULTSnA total of 534 parathyroid lesions were excised. Of the 462 patients, 409 had one lesion, whereas 53 had multiple lesions. Reading all images together was more accurate (89%, P = .001) than was reading early (79%), late (85%), subtraction (86%), and SPECT (83%) images separately; however, it was not significantly more accurate than reading planar images (88%) or early and late images together (87%). Reading all images was significantly less sensitive in the detection of lesions with a median weight of 600 mg or less than in the detection of lesions with a median weight of more than 600 mg (86% vs 94%, P = .004). Per-lesion sensitivity for reading all images was significantly higher for SGD than for MGD (90% vs 66%, P < .001). Sensitivity of reading all images together in the identification of patients with MGD was 62%.nnnCONCLUSIONnReviewing early, late, and subtraction pinhole images together with SPECT images maximizes parathyroid lesion detection accuracy. Test sensitivity is adversely affected by decreasing lesion weight and MGD.

Infection and Inflammation

Despite dramatic advances in its prevention and treatment, infection remains a major cause of morbidity in children, accounting for approximately 30 % of childhood deaths worldwide (Children’s Infection Defense Center, St. Jude Children’s Research Hospital, 2004). The development of powerful antimicrobial agents has improved patient survival, but timely diagnosis is equally, if not more, important. In adults, most infections can be diagnosed with a thorough history, a complete physical examination, and appropriate laboratory tests. In the pediatric population, unfortunately, this is a difficult task. Children do not, or will not, verbalize their feelings, and often the history is little more than secondhand information obtained from a parent. The physical examination of an ailing child can be difficult, if not impossible. Further complicating matters is the fact that conditions such as vasculitis and other inflammatory diseases can mimic infection. Consequently, empiric treatment with antibiotics, which may be neither appropriate nor effective, often is instituted. Imaging procedures usually are reserved for those patients in whom symptoms or physical findings point to a specific region of the body. Because of concerns about radiation exposure, pediatricians tend to utilize radionuclide imaging only as a last recourse after all other resources have been exhausted. The nuclear physician often is faced with the formidable task of diagnosing and localizing infection and inflammation late in the course of an illness when an expeditious and correct diagnosis is even more critical.

Sestamibi parathyroid scintigraphy in multigland disease.

PurposeFor sestamibi (MIBI) studies in patients with primary hyperparathyroidism, some investigations found that the test sensitivity is lower in patients with multigland disease (MGD) than in those with single-gland disease (SGD), whereas other investigations reported that the sensitivity of MIBI imaging is similar in MGD and SGD. The objectives of this investigation, therefore, were to determine (a) whether there are differences in the sensitivity and specificity of MIBI imaging for detecting parathyroid lesions in patients with MGD and in patients with SGD, (b) whether there is a relationship between test sensitivity and the number of glands involved, (c) whether there are differences in weight between parathyroid lesions in MGD and SGD, (d) whether there are differences in lesion locations between MGD and SGD, and (e) whether MIBI sensitivity in MGD is related to the number, weight, or location of the lesions. Materials and methodsThis was a retrospective investigation of data for 651 patients with biochemically confirmed primary hyperparathyroidism limited to the neck, who underwent preoperative parathyroid lesion localization using a dual tracer 99mTc-MIBI/99mTcO4− protocol that included early and late planar pinhole 99mTc-MIBI, pinhole thyroid imaging, image subtraction, and single photon emission computed tomography. All patients underwent surgery subsequently. Lesion locations were obtained from operative reports; lesion weights were obtained from pathology reports. One experienced nuclear physician, who had no knowledge of the other test results or the final diagnoses, graded studies on a 5-point scale (0=definitely normal to 4=definitely abnormal) while reading all scintigraphic images simultaneously. ResultsThere were 851 lesions among the 651 patients. One hundred and thirty-one (20%) patients had MGD and 520 (80%) patients had SGD. Among the patients with MGD, 74 had two lesions, 45 had three lesions, and 12 had four lesions. MIBI imaging was significantly less sensitive (61 vs. 97%, P<0.0001) and specific (84 vs. 93%, P<0.0001) for MGD than for SGD. Weights of MGD lesions were significantly lower than those of SGD lesions [median 190 mg (10–14 600 mg) vs. median 500 mg (48–27 000 mg), Wilcoxon P<0.0001]. Lesion weights decreased significantly with increasing lesion number (r=−0.42, P<0.0001). MIBI sensitivity for 249 MGD lesions (65%) was significantly less (P<0.0001) than for 249 weight-matched SGD lesions (94%). For these weight-matched lesions, the test sensitivity decreased progressively with increasing lesion number (r=0.97, P=0.006). The spatial distribution of MGD and SGD lesions was similar (P=0.19), and the sensitivity was not related to lesion location for MGD (P=0.32) or SGD (P=0.11) lesions. ConclusionMIBI is significantly less sensitive and specific for detecting parathyroid lesions in MGD than in SGD. Decreased sensitivity is not explained by lesion weight or location, and further studies of factors affecting MIBI imaging in MGD are warranted.

Pinhole Versus Parallel-Hole Collimators for Parathyroid Imaging: An Intraindividual Comparison

This study was undertaken to determine the effects of collimators on the accuracy of preoperative sestamibi parathyroid imaging of the neck. Methods: Forty-nine patients with primary hyperparathyroidism underwent preoperative 99mTc-sestamibi parathyroid imaging. The protocol included early and late pinhole and parallel-hole imaging. One experienced nuclear physician, without knowledge of other test results or final diagnoses, interpreted studies. For both pinhole and parallel-hole images, focally increased sestamibi accumulation outside the normal tracer biodistribution that persisted or increased in intensity from early to late images was interpreted as positive for a parathyroid lesion. Final diagnoses were operatively confirmed in all patients. Results: Fifty-four parathyroid lesions were resected from the 49 patients. Forty-five patients had single-gland disease. Four patients had multigland disease: 3 had 2 lesions and 1 had 3 lesions. Median lesion weight was 840 mg. Pinhole imaging was significantly more sensitive than parallel-hole imaging (89% vs. 56%; P = 0.0003) for all 54 lesions. Specificity did not significantly differ between pinhole and parallel-hole imaging (93% vs. 96%, P = 0.29). Pinhole imaging was significantly more sensitive than parallel-hole imaging for lesions above (100% vs. 68%, P = 0.003) and below (77% vs. 42%, P = 0.03) the median weight and for single-gland disease (96% vs. 67%, P = 0.001). Pinhole imaging also was more sensitive for multigland disease, although the difference was only marginally significant (55% vs. 0%, P = 0.037). Conclusion: Because sensitivity is significantly higher, sestamibi parathyroid imaging of the neck should be performed with a pinhole collimator.

Pulmonary activity on labelled leukocyte images: Patterns of uptake and their significance

The objective of this study was to characterize, and determine the significance of, pulmonary activity on labelled leukocyte images. This retrospective review included 137 immunocompetent patients who had undergone 111In labelled autologous leukocyte chest imaging and chest X-ray within 7 days. Pulmonary activity was classified as normal, focally increased, or diffusely increased. Images were correlated with chest X-rays and final diagnoses. One hundred and twelve patients (82%) had normal pulmonary activity. Seventy-six had normal chest X-rays; none had pulmonary infection. Thirty-six patients had chest X-ray abnormalities; only one had pulmonary infection. Twenty-five patients had abnormal pulmonary activity. In 13 patients it was segmental or lobar in distribution. The chest X-ray was abnormal in 12: pneumonia (11) and cystic fibrosis (one). The chest X-ray was normal in one patient with pneumonia. Two patients with non-segmental pulmonary activity did not have pulmonary infection. The chest X-ray was abnormal in one (pulmonary edema) and normal in one (sepsis). Ten patients had diffuse pulmonary activity. Chest X-ray was abnormal in two patients: adult respiratory distress syndrome (ARDS) (one) and drug toxicity (one). No patient with diffuse pulmonary activity had pulmonary infection. In summary, negative labelled leukocyte imaging excludes pulmonary infection with a high degree of certainty (the negative predictive value was 99% in this series), and can exclude pneumonia as the cause of a chest X-ray abnormality. Focal pulmonary activity strongly suggests pneumonia, while diffuse pulmonary activity is unlikely to indicate infection.

Spect and Subtraction Imaging of an Ectopic Parathyroid Adenoma

Primary hyperparathyroidism is a disease best managed surgically; resection of the lesion(s) is curative. Although the routine use of localizing procedures is controversial before surgery, it is generally agreed that these techniques are useful in cases of reexploration. The authors have recently studied a patient with long-standing hyperparathyroidism, in whom initial surgery was unsuccessful. Although planar imaging with Tc-99m sestamibi is usually sufficient for identification and localization of the lesion, both SPECT and subtraction imaging provided additional information that contributed to the success of the subsequent surgery. Single-proton emission computed tomography provided critical information about the position of the ectopic parathyroid adenoma in relation to the right submandibular salivary gland, whereas subtraction imaging confirmed that the focus was indeed a parathyroid lesion, and not merely an anatomic variant of a normal salivary gland.

Comparison of criteria to truncate gastric emptying tests.

PurposeStandardized scintigraphic gastric emptying (GE) protocols to detect gastroparesis (GP) require collecting data for 4 h. This investigation was undertaken to compare seven methods to reduce the duration of the test. Materials and methodsThis was a retrospective study of GE data collected using a standardized protocol at 0, 1, 2, 3, and 4 h for 602 patients being evaluated for GP. The reference standard was GP defined conventionally as percentage of gastric retention (GR) at 4 h (p4) of greater than 10%. For data up to 2 h the results were derived as follows: (a) confirming as being positive for GP if GR at 2 h was greater than 65%, negative for GP if GR at 2 h was less than 45%, and indeterminate otherwise; (b) by linear extrapolation; and (c) by monoexponential extrapolation. For data beyond 2 h, further evaluations were made and results were derived as follows: (a) confirming as being positive for GP if GR at 2.5 h was greater than 40%; (b) ascertainment of GR at 3 h; (c) by biphasic fit; and (d) by observation of maximum GR for normal patients at time points earlier than 4 h. ResultsThirty percent of all patients had GP. Eighty percent were determinate by Method 1; for these patients sensitivity to detect GP was similar (P=0.11) for Methods 1–3 (69–79%). For data beyond 2 h, sensitivity of the seven methods ranged from 64 to 92%, and the sensitivity of every method was significantly lower than that of the reference standard (P<0.001). ConclusionConsidering that sensitivity to detect GP was significantly reduced for data collection limited to 3 h or less, it is not advisable to truncate GE studies earlier than 4 h.

Phantom experiments to improve parathyroid lesion detection

This investigation tested the hypothesis that visual analysis of iteratively reconstructed tomograms by ordered subset expectation maximization (OSEM) provides the highest accuracy for localizing parathyroid lesions using 99mTc-sestamibi SPECT data. From an Institutional Review Board approved retrospective review of 531 patients evaluated for parathyroid localization, image characteristics were determined for 85 99mTc-sestamibi SPECT studies originally read as equivocal (EQ). Seventy-two plexiglas phantoms using cylindrical simulated lesions were acquired for a clinically realistic range of counts (mean simulated lesion counts of 75 +/- 50 counts/pixel) and target-to-background (T:B) ratios (range = 2.0 to 8.0) to determine an optimal filter for OSEM. Two experienced nuclear physicians graded simulated lesions, blinded to whether chambers contained radioactivity or plain water, and two observers used the same scale to read all phantom and clinical SPECT studies, blinded to pathology findings and clinical information. For phantom data and all clinical data, T : B analyses were not statistically different for OSEM versus FB, but visual readings were significantly more accurate than T : B (88 +/- 6% versus 68 +/- 6%, p = 0.001) for OSEM processing, and OSEM was significantly more accurate than FB for visual readings (88 +/- 6% versus 58 +/- 6%, p < 0.0001). These data suggest that visual analysis of iteratively reconstructed MIBI tomograms should be incorporated into imaging protocols performed to localize parathyroid lesions.