Status of F-18 fluorodeoxyglucose uptake in normal and hibernating myocardium after glucose and insulin loading.

OBJECTIVE: F-18 fluorodeoxyglucose (FDG) positron emission tomography (PET) has been increasingly used in myocardial viability imaging. In routine PET viability studies, oral glucose and intravenous insulin loading is commonly utilized. In an optimal study, glucose and insulin loading is expected to cause FDG uptake both in hibernating and normal myocardium. However, in routine studies it is not uncommon to see absent or reduced FDG uptake in normal myocardium. In this retrospective study we further analyzed our PET viability images to evaluate FDG uptake status in myocardium under the oral glucose and intravenous insulin loading protocol that we use in our hospital. METHODS: Patients who had both myocardial perfusion single photon emission computed tomography (SPECT) and FDG PET cardiac viability studies were selected for analysis. FDG uptake status in normal and abnormal myocardial segments on perfusion SPECT was evaluated. Based on SPECT and PET findings, patients were divided into two main groups and four subgroups. Group 1 included PET viable studies and Group 2 included PET-nonviable studies. Subgroups based on FDG uptake in normal myocardium were 1a and 2a (normal uptake) and 1b and 2b (absent or significantly reduced uptake). RESULTS: Seventy-one patients met the inclusion criteria. Forty-two patients were PET-viable and 29 were PET-nonviable. In 33 of 71 patients (46.4%) there was absent or significantly reduced FDG uptake in one or more normal myocardial segments, which was identified more in PET-viable than PET-nonviable patients (59.5% vs. 27.5%, p = 0.008). This finding was also more frequent in diabetic than nondiabetic patients (53% vs. 31.8%), but the difference was not significant (p = 0.160). CONCLUSIONS: In nearly half of our patients, one or more normal myocardial segments showed absent or significantly reduced FDG uptake. This finding, particularly if it is diffuse, could be from suboptimal study, inadequacy of current glucose and insulin loading protocols, or various other patient-related causes affecting FDG uptake both in the normal and hibernating myocardium. In cases with significantly reduced FDG uptake in normal myocardium, PET images should be interpreted cautiously to prevent false-negative results for viability.

(99m)Tc-MIBI Whole Body Scan: A Potentially Useful Technique for Evaluating Metabolic Bone Disease.

Metabolic bone disease due to hyperparathyroidism is characterized by increased bone resorption and new bone formation. (99m)Tc- hexakis-2-methoxyisobutylisonitrile ((99m)Tc MIBI) accumulation is controlled by metabolic function and cell viability. To investigate, for the first time, the potential of whole body (99m)Tc MIBI scan for detecting, visually and with the aid of quantitative analysis, bony changes associated with hyperparathyroidism. Eighty-six patients with hyperparathyroidism, referred routinely for parathyroid localization, were included in this case-control prospective study. Each patient was injected with 20-25 mCi of (99m)Tc MIBI. Routine anterior cervico-thoracic images were obtained for parathyroid localization. Two extra whole body images were acquired and assessed visually and by drawing regions of interest over the mandible, sternum, femur, humeri, spine, and the soft tissue adjacent to the bone. The ratios of bone to soft tissue were calculated and compared to ratios drawn in a control group routinely referred for cardiac imaging and injected with (99m)Tc MIBI, after confirming the absence of any bone disease. The visual interpretation of the scans showed 48 patients to have increased bone uptake. Quantitative assessment showed significant difference between the mean ratios of the case and control groups. The Kruskal-Wallis test showed significant agreement between visual and quantitative ratios drawn from delayed right and left femora and left humerus images (P < 0.05). (99m)Tc MIBI whole body imaging is a potentially useful technique for assessing metabolic bone disease associated with hyperparathyroidism. Quantitative analysis helped in confirming the visual findings.

Chronic Recurrent Multifocal Osteomyelitis in Children: A Multidisciplinary Approach is needed to establish a Diagnosis.

Chronic recurrent multifocal osteomyelitis (CRMO) is an inflammatory disease of unknown cause. In general, CRMO follows a characteristic clinical course and is regarded at present as a distinct entity. It affects bone and occurs predominantly in children and adolescents. The clinical, radiologic and pathologic findings are non-specific. The recognition of this rare entity is often delayed and difficulties in patient management sometimes emerge from its usual protracted course. We present a 6-year-old girl diagnosed with CRMO involving tibia and lumbar vertebra where a multidisciplinary approach was essential in making the diagnosis.

Metastatic bone disease: evaluation by functional imaging in correlation with morphologic modalities.

The diagnosis of presence, location and load of metastatic, bone involvement has important implication on patient management and prognosis. This requires collection of data obtained using different imaging modalities. Bone scintigraphy is a highly sensitive and cost-effective screening modality. However, to overcome its lower specificity and its limitation in evaluation of vertebral metastases, CT, PET or MRI can be utilized to verify the nature of suspicious lesions. Expansion of SPECT/ CT may fine tune the highly sensitive bone scintigraphy. PET has an emerging and leading role in many tumors, occasionally obviating the need for bone scintigraphy, particularly in evaluation of response to therapy. PET and whole body MRI offers a potentially important tool to provide the earliest clue of bone marrow metastasis. The value of F-18 PET as a sensitive bone imaging tool needs to be further evaluated on a larger scale in different setting including treated and untreated cancer patients and to evaluate also whether potentially better resolution would lead to more benign lesions detection mimicking metastasis such as fractures, inflammatory, infection, and degenerative involvement of bone. The added value of PET-CT is also to be further examined with this regard.

Multifocal post-traumatic scintigraphic changes mimicking bone metastases in a battered adult.

Several pathologies have been reported to cause scintigraphic patterns similar to multiple bony metastases. Heterotopic bone formation is known to mimic several inflammatory and neoplastic conditions including recurrent tumors. However, no reports on multifocal heterotopic bone formation simulating the typical pattern of randomly distributed foci of increased uptake of metastases on bone scan were found in literature. We present a case of a young adult who was repeatedly assaulted by others over a period of one month and on bone scan had a pattern similar to bony metastasis due to multiple foci of heterotopic bone formation and fractures.

Horizons in nuclear medicine and molecular imaging: highlights of the Third Gulf Nuclear Medicine Conference.

The Third Gulf Nuclear Medicine Conference took place in the state of Kuwait at Salwa Al Sabah hall, Safir marina hotel in Salmiya. The event extended from March 29th to April 1st 2009. The assembly was a great chance for all nuclear medicine, i.e. physicians, technologists and researchers in the field to meet and exchange experience and knowledge. The number of participators registered for this conference was beyond expectations; total registrants of 611 attended the event and actively end it. The conference was attended by international, regional and local participants. There were 23 speakers, including 13 invited guest speakers who came from USA, Canada, Europe and the Gulf region. In addition to the lectures and oral presentations, there were 30 poster presentations. The latest updates in the field together with most recent findings in the participants' own research were presented. The lectures and posters covered different basic and clinical categories of nuclear medicine. This article summarizes the highlights of the major topics discussed with some recommendations when applicable. Proceedings of the conference can be found in the World Journal of Nuclear Medicine of April, 2009.

Effect of hyperthermia on the function of thyroid gland.

Hyperthermia may be a consequence of environmental conditions, bacterial or viral infections and/or thyroid storm. This study investigates the acute effect of body temperature elevation on thyroid function and on its scintigraphy studies. Thyroid scintigraphy was performed on New Zealand White rabbits weighing approximately 3-3.5 kg. Each rabbit was injected with 115 MBq (3.1 mCi) technetium-99 m pertechnetate ((99m)Tc pertechnetate). Studies were performed using Gamma camera equipped with a low energy, high resolution, pinhole collimator interfaced with a computer. Static images were acquired 20 min after administration of the radiotracer. Two days later the same protocol was repeated for the same rabbit after increasing the body temperature by 2 degrees C. The experiment was repeated again after a 2-day interval at 3 degrees C, and then after another 2-day interval at 4 degrees C. Plasma free thyroxine (FT(4)), free triiodothyronine (FT(3)) and thyroid stimulating hormone (TSH) were measured at control and at different hyperthermic temperatures (+2, 3, 4 degrees C). We recorded isometric tension of rabbit thyroid artery strips in organ baths during stepwise temperature elevation. During hyperthermia the decrease in thyroid function and thyroid scintigraphy studies was proportional to body temperature elevation. The recording of isometric tension in rabbit thyroid artery strips in organ baths showed vasoconstriction during hyperthermia which is proportional to the heating temperature. Plasma FT(4) and FT(3) level were decreased while TSH levels were not affected by acute fever. Our results indicate that hyperthermia causes a transient decrease in thyroid gland function and scintigraphic patterns on radionuclide studies. Thus, body temperatures must be measured before radionuclide studies in order to ensure that interpretation of data is not influenced by hyperthermia.

Role of positron emission tomography (PET) in the management of lymphoma.

PET enhances staging of lymphoma and is superior to CT scan. It consequently provides more accurate basis for treatment regimens. It provides a better assessment of response to therapy and is the most useful non-invasive modality to differentiate residual tumor from fibrosis/necrosis. Persistent uptake during and after chemotherapy appear to have a high sensitivity in predicting subsequent relapse although some patients may remain in prolonged remission. A negative finding after therapy indicates a very favorable prognosis. We still need better refinement to set off patients who could really benefit from the additional information and better definition of the optimal timing of imaging in clinical practice, The use of early PET response in determining choice of therapy should be utilized with caution until some critical questions are answered. These include: When is the best time to use PET for response assessment? what is the most suitable methodology, visual or quantitative? can early responders be cured with less intensive therapy? will survival be better for patients treated more intensively because they have a poor interim metabolic response?. Further evaluation of alternative PET radiotracers and whether they are superior to FDG and evaluation of the added value of dual FDG-PET acquisition are needed. When PET is not available, Ga-67 imaging of lymphoma can also provide information regarding the presence or absence of active lymphoma particularly in assessing the response to therapy and predicting the outcome.

Synergistic effects of ethanol and hyperthermia on carotid artery vasoconstriction.

BACKGROUND: Heatstroke is a serious condition and clinical studies indicate that vascular stroke increases with excessive consumption of alcohol (ethanol). It was our objective to test the influence of ethanol on cerebral perfusion at normal and higher temperatures. METHODS: Recording of isometric tension in rabbit carotid artery strips in organ baths with different concentrations of ethanol at 37 degrees C and during hyperthermia (39-43 degrees C) and scintigraphic cerebral imaging of a radioactive isotope in the control situation and during hyperthermia. RESULTS: Stepwise heating induced reproducible reversible graded contraction, proportional to temperature. At high concentrations (toxic levels), ethanol induced an increase in tension and heating potentiated these responses. Extracellular Mg(2+) potentiated both heat-induced contraction and ethanol-induced contraction while extracellular Ca(2+) had no effect on these responses. During hyperthermia and ethanol scintigraphic isotope uptake was reduced in cortical and cerebellar regions. CONCLUSIONS: Carotid artery vasomotor tone is temperature dependent and heating induces vasoconstriction. Alcohol (ethanol) at 37 degrees C elicited carotid artery contraction at high concentrations (toxic levels) but at any concentration during elevated temperature (39-43 degrees C). Ethanol potentiated the effect of hyperthermia-induced vasoconstriction and reduced cerebral perfusion as shown by radionuclide imaging. The synergistic effect of ethanol and hyperthermia may induce heat stroke and brain damage.

Impact of operator on determining functional parameters of nuclear medicine procedures.

OBJECTIVE: The study was designed to assess the significance of the interoperator variability in the estimation of functional parameters for four nuclear medicine procedures. MATERIALS AND METHODS: Three nuclear medicine technologists with varying years of experience processed the following randomly selected 20 cases with diverse functions of each study type: renography, renal cortical scans, myocardial perfusion gated single-photon emission computed tomography (MP-GSPECT) and gated blood pool ventriculography (GBPV). The technologists used the same standard processing routines and were blinded to the results of each other. The means of the values and the means of differences calculated case by case were statistically analyzed by one-way ANOVA. The values were further analyzed using Pearson correlation. RESULTS: The range of the mean values and standard deviation of relative renal function obtained by the three technologists were 50.65 +/- 3.9 to 50.92 +/- 4.4% for renography, 51.43 +/- 8.4 to 51.55 +/- 8.8% for renal cortical scans, 57.40 +/- 14.3 to 58.30 +/- 14.9% for left ventricular ejection fraction from MP-GSPECT and 54.80 +/- 12.8 to 55.10 +/- 13.1% for GBPV. The difference was not statistically significant, p > 0.9. The values showed a high correlation of more than 0.95. Calculated case by case, the mean of differences +/- SD was found to range from 0.42 +/- 0.36% in renal cortical scans to 1.35 +/- 0.87% in MP-GSPECT with a maximum difference of 4.00%. The difference was not statistically significant, p > 0.19. CONCLUSION: The estimated functional parameters were reproducible and operator independent as long as the standard processing instructions were followed.

Skeletal imaging of Gorlin's syndrome.

OBJECTIVE: To report a case of a patient with many of the common manifestations of Gorlin's syndrome, a rare inherited condition. CLINICAL PRESENTATION AND INTERVENTION: A 26-year-old female with longstanding left hip pain was referred for bone scintigraphy to find the cause of pain. The findings on bone scintigraphy as well as prior radiographic studies illustrated many of the defining features of Gorlin's syndrome, i.e. jaw keratocysts, falcine calcifications, short and deformed ribs, Sprengel deformity and a sclerotic bone lesion. The past medical history also revealed dermatologic, cardiac and gynecological findings related to the syndrome. CONCLUSION: Our case highlights the multisystemic involvement of Gorlin's syndrome, based particularly on the skeletal findings. Practicing physicians, including imaging specialists, should be familiar with these findings to reach the diagnosis.

The effect of intermittent pneumatic compression on the bone uptake of (99m)Tc-labelled methylene diphosphonate in the lower limb.

INTRODUCTION: Venous compression of the lower limbs will obstruct outflow through the deep and superficial veins, yet inflow will continue, without continual swelling of the limb. It is hypothesised that venous channels in the long bones act as collateral channels to restore outflow, and therefore general blood flow through bone will increase. Such a hemodynamic change should affect the uptake of radiopharmaceuticals by the bone, though uptake changes in themselves would not definitely indicate flow changes. The purpose of this study, therefore, was to determine whether bone uptake in the lower limb is affected by intermittent venous compression, irrespective of the mechanism involved. MATERIALS AND METHODS: The effect of intermittent pneumatic compression of the thigh and calf on the uptake of (99m)Tc-methylene diphosphonate (MDP) was studied in 24 patients. All were undergoing routine bone imaging for medical conditions that were not focused on their lower limbs, and received 1 h of the therapy at 60 mmHg on one limb only, after injection of the radiopharmaceutical. Three hours after injection the relative difference in uptake (net counts per pixel) between the two limbs was calculated. The standard imaging protocol was otherwise unchanged. RESULTS: The median differences in uptake in the intermittently compressed limb compared with the contralateral limb were +7.6% (interquartile range +3.9% to +16.0%, p<0.0005 [Wilcoxon]) for the anterior aspect of the femur; +11.7% (interquartile range +4.3% to +22.2%, p<0.0005) posterior, femur; +10.5% (interquartile range +6.5% to +13.8%, p<0.0005) anterior, tibia; +10.6% (interquartile range +5.5% to +17.6%, p<0.0005) posterior, tibia. CONCLUSION: Intermittent pneumatic compression clearly and significantly increased the uptake of (99m)Tc-MDP in long bones. These data are consistent with increases in blood flow through bone, though a direct mechanical influence on the bone cannot be excluded. This effect should be given consideration during routine therapeutic and thromboprophylactic use of intermittent compression, and if the mechanism of the uptake changes can be established, their possible clinical uses should be investigated.

Tc-99m DMSA renal scan in first-time versus recurrent urinary tract infection-yield and patterns of abnormalities.

PURPOSE: To determine the yield and patterns of abnormalities noted by Tc-99m DMSA renal imaging in cases of first-time versus recurrent urinary tract infections (UTIs) in children. MATERIALS AND METHODS: We reviewed 101 Tc-99m DMSA studies performed for 52 first-time and 49 recurrent UTIs in 99 children during a period of 1 year. The average age of the patients was 4.4 years, and the female:male ratio was 7:1. Static images of the kidneys were acquired 2 hours after injection of Tc-99m DMSA in anterior, posterior, and right and left posterior oblique views. SPECT was performed in 9% of the cases. The studies were scored as normal or abnormal. RESULTS: The yield of abnormal scans in first-time UTIs was 22 (42%) and in recurrent UTI 27 (55%). Three categories of abnormalities were noted: 1) renal cortical defects (55% of the abnormal scans in first-time UTIs and 59% of the abnormal scans in recurrent UTIs; P = 0.40); 2) dilated pelvicalyceal system (27% of the abnormal studies in first-time UTIs and 63% of the abnormal studies in recurrent UTIs; P < 0.01); and 3) renal swelling showing disproportionate function with size (41% of the abnormal scans in first-time UTIs and 22% of the abnormal scans in recurrent UTIs; P = 0.21). CONCLUSIONS: The high yield of renal abnormalities by Tc-99m DMSA scanning emphasizes the importance of testing all cases of UTI, including patients with a first-time infection. Documentation of the pattern of abnormalities may help in planning for subsequent management of UTIs in these patients.

Cyclic cystography: diagnostic yield in selected pediatric populations.

PURPOSE: To test the hypothesis that the diagnostic yield of cyclic cystography is related to the prevalence of vesicoureteral reflux (VUR) in the population being evaluated. MATERIALS AND METHODS: Two groups of children were examined prospectively: 124 with severe urinary tract infection, defined as patient hospitalization or a maximum temperature greater than 39.5 degrees C, and 135 with previously diagnosed VUR. Nuclear cystography was performed in 249 patients, and fluoroscopic cystography was performed in 10. If VUR was not seen during the first cycle of bladder filling and voiding, a second cycle was performed. RESULTS: VUR was present during cycle 1 in 40 (32%) of 124 patients with severe urinary tract infection and 90 (67%) of 135 children in the VUR follow-up group (P < .001). VUR was demonstrated during cycle 2 in seven (9%) of 76 of the severe urinary tract infection group and eight (24%) of 34 of the VUR follow-up group (P = .045). Of 15 patients with VUR during cycle 2, two had grade III VUR and 13 had grade I or II VUR. CONCLUSION: The second cycle of cyclic cystography has a higher diagnostic yield in patients undergoing VUR follow-up than in patients with severe urinary tract infection. The decision to perform a second cycle of bladder filling and voiding should take into account the pretest probability of VUR in the child being examined.

A new experimental model for partial ureteric obstruction in sheep.

This study aimed to develop a new experimental model of partial ureteric obstruction in sheep. Graded obstruction of the ureter using various sized catheters (Fr 3-8) for variable durations up to 6 weeks was performed in 19 sheep. The kidneys were studied by radionuclide diuretic renography for up to 21 weeks and had histopathological examination at the end of the experiment. Catheters of Fr 3 or Fr 5 should be used to block the ureter for a minimum of three weeks to produce sufficient functional and pathological changes to be studied. The advantages and disadvantages of this model are discussed.

Assessment of 99Tcm-tetrofosmin lung uptake: a modified method to avoid the contribution from high chest wall activity.

Evaluation of lung uptake during routine 99Tcm-tetrofosmin myocardial SPET (single photon emission tomography) studies may be hindered by substantial chest muscle uptake, particularly post-exercise. This study investigated this proposal and analysed the various components of chest activity that may add to the real lung uptake. Exercise SPET studies were performed on normal subjects using 99Tcm-tetrofosmin and compared with the results of 99Tcm-sestamibi and 201Tl studies. The chest to heart count ratio (CHR) was calculated from the anterior SPET projection and further subclassified into lung, anterior chest and posterior chest to heart ratios (LHR, AHR, PHR) from the left anterior oblique (LAO) projection. On post-exercise images, the 99Tcm-tetrofosmin CHR was significantly higher than that of 201Tl and 99Tcm-sestamibi. Both the 99Tcm-tetrofosmin AHR and PHR were higher than those of 201Tl and 99Tcm-sestamibi. However, the LHR was similar for all three radiopharmaceuticals. In contrast, the rest 99Tcm-tetrofosmin images differed little from the 201Tl and 99Tcm-sestamibi ones. Thus, 99Tcm-tetrofosmin lung uptake post-exercise should be interpreted with caution, as chest muscle uptake is higher than normal. A more accurate evaluation of 99Tcm-tetrofosmin lung uptake is achieved from the LAO projection, where the contribution from chest muscle counts is much less than in the routinely used anterior projection.

Imaging of infection: a correlative and algorithmic approach.

Detection and localization of infection can still be a dilemma for both clinicians and imaging specialists. The list of morphologic and physiologic modalities is increasing with the advancement of research, expanding the applications of existing modalities and developing new radiopharmaceuticals for infection imaging.Since no single modality is appropriate for all situations, imaging strategy for the diagnosis of infection in both soft tissue and bone should be tailored for individual patients according to the detailed clinical data including the history of underlying and previous disease processes and the site of suspected infection for proper and cost effective utilization of the different imaging modalities.