Comprehensive ventilation/perfusion SPECT.

Lung scintigraphy is the primary tool for diagnostics of pulmonary embolism. A perfusion study is often complemented by a ventilation study. Intermediate probability scans are frequent. Our goal was to develop a fast method for tomographic ventilation and perfusion scintigraphy to improve the diagnostic value of lung scintigraphy. METHODS: SPECT was performed with a dual-head gamma camera. Acquisition parameters were determined using a thorax phantom. Ventilation tomography after inhalation of 30 MBq (99m)Tc-diethylenetriaminepentaacetate (DTPA) aerosol was, without patient movement, followed by perfusion tomography after an intravenous injection of 100 MBq (99m)Tc-labeled macroaggregated albumin (MAA). Total SPECT acquisition time was 20 min. (99m)Tc-DTPA clearance, calculated from initial and final SPECT projections, was used for correction of the ventilation projection set before iterative reconstruction of ventilation and perfusion. The ventilation background was subtracted from the perfusion tomograms. A normalized ventilation/perfusion quotient (V/P quotient) image set was calculated. The method was evaluated on a trial group of 15 patients. RESULTS: Ventilation and perfusion images had adequate quality and showed ventilation/perfusion (V/Q quotient) relationships more clearly than did planar images. Frontal and sagittal slices were superior to planar scintigraphy for characterization of embolized areas. The V/Q quotient was supportive, particularly in the patients with chronic obstructive pulmonary disease. CONCLUSION: Fast, high-quality, ventilation/perfusion SPECT with standard isotopes doses is feasible and may contribute to higher objectivity in evaluating lung embolism as well as other lung diseases. The costs for the procedure and patient care until diagnosis are low because of the comprehensive system for the study and, particularly, the short time for its completion.     

Ventilation scintigraphy with lipophilic cationic compounds

OBJECTIVE: On the basis of our hypothesis that lipophilic cations may be more suitable for ventilation lung scintigraphy than the conventional technetium-99m diethylenetriamine penta-acetic acid (Tc-DTPA), comparative studies were carried out. BASIC METHODS: The nebulization potential of nine routine radiopharmaceuticals was compared on medical and scintigraphy-specific nebulizers. This was followed by ventilation scintigraphy in 14 patients with chronic obstructive airway disease (n=13) or pulmonary embolism (n=1) where either 99mTc-methoxyisobutylisonitrile (n=10) or Tc-tetrofosmin (n=4) was used. Same-patient comparison with 99mTc-DTPA ventilation scan was available in six patients using the same acquisition protocol. Comparison with 99mTc-DTPA was made with respect to the nebulization rates, radioactivity delivered per unit of radioactivity available for inhalation, and regional distribution of inhaled counts. RESULTS: Lipophilic cation solutions had a significantly higher nebulization rate compared with 99mTc-DTPA using the medical nebulizer (235%, P<0.01) and 370% on scintigraphy-specific nebulizer (P<0.01). More than three times the counts of 99mTc-methoxyisobutylisonitrile or 99mTc-tetrofosmin was deposited in the body compared with Tc-DTPA aerosol per megabecquerel activity inhaled (1.5 vs. 0.4 kcounts/MBq) (P<0.001), preferentially in the lungs (75.2 vs. 65.2%), at the expense of oropharynx and stomach. Within the lungs, about 50% more counts were deposited in the outer one-third lung with lipophilic cations. Overall, therefore, more than 12 times the radioactivity deposition was achieved in the peripheral one-third of the lungs with the lipophilic cations. CONCLUSION: Ventilation lung scanning with lipophilic cations is a viable substitute of nanoparticle scintigraphy (technegas and pertechnegas, which are expensive and technically far more demanding).     

Mismatch between99mTc-DTPA aerosol and81mKr lung ventilation scintigraphy: a pitfall of radionuclide imaging

Pulmonary ventilation and perfusion scintigraphies were performed using^99mTc-MAA,^81mKr, and^99mTc-DTPA aerosol in a patient with asthma. Lung perfusion scintigraphy and^99mTc-DTPA aerosol scintigraphy showed multiple matching defects, however,^81mKr ventilation scintigraphy showed mismatch with lung perfusion scintigraphy. A pitfall of this examination was discussed.     

Generation of parametric images during routine Tc-99m PYP inhalation/Tc-99m MAA perfusion lung scintigraphy. Technical note.

A simple technique is described for generating ventilation/perfusion ratio and perfusion/ventilation ratio images from the posterior Tc-99m PYP aerosol inhalation and Tc-99m MAA perfusion images obtained during routine lung scintigraphy. These images highlight areas of ventilation/perfusion incongruence--mismatch or reverse mismatch--that may sometimes be difficult to detect on conventional images.     

Clinical application of 133-Xe ventilation scintigraphy

Xenon-133 ventilation scintigraphy provides three sets of scintigrams: wash-in, equilibrium, and washout images. Krypton-81m or 99mTc-Technegas can be used as alternatives depending on their physical characteristics and the purpose of scintigraphy. Xenon-133 scintigraphy is compatible with SPECT when a multi-detector gamma camera is used. Ventilation images are analyzed by the height/area method to calculate regional lung volume and the mean transit time of the posterior planar view. If perfusion scintigraphy is done during the same examination, a ventilation/perfusion ratio image is also obtained. Factor analysis is applicable to the washout phase and permits a more detailed depiction of uneven ventilation. Series of consecutive SPECT during washout (dynamic SPECT) visualize ventilation in cross section and provide three-dimensional images of regional lung volume and poorly ventilated areas. A major indication for 133Xe scintigraphy is acute pulmonary thromboembolism (PTE) when used in combination with perfusion scintigraphy. The scintigraphic diagnosis of PTE is not inferior to that of contrast-enhanced helical CT, although the latter was initially reported to have higher sensitivity and specificity than scintigraphy. Other important indications are differentiation between primary pulmonary hypertension and chronic pulmonary thromboembolism, and the prediction of postoperative pulmonary function. Ongoing trials are attempting to create functional images of ventilation by CT or MRI, both of which may become rivals of scintigraphy because of their higher image resolution.     

Tracers for aerosol ventilation scintigraphy: Tc-99m versus In-113m

113mIn has been proposed as a suitable tracer for aerosol ventilation scintigraphy in combination with 99mTc pulmonary perfusion scintigraphy. The high energy (393 keV) of 113mIn allows it to be detected in the presence of 99mTc, but degrades the spatial resolution which can be achieved. We have compared the resolution obtained with 99mTc and 113mIn in phantom experiments and in aerosol ventilation scans in 14 patients with airways disease. The resolution at the distances from the collimator encountered in lung scintigraphy was 10-20 mm for 99mTc and 15-40 mm for 113mIn. Aerosol ventilation images were abnormal in all patients. The 99mTc images showed peripheral defects and frequently central hot spots reflecting increased local aerosol deposition. In the 113mIn images, the lower resolution had a smoothing effect, the central hot spots were less striking, and the distribution of activity appeared more uniform, some detail was lost in the periphery. It is suggested that 113mIn is useful for ventilation scintigraphy in the diagnosis of pulmonary embolism, but that 99mTc is the tracer of choice if aerosol ventilation scintigraphy is used to study airways disease.     

99mTc-alafosfalin: an antibiotic peptide infection imaging agent

The radiolabeled antibiotic peptide (99m)Tc-alafosfalin was assessed as an infection imaging agent in a rat model by comparison with (99m)Tc-DTPA and (99m)Tc-leukocytes. (99m)Tc-alafosfalin was prepared via an instant cold kit and (99m)Tc-leukocytes were prepared using (99m)Tc-stannous fluoride colloid in an ex vivo labeling procedure of whole blood. In separate experiments, the three radiotracers were administered to rats infected with staphylococcus aureus. Quantitative biodistribution studies were performed as well as scintigraphic images and histopathology. (99m)Tc-alafosfalin is a stable product, obtained in high radiochemical purity (>95%). This agent was mainly renally excreted, with low liver, spleen and bone uptake, and resulted in a mean ratio of infected/non-infected thighs of 4.3/1.0 at 4 hr post radiotracer injection. (99m)Tc-DTPA gave a corresponding ratio of 1.9/1.0 and (99m)Tc-leukocytes gave 20.0/1.0 at the same time point. An in vitro assay found the level of (99m)Tc-alafosfalin binding to staphylococcus aureas higher than (99m)Tc-DTPA (10% versus 1% respectively). (99m)Tc-alafosfalin accumulates at sites of infection in a rat model better than the perfusion molecule (99m)Tc-DTPA, yet less than (99m)Tc-leukocytes. The distribution characteristics of this (99m)Tc-antibiotic peptide would be an advantage in imaging abdominal and soft tissue infection.     

Lung ventilation/perfusion SPECT in the artificially embolized pig.

Planar lung scintigraphy is a standard method used for the diagnosis of lung embolism, but it is hampered by the high incidence of nondiagnostic tests. Ventilation/perfusion SPECT may possibly improve this situation. The objective of this study was to compare planar lung scintigraphy with ventilation/perfusion SPECT using pigs with artificially engendered lung emboli labeled with (201)Tl. METHODS: Sixteen anesthetized pigs were each injected with zero to 4 latex emboli. Cylindric emboli were used in the first 7 pigs and flat 3-tailed emboli were used in the remaining 9 pigs. The pigs spontaneously inhaled 30 MBq (99m)Tc-diethylenetriaminepentaacetic acid aerosol for ventilation scintigraphy. Planar scintigraphy and SPECT were performed using a double-head gamma camera in (99m)Tc and (201)Tl windows. Immediately thereafter, 100 MBq (99m)Tc-labeled macroaggregated albumin were injected intravenously followed by SPECT and, finally, planar scintigraphy. The ventilation background was subtracted from the perfusion tomograms for calculation of a normalized ventilation/perfusion (V/P) quotient image set. RESULTS: The cylindric emboli caused artifacts in the ventilation images; therefore, these were excluded from the final analysis. However, for the planar perfusion images of these pigs, sensitivity and specificity were 71% and 91%, respectively, whereas SPECT yielded 100% for both. For the 3-tailed emboli and ventilation/perfusion images, the sensitivity and specificity were 64% and 79%, respectively, for the planar modality, whereas SPECT yielded values of 91% and 87%, respectively. CONCLUSION: V/P SPECT may improve the diagnostic power of lung scintigraphy.     

A combined procedure for 99mTc aerosol ventilation and perfusion imaging

For several years, radioaerosols have been successfully used to provide detailed images of regional ventilation to aid in the differential diagnosis of pulmonary embolism. It has been widely advocated that the ventilation images should follow the perfusion scan and that the amount of aerosol deposited in the patient's lungs should be three times greater than the perfusion dose. We employed an alternative approach which avoided the deposition of an unpredictable amount of aerosol in individual patients. The aerosol study was performed first, and the activity of the microspheres used for the perfusion images was then tailored to the actual amount of aerosol which the patient had retained. This allowed a microsphere/aerosol activity ratio of 10:1 to be readily achieved, thus successfully masking the ventilation pattern by the perfusion activity. The faster biological clearance of ^99mTc-DTPA aerosol from the lung fields, as compared to ^99mTc-sulphur-colloid aerosol, allowed higher initial activities to be deposited in the lungs, thus enabling a high-resolution collimator to be used. When the perfusion study was delayed by 1 h (one effective half-life for the ^99mTc-DTPA aerosol), it was not necessary to increase the perfusion activity required to mask the ventilation image.     

Tracers for aerosol ventilation scintigraphy: Tc-99m versus In-113m

^113mIn has been proposed as a suitable tracer for aerosol ventilation scintigraphy in combination with ^99mTc pulmonary perfusion scintigraphy. The high energy (393 keV) of^113mIn allows it to be detected in the presence of ^99mTc, but degrades the spatial resolution which can be achieved. We have compared the resolution obtained with ^99mTc and ^113mIn in phantom experiments and in aerosol ventilation scans in 14 patients with airways disease. The resolution at the distances from the collimator encountered in lung scintigraphy was 10–20 mm for ^99mTc and 15–40 mm for ^113mIn. Aerosol ventilation images were abnormal in all patients. The ^99mTc images showed peripheral defects and frequently central hot spots reflecting increased local aerosol deposition. In the ^113mIn images, the lower resolution had a smoothing effect, the central hot spots were less striking, and the distribution of activity appeared more uniform, some detail was lost in the periphery. It is suggested that ^113mIn is useful for ventilation scintigraphy in the diagnosis of pulmonary embolism, but that ^99mTc is the tracer of choice if aerosol ventilation scintigraphy is used to study airways disease.     

Detection of bronchopleural fistula by ventilation scintigraphy. Based on one case

Bronchopleural fistula (BPF) is a rare but extremely serious complication of lung resection surgery. Its diagnosis is often overlooked in the clinical evolution of the patients undergoing surgery due to the subacute presentation of the picture. The procedures used to detect it are either invasive or have low accuracy. We report the case of a patient with lung carcinoma treated by left pneumonectomy in whom BPF was suspected after an episode of coughing and expectoration. The conventional chest x-ray did not show any significant findings while the (99m)Tc-DTPA ventilation lung scintigraphy demonstrated bronchopleural communication in a very early phase.     

Technetium-99m-<Emphasis Type="Italic">N,N</Emphasis>-ethylenedicysteine and Tc-99m DMSA scintigraphy in the evaluation of renal parenchymal abnormalities in children

Technetium-99m dimercaptosuccinic acid (Tc-99m DMSA) as a static renal agent is currently the most frequently used agent in the detection of renal scarring, and allows accurate calculation of differential renal function (DRF). But this agent has some disadvantages such as relatively higher radiation dose and time consumption. METHODS: The purpose of this study was to evaluate the potential of summed image that obtained from parenchymal phase of the dynamic technetium-99m-N,N-ethylenedicysteine (Tc-99m EC) scintigraphy in the detection of renal parenchymal defects and in the estimation of DRF, and to compare the results of this method with those of Tc-99m DMSA scintigraphy. The uptake ratios of the kidney to body background were also calculated for these two methods. Twenty-nine children with various renal disorders underwent both static Tc-99m DMSA and dynamic Tc-99m EC scintigraphy. The cortical analysis of Tc-99m EC scintigraphy was performed on the summed image obtained from dynamic images using the time interval between the first 45-120 sec. RESULTS: There was a very close correlation between these two methods with respect to DRF (r = 0.99). In the detection of renal parenchymal lesions, scintigraphy with Tc-99m DMSA detected more lesions, and the sensitivity and specificity of the summed Tc-99m EC images were calculated as 92.6% and 100%, respectively. In addition, the ratios of mean uptake values for Tc-99m DMSA and Tc-99m EC images were 7.59 +/- 2.17 and 2.95 +/- 0.91, respectively. This ratio of Tc-99m EC seems to be acceptable and allows good delineation of the kidneys. But, the main disadvantages of the summed Tc-99m EC images in comparison with static Tc-99m DMSA images are the use of only posterior projection that may be an important drawback in patients with abnormal kidney positions, lower image counts and higher pixel size because of dynamic acquisition. CONCLUSION: These results show that summed Tc-99m EC images with an acceptable high image contrast provide an accurate DRF calculation in patients without abnormal kidney positions and allow the detection of most renal parenchymal abnormalities. However, Tc-99m DMSA scintigraphy remains the gold standard method because of its well known advantages.     

A simple method for preparing radioactive capsules in colon transit study

Colon transit study is currently performed by delivering technetium-99m or indium-111 labelled activated charcoal to the colon in a methacrylate-coated capsule (coated capsule). However, the coating procedure is complicated and methacrylate has not been approved by the Food and Drug Administration. Therefore, a simpler method is needed for the clinical routine use of colon transit study. In this study, we used a commercial empty enteric capsule and a coated capsule for the measurement of colon transit time. We compared the in vitro stability and in vivo scintigraphy of ^99mTc-labelled activated charcoal in the coated capsule and the enteric capsule to evaluate the possibility of clinical usage of the enteric capsule for colon transit time study. Activated charcoal powder was mixed with ^99mTc-diethylene triamine penta-acetic acid (DTPA) and vaporized to dryness. The dry ^99mTc-DTPA activated charcoal was loaded into the coated capsule and the enteric capsule. In vitro stability study was performed by immersing these capsules in a colourless buffer of variable pH which mimicked the conditions in the stomach and the small bowel. Capsule disruption was determined. Colon transit scintigraphy with ^99mTc-DTPA charcoal was performed in five normal volunteers using these two capsules. The in vitro stability of these two types of capsule was similar and the colon transit scintigraphy findings were almost identical. Most capsules dissolved in the ascending colon and very few in the terminal ileum. It is concluded that enteric capsule is a suitable alternative to coated capsule for measurement of colon transit. Received 14 December 1999 and in revised form 14 March 2000     

Role of technetium-99m N,N-ethylenedicysteine renal scintigraphy in the evaluation of differential renal function and cortical defects

PURPOSE: This study was performed to evaluate the effectiveness of technetium-99m N,N-ethylenedicysteine (Tc-99m EC) in comparison to technetium-99m dimercaptosuccinic acid (Tc-99m DMSA) scintigraphy. Differential renal function (DRF) was calculated by both methods and the cortical-phase images of dynamic Tc-99m EC scintigraphy were evaluated for parenchymal defects. MATERIALS AND METHODS: A total of 62 patients with various kidney disorders ranging in age from 1 to 44 years underwent both Tc-99m DMSA and Tc-99m EC scintigraphy. Tc-99m EC summed images of the cortical phase and Tc-99m DMSA images were evaluated visually and quantitatively. Visual analysis was used to define renal parenchymal abnormalities. Quantitative analysis was used in the calculation of DRF. The Tc-99m DMSA scan was taken as the gold standard, and the summed Tc-99m EC scan findings were compared against it. RESULTS: The images obtained with Tc-99m DMSA and Tc-99m EC scintigraphy revealed 99 and 97 focal defects, respectively. The 2 renal parenchyma defects located in the ventral middle sections remained undetected with Tc-99m EC scintigraphy. DRF of the kidneys in each patient was compared using both radiopharmaceuticals. Highly positive correlation between the differential function of these 2 investigations was found (R = 0.91, P = 0.001). The values of mean DRF of the left kidney on Tc-99m EC and Tc-99m DMSA images were 45.8 +/- 19.1 and 45.0 +/- 20.4, respectively. There were no significant differences (P > 0.05). CONCLUSION: This study suggests that although Tc-99m DMSA scintigraphy remains the gold standard method for evaluating parenchymal abnormalities, Tc-99m EC scintigraphy can be a reliable single-modality study to evaluate renal cortical defects, DRF, perfusion, drainage of the urinary system, and indirect evidence of vesicoureteric reflux with the added advantage of low radiation exposure to the patient.     

Evaluation of hepatic function with (99m)Tc-galactosylated serum albumin scintigraphy in patients with malaria: comparison with (99m)Tc-colloid scintigraphy and liver ultrasonography

OBJECTIVE: Malarial parasites injected by the mosquito rapidly target hepatocytes, and hepatomegaly is commonly observed during the progress of the disease in malaria patients. To evaluate the degree of hepatic damage and functional status of hepatocytes in malaria patients, we performed liver scintigraphy using (99m)Tc-galactosylated serum albumin (GSA) prospectively and the findings were compared with those of (99m)Tc-colloid scintigraphy, ultrasonography and clinical results in the same subject. METHODS: Eight malaria patients (all male, mean age 22 years) confirmed to be infected with Plasmodium vivax underwent (99m)Tc-GSA liver scintigraphy, followed by liver ultrasonography and (99m)Tc-colloid scintigraphy using phytate within 3 days. For hepatocyte scintigraphy, anterior images of cardiac blood-pool and liver were continuously acquired for 30 min after injection of 185 MBq (99m)Tc-GSA (3 mg). In addition to visual interpretation of the images, quantitative measurement of hepatic function was performed with several functional parameters, such as hepatic uptake index (LHL15), blood clearance index (HH15) and modified receptor index (LHL/HH) calculated from the radioactivity of the liver and heart. (99m)Tc-colloid images were assessed and graded visually. Severity of hepatic dysfunction or reticuloendothelial system activation was classified as normal, mild, moderate and severe on GSA or colloid images. RESULTS: Hepatomegaly was observed in five and splenomegaly in seven of the eight patients. Serum levels of transaminase and alkaline phosphatase were mildly elevated in two. Visual assessment of GSA scintigraphy revealed normal findings in all subjects, except for mild increases in size. The mean values of LHL15, HH15 and LHL/HH were 0.928+/-0.014, 0.537+/-0.031 and 1.732+/-0.106, respectively. They were graded as normal in five, and near-normal to mild dysfunction in three subjects. In contrast, (99m)Tc-colloid scintigraphy revealed abnormal findings in all of the subjects, and graded as moderate in three or severe reticuloendothelial system activation in five subjects. Liver ultrasonographic findings were normal for all subjects except mild hepatomegaly. CONCLUSIONS: Malaria-induced injury of the hepatocyte is likely to be minimal whereas hepatomegaly is commonly seen during disease process. This suggests that hepatic damage in malarial infection is mainly due to involvement of the reticuloendothelial system. (99m)Tc-GSA scintigraphy can be used in differentiating hepatocellular damage from reticuloendothelial system involvement in patients with infectious disease showing hepatomegaly.     

继发性甲状旁腺功能亢进的99Tcm-MIBI双时相显像

目的评价９９Ｔｃｍ甲氧基异丁基异腈（ＭＩＢＩ）双时相显像法在肾性继发性甲状旁腺功能亢进（ＳＨＰ）患者中的诊断价值。方法２０例因慢性肾功能衰竭行血液透析患者,临床诊断为ＳＨＰ,均行双时相法９９ＴｃｍＭＩＢＩ甲状旁腺显像。运用甲状旁腺／甲状腺（ＰＴ／Ｔ）比值及甲状旁腺指数（ＰＴＩ）观察阳性病灶对ＭＩＢＩ的清除。３例行颈部探查术并作甲状旁腺自体移植。结果８例显像阳性,其中３例手术摘除９枚甲状旁腺,均经病理证实为增生。９９ＴｃｍＭＩＢＩ显像发现其中的８枚,其灵敏度为８８９％。在透析年限长、甲状旁腺素分泌高的患者中,有更高的阳性率。发现有３种ＭＩＢＩ清除类型。结论９９ＴｃｍＭＩＢＩ双时相显像在ＳＨＰ患者中有较高的定位诊断价值。阅片时应考虑病灶清除ＭＩＢＩ的多样性,以免漏诊     

16-Detector multislice CT in the detection of stress fractures: a comparison with skeletal scintigraphy

AIMS: To test the hypothesis that the improved resolution afforded by 16-detector computed tomography (CT) would translate to better stress fracture detection when compared with skeletal scintigraphy. MATERIALS AND METHODS: Thirty-three cases of suspected stress fractures in 26 patients were investigated using skeletal scintigraphy and 16-detector CT performed on the same day. Planar images of the lower limbs were taken 3h post-injection of 400MBq (99m)Tc-methylene diphosphonate ((99m)Tc-MDP). (99m)Tc-MDP uptake was quantified at suspected fracture sites. CT was performed using a 16-detector multisection machine employing 0.75mm detectors and images reconstructed in 0.5mm increments. Examinations were reported independently and discordant results were compared at follow-up. RESULTS: At initial reporting scintigraphy identified fractures in 13 of the 33 cases and CT identified four of the 33. In one case, on review of the CT images, a fracture was present in the distal fibula that was not initially identified. This resulted in eight scintigraphic-positive CT-negative discordant cases. The (99m)Tc-MDP uptake was significantly lower in the discordant fracture group compared with the concordant group (p<0.01). CONCLUSIONS: Despite technological advances in CT, scintigraphy appeared to detect more stress fractures. As such, multidetector CT should not be used as a routine initial investigation in stress fracture detection. The potential use of (99m)Tc-MDP quantification at fracture sites is of interest and may be worth further investigation.     

Scintigraphic evaluation of pulmonary embolism after total hip replacement, using a dry 99mTc-microaerosol for regional ventilation

A new 99mTc-microaerosol was used for ventilation scintigraphy in combination with perfusion scintigraphy for studying the incidence of pulmonary embolism (PE) from 189 consecutive investigations in patients undergoing total hip replacement. Diagnostic criteria are presented. Perfusion defects of triangular shape were significantly more frequent in combination with ventilation mismatch (PE) than with ventilation match (not PE) (P less than 0.001). Reevaluation of the scintigrams more than 2 months later gave identical results in more than 90% of patients and as regards the diagnosis of PE, in 93%. Attacks of sudden chest pain were more frequent in patients with pulmonary embolism (P less than 0.01), but measurement of arterial blood gases did not discriminate between patients with and without PE. The 99mTc-microaerosol provides a high resolution and images that are directly comparable to perfusion studies using the same, easily available isotope. In many aspects this new microaerosol seems to be superior to previously described radioaerosols and to 133Xe for ventilation studies.     

Imaging of disease activity in Graves' orbitopathy with different methods: comparison of (99m)Tc-DTPA and (99m)Tc-depreotide single photon emission tomography, magnetic resonance imaging and clinical activity scores

BACKGROUND: The immunosuppressive treatment of Graves' orbitopathy (GO) influences the course of the disease in the early, active, retrobulbar inflammatory phase (active GO), which cannot be detected by direct clinical examination. AIM: To evaluate the clinical effectiveness of a newly developed method for the detection of intraorbital inflammatory activity in patients suffering from Graves' orbitopathy, utilizing a four-headed single photon emission tomograph (SPET) camera and (99m)Tc-diethylenetriamine pentaacetic acid (Tc-DTPA). METHODS: The magnetic resonance imaging (MRI) T2 relaxation time score, as a measure of ongoing orbital inflammation (reference method), was compared with the uptake activities (UA) of (99m)Tc-DTPA orbital SPET and the more specific (99m)Tc-Neospect ((99m)Tc-depreotide) SPET, as well as the clinical activity scores (CAS), in 21 patients (42 orbits). RESULTS: By visual inspection, the 'eye SPET' frames of patients suffering from active GO could be easily distinguished from those with inactive GO. Although the distributions of the two radiopharmaceuticals were mildly different, the information obtained was essentially the same. The MRI activity scores correlated well with both (99m)Tc-DTPA and Tc-depreotide UA. The mean (99m)Tc-DTPA UA value of 25 inactive GO orbits was (6.55 +/- 1.4) x 10(-6) ID x cm3 (where ID is the injected dose); the values of the active GO orbits (12 orbits with an MRI score of 1 and five orbits with an MRI score of 2) were significantly higher: (8.87 +/- 1.63) x 10(-6) and (10.36 +/- 1.60) x 10(-6) ID x cm3, respectively. Similar differences were observed for the (99m)Tc-depreotide UA values: the averages in the inactive and active groups with MRI scores of 1 and 2 were (5.23 +/- 1.23) x 10(-6), (7.69+/-2.24) x 10 and (10.92 +/- 3.85) x 10(-6) ID x cm3, respectively. The (99m)Tc-DTPA accumulation pattern in the orbital region of active GO patients was similar to that of the more specific (99m)Tc-depreotide. There was a good correlation (r = 0.71, P<0.001) between the UA values of the two radiopharmaceuticals, but CAS did not correlate with either of the UA values. CONCLUSIONS: (99m)Tc-DTPA eye SPET is a potentially useful method, allowing rapid imaging at an acceptable cost. It provides essential supplementary information to traditional CAS in assessing disease activity in Graves' orbitopathy.