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DOI: 10.1148/radiol.2211001047
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(Radiology. 2001;221:201-206.)
© RSNA, 2001

Nuclear Medicine

Thymic Lesions in Patients with Myasthenia Gravis: Characterization with Thallium 201 Scintigraphy1

Takahiro Higuchi, MD, Junichi Taki, MD, Seigo Kinuya, MD, Masahito Yamada, MD, Michio Kawasuji, MD, Osamu Matsui, MD, Akitaka Nonomura, MD, Hisashi Bunko, MD and Norihisa Tonami, MD

1 From the Departments of Nuclear Medicine (T.H., J.T., S.K., H.B., N.T.), Neurology (M.Y.), First Surgery (M.K.), Radiology (O.M.), and Pathology (A.N.), Kanazawa University School of Medicine, Takaramachi 13-1, Kanazawa, Ishikawa, Japan. Received June 5, 2000; revision requested July 28; final revision received April 3, 2001; accepted April 9. Address correspondence to T.H. (e-mail: higuchi@med.kanazawa-u.ac.jp).


   ABSTRACT
TOP
 ABSTRACT
INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 REFERENCES
 
PURPOSE: To assess thallium 201 (201Tl) single photon emission computed tomography (SPECT) for evaluation of thymic lesions associated with myasthenia gravis (MG), including lymphoid follicular hyperplasia (LFH) and thymoma.

MATERIALS AND METHODS: 201Tl SPECT and computed tomography (CT) were performed preoperatively in 46 patients with MG who had undergone thymectomy. SPECT was conducted 15 (early image) and 180 (delayed image) minutes after 201Tl injection. Results were visually assessed, and 201Tl uptake ratios (thymic lesion count density/lung count density) were measured for quantitative analysis. Uptake was analyzed among the normal thymus, LFH, and thymoma patient groups.

RESULTS: Histopathologic results indicated a normal thymus, LFH, and thymoma in 19, 16, and 11 patients, respectively. Mean uptake ratios in the normal thymus, LFH, and thymoma were 0.96 (95% CI: 0.90, 1.03), 1.14 (95% CI: 1.04, 1.25), and 1.87 (95% CI: 1.56, 2.25), respectively, on early images and 1.09 (95% CI: 1.00, 1.18), 1.65 (95% CI: 1.48, 1.85), and 2.03 (95% CI: 1.65, 2.50), respectively, on delayed images. Thymoma showed more intense 201Tl accumulation than did the normal thymus (P < .001) and LFH (P < .001) on early images. Both thymoma (P < .001) and LFH (P < .001) displayed more intense uptake than did the normal thymus on delayed images.

CONCLUSION: 201Tl SPECT can enable differentiation between normal thymus, LFH, and thymoma in patients with MG.

Index terms: Mediastinum, radionuclide studies, 675.12162 • Myasthenia gravis • Thallium, radioactive • Thymus, CT, 675.1211 • Thymus, neoplasms, 675.3154, 675.3155, 675.3169 • Thymus, radionuclide studies, 675.12162


   INTRODUCTION
TOP
 ABSTRACT
 INTRODUCTION
MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 REFERENCES
 
Myasthenia gravis (MG) is a disease associated with impaired neuromuscular transmission and is characterized clinically by exercise-induced increasing fatigue, which is caused by an antibody-mediated autoimmune response against nicotinic acetylcholine receptors (1). Most patients with MG demonstrate thymic abnormalities, including thymic lymphoid follicular hyperplasia (LFH) and thymoma (2). The pathogenesis of MG, including the role of the thymus and the factors that initiate and maintain the autoimmune response, is not fully understood; however, the thymus is thought to play a critical role (3).

Thymectomy has been attempted in a large number of patients with MG. The procedure is recognized as an effective treatment for sustaining improvement of symptoms and preventing invasiveness and metastatic spread of thymoma (4). Currently, thymectomy is used when medical treatment of patients is not successful or when thymoma is suspected. The factors that determine the response to thymectomy in patients with MG have been investigated in several reports (5–8). The authors concluded that the pathologic findings of the thymus might be important predictors of clinical outcome. Namely, LFH has been associated with the highest rate of clinical remission following thymectomy. Therefore, the preoperative evaluation of thymic status is important in planning the therapeutic strategy.

Moreover, minimally invasive surgical approaches, including transcervical incision and video-assisted thoracoscopic surgery, have been under investigation (9,10). These methods are not recommended in cases of thymoma because of the risk of incomplete resection that is attributable to technical difficulties and a limited field of vision (6,9). Currently, preoperative evaluation of the thymus associated with MG is performed with computed tomography (CT). However, CT has demonstrated insufficient results—for example, LFH does not always show an enlarged thymus, which may be overlooked at CT (11–15).

Thallium 201 (201Tl) uptake is considered to reflect various factors, including cellular metabolic activity, regional blood flow, and the number of viable cells in the lesion (16–19). Therefore, we hypothesized that, as a functional imaging technique, 201Tl single photon emission CT (SPECT) may be effective in the evaluation of thymic lesions associated with MG. The purpose of our study was to assess the usefulness of 201Tl SPECT in the evaluation of thymic lesions associated with MG, including LFH and thymoma.


   MATERIALS AND METHODS
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
RESULTS
 DISCUSSION
 REFERENCES
 
Forty-six consecutive patients with a diagnosis of MG who had undergone thymectomy were examined in this study. Diagnosis of MG was confirmed on the basis of clinical, pharmacologic, electrophysiologic, and immunologic criteria (4). All patients with a confirmed diagnosis of MG underwent thymectomy. Exceptions included patients with conditions restricted to ocular involvement (grade 1) or patients older than 80 years. Thoracic 201Tl SPECT and CT were performed before thymectomy. In addition, postoperative histopathologic findings were available in all patients. Our institutional review board approved this study.

Early and delayed 201Tl SPECT was performed 15 and 180 minutes, respectively, after 201Tl chloride (111 MBq) injection. A triple-detector gamma camera system (9300A; Toshiba Medical, Tokyo, Japan) equipped with low-energy, high-spatial-resolution, parallel-hole collimators was used. Data were acquired from 60 projections (40 seconds per projection) over 360° by using 64 x 64 matrices. Filtered-back projection with ramp filters and Butterworth filters with an order of 8 and cutoff frequencies of 0.31 cycles per centimeter was performed for reconstruction. All patients were instructed to relax while in the chair for at least 10 minutes before 201Tl injection; moreover, exercise was prohibited until after delayed imaging. The patients’ arms were positioned upward during image acquisition.

201Tl uptake in the thymic lesion was evaluated on the early and delayed 201Tl images both visually and quantitatively with knowledge that the patients had MG. At visual analysis, two observers (T.H., J.T.) independently evaluated the degree of radionuclide uptake in the thymic lesion by using the following five-point uptake scoring system, with no information on the CT findings: 0, uptake equal to background activity within the lung; 1, slight increase in uptake; 2, moderate increase in uptake; 3, strong increase in uptake; and 4, uptake greater than heart uptake. When uptake scores differed between the observers, a third observer (S.K.) was consulted and differences were resolved with consensus.

At quantitative analysis, two authors (T.H., J.T.) in consensus manually drew regions of interest (ROIs) on the entire area of uptake in the thymic lesion or thymus on the transverse sections that demonstrated the highest 201Tl uptake (Fig 1). To set ROIs, the CT images were referenced to determine the location and size of the thymic lesions. The background ROI was set on the entire right lung depicted on a 201Tl section identical to the SPECT section that showed the thymic lesion (Fig 1). The count densities of the ROIs were measured. The uptake ratio was then calculated by dividing the count density of the thymic lesion by the count density of the background.



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  		Figure 1. Example of ROI setting for calculating 201Tl uptake ratio. Transverse 201Tl scintigram on which ROIs are placed on the entire right lung (A) and on the entire area of uptake in the thymic lesion (B). 201Tl uptake in the muscles (arrowheads) is seen at the posterolateral margin of the thorax.

 
Preoperative thoracic CT examinations were performed in all patients by using a scanning unit (9800 HiLight Advantage; GE Medical Systems, Milwaukee, Wis). Transverse scans of 10-mm thickness were obtained from above the pulmonary apex to the diaphragm during breath holding at deep inspiration. Contrast material was not used. CT results were interpreted as normal when no abnormalities were detected. Age-related changes were considered in the interpretations. A CT-based diagnosis of LFH was made when diffuse lobulated enlargement of the thymus was present; a diagnosis of thymoma was made when a focal mass in the anterior mediastinum was observed. Evaluations were performed by one of the authors (O.M.).

Histopathologic examination of specimens obtained at surgery was conducted by one of the authors (A.N.), who was blinded to 201Tl SPECT and CT results. Samples were defined as thymoma, LFH, or normal thymus.

Differences in age, 201Tl uptake ratio, change in 201Tl uptake ratio between early and delayed imaging, and 201Tl uptake score were statistically analyzed among the three histopathologic groups: normal thymus, LFH, and thymoma. The association between age and 201Tl uptake was assessed by using the Pearson correlation test.

For multiple-group comparisons of age and 201Tl uptake ratio, homogeneity of variance was assessed by using the Bartlett test. In addition, parametric comparisons were performed with one-way analysis of variance. The significance of individual differences was evaluated by using the Scheffé F test in cases in which one-way analysis of variance results were significantly different. Changes in 201Tl uptake ratio on early and delayed images were assessed by performing repeated-measures analysis of the histopathologic findings. Moreover, changes in the 201Tl uptake ratio in the individual histopathologic groups were assessed by using the paired t test. Comparisons of 201Tl uptake scores were evaluated by using the Kruskal-Wallis H test, followed by the Dunn test for multiple comparisons, because the 201Tl uptake score was assumed to be rank ordered. P values less than .05 were considered to indicate statistically significant differences.

Normally distributed data were expressed as means plus or minus the SD. Data that were not normally distributed were logarithmically transformed to improve normality before statistical analysis was performed. Data were expressed as the mean with a 95% CI, which was calculated in logarithmic scale and back transformed to the original units.


   RESULTS
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
DISCUSSION
 REFERENCES
 
The patient population consisted of 16 men and 30 women (mean age ± SD, 47.6 years ± 13.3; age range, 22–72 years). Histopathologic examinations following thymectomy revealed a normal thymus, LFH, and thymoma in 19, 16, and 11 patients, respectively. The mean ages of patients in the three groups were 48.2 years ± 9.6, 40.3 years ± 15.2, and 57.3 years ± 9.7, respectively. The groups differed (Scheffé F = 6.7, df = 2, P = .003) in that the patients with LFH were younger than those with thymoma (P = .003). However, the ages of the healthy patients were not significantly different from those of either the patients with thymoma (P = .16) or those with LFH (P = .14). Moreover, Pearson correlation coefficients, which were used to assess the relation between age and 201Tl uptake score, were -0.22 and -0.15 for patients with a normal thymus at early and delayed imaging, respectively. Therefore, we believe that this distinction possibly did not affect the diagnostic usefulness of 201Tl SPECT in the present study.

The results of visual analysis of the 201Tl SPECT images are summarized in Table 1. Meaningful differences in 201Tl uptake scores were observed on early images ({chi}2 = 34, df = 3, P < .001). The patients with LFH (Fig 2) and a normal thymus did not show significant differences at SPECT; however, those with thymoma (Fig 3) had elevated scores compared with those of the other two groups (P < .01). There were also significant differences in 201Tl uptake scores at delayed SPECT ({chi}2 = 30.5, df = 3, P < .001). The uptake scores of the patients with LFH and thymoma were not markedly different; however, compared with the other two groups, the normal thymus group had lower scores (P < .01).


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  		TABLE 1. Relationship between Histopathologic Findings and 201Tl Uptake Score

 


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  		Figure 2a. LFH in a 56-year-old woman with MG. (a) Nonenhanced transverse CT scan shows no apparent enlargement of the thymus (arrow). (b) Early transverse 201Tl scintigram shows no increased 201Tl uptake in the lesion (uptake ratio, 1.2). (c) Delayed transverse 201Tl scintigram shows intense accumulation (arrow) in the anterior part of the mediastinum (uptake ratio, 1.5).

 


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  		Figure 2b. LFH in a 56-year-old woman with MG. (a) Nonenhanced transverse CT scan shows no apparent enlargement of the thymus (arrow). (b) Early transverse 201Tl scintigram shows no increased 201Tl uptake in the lesion (uptake ratio, 1.2). (c) Delayed transverse 201Tl scintigram shows intense accumulation (arrow) in the anterior part of the mediastinum (uptake ratio, 1.5).

 


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  		Figure 2c. LFH in a 56-year-old woman with MG. (a) Nonenhanced transverse CT scan shows no apparent enlargement of the thymus (arrow). (b) Early transverse 201Tl scintigram shows no increased 201Tl uptake in the lesion (uptake ratio, 1.2). (c) Delayed transverse 201Tl scintigram shows intense accumulation (arrow) in the anterior part of the mediastinum (uptake ratio, 1.5).

 


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  		Figure 3a. Thymoma in a 68-year-old man with MG. (a) Nonenhanced transverse CT scan demonstrates a focal mass (arrow) in the anterior part of the mediastinum. Both the (b) early (uptake ratio, 1.8) and (c) delayed (uptake ratio, 1.5) 201Tl transverse SPECT images show remarkable uptake in the tumor (arrow).

 


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  		Figure 3b. Thymoma in a 68-year-old man with MG. (a) Nonenhanced transverse CT scan demonstrates a focal mass (arrow) in the anterior part of the mediastinum. Both the (b) early (uptake ratio, 1.8) and (c) delayed (uptake ratio, 1.5) 201Tl transverse SPECT images show remarkable uptake in the tumor (arrow).

 


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  		Figure 3c. Thymoma in a 68-year-old man with MG. (a) Nonenhanced transverse CT scan demonstrates a focal mass (arrow) in the anterior part of the mediastinum. Both the (b) early (uptake ratio, 1.8) and (c) delayed (uptake ratio, 1.5) 201Tl transverse SPECT images show remarkable uptake in the tumor (arrow).

 
The mean uptake ratios on early images of the normal thymus, LFH, and thymoma were 0.96 (95% CI: 0.90, 1.03), 1.14 (95% CI: 1.04, 1.25), and 1.87 (95% CI: 1.56, 2.25), respectively; the corresponding values on delayed images were 1.09 (95% CI: 1.00, 1.18), 1.65 (95% CI: 1.48, 1.85), and 2.03 (95% CI: 1.65, 2.50), respectively. The early 201Tl uptake ratio in patients with thymoma differed significantly (Scheffé F = 39.1, df = 2, P < .001): These values were higher than those in patients with a normal thymus (P < .001) and in those with LFH (P < .001); however, there were no significant differences in uptake ratios between the LFH and normal thymus patient groups (P = .21). On delayed images, uptake ratios were significantly different (Scheffé F = 22.3, df = 2, P < .001). The values in patients with thymoma were higher than those in patients with LFH (P = .035); moreover, the values in the thymoma (P < .001) and LFH (P < .001) groups were higher than those in the normal thymus group.

There were significant differences in changes in 201Tl uptake ratio among the groups (Scheffé F = 10.4, df = 2, P < .001). Increases in uptake ratio from early to delayed image were significant in the LFH (P < .001) and normal thymus groups (P = .025) (Fig 4). No meaningful changes (P = .508) were observed in the thymoma group.



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  		Figure 4. Graph illustrates early (Ea) and delayed (De) 201Tl uptake ratios in each patient. On early images, thymoma demonstrated a significantly higher 201Tl uptake ratio than did LFH and the normal thymus. On delayed images, however, both LFH and thymoma showed higher 201Tl uptake ratios than did the normal thymus. The error bars indicate the ranges of 95% CIs.

 
Three of the 19 patients with a histopathologically normal thymus received a diagnosis of LFH at CT. CT enabled the correct diagnosis in only five of the 16 patients with LFH. Moreover, two patients with LFH were considered to have thymoma at CT. A focal thymic mass was depicted at CT in 11 of 11 patients with thymoma (Table 2).


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  		TABLE 2. Thallium 201 SPECT (Quantitative and Visual Analyses) versus CT in the Differential Diagnosis of the Thymus

 
The usefulness of 201Tl SPECT in differentiating thymic lesions was assessed by using quantitative and visual analyses. Receiver operating curve analysis was performed to determine the cutoff uptake ratio and uptake score points that yielded maximum sensitivity, specificity, and accuracy. At quantitative analysis, the lesions that demonstrated early and delayed uptake ratios of less than 1.5 and less than 1.4, respectively, were considered normal; the lesions with early and delayed uptake ratios of less than 1.5 and greater than or equal to 1.4, respectively, were considered to be LFH (Figs 2, 4); and the lesions with an early uptake ratio of greater than or equal to 1.5 in association with any delayed ratio were considered to be thymoma (Figs 3, 4).

At visual analysis, the lesions with a score of 0 for both early and delayed images were considered normal. Lesions with an early image score of 0 and a delayed image score higher than 1 were considered to be LFH. Lesions with an early image score higher than 1 were considered to be thymoma. The numbers of patients with a diagnosis of LFH and thymoma according to these image criteria are presented in Table 2.

With 201Tl SPECT, accurate diagnoses were obtained in 40 (87%) and 36 (78%) of 46 patients by using quantitative analysis and visual uptake scores, respectively. In contrast, accurate diagnoses were obtained with CT in 32 (70%) of 46 patients. The differing proportions of accurate diagnoses achieved by using 201Tl uptake ratio and CT were evaluated by performing the Fisher exact test. 201Tl uptake ratio was more accurate than CT in enabling the detection of LFH (13 vs five of 16 patients; P = .006). Moreover, no significant difference in thymoma detection was observed between the two modalities (nine vs 11 of 11 patients; P = .23).


   DISCUSSION
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
REFERENCES
 
201Tl scintigraphy has been used to detect a variety of tumors; moreover, an increased 201Tl uptake in thymic neoplasms, such as benign and malignant thymomas, has been demonstrated in several studies (19–22). However, to our knowledge, no data regarding the usefulness of this modality in assessing the histopathologic thymic abnormalities associated with MG exist.

According to the results of this study, thymoma should be considered when increased 201Tl uptake is detected on both early and delayed images, whereas LFH should be suspected when more intense uptake is observed on the delayed image relative to that on the early image. Detection of LFH with 201Tl SPECT was superior to that with CT in this study. In addition, our study results were superior to those obtained in previous investigations (11–15) involving CT. LFH diagnosis is based on microscopic findings of thymic germinal centers; furthermore, LFH associated with MG occasionally does not manifest actual macroscopic enlargement (13,15). This observation may account for the poor detection of LFH with CT in our study.

Visual analysis of 201Tl SPECT findings revealed that CT had similar sensitivity in the detection of thymoma. However, CT may have some advantages over 201Tl SPECT in the detection of small tumors or in the assessment of tumor shape or precise tumor location owing to its higher spatial resolution. In contrast, the limitation of CT in depicting thymoma is due to difficulty in differentiating thymoma from LFH on the basis of lesion shape. Moreover, LFH may appear as a focal mass at CT and consequently be incorrectly diagnosed as thymoma (12). Two such cases of LFH occurred in this study.

The mechanism of 201Tl uptake is not clearly understood. Factors that possibly influence 201Tl uptake include blood flow, cell viability, number of cells in the lesion, tumor type, Na+-K+ ATPase, calcium ion channel, and vascular permeability (16–18, 23,24). Thymoma has higher vascularity and greater blood flow; therefore, rapid delivery of 201Tl is promoted and may result in greater 201Tl uptake by thymoma lesions on early images. In LFH, 201Tl accumulates mainly on the delayed image. LFH vascularity is usually lower than that of thymoma. LFH, however, exhibits lymphoid follicles that consist of packed small cell nests displaying higher cellular activity. This occurrence may be a reason for the 201Tl accumulation mainly on the delayed image in LFH.

In the current study, neither thin-section CT nor contrast material administration was performed. However, in a previous investigation (11), contrast enhancement did not provide additional information in the differential diagnosis of thymic lesions in patients with MG. The advantage of thin-section CT is that it enables the observation of lesion details; however, its effectiveness to enable the diagnosis of LFH in MG is unknown.

Magnetic resonance (MR) imaging was not performed in our study patients. To our knowledge, there are few reports regarding the MR imaging evaluation of thymic hyperplasia in patients with MG. However, Batra et al (13), in a series of 16 patients with MG, examined the correlation between CT and MR imaging of thymic lesions associated with MG and concluded that MR examination of the thymus added no clinically important information to the CT results.

Uptake of indium 111 (111In) octreotide, a somatostatin receptor imaging agent, was reportedly substantial in thymoma but not in LFH; this finding indicated the capability of this agent to enable differentiation of thymoma from LFH (25). However, 111In octreotide cannot enable the differentiation of LFH from a normal thymus, because it does not accumulate in either LFH or the normal thymus.

In several reports (26–28), thymic lesions have been evaluated with 2-[fluorine-18]fluoro-2-deoxy-D-glucose (FDG) positron emission tomography (PET). Conclusions indicate that FDG may be helpful in evaluating the malignant nature of mediastinal tumors. In addition, FDG has an advantage over 201Tl with respect to quantification of uptake (29). However, FDG PET is not available in most medical centers. Moreover, to our knowledge, the evaluation of thymic lesions associated with MG by using FDG PET has not yet been investigated.

Visual and quantitative evaluations of 201Tl accumulation were performed in the current study. Although visual analysis for the detection of LFH was superior to that of CT, quantification of 201Tl uptake allowed more accurate diagnoses. Therefore, we recommend calculating the 201Tl uptake ratio in each case, in addition to performing visual evaluation for assessment of the thymus in MG. The entire lung on a 201Tl SPECT section was used as a reference ROI in the quantitative evaluation, because the ROI setting on the entire lung was readily obtained and reproducible on the identical SPECT section of the thymic lesion. In the current investigation, no patients presented with symptoms of pulmonary disease or heart failure, which may cause 201Tl uptake in the lung (30) and thereby result in an underestimation of the uptake ratio. Determining the reference ROI for calculation of the uptake ratio requires particular caution in such cases.

In summary, accumulation of 201Tl on early and delayed SPECT images reflects the histopathologic findings of thymic lesions associated with MG. In our patient population, the normal thymus showed no increase in 201Tl uptake on either early and delayed images, whereas LFH exhibited moderate 201Tl uptake on only delayed images. Moreover, thymoma displayed significant (moderate to strong) 201Tl uptake on early and delayed images. 201Tl SPECT had greater sensitivity for the diagnosis of LFH than did CT. The results of this study may justify routine use of this scintigraphic method as a preoperative examination in patients with MG. Further prospective evaluation of this method with large patient populations is warranted.


   FOOTNOTES
 
Abbreviations: FDG = 2-[fluorine-18]fluoro-2-deoxy-D-glucose, LFH = lymphoid follicular hyperplasia, MG = myasthenia gravis, ROI = region of interest

Author contributions: Guarantor of integrity of entire study, N.T.; study concepts and design, J.T., T.H.; literature research, T.H.; clinical studies, A.N., M.Y., M.K.; data acquisition, T.H., N.T.; data analysis/interpretation, T.H., J.T., S.K., O.M.; statistical analysis, T.H.; manuscript preparation, T.H.; manuscript definition of intellectual content, J.T., S.K., T.H.; manuscript editing, T.H., J.T., S.K.; manuscript revision/review, J.T., H.B., M.Y.; manuscript final version approval, all authors.


   REFERENCES
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 REFERENCES
 

  1. Lindstrom J, Shelton D, Fujii Y. Myasthenia gravis. Adv Immunol 1988; 42:233-284.[Medline]
  2. Wekerle H, Muller-Hermelink HK. The thymus in myasthenia gravis. Curr Top Pathol 1986; 75:179-206.[Medline]
  3. Marx A, Wilisch A, Schultz A, Gattenlohner S, Nenninger R, Muller-Hermelink HK. Pathogenesis of myasthenia gravis. Virchows Arch 1997; 430:355-364.[CrossRef][Medline]
  4. Drachman DB. Myasthenia gravis. N Engl J Med 1994; 330:1797-1810.[Free Full Text]
  5. Nieto IP, Robledo JP, Pajuelo MC, et al. Prognostic factors for myasthenia gravis treated by thymectomy: review of 61 cases. Ann Thorac Surg 1999; 67:1568-1571.[Abstract/Free Full Text]
  6. O’Riordan JI, Miller DH, Mottershead JP, Pattison C, Hirsch NP, Howard RS. Thymectomy: its role in the management of myasthenia gravis. Eur J Neurol 1998; 5:203-209.[CrossRef][Medline]
  7. Mulder DG, Graves M, Herrmann C. Thymectomy for myasthenia gravis: recent observations and comparisons with past experience. Ann Thorac Surg 1989; 48:551-555.[Abstract]
  8. Alpert LI, Papatestas AE, Kark AE, Osserman RS, Osserman K. A histologic reappraisal of the thymus in myasthenia gravis: a correlative study of thymic pathology and response to thymectomy. Arch Pathol 1971; 91:55-61.[Medline]
  9. Calhoun RF, Ritter JH, Guthrie TJ, et al. Results of transcervical thymectomy for myasthenia gravis in 100 consecutive patients. Ann Surg 1999; 230:555-559.[CrossRef][Medline]
  10. Scelsi R, Ferro MT, Scelsi L, et al. Detection and morphology of thymic remnants after video-assisted thoracoscopic extended thymectomy (VATET) in patients with myasthenia gravis. Int Surg 1996; 81:14-17.[Medline]
  11. Nicolaou S, Muller NL, Li DK, Oger JJ. Thymus in myasthenia gravis: comparison of CT and pathologic findings and clinical outcome after thymectomy. Radiology 1996; 201:471-474.[Abstract/Free Full Text]
  12. Hale DA, Cohen AJ, Schaefer P, et al. Computerized tomography in the evaluation of myasthenia gravis. South Med J 1990; 83:414-416.[Medline]
  13. Batra P, Herrmann C, Jr, Mulder D. Mediastinal imaging in myasthenia gravis: correlation of chest radiography, CT, MR, and surgical findings. AJR Am J Roentgenol 1987; 148:515-519.[Abstract/Free Full Text]
  14. Thorvinger B, Lyttkens K, Samuelsson L. Computed tomography of the thymus gland in myasthenia gravis. Acta Radiol 1987; 28:399-401.[Medline]
  15. Brown LR, Muhm JR, Sheedy PF, Unni KK, Bernatz PE, Hermann RC, Jr. The value of computed tomography in myasthenia gravis. AJR Am J Roentgenol 1983; 140:31-35.[Free Full Text]
  16. Taki J, Sumiya H, Tsuchiya H, Tomita K, Nonomura A, Tomami N. Evaluating benign and malignant bone and soft tissue lesions with technetium-99m-MIBI scintigraphy. J Nucl Med 1997; 38:501-506.[Abstract/Free Full Text]
  17. Elgazzar AH, Fernandez-Ulloa M, Silberstein EB. 201Tl as a tumour-localizing agent: current status and future considerations. Nucl Med Commun 1993; 14:96-103.[Medline]
  18. Waxman AD. Thallium-201 in nuclear oncology In: Nuclear medicine annual. New York, NY: Raven, 1991; 193-209.
  19. Maticke GJ, Sokol JA, Jozwiak J, Ruisi JA. Detection of thymoma by SPECT thallium imaging. J Nucl Cardiol 1998; 5:449-450.[CrossRef][Medline]
  20. Ohta H, Taniguchi T, Watanabe H, Komibuchi T, Nakade M, Kohno K. Tl-201 and Tc-99m HMPAO SPECT in a patient with recurrent thymoma. Clin Nucl Med 1996; 21:902-903.[CrossRef][Medline]
  21. Adalet I, Kocak M, Ece T, Yilmazbayhan D, Cantez S. Tc-99m MIBI and TI-201 uptake in a benign thymoma. Clin Nucl Med 1995; 20:733-734.[CrossRef][Medline]
  22. Tonami N, Yokoyama K, Nonomura A, et al. Intense accumulation of Tl-201 in carcinoid tumor of the thymus. Clin Nucl Med 1994; 19:408-412.[CrossRef][Medline]
  23. Caluser C, Macapinlac H, Healey J, et al. The relationship between thallium uptake, blood flow, and blood pool activity in bone and soft tissue tumors. Clin Nucl Med 1992; 17:565-572.[CrossRef][Medline]
  24. Sehweil AM, McKillop JH, Milroy R, Wilson R, Abdel-Dayem HM, Omar YT. Mechanism of 201Tl uptake in tumours. Eur J Nucl Med 1989; 15:376-379.[CrossRef][Medline]
  25. Lastoria S, Vergara E, Palmieri G, et al. In vivo detection of malignant thymic masses by indium-111-DTPA-D-Phe1-octreotide scintigraphy. J Nucl Med 1998; 39:634-639.[Abstract/Free Full Text]
  26. Sasaki M, Kuwabara Y, Ichiya Y, et al. Differential diagnosis of thymic tumors using a combination of 11C-methionine PET and FDG PET. J Nucl Med 1999; 40:1595-1601.[Abstract/Free Full Text]
  27. Kubota K, Yamada S, Kondo T, et al. PET imaging of primary mediastinal tumors. Br J Cancer 1996; 73:882-886.[Medline]
  28. Liu RS, Yeh SH, Huang MH, et al. Use of fluorine-18 fluorodeoxyglucose positron emission tomography in the detection of thymoma: a preliminary report. Eur J Nucl Med 1995; 22:1402-1407.[CrossRef][Medline]
  29. Sadato N, Tsuchida T, Nakaumra S, et al. Non-invasive estimation of the net influx constant using the standardized uptake value for quantification of FDG uptake of tumours. Eur J Nucl Med 1998; 25:559-564.[CrossRef][Medline]
  30. Martinez EE, Horowitz SF, Castello HJ, et al. Lung and myocardial thallium-201 kinetics in resting patients with congestive heart failure: correlation with pulmonary capillary wedge pressure. Am Heart J 1992; 123:427-432.[CrossRef][Medline]



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