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Depiction of celiac ganglia on positron emission tomography and computed tomography in patients with lung cancer
Clinical Imaging 38 (2014) 292–295
Contents lists available at ScienceDirect
Clinical Imaging journal homepage: http://www.clinicalimaging.org
Depiction of celiac ganglia on positron emission tomography and computed tomography in patients with lung cancer Seyed Mahdi Abtahi ⁎, Azadeh Elmi, Sandeep S. Hedgire, Yuen Chi Ho, Sarvenaz Pourjabbar, Sarabjeet Singh, Mannudeep Kalra, Mukesh Harisinghani Department of Radiology, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts, USA
a r t i c l e
i n f o
Article history: Received 18 September 2013 Received in revised form 19 December 2013 Accepted 26 December 2013 Keywords: Celiac ganglia PET-CT CT Postmortem MDCT Lung cancer
a b s t r a c t Objective: To differentiate imaging characteristics of celiac ganglia from metastatic lesion on positron emission tomography–computed tomography (PET-CT) in patients with lung cancer and correlate these findings to postmortem multidetector row computed tomography (MDCT). Methods: One hundred twentynine patients were included. Imaging characteristics and fluorodeoxyglucose (FDG) avidity of the celiac ganglia were recorded. Postmortem MDCT of 20 subjects were reviewed. Results: Celiac ganglia were identified unilaterally in 127 and bilaterally in 108 patients without abnormal FDG uptake. Postmortem images showed celiac ganglia in all cases with no significant difference compared to our patients. Conclusions: Familiarity with CT characteristics and FDG-avidity of celiac ganglia enable us to distinguish them from metastatic lesions in their vicinity. © 2014 Elsevier Inc. All rights reserved.
1. Introduction The celiac plexus, the largest of autonomic fiber plexuses, is located at the level of the upper part of the L1 and is composed of two large ganglia, the celiac ganglia, and a dense network of nerve fibers uniting them together. As described in anatomic studies, the celiac ganglia have nodular morphology similar to lymph nodes and are located one on either side of the midsagittal line anterior to the crura of the diaphragm [1]. The number of ganglia varies from 1 to 5 and reported size ranges from 5 to 45 mm [2]. Celiac ganglia are routinely visualized on cross sectional imaging modalities and on multidetector row computed tomography (MDCT) both the left and right celiac ganglia are identified at the level between the origins of celiac and superior mesenteric arteries, anterior to the crura of the diaphragm. The ability to reliably identify celiac ganglia by CT facilitates invasive procedure like celiac ganglia block and prevent misidentification of celiac ganglion for lymph nodes [3]. Because of similar soft tissue density and morphology, a large celiac ganglion may be easily mistaken for metastatic lymph nodes or retroperitoneal metastatic tumor deposits or metastatic adrenal nodule, thereby affecting patient management [4,5]. However, there are very few published studies highlighting the difference between celiac
⁎ Corresponding author. Massachusetts General Hospital, Division of Abdominal Imaging and Interventional Radiology, 55 Fruit St., White 270, Boston, MA 02114. Tel.: + 1 617 726 8380. E-mail address: [email protected] (S.M. Abtahi). 0899-7071/$ – see front matter © 2014 Elsevier Inc. All rights reserved. http://dx.doi.org/10.1016/j.clinimag.2013.12.017
ganglion and metastatic cancers lesions which is critical for prognosis of malignancies and planning for future interventional procedures. Lung cancer as the most fatal and second most common cancer in US has a high incidence of adrenal metastasis and may also lead to abdominal lymph node metastasis [6,7]. Because of similarity in location, density, and appearance distinguishing celiac ganglia from metastatic lesions could be challenging and critical for management in patients with primary lung cancer. In this study in order to better characterize celiac ganglia and distinguish them from any metastatic lesions in its vicinity, we assessed the depiction of celiac ganglia on positron emission tomography-computed tomography (PET-CT) with [ 18F]-fluorodeoxyglucose ( 18FDG) in patients with history of lung cancer. We also correlated these finding to postmortem high dose MDCT scans performed in unrelated subjects. 2. Material and methods Institutional review board approval was obtained for this HIPAAcompliant retrospective study. The correlated postmortem CTs were also performed under an institutional review board study. A total of 129 consecutive patients with lung cancer (70 women and 59 men; mean age, 66.0 years) who underwent PET-CT for staging of tumors from January 2005 to May 2010 at our institution were included. As outlined above, patients with lung cancer were chosen as adrenal metastases and/or upper abdominal lymph nodes metastases can occur in these patients so distinguishing normal celiac ganglia structure from these metastatic lesions could be challenging in some cases. Follow-up MDCT scans until 30 May 2012 for restaging
S.M. Abtahi et al. / Clinical Imaging 38 (2014) 292–295
of tumor were also obtained to evaluate the changes in the structures during the follow-up. Those patients with no follow-up CT scans 3 months after the initial study were excluded from study. To better demonstrate the characteristic of celiac ganglia, we also studied 20 postmortem high-dose MDCT scans in unrelated cases and correlated the findings to CT findings in the lung cancer patients. 2.1. PET-CT scans All PET-CT scans were performed with 64-slice multidetector row PET scanner (LightSpeed, General Electric, Milwaukee, WI, USA) using the following protocol. 18FDG was injected according to patient’s body weight. Multiplanar PET images were obtained 60 minutes after injection. Non-contrast CT with 5 mm slice thickness was also obtained. A 100-ml bolus of iohexol (Omnipaque 300; NycomedAmersham, Princeton, NJ, USA) was given at 2 ml/s and post-contrast CT with 2.5 mm slice thickness of skull base to pelvis were also obtained after 60 seconds delay. Follow-up MDCT scans for restaging of tumor were also retrieved until 30 May 2012. The scans were performed after a 100-ml bolus of iohexol at 2 ml/s, and 2.5-mm-slice-thickness scans of thorax to pelvis were also obtained with 64-slice multidetector row CT scanner (LightSpeed, General Electric, Milwaukee, WI) after 60 seconds delay. 2.2. Postmortem CT scan All unenhanced postmortem CT examinations were performed within 12 hours of death on a second generation 64 channel dual source CT scanner (Somatom Definition Flash, Siemens HealthCare, Forchheim, Germany) at two- to threefold higher radiation dose than routine abdomen CT (mean CT dose index of 26.7±4.9 mGy; range, 20–32) with slice thickness of 5 mm and 5-mm increment. 2.3. Image interpretation The images were reviewed on a picture archiving communication system workstation (Impax; Agfa, Mortsel, Belgium) by an expert
293
radiologist with over 10 years of experience. The frequency of visualization, location, morphologic features, size, enhancement pattern, and FDG avidity of the celiac ganglia were recorded. The location of celiac ganglia was recorded according to the relationship to left adrenal, abdominal aorta, and vertebral level. The bidimensional size of the celiac ganglia was measured in the axial plane. The density was measured by putting a region of interest (ROI). The circular ROI was drawn covering the maximum portion of the ganglia, excluding the edges. The ROIs were placed on two consecutive slices and the average was recorded. The FDG avidity of celiac ganglia was also recorded. On follow-up CT scans, any morphologic change in the celiac ganglia was recorded. 3. Results Structures consistent with celiac ganglia were identified in 127 cases (98%). The celiac ganglia were observed bilaterally in 108 patients (91% of total patients). The left celiac ganglion was visualized slightly more often than the right ganglion; however, the difference was not significant (P= .74). They appeared as discoid or lobulated structures, with smooth margin (in 68.3% of patients) ranging in short axis from 2 to 22 mm (mean, 7.1 mm) and long axis from 6.9 to 35.3 mm (mean, 19.4 mm). Location of most of these ganglia was at the level of T12-L1 between the adrenal gland and diaphragmatic crura adjacent to the abdominal aorta; two celiac ganglia were found at the level of L2. The distance from aorta was 1–15.3 mm (mean 4.5 mm) and from ipsilateral adrenal gland was 0–13.2 mm (mean 2.9 mm) (Fig. 1). On non-contrast scans, the ganglia appeared hypodense with illdemarcated margin. There was a substantial increase in mean Hounsfield units (HU) in all of the cases on enhanced CT (11 vs. 68, P= .004). There was no evidence of abnormal FDG uptake in the celiac ganglia on PET scans. During follow-up (mean: 20.1 months; range 1.47–73.07 months) the ganglia did not change in size in 123 patients (95% of cases). Celiac ganglia could not be identified in 6 cases on follow up CT (mean follow up 38.9 months; range 26.67-67 months). This was due to the progression of adrenal metastasis in 3
Fig. 1. A 55-year-old male with lung cancer. Axial CT images (A, B) show smooth bilateral celiac ganglia (arrows) in pre- (A) and post-contrast images (B). There is no FDG avidity in the region of ganglia (yellow circles) (C). Follow-up CT after 26 months shows no change in size (D).
294
S.M. Abtahi et al. / Clinical Imaging 38 (2014) 292–295
Fig. 2. A 69-year-old male with lung cancer. Axial images (A,B) shows bilateral celiac ganglia (solid arrows) on CT scan, left celiac ganglia is adjacent to paraortic lymph node (dotted arrow). Lymph node shows increase in FDG avidity (black circle) (C). On follow-up CT scan, the lymph node is seen engulfing the left celiac ganglion (D).
cases, surrounded and obscured by paraaortic lymph nodes in 3 cases (Fig. 2). In the postmortem subjects, celiac ganglia were identified in all 20 cases and were found bilaterally in 19 cases (95% of all cadavers) at the level of T12-L1 vertebrae (Fig. 3). In 10 cases (50%) the margin of ganglia was smooth and in the other 10 cases the wall was lobulated which had no significant differences when compared to the primary lung cancer patient cohort (P=.192). The size ranged from 3 to 9 mm (mean 6.3 mm) in short axis to 7–23 mm (mean 17.3 mm) for long axis with no significant difference to the primary patient cohort (P= .138 for long axis and P= .905 for short axis). The mean distance from abdominal aorta was 5.4 mm (P= .201) and from ipsilateral adrenal gland was 3.4 mm (P=.355). Mean HU in cadaver shows significant difference with pre-contrast HU in lung cancer patients (25 vs. 11, P= .001) (Table 1). 4. Discussion Because of segmental embryonic origin of celiac ganglia, any small lesions in its vicinity could represent non-fused components of the
celiac ganglion and not necessarily enlarged lymph nodes or other pathological processes such as metastasis. As the morphology and tissue density may be similar for these structures it would be helpful to differentiate these structures based on FDG avidity. This fact would highlight the importance of identifying celiac ganglia on PET-CT to differentiate it from metastatic lesion to the adjacent lymph nodes or adrenal glands in patients with history of malignancy which to the best of our knowledge has not been reported. In this study we evaluated PET-CT scans in patients diagnosed with lung cancer and identified celiac ganglion bilaterally in most of the cases based on typical morphological features. The finding is consistent with description of celiac ganglion in anatomic studies [3]. With improved imaging technology, the spatial resolution of PET scan is now improved and generally considered to be around 6 mm [8]. Furthermore, PET detection and resolution are also dependent on the difference of tracer levels between pathological process and background. It is likely that small structures with metabolically active disease can be shown up against background low activity. Our results demonstrated no FDG avidity in celiac ganglia. We believed that the lack of abnormal FDG uptake in the normal celiac ganglia on PET scans allows robust distinction of these structures from metastatic lesions.
Table 1 Patients’ characteristics
Fig. 3. Lobulated celiac ganglia on axial postmortem MDCT (solid arrow).
Celiac ganglia
Patients (N=129)
Cadaver (N=20)⁎
P
Visualized at CT (%) Margin Smooth (%) Lobulated (%) Dimensions Long axis Short axis Distance from Aorta Same side adrenal HU Pre-contrast Post-contrast
127 (98)
19 (95)
.306
88 (68.3) 41 (31.7)
10 (50) 10 (50)
.192
19.4 (6.9−35.3) 7.1 (2−22)
17.3 (7−23) 6.3 (3−9)
.138 .905
4.5 (1−15.3) 2.9 (0−13.2)
5.4 (1−14) 3.4 (0−9)
.201 .355
11 (−1 to 35) 68 (21−122)
25 (12–44) N/A
.001
HU: Hounsfield unit. ⁎ Separate group of subjects.
S.M. Abtahi et al. / Clinical Imaging 38 (2014) 292–295
Also demonstration of stability during follow-up (mean: 20.1 months) may aid in distinguishing the ganglia from metastatic deposits. This fact would be valid finding that any change or lack of visibility in celiac ganglia could be due to the pathological process in its vicinity. In our study the most common reason for not identifying the normal celiac ganglia were presence of adrenal metastasis or masking of the ganglia by the enlarged paraaortic lymph nodes. The left celiac ganglia are consistently seen anteromedial to the left adrenal gland, and the right celiac ganglia are frequently seen between inferior vena cava and right diaphragmatic crura which is consistent with our postmortem study. We identified the right celiac ganglia more frequently than was previously described, probably attributed to the increased awareness of characteristic morphology, location and improved cross sectional imaging modalities [3]. We found the right celiac ganglia more difficult to identify compared with the left counterpart, likely related to the tiny anatomical space with little intervening retroperitoneal fat. In our experience, we found that it is useful to find the left ganglia first, and then look at corresponding level at the right side for a structure with similar morphology and tissue density. As the celiac ganglia is a conglomeration of two to three ganglia together giving rise to lobulated border on the other hand lymph nodes are often oval, although this may not always help in differentiating these two. The enhancement of the celiac ganglia is substantial and slightly heterogeneous and this probably reflects its intrinsic composition of neuronal and nerve fiber tissues. It serves as a useful distinguishing feature from metastatic lymph nodes, which are typically hypodense with necrotic areas. The left celiac ganglia could also easily be differentiated from the diseased left adrenal gland based on such tissue heterogeneity. To validate our findings we correlated our measurements to postmortem MDCT. One of the reasons to include high dose CT in post mortem CT was to see if visibility of celiac ganglia is impaired at lower dose clinical CT exams. Celiac ganglia were better visualized due to higher dose of exposure. The tissue attenuation was significantly higher on postmortem CT when compared with the pre-contrast CT scans of our cohort of patients which could be due to the intravascular coagulation in the cadaver. Other postmortem findings like dimension, margin and distance from aorta and adrenal did not show significant difference with our measurements in cancer patients. This correlative study confirmed the imaging features of the celiac ganglia and would contribute to better characterization of these structures. The main limitation of our study was lack of pathology confirmation for structures identified as celiac ganglion which was
295
ethically not possible. The lack of pathological correlation is attributable to the fact that these patients did not undergo surgery/ biopsy of these lesions (due to lack of FDG avidity on PET CT). However, our findings have close correlation with the postmortem study. Another limitation of our study was comparing cadaver MDCT scan with MDCT in patients with lung cancer, scanning normal subjects for comparative purposes is not ethically possible. Also, all of our patients had lung cancer in whom the appearance of lymph nodes may be different in patients with other malignancies. Further studies on different group of patients are needed to confirm our findings. As our results showed there is no significant difference in characteristics of celiac ganglia between the routine MDCT scan and high dose post mortem imaging. This may imply the importance of routine MDCT in visualizing and evaluating celiac ganglia. However an experienced radiologist interpreted the images there might be some bias in our results. 5. Conclusion Familiarity with CT scan characteristics and FDG avidity of celiac ganglia allow proper identification of them. It helps in distinguishing these normal structures from other pathologic lesions such as metastasis to adrenal or enlarged adjacent lymph node thereby aiding in appropriate clinical management. References [1] Gray H, Lewis WHWH. Anatomy of the human body/Henry Gray. [electronic resource]/Bartleby.com ed ed: Bartleby.com; 2000. [2] Ward EM, Rorie DK, Nauss LA, Bahn RC. The celiac ganglia in man: normal anatomic variations. Anesth Analg 1979;58:461–5. [3] Wang ZJ, Webb EM, Westphalen AC, Coakley FV, Yeh BM. Multi-detector row computed tomographic appearance of celiac ganglia. J Comput Assist Tomogr 2010;34:343–7. [4] Gerke H, Silva RG, Shamoun D, Johnson CJ, Jensen CS. EUS characteristics of celiac ganglia with cytologic and histologic confirmation. Gastrointest Endosc 2006;64: 35–9. [5] Ha TI, Kim GH, Kang DH, Song GA, Kim S, Lee JW. Detection of celiac ganglia with radial scanning endoscopic ultrasonography. Korean J Intern Med 2008;23:5–8. [6] Centers for Disease Control and Prevention (CDC). Invasive cancer incidence — United States, 2009. MMWR Morb Mortal Wkly Rep 2013;62:113–8. [7] Izquierdo-Vidal C, Fau - Molins L, Molins L Fau, Boada M, Boada M Fau, Cladellas E, Cladellas E Fau, Gomez-Caro A, Gomez-Caro A Fau, Gimferrer JM, Gimferrer JM. Surgical treatment of solitary adrenal metastases in patients with lung cancer. Med Clin (Barc) 2013;140(9):406–8. http://dx.doi.org/10.1016/j.medcli. 2012.11.029 [LID - S0025-7753(12)00982-7 [pii] LID -]. [8] Stickel JR, Cherry SR. High-resolution PET detector design: modelling components of intrinsic spatial resolution. Phys Med Biol 2005;50:179–95.
Contents lists available at ScienceDirect
Clinical Imaging journal homepage: http://www.clinicalimaging.org
Depiction of celiac ganglia on positron emission tomography and computed tomography in patients with lung cancer Seyed Mahdi Abtahi ⁎, Azadeh Elmi, Sandeep S. Hedgire, Yuen Chi Ho, Sarvenaz Pourjabbar, Sarabjeet Singh, Mannudeep Kalra, Mukesh Harisinghani Department of Radiology, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts, USA
a r t i c l e
i n f o
Article history: Received 18 September 2013 Received in revised form 19 December 2013 Accepted 26 December 2013 Keywords: Celiac ganglia PET-CT CT Postmortem MDCT Lung cancer
a b s t r a c t Objective: To differentiate imaging characteristics of celiac ganglia from metastatic lesion on positron emission tomography–computed tomography (PET-CT) in patients with lung cancer and correlate these findings to postmortem multidetector row computed tomography (MDCT). Methods: One hundred twentynine patients were included. Imaging characteristics and fluorodeoxyglucose (FDG) avidity of the celiac ganglia were recorded. Postmortem MDCT of 20 subjects were reviewed. Results: Celiac ganglia were identified unilaterally in 127 and bilaterally in 108 patients without abnormal FDG uptake. Postmortem images showed celiac ganglia in all cases with no significant difference compared to our patients. Conclusions: Familiarity with CT characteristics and FDG-avidity of celiac ganglia enable us to distinguish them from metastatic lesions in their vicinity. © 2014 Elsevier Inc. All rights reserved.
1. Introduction The celiac plexus, the largest of autonomic fiber plexuses, is located at the level of the upper part of the L1 and is composed of two large ganglia, the celiac ganglia, and a dense network of nerve fibers uniting them together. As described in anatomic studies, the celiac ganglia have nodular morphology similar to lymph nodes and are located one on either side of the midsagittal line anterior to the crura of the diaphragm [1]. The number of ganglia varies from 1 to 5 and reported size ranges from 5 to 45 mm [2]. Celiac ganglia are routinely visualized on cross sectional imaging modalities and on multidetector row computed tomography (MDCT) both the left and right celiac ganglia are identified at the level between the origins of celiac and superior mesenteric arteries, anterior to the crura of the diaphragm. The ability to reliably identify celiac ganglia by CT facilitates invasive procedure like celiac ganglia block and prevent misidentification of celiac ganglion for lymph nodes [3]. Because of similar soft tissue density and morphology, a large celiac ganglion may be easily mistaken for metastatic lymph nodes or retroperitoneal metastatic tumor deposits or metastatic adrenal nodule, thereby affecting patient management [4,5]. However, there are very few published studies highlighting the difference between celiac
⁎ Corresponding author. Massachusetts General Hospital, Division of Abdominal Imaging and Interventional Radiology, 55 Fruit St., White 270, Boston, MA 02114. Tel.: + 1 617 726 8380. E-mail address: [email protected] (S.M. Abtahi). 0899-7071/$ – see front matter © 2014 Elsevier Inc. All rights reserved. http://dx.doi.org/10.1016/j.clinimag.2013.12.017
ganglion and metastatic cancers lesions which is critical for prognosis of malignancies and planning for future interventional procedures. Lung cancer as the most fatal and second most common cancer in US has a high incidence of adrenal metastasis and may also lead to abdominal lymph node metastasis [6,7]. Because of similarity in location, density, and appearance distinguishing celiac ganglia from metastatic lesions could be challenging and critical for management in patients with primary lung cancer. In this study in order to better characterize celiac ganglia and distinguish them from any metastatic lesions in its vicinity, we assessed the depiction of celiac ganglia on positron emission tomography-computed tomography (PET-CT) with [ 18F]-fluorodeoxyglucose ( 18FDG) in patients with history of lung cancer. We also correlated these finding to postmortem high dose MDCT scans performed in unrelated subjects. 2. Material and methods Institutional review board approval was obtained for this HIPAAcompliant retrospective study. The correlated postmortem CTs were also performed under an institutional review board study. A total of 129 consecutive patients with lung cancer (70 women and 59 men; mean age, 66.0 years) who underwent PET-CT for staging of tumors from January 2005 to May 2010 at our institution were included. As outlined above, patients with lung cancer were chosen as adrenal metastases and/or upper abdominal lymph nodes metastases can occur in these patients so distinguishing normal celiac ganglia structure from these metastatic lesions could be challenging in some cases. Follow-up MDCT scans until 30 May 2012 for restaging
S.M. Abtahi et al. / Clinical Imaging 38 (2014) 292–295
of tumor were also obtained to evaluate the changes in the structures during the follow-up. Those patients with no follow-up CT scans 3 months after the initial study were excluded from study. To better demonstrate the characteristic of celiac ganglia, we also studied 20 postmortem high-dose MDCT scans in unrelated cases and correlated the findings to CT findings in the lung cancer patients. 2.1. PET-CT scans All PET-CT scans were performed with 64-slice multidetector row PET scanner (LightSpeed, General Electric, Milwaukee, WI, USA) using the following protocol. 18FDG was injected according to patient’s body weight. Multiplanar PET images were obtained 60 minutes after injection. Non-contrast CT with 5 mm slice thickness was also obtained. A 100-ml bolus of iohexol (Omnipaque 300; NycomedAmersham, Princeton, NJ, USA) was given at 2 ml/s and post-contrast CT with 2.5 mm slice thickness of skull base to pelvis were also obtained after 60 seconds delay. Follow-up MDCT scans for restaging of tumor were also retrieved until 30 May 2012. The scans were performed after a 100-ml bolus of iohexol at 2 ml/s, and 2.5-mm-slice-thickness scans of thorax to pelvis were also obtained with 64-slice multidetector row CT scanner (LightSpeed, General Electric, Milwaukee, WI) after 60 seconds delay. 2.2. Postmortem CT scan All unenhanced postmortem CT examinations were performed within 12 hours of death on a second generation 64 channel dual source CT scanner (Somatom Definition Flash, Siemens HealthCare, Forchheim, Germany) at two- to threefold higher radiation dose than routine abdomen CT (mean CT dose index of 26.7±4.9 mGy; range, 20–32) with slice thickness of 5 mm and 5-mm increment. 2.3. Image interpretation The images were reviewed on a picture archiving communication system workstation (Impax; Agfa, Mortsel, Belgium) by an expert
293
radiologist with over 10 years of experience. The frequency of visualization, location, morphologic features, size, enhancement pattern, and FDG avidity of the celiac ganglia were recorded. The location of celiac ganglia was recorded according to the relationship to left adrenal, abdominal aorta, and vertebral level. The bidimensional size of the celiac ganglia was measured in the axial plane. The density was measured by putting a region of interest (ROI). The circular ROI was drawn covering the maximum portion of the ganglia, excluding the edges. The ROIs were placed on two consecutive slices and the average was recorded. The FDG avidity of celiac ganglia was also recorded. On follow-up CT scans, any morphologic change in the celiac ganglia was recorded. 3. Results Structures consistent with celiac ganglia were identified in 127 cases (98%). The celiac ganglia were observed bilaterally in 108 patients (91% of total patients). The left celiac ganglion was visualized slightly more often than the right ganglion; however, the difference was not significant (P= .74). They appeared as discoid or lobulated structures, with smooth margin (in 68.3% of patients) ranging in short axis from 2 to 22 mm (mean, 7.1 mm) and long axis from 6.9 to 35.3 mm (mean, 19.4 mm). Location of most of these ganglia was at the level of T12-L1 between the adrenal gland and diaphragmatic crura adjacent to the abdominal aorta; two celiac ganglia were found at the level of L2. The distance from aorta was 1–15.3 mm (mean 4.5 mm) and from ipsilateral adrenal gland was 0–13.2 mm (mean 2.9 mm) (Fig. 1). On non-contrast scans, the ganglia appeared hypodense with illdemarcated margin. There was a substantial increase in mean Hounsfield units (HU) in all of the cases on enhanced CT (11 vs. 68, P= .004). There was no evidence of abnormal FDG uptake in the celiac ganglia on PET scans. During follow-up (mean: 20.1 months; range 1.47–73.07 months) the ganglia did not change in size in 123 patients (95% of cases). Celiac ganglia could not be identified in 6 cases on follow up CT (mean follow up 38.9 months; range 26.67-67 months). This was due to the progression of adrenal metastasis in 3
Fig. 1. A 55-year-old male with lung cancer. Axial CT images (A, B) show smooth bilateral celiac ganglia (arrows) in pre- (A) and post-contrast images (B). There is no FDG avidity in the region of ganglia (yellow circles) (C). Follow-up CT after 26 months shows no change in size (D).
294
S.M. Abtahi et al. / Clinical Imaging 38 (2014) 292–295
Fig. 2. A 69-year-old male with lung cancer. Axial images (A,B) shows bilateral celiac ganglia (solid arrows) on CT scan, left celiac ganglia is adjacent to paraortic lymph node (dotted arrow). Lymph node shows increase in FDG avidity (black circle) (C). On follow-up CT scan, the lymph node is seen engulfing the left celiac ganglion (D).
cases, surrounded and obscured by paraaortic lymph nodes in 3 cases (Fig. 2). In the postmortem subjects, celiac ganglia were identified in all 20 cases and were found bilaterally in 19 cases (95% of all cadavers) at the level of T12-L1 vertebrae (Fig. 3). In 10 cases (50%) the margin of ganglia was smooth and in the other 10 cases the wall was lobulated which had no significant differences when compared to the primary lung cancer patient cohort (P=.192). The size ranged from 3 to 9 mm (mean 6.3 mm) in short axis to 7–23 mm (mean 17.3 mm) for long axis with no significant difference to the primary patient cohort (P= .138 for long axis and P= .905 for short axis). The mean distance from abdominal aorta was 5.4 mm (P= .201) and from ipsilateral adrenal gland was 3.4 mm (P=.355). Mean HU in cadaver shows significant difference with pre-contrast HU in lung cancer patients (25 vs. 11, P= .001) (Table 1). 4. Discussion Because of segmental embryonic origin of celiac ganglia, any small lesions in its vicinity could represent non-fused components of the
celiac ganglion and not necessarily enlarged lymph nodes or other pathological processes such as metastasis. As the morphology and tissue density may be similar for these structures it would be helpful to differentiate these structures based on FDG avidity. This fact would highlight the importance of identifying celiac ganglia on PET-CT to differentiate it from metastatic lesion to the adjacent lymph nodes or adrenal glands in patients with history of malignancy which to the best of our knowledge has not been reported. In this study we evaluated PET-CT scans in patients diagnosed with lung cancer and identified celiac ganglion bilaterally in most of the cases based on typical morphological features. The finding is consistent with description of celiac ganglion in anatomic studies [3]. With improved imaging technology, the spatial resolution of PET scan is now improved and generally considered to be around 6 mm [8]. Furthermore, PET detection and resolution are also dependent on the difference of tracer levels between pathological process and background. It is likely that small structures with metabolically active disease can be shown up against background low activity. Our results demonstrated no FDG avidity in celiac ganglia. We believed that the lack of abnormal FDG uptake in the normal celiac ganglia on PET scans allows robust distinction of these structures from metastatic lesions.
Table 1 Patients’ characteristics
Fig. 3. Lobulated celiac ganglia on axial postmortem MDCT (solid arrow).
Celiac ganglia
Patients (N=129)
Cadaver (N=20)⁎
P
Visualized at CT (%) Margin Smooth (%) Lobulated (%) Dimensions Long axis Short axis Distance from Aorta Same side adrenal HU Pre-contrast Post-contrast
127 (98)
19 (95)
.306
88 (68.3) 41 (31.7)
10 (50) 10 (50)
.192
19.4 (6.9−35.3) 7.1 (2−22)
17.3 (7−23) 6.3 (3−9)
.138 .905
4.5 (1−15.3) 2.9 (0−13.2)
5.4 (1−14) 3.4 (0−9)
.201 .355
11 (−1 to 35) 68 (21−122)
25 (12–44) N/A
.001
HU: Hounsfield unit. ⁎ Separate group of subjects.
S.M. Abtahi et al. / Clinical Imaging 38 (2014) 292–295
Also demonstration of stability during follow-up (mean: 20.1 months) may aid in distinguishing the ganglia from metastatic deposits. This fact would be valid finding that any change or lack of visibility in celiac ganglia could be due to the pathological process in its vicinity. In our study the most common reason for not identifying the normal celiac ganglia were presence of adrenal metastasis or masking of the ganglia by the enlarged paraaortic lymph nodes. The left celiac ganglia are consistently seen anteromedial to the left adrenal gland, and the right celiac ganglia are frequently seen between inferior vena cava and right diaphragmatic crura which is consistent with our postmortem study. We identified the right celiac ganglia more frequently than was previously described, probably attributed to the increased awareness of characteristic morphology, location and improved cross sectional imaging modalities [3]. We found the right celiac ganglia more difficult to identify compared with the left counterpart, likely related to the tiny anatomical space with little intervening retroperitoneal fat. In our experience, we found that it is useful to find the left ganglia first, and then look at corresponding level at the right side for a structure with similar morphology and tissue density. As the celiac ganglia is a conglomeration of two to three ganglia together giving rise to lobulated border on the other hand lymph nodes are often oval, although this may not always help in differentiating these two. The enhancement of the celiac ganglia is substantial and slightly heterogeneous and this probably reflects its intrinsic composition of neuronal and nerve fiber tissues. It serves as a useful distinguishing feature from metastatic lymph nodes, which are typically hypodense with necrotic areas. The left celiac ganglia could also easily be differentiated from the diseased left adrenal gland based on such tissue heterogeneity. To validate our findings we correlated our measurements to postmortem MDCT. One of the reasons to include high dose CT in post mortem CT was to see if visibility of celiac ganglia is impaired at lower dose clinical CT exams. Celiac ganglia were better visualized due to higher dose of exposure. The tissue attenuation was significantly higher on postmortem CT when compared with the pre-contrast CT scans of our cohort of patients which could be due to the intravascular coagulation in the cadaver. Other postmortem findings like dimension, margin and distance from aorta and adrenal did not show significant difference with our measurements in cancer patients. This correlative study confirmed the imaging features of the celiac ganglia and would contribute to better characterization of these structures. The main limitation of our study was lack of pathology confirmation for structures identified as celiac ganglion which was
295
ethically not possible. The lack of pathological correlation is attributable to the fact that these patients did not undergo surgery/ biopsy of these lesions (due to lack of FDG avidity on PET CT). However, our findings have close correlation with the postmortem study. Another limitation of our study was comparing cadaver MDCT scan with MDCT in patients with lung cancer, scanning normal subjects for comparative purposes is not ethically possible. Also, all of our patients had lung cancer in whom the appearance of lymph nodes may be different in patients with other malignancies. Further studies on different group of patients are needed to confirm our findings. As our results showed there is no significant difference in characteristics of celiac ganglia between the routine MDCT scan and high dose post mortem imaging. This may imply the importance of routine MDCT in visualizing and evaluating celiac ganglia. However an experienced radiologist interpreted the images there might be some bias in our results. 5. Conclusion Familiarity with CT scan characteristics and FDG avidity of celiac ganglia allow proper identification of them. It helps in distinguishing these normal structures from other pathologic lesions such as metastasis to adrenal or enlarged adjacent lymph node thereby aiding in appropriate clinical management. References [1] Gray H, Lewis WHWH. Anatomy of the human body/Henry Gray. [electronic resource]/Bartleby.com ed ed: Bartleby.com; 2000. [2] Ward EM, Rorie DK, Nauss LA, Bahn RC. The celiac ganglia in man: normal anatomic variations. Anesth Analg 1979;58:461–5. [3] Wang ZJ, Webb EM, Westphalen AC, Coakley FV, Yeh BM. Multi-detector row computed tomographic appearance of celiac ganglia. J Comput Assist Tomogr 2010;34:343–7. [4] Gerke H, Silva RG, Shamoun D, Johnson CJ, Jensen CS. EUS characteristics of celiac ganglia with cytologic and histologic confirmation. Gastrointest Endosc 2006;64: 35–9. [5] Ha TI, Kim GH, Kang DH, Song GA, Kim S, Lee JW. Detection of celiac ganglia with radial scanning endoscopic ultrasonography. Korean J Intern Med 2008;23:5–8. [6] Centers for Disease Control and Prevention (CDC). Invasive cancer incidence — United States, 2009. MMWR Morb Mortal Wkly Rep 2013;62:113–8. [7] Izquierdo-Vidal C, Fau - Molins L, Molins L Fau, Boada M, Boada M Fau, Cladellas E, Cladellas E Fau, Gomez-Caro A, Gomez-Caro A Fau, Gimferrer JM, Gimferrer JM. Surgical treatment of solitary adrenal metastases in patients with lung cancer. Med Clin (Barc) 2013;140(9):406–8. http://dx.doi.org/10.1016/j.medcli. 2012.11.029 [LID - S0025-7753(12)00982-7 [pii] LID -]. [8] Stickel JR, Cherry SR. High-resolution PET detector design: modelling components of intrinsic spatial resolution. Phys Med Biol 2005;50:179–95.