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Multiplanar reconstruction MR image of primary adenoid cystic carcinoma of the central airway: (MPR of central airway adenoid cystic carcinoma)
Journal of Clinical Imaging 25 (2001) 332 – 336
Multiplanar reconstruction MR image of primary adenoid cystic carcinoma of the central airway: MPR of central airway adenoid cystic carcinoma Soichi Akataa,*, Yasuo Ohkuboa, Jinho Parka, Taizo Ozukia, Tetsuya Yamagishia, Mana Yoshimuraa, Fumio Kotakea, Dai Kakizakia, Harubumi Katob, Kimihiko Abea a
Department of Radiology, Tokyo Medical University, 6-7-1 Nishi-shinjuku, Shinjuku-ku, Tokyo 160-0023, Japan b Department of Surgery, Tokyo Medical University, 6-7-1 Nishi-shinjuku, Shinjuku-ku, Tokyo 160-0023, Japan Received 30 May 2001
Abstract Multiplanar reconstruction (MPR) is a method that allows free selection of computerized reconstruction images. We reviewed a total of six MPR magnetic resonance (MR) examinations in five cases of adenoid cystic carcinoma of the central airway, which is a rare low-grade malignant tumor. MPR MR provides images either longitudinally or at right angles to the longitudinal axis of the trachea and main bronchi, so it was useful to diagnose tumor extent along airways more precisely and to evaluate therapeutic effects. MPR MR may help in planning therapeutic strategy and in posttherapeutic follow-up. D 2001 Elsevier Science Inc. All rights reserved. Keywords: Central airways; Adenoid cystic carcinoma; Computed tomography; Magnetic resonance imaging; Multiplanar reconstruction
1. Introduction
2. Materials and methods
Adenoid cystic carcinoma is a rare low-grade malignant tumor [1] that occurs mainly in salivary glands or central airways such as the trachea and the main bronchi [2]. Recently, tracheobronchoplasty, radiotherapy, or laser therapy has been performed in such cases [3,4]. It is, therefore, important to delineate the intra- and extraluminal tumor extent correctly before treatment. Multiplanar reconstruction (MPR) is a method that allows free selection of computerized reconstruction images. Although computed tomography (CT) scan is usually used to diagnose the extent of intrathoracic tumors, we considered that MPR on magnetic resonance (MR) images could be more useful because of high soft tissue contrast resolution and multiplanar imaging. We reviewed six MPR MR procedures in five cases of adenoid cystic carcinoma and evaluated the usefulness of MPR MR to determine intra- and extraluminal tumor extension.
Subjects consisted of five cases of pathologically proven adenoid cystic carcinoma (Table 1). There were three men and two women ranging from 31 to 72 years of age (mean = 57.4). Pathological proof was based on surgery in two patients and on transbronchial biopsy in three. Two cases underwent tracheobronchoplasty and three other cases were treated by laser therapy. One patient underwent MR examination twice during a period of 2 years to evaluate therapeutic effects of laser therapy. The MR equipment used was the superconductive type Toshiba MRT-50A (0.5 T) and ECG gating was used in all cases. The sequence we used was the T1-weighted image to evaluate the anatomical structure [5], so the repetition time (TR) was the R –R interval on ECG and echo time (TE) was 30 ms. The matrix was 256 256, the number of excitations (NEX ) was two times, and the slice thickness was 7 mm gapless interleaved multislice. The field of view (FOV) was 350 350 mm. The image plane we obtained was basically the axial image from which coronal image were taken for each case. MPR is a three-dimensional reconstruction method that allows any desired section orientation to be obtained from a two-dimensional data
* Corresponding author. Tel.: +81-3-3342-6111x5818; fax: +81-33348-6314.
0899-7071/01/$ – see front matter D 2001 Elsevier Science Inc. All rights reserved. PII: S 0 8 9 9 - 7 0 7 1 ( 0 1 ) 0 0 3 1 7 - 5
S. Akata et al. / Journal of Clinical Imaging 25 (2001) 332–336 Table 1 Cases of adenoid cystic carcinoma
333
udinal axis of the trachea and main bronchi were reconstructed from coronal and axial images.
Case number
Age/sex
Location
MPR MR
1 2
67/female 72/male
3 4
31/female 42/male
pre-operation pre- and postlaser therapy pre-laser therapy pre-laser therapy
5
75/male
trachea trachea – right main bronchus left main bronchus trachea – left main bronchus trachea
pre-operation
set. As such, examination time can be minimized and section orientations appropriate for measurements can be chosen during postprocedure processing as needed [6]. MPR images either along or at right angles to the longit-
3. Results Although chest X-ray revealed tumors as causing stenosis of central airways in all five adenoid cystic carcinoma cases, extraluminal tumor extension was not clearly depicted. CT and MR indicated not only the intra- but also the extraluminal tumor extent. In particular, the MPR image clearly depicted the extraluminal tumor extension both longitudinally and at right angles to the longitudinal axes of major airways upon free selection of computerized reconstruction images. CT and MR especially combined
Fig. 1. Case 1: A 61-year-old woman with adenoid cystic carcinoma located in the trachea. (A) Chest X-ray showing the circular stenosis of the right side of the trachea due to mass (arrow) but the extraluminal extent of the tumor is obscure. (B) CT clearly demonstrating the tumor (arrow) and surrounding structures. (C) Coronal image of MR showing the tumor (arrow) but does not show the entire trachea on one image. (D) MPR coronal image along the longitudinal axis of the trachea showing the entire portion of the trachea from the cervical portion to the carina and distinctly depicting the location of tumor (arrow) in the trachea and surrounding tissues.
334
S. Akata et al. / Journal of Clinical Imaging 25 (2001) 332–336
Fig. 2. Case 2: A 72-year-old man with adenoid cystic carcinoma from the trachea to the right main bronchus. (A) MPR coronal image depicting tumor extending from the right side of the lower trachea to the periphery of the right main bronchus (arrow). MPR images along either longitudinally (B) or at right angles to the longitudinal axis of the right main bronchus (C) recognizing the tumor extension (arrow) stenosis of the main bronchus. After 2 years of laser therapy, therapeutic effects such as improvement of intraluminal stenosis and decrease in tumor size (arrow) were recognized on MPR coronal image (D) and
S. Akata et al. / Journal of Clinical Imaging 25 (2001) 332–336
with MPR images before and after treatment have proven to be useful in the assessment of therapeutic effects.
4. Illustrative case reports 4.1. Case 1 In a 67-year-old woman, chest X-ray showed round stenosis on the right wall of the trachea due to tumor, but extraluminal tumor extension was unclear (Fig. 1A). CT demonstrated the tumor and surrounding structures clearly (Fig. 1B). Coronal image of MR showed the tumor but apparently did not show the entire trachea on one image (Fig. 1C). The MPR coronal image along the longitudinal axis of the trachea from the cervical portion to the carina was useful for planning tracheoplasty precisely because it clearly depicted the location of the tumor in the trachea and in surrounding tissues (Fig. 1D). 4.2. Case 2 In a 72-year-old man, MPR coronal image depicted a tumor from the right side of lower trachea to the bifurcation of upper lobe bronchus (Fig. 2A). MPR images both along and at right angles to the longitudinal axis of the right main bronchus showed the tumor extent and stenosis in the main bronchus (Fig. 2B and C). Two years after laser therapy, therapeutic effects such as improvement of stenosis and decrease in tumor size were recognized on the MPR coronal image and MPR image, both along and at right angles to the longitudinal axis of the right main bronchus (Fig. 2D, E, and F).
5. Discussion The most common primary neoplasms of central airways are squamous cell carcinomas and adenoid cystic carcinomas [1]. Since central airway tumors are relatively rare and have few symptoms at an early stage, they are frequently diagnosed only at a late stage, and many cases of slowly progressive symptoms of central airway obstruction are misdiagnosed for long periods as asthma or chronic bronchitis [1,2]. Conventional tomography is still useful to some degree as an imaging modality for the central airway because it permits visualization of the trachea in the coronal and sagittal planes without any need for computed reconstruction [7]. However, computed reconstruction images are known to provide various advantages in image quality. Chest X-ray and conventional tomography generally provide images of the lumens of only major airways such as the trachea and main bronchi. CT and MR can be used to assess neoplasms of central airways for precise localization of both intra- and extraluminal components and to detect
335
lymph node metastases because they not only allow evaluation of the lumen but also the tracheal wall and the surrounding tissues. Although CT is unquestionably superior to MR in terms of spatial resolution, MR can provide direct imaging in multidirectional planes [8]. The central airway can be adequately studied by MR without requiring intravenous contrast media [9]. Axial, coronal, and sagittal images that which used MPR revealed tumor extent more accurately than CT and routine MR because the MPR method can make vertical images for the trachea and main bronchi, which have the least partial volume effect, and can make images along the longitudinal axes of the trachea and main bronchi. Therefore, it is suggested that MPR may be more useful for tumors in central airways, such as adenoid cystic carcinoma. Many malignant tumors extend microscopically beyond the grossly visible and palpable limits of growth. This is particularly common in cases of adenoid cystic carcinoma, in which significant microscopically recognizable extension of 1 cm or more in length is frequently encountered. Such extension usually occurs distally and proximally in the submucosa and in the perineural spaces on the external surface of the trachea [10]. Surgeons, therefore, need to know actual tumor length for the most appropriate tracheoplasty and tracheobronchoplasty. MPR is thought to be useful for them in planning operative strategy precisely due to images along the longitudinal axis of trachea or main bronchi. The interleaf method is necessary in order to use the MPR method in MR because the interslice gap makes irregular MPR images and sequential acquisitions result in interference between slices. Although the thinner slice thickness yields a smoother MPR image, it has a worse signal-to-noise ratio. For the purpose of increased accuracy in MR diagnosis of central airway tumors such as adenoid cystic carcinoma, we plan to construct high-resolution surface coils for better spatial resolution. This should make MR a more useful tool to detect central airway neoplasms and to depict the extraluminal tumor extent. The use of contrast media in MR of central airway tumors might show tumor invasion more precisely due to excellent soft tissue contrast resolution. Although MPR images on multidetector CT (MDCT) must have superior spatial resolution than that on MR because of no respiratory misregistration on MDCT [11,12], the disadvantages of MPR images on MDCT may be poor soft tissue contrast resolution and radiation.
Acknowledgments We thank Prof. J.P. Barron of the International Medical Communications Center of Tokyo Medical University for reviewing the manuscript in English.
336
S. Akata et al. / Journal of Clinical Imaging 25 (2001) 332–336
References [1] Hajdu SI, Huvos AG, Goodner JT, Foote FW, Beattie EJ. Carcinoma of the trachea. Cancer 1970;25:1448 – 56. [2] Houston HE, Payne WS, Harrison EG, Olsen AM. Primary cancers of trachea. Arch Surg 1969;99:132 – 40. [3] Jose PDJ, Mercedes CC, Jose MA. Nd – YAG laser photoresection of low-grade malignant tumors of the tracheobronchial tree. Chest 1990; 97:920 – 2. [4] Pierce RJ, Mestitz H, Simpson LW, Daniel FJ. Endobronchial resection with the Nd – YAG laser—two years experience in an Australian unit. Aust NZ J Med 1990;20:120 – 6. [5] Gamus G, Sostman D. Magnetic resonance imaging of the thorax. Am Rev Respir Dis 1989;139:254 – 74. [6] Vogl TJ, Diebold T, Bergman C, Do¨hlemann C, Mantel K, Roland F, Lissner J. MRI in pre- and postoperative assessment of tracheal stenosis due to pulmonary artery sling. J Comput-Assisted Tomogr 1993;17: 878 – 86.
[7] Naidich DP. CT/MR correlation in the evaluation of tracheobronchial neoplasia. Radiol Clin North Am 1990;28:555 – 71. [8] Webb WR, Gamus G, Crooks LE. Multisection sagittal and coronal magnetic resonance imaging of the mediastinum and hila. Radiology 1987;150:475 – 8. [9] Weber AL, Grillo HC. Tracheal tumors: a radiological, clinical and pathological evaluation of 84 cases. Radiol Clin North Am 1978;16: 27 – 246. [10] Pearson FG. Advances in tracheal surgery. Adv Surg 1983;16: 197 – 223. [11] Hu H, He HD, Foley WD, Fox SH. Four multidetector-row helical CT: image quality and volume coverage speed. Radiology 2000;215: 55 – 62. [12] Rubin GD. Data explosion: the challenge of multidetector-row CT. Eur J Radiol 2000;36:74 – 80.
Multiplanar reconstruction MR image of primary adenoid cystic carcinoma of the central airway: MPR of central airway adenoid cystic carcinoma Soichi Akataa,*, Yasuo Ohkuboa, Jinho Parka, Taizo Ozukia, Tetsuya Yamagishia, Mana Yoshimuraa, Fumio Kotakea, Dai Kakizakia, Harubumi Katob, Kimihiko Abea a
Department of Radiology, Tokyo Medical University, 6-7-1 Nishi-shinjuku, Shinjuku-ku, Tokyo 160-0023, Japan b Department of Surgery, Tokyo Medical University, 6-7-1 Nishi-shinjuku, Shinjuku-ku, Tokyo 160-0023, Japan Received 30 May 2001
Abstract Multiplanar reconstruction (MPR) is a method that allows free selection of computerized reconstruction images. We reviewed a total of six MPR magnetic resonance (MR) examinations in five cases of adenoid cystic carcinoma of the central airway, which is a rare low-grade malignant tumor. MPR MR provides images either longitudinally or at right angles to the longitudinal axis of the trachea and main bronchi, so it was useful to diagnose tumor extent along airways more precisely and to evaluate therapeutic effects. MPR MR may help in planning therapeutic strategy and in posttherapeutic follow-up. D 2001 Elsevier Science Inc. All rights reserved. Keywords: Central airways; Adenoid cystic carcinoma; Computed tomography; Magnetic resonance imaging; Multiplanar reconstruction
1. Introduction
2. Materials and methods
Adenoid cystic carcinoma is a rare low-grade malignant tumor [1] that occurs mainly in salivary glands or central airways such as the trachea and the main bronchi [2]. Recently, tracheobronchoplasty, radiotherapy, or laser therapy has been performed in such cases [3,4]. It is, therefore, important to delineate the intra- and extraluminal tumor extent correctly before treatment. Multiplanar reconstruction (MPR) is a method that allows free selection of computerized reconstruction images. Although computed tomography (CT) scan is usually used to diagnose the extent of intrathoracic tumors, we considered that MPR on magnetic resonance (MR) images could be more useful because of high soft tissue contrast resolution and multiplanar imaging. We reviewed six MPR MR procedures in five cases of adenoid cystic carcinoma and evaluated the usefulness of MPR MR to determine intra- and extraluminal tumor extension.
Subjects consisted of five cases of pathologically proven adenoid cystic carcinoma (Table 1). There were three men and two women ranging from 31 to 72 years of age (mean = 57.4). Pathological proof was based on surgery in two patients and on transbronchial biopsy in three. Two cases underwent tracheobronchoplasty and three other cases were treated by laser therapy. One patient underwent MR examination twice during a period of 2 years to evaluate therapeutic effects of laser therapy. The MR equipment used was the superconductive type Toshiba MRT-50A (0.5 T) and ECG gating was used in all cases. The sequence we used was the T1-weighted image to evaluate the anatomical structure [5], so the repetition time (TR) was the R –R interval on ECG and echo time (TE) was 30 ms. The matrix was 256 256, the number of excitations (NEX ) was two times, and the slice thickness was 7 mm gapless interleaved multislice. The field of view (FOV) was 350 350 mm. The image plane we obtained was basically the axial image from which coronal image were taken for each case. MPR is a three-dimensional reconstruction method that allows any desired section orientation to be obtained from a two-dimensional data
* Corresponding author. Tel.: +81-3-3342-6111x5818; fax: +81-33348-6314.
0899-7071/01/$ – see front matter D 2001 Elsevier Science Inc. All rights reserved. PII: S 0 8 9 9 - 7 0 7 1 ( 0 1 ) 0 0 3 1 7 - 5
S. Akata et al. / Journal of Clinical Imaging 25 (2001) 332–336 Table 1 Cases of adenoid cystic carcinoma
333
udinal axis of the trachea and main bronchi were reconstructed from coronal and axial images.
Case number
Age/sex
Location
MPR MR
1 2
67/female 72/male
3 4
31/female 42/male
pre-operation pre- and postlaser therapy pre-laser therapy pre-laser therapy
5
75/male
trachea trachea – right main bronchus left main bronchus trachea – left main bronchus trachea
pre-operation
set. As such, examination time can be minimized and section orientations appropriate for measurements can be chosen during postprocedure processing as needed [6]. MPR images either along or at right angles to the longit-
3. Results Although chest X-ray revealed tumors as causing stenosis of central airways in all five adenoid cystic carcinoma cases, extraluminal tumor extension was not clearly depicted. CT and MR indicated not only the intra- but also the extraluminal tumor extent. In particular, the MPR image clearly depicted the extraluminal tumor extension both longitudinally and at right angles to the longitudinal axes of major airways upon free selection of computerized reconstruction images. CT and MR especially combined
Fig. 1. Case 1: A 61-year-old woman with adenoid cystic carcinoma located in the trachea. (A) Chest X-ray showing the circular stenosis of the right side of the trachea due to mass (arrow) but the extraluminal extent of the tumor is obscure. (B) CT clearly demonstrating the tumor (arrow) and surrounding structures. (C) Coronal image of MR showing the tumor (arrow) but does not show the entire trachea on one image. (D) MPR coronal image along the longitudinal axis of the trachea showing the entire portion of the trachea from the cervical portion to the carina and distinctly depicting the location of tumor (arrow) in the trachea and surrounding tissues.
334
S. Akata et al. / Journal of Clinical Imaging 25 (2001) 332–336
Fig. 2. Case 2: A 72-year-old man with adenoid cystic carcinoma from the trachea to the right main bronchus. (A) MPR coronal image depicting tumor extending from the right side of the lower trachea to the periphery of the right main bronchus (arrow). MPR images along either longitudinally (B) or at right angles to the longitudinal axis of the right main bronchus (C) recognizing the tumor extension (arrow) stenosis of the main bronchus. After 2 years of laser therapy, therapeutic effects such as improvement of intraluminal stenosis and decrease in tumor size (arrow) were recognized on MPR coronal image (D) and
S. Akata et al. / Journal of Clinical Imaging 25 (2001) 332–336
with MPR images before and after treatment have proven to be useful in the assessment of therapeutic effects.
4. Illustrative case reports 4.1. Case 1 In a 67-year-old woman, chest X-ray showed round stenosis on the right wall of the trachea due to tumor, but extraluminal tumor extension was unclear (Fig. 1A). CT demonstrated the tumor and surrounding structures clearly (Fig. 1B). Coronal image of MR showed the tumor but apparently did not show the entire trachea on one image (Fig. 1C). The MPR coronal image along the longitudinal axis of the trachea from the cervical portion to the carina was useful for planning tracheoplasty precisely because it clearly depicted the location of the tumor in the trachea and in surrounding tissues (Fig. 1D). 4.2. Case 2 In a 72-year-old man, MPR coronal image depicted a tumor from the right side of lower trachea to the bifurcation of upper lobe bronchus (Fig. 2A). MPR images both along and at right angles to the longitudinal axis of the right main bronchus showed the tumor extent and stenosis in the main bronchus (Fig. 2B and C). Two years after laser therapy, therapeutic effects such as improvement of stenosis and decrease in tumor size were recognized on the MPR coronal image and MPR image, both along and at right angles to the longitudinal axis of the right main bronchus (Fig. 2D, E, and F).
5. Discussion The most common primary neoplasms of central airways are squamous cell carcinomas and adenoid cystic carcinomas [1]. Since central airway tumors are relatively rare and have few symptoms at an early stage, they are frequently diagnosed only at a late stage, and many cases of slowly progressive symptoms of central airway obstruction are misdiagnosed for long periods as asthma or chronic bronchitis [1,2]. Conventional tomography is still useful to some degree as an imaging modality for the central airway because it permits visualization of the trachea in the coronal and sagittal planes without any need for computed reconstruction [7]. However, computed reconstruction images are known to provide various advantages in image quality. Chest X-ray and conventional tomography generally provide images of the lumens of only major airways such as the trachea and main bronchi. CT and MR can be used to assess neoplasms of central airways for precise localization of both intra- and extraluminal components and to detect
335
lymph node metastases because they not only allow evaluation of the lumen but also the tracheal wall and the surrounding tissues. Although CT is unquestionably superior to MR in terms of spatial resolution, MR can provide direct imaging in multidirectional planes [8]. The central airway can be adequately studied by MR without requiring intravenous contrast media [9]. Axial, coronal, and sagittal images that which used MPR revealed tumor extent more accurately than CT and routine MR because the MPR method can make vertical images for the trachea and main bronchi, which have the least partial volume effect, and can make images along the longitudinal axes of the trachea and main bronchi. Therefore, it is suggested that MPR may be more useful for tumors in central airways, such as adenoid cystic carcinoma. Many malignant tumors extend microscopically beyond the grossly visible and palpable limits of growth. This is particularly common in cases of adenoid cystic carcinoma, in which significant microscopically recognizable extension of 1 cm or more in length is frequently encountered. Such extension usually occurs distally and proximally in the submucosa and in the perineural spaces on the external surface of the trachea [10]. Surgeons, therefore, need to know actual tumor length for the most appropriate tracheoplasty and tracheobronchoplasty. MPR is thought to be useful for them in planning operative strategy precisely due to images along the longitudinal axis of trachea or main bronchi. The interleaf method is necessary in order to use the MPR method in MR because the interslice gap makes irregular MPR images and sequential acquisitions result in interference between slices. Although the thinner slice thickness yields a smoother MPR image, it has a worse signal-to-noise ratio. For the purpose of increased accuracy in MR diagnosis of central airway tumors such as adenoid cystic carcinoma, we plan to construct high-resolution surface coils for better spatial resolution. This should make MR a more useful tool to detect central airway neoplasms and to depict the extraluminal tumor extent. The use of contrast media in MR of central airway tumors might show tumor invasion more precisely due to excellent soft tissue contrast resolution. Although MPR images on multidetector CT (MDCT) must have superior spatial resolution than that on MR because of no respiratory misregistration on MDCT [11,12], the disadvantages of MPR images on MDCT may be poor soft tissue contrast resolution and radiation.
Acknowledgments We thank Prof. J.P. Barron of the International Medical Communications Center of Tokyo Medical University for reviewing the manuscript in English.
336
S. Akata et al. / Journal of Clinical Imaging 25 (2001) 332–336
References [1] Hajdu SI, Huvos AG, Goodner JT, Foote FW, Beattie EJ. Carcinoma of the trachea. Cancer 1970;25:1448 – 56. [2] Houston HE, Payne WS, Harrison EG, Olsen AM. Primary cancers of trachea. Arch Surg 1969;99:132 – 40. [3] Jose PDJ, Mercedes CC, Jose MA. Nd – YAG laser photoresection of low-grade malignant tumors of the tracheobronchial tree. Chest 1990; 97:920 – 2. [4] Pierce RJ, Mestitz H, Simpson LW, Daniel FJ. Endobronchial resection with the Nd – YAG laser—two years experience in an Australian unit. Aust NZ J Med 1990;20:120 – 6. [5] Gamus G, Sostman D. Magnetic resonance imaging of the thorax. Am Rev Respir Dis 1989;139:254 – 74. [6] Vogl TJ, Diebold T, Bergman C, Do¨hlemann C, Mantel K, Roland F, Lissner J. MRI in pre- and postoperative assessment of tracheal stenosis due to pulmonary artery sling. J Comput-Assisted Tomogr 1993;17: 878 – 86.
[7] Naidich DP. CT/MR correlation in the evaluation of tracheobronchial neoplasia. Radiol Clin North Am 1990;28:555 – 71. [8] Webb WR, Gamus G, Crooks LE. Multisection sagittal and coronal magnetic resonance imaging of the mediastinum and hila. Radiology 1987;150:475 – 8. [9] Weber AL, Grillo HC. Tracheal tumors: a radiological, clinical and pathological evaluation of 84 cases. Radiol Clin North Am 1978;16: 27 – 246. [10] Pearson FG. Advances in tracheal surgery. Adv Surg 1983;16: 197 – 223. [11] Hu H, He HD, Foley WD, Fox SH. Four multidetector-row helical CT: image quality and volume coverage speed. Radiology 2000;215: 55 – 62. [12] Rubin GD. Data explosion: the challenge of multidetector-row CT. Eur J Radiol 2000;36:74 – 80.