Ann Thorac Surg 2003;75:388-392
© 2003 The Society of Thoracic Surgeons
Original article: general thoracic
Use of three-dimensional computed tomographic angiography of pulmonary vessels for lung resections
Shun-ichi Watanabe, MD*a,
Kazunori Arai, MDa,
Toshio Watanabe, MDa,
Wataru Koda, MDa,
Hiroshi Urayama, MDa
a Departments of Thoracic and Vascular Surgery and Radiology, Kurobe City Hospital, Kurobe, Japan
Accepted for publication August 29, 2002.
* Address reprint requests to Dr Watanabe, Division of Thoracic Surgery, National Cancer Center Hospital, Tokyo 104-0045, Japan
e-mail: syuwatan{at}ncc.go.jp
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Abstract
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BACKGROUND: Identification and appropriate treatment of the pulmonary artery (PA) is a key to successful anatomic resection of the lung. Preoperative identification of branching pattern of the PA seems to make pulmonary resection easier and safer especially when there is severe adhesion or incomplete fissure between the lobes. With the development of the multidetector row spiral computed tomography (MDCT), three-dimensional (3D) CT angiography can be obtained easily and can provide very useful information about various organs. We studied the usefulness of 3D-CT pulmonary angiography (3D-CTPA) in evaluating the PA branching pattern before anatomic pulmonary resection.
METHODS: Fourteen patients with primary lung cancer undergoing anatomic pulmonary resections were the subjects of this study. The 3D-CTPA images were obtained using MDCT. The obtained images of the PA branching pattern were compared with intraoperative findings in each case at the time of thoracotomy.
RESULTS: MDCT scanning required approximately 15 seconds per patient during a single respiratory pause and the 3D images were processed within 10 minutes after scannning. According to intraoperative findings, 98% (84 of 86) of PA branches were revealed to be successfully identified on preoperative 3D-CTPA. Two missed branches on 3D-CTPA were small vessels, which were less than 1.5 mm in actual diameter. Pulmonary vessels were clearly identified even when contrast medium was not administered intravenously.
CONCLUSIONS: Obtaining 3D-CTPA using MDCT is noninvasive yet it provides precise preoperative information regarding pulmonary vessels. This technique is a far less invasive and an easier investigation than conventional pulmonary angiography. The 3D-CTPA navigation may have the potential to increase the safety of surgical procedure and to reduce surgical morbidity in anatomic lung resection.
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Introduction
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During pulmonary resection surgeons occasionally encounter unexpected bleeding from the pulmonary artery (PA), which has massive blood flow and a very fragile wall. Although appropriate treatment of PA branches is a key to successful pulmonary resection, anatomic variations in the PA make lung resection more difficult especially when there is severe adhesion or incomplete fissure between lobes. Moreover in thoracoscopic surgery, bleeding from the PA often obliges surgeons to convert to open thoracotomy to prevent intraoperative fatality. The surgeon must be familiar with anatomy of pulmonary vessels to successfully accomplish an anatomic pulmonary resection. If individual information about the exact number, location, or anatomic variation of PA branches that have to be divided can be obtained preoperatively in each case the subsequent lung resection will be safer and proceed more easily. With the recent development of multidetector row helical computed tomography (MDCT), three-dimensional computed tomographic (3D-CT) angiography can easily and quickly be obtained and provide very useful visual information in various diseases [1]. This study investigated the usefulness of 3D-CT pulmonary angiography (3D-CTPA) as a navigation for treatment of pulmonary vessels in lung surgery.
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Patients and methods
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Fourteen patients who underwent anatomic resection for primary lung cancer between February and September 2001 were included in this study. The 3D-CTPA images were obtained using an MDCT scanner (Somatom Plus 4-VZ; Siemens Medical System, Erlangen, Germany). Iodinated contrast medium was administered intravenously from the upper limb at a rate of 3.0 mL/s with a total dose of 100 mL by a mechanical injector. Images of the arterial phase were obtained by commencing the scanning when the injected contrast medium reached the ascending aorta. Collimation of 1.0 mm was used with a pitch of 6.0. Images were processed with a volume-rendering module in a workstation system. Construction of the 3D-CTPA images was performed by subtracting parts of the vertebra, ribs, heart, and superior vena cava (Fig 1).
Before thoracotomy, lobar and segmental arteries branching directly from the main PA were identified meticulously by rotating the obtained 3D image on the display (Fig 2).
Main, lobar, and segmental PA was exposed at the time of pulmonary resection and the intraoperative findings of the PA branching pattern were compared with the preoperatively obtained 3D-CTA images (Fig 2D) in each case. In the pneumonectomy case PA branches were confirmed on the resected specimen.
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Fig 1. Three-dimensional computed tomography pulmonary angiography image of the right pulmonary artery. Branches of the pulmonary artery were clearly identified at the subsegmental or more peripheral levels.
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Fig 2. Three-dimensional computed tomography pulmonary angiography images of the left pulmonary artery. Before thoracotomy, the obtained three-dimensional image was rotated on the display (A, B, and C), and then all lobar and segmental arteries branching directly from the main pulmonary artery were identified (D). (a = anterior artery; b = apical artery; c = posterior artery; d = lingular arteries; e = superior segmental arteries; f = common basal artery; Ao = aortic arch; LMPA = left main pulmonary artery; LSPV = left superior pulmonary vein.)
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Results
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Scanning time
MDCT scanning required approximately 15 seconds per patient during a single respiratory pause, and the 3D images of pulmonary vessels were processed within 5 to 10 minutes after scanning.
Quality of images
PA branches were clearly identified at the subsegmental or more peripheral levels (Fig 1). Wearing special glasses offered more comprehensible 3D images. The reconstructed 3D-CTPA image of the PA could be rotated 360 degrees in any direction on the display screen. Although both PA and PV are visible in this 3D image, they can be discriminated easily on the display by wearing the special glasses and rotating the image. The quality of PA images was sufficient even when contrast medium was not administered (Fig 3).
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Fig 3. Three-dimensional computed tomography pulmonary angiography with contrast medium (right) or without contrast medium (left). Pulmonary artery branches were clearly identified regardless of contrast medium administration.
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Comparing obtained 3D-CTPA images and intraoperative findings
Right and left thoracotomy was performed in 8 and 6 patients, respectively. According to the intraoperative findings, 97.7% (84 of 86) of PA branches were precisely identified on preoperative 3D-CTPA (Table 1).
There was no significant difference in concordance rate between the right (97.4%) and the left sides (97.7%). Both of the two missed branches were less than 1.5 mm in actual diameter in patients with small stature.
Surgical results
All surgeries were completed without massive bleeding and no blood transfusions were required.
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Comment
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Anatomic pulmonary resection such as lobectomy and segmentectomy is a common and basic procedure to treat various pulmonary tumors. Identification and appropriate treatment of the PA branches is a particularly important key to successful anatomic pulmonary resection although there are a multitude of anatomic variations in the PA branching pattern [2]. Because no one pattern for either the right or the left PA can be described as standard the thoracic surgeon must be mindful of the high degree of variability in the PA branching pattern and carefully identify each branch before ligation. Therefore preoperative comprehension of the PA branching pattern will make pulmonary resection safer and easier, especially when there is dense interlobar adhesion or incomplete fissure.
In recent years 3D-CT has been used as a useful investigation because it can offer a clear image that is easy to comprehend visually [3, 4]. In the thoracic field virtual endoscopy trials involving the tracheobronchial system as an alternative to fiberoptic bronchoscope are already in progress [5]. In this study 3D-CT was used as a less invasive and easier imaging investigation of the pulmonary vessels compared with conventional angiographic studies. This technique also has the advantage of short exposure times [1] and the quality of obtained images is comparable with conventional angiography (Fig 1). Processing 3D-CT angiographic image with a single-detector row spiral CT (SDCT) was previously recognized as time-consuming work [6], therefore this technique had not become prevalent in clinical settings. With the recent development of the MDCT scanner, however, many types of 3D-CT images became available very easily and quickly. Roptopoulos and Boiselle [7] reported that the use of MDCT improved PA visualization compared with SDCT in evaluating pulmonary embolism. Also in our study pulmonary branches were clearly identified preoperatively using this technique. Furthermore MDCT took only 15 seconds to complete scanning and less than 10 minutes to obtain 3D-CTPA images on the display. The shorter breathhold will make examinations more comfortable for the patients and the shorter image-processing time will reduce drudgery for the staff. Although a few very small vessels could not be displayed treatment of PA branches was accomplished easily and safely without massive bleeding in this series. The use of 3D-CTPA will decrease the risk of unexpected bleeding and blood transfusion. From the surgeon’s mental point of view this preoperative information sets the surgeon’s mind at ease during lung resections. 3D-CTPA will become a helpful investigative modality for anatomic pulmonary resection, which requires ligation and division of PA branches such as lobectomy or segmentectomy.
Furthermore the additional cost for this investigation is almost zero because CT with injecting contrast medium is always taken in lung cancer cases in our institution for evaluation of lymph node enlargement. After taking this routine CT image we can process and watch the 3D-CTA images on the display at any time. This aspect will be one of the advantages of this technique.
Interestingly the present study demonstrated that 3D-CTPA clearly displayed pulmonary vessels regardless of contrast medium administration. The quality of obtained 3D-CTPA without contrast medium was almost the same as that with contrast medium probably because there was large difference in attenuation between pulmonary vessels and the lung. Air in the lung is considered to have become a good negative contrast medium for vessels in the thoracic cavity. This aspect will be a great advantage of 3D-CT angiography of pulmonary vessels compared with that of other organs and suggests that 3D-CTPA can be a safe investigation even when the patient is allergic to iodine or has renal failure.
Another advantage of 3D-CTPA compared with conventional pulmonary angiography is that we can get favorable images that can be rotated 360 degrees in any direction as desired allowing thoracoscopic view, open thoracotomy view, operator’s view, assistant’s view and so on. Those images are reproducible on the display at any time, therefore the surgeon can simulate the surgical process using those images before or even during thoracotomy. This system may also become an educational material demonstrating the anatomy of pulmonary vessels to students or junior residents.
As detection of early-stage peripheral lung cancer is increasing, trials of minimally invasive thoracic surgery have been undertaken [8, 9]. Recent development of thoracoscopic devices enabled surgeons to perform anatomic resection through small wounds, such as video-assisted thoracic surgery (VATS) lobectomy, even with lymph node dissection [10]. VATS has a cosmetic advantage and offers good quality of life; however, it must occasionally be converted to open thoracotomy because of unexpected massive bleeding mainly from fragile branches of the PA. In the neurosurgical field, navigation surgery using computer graphics of magnetic resonance and CT images has already been used to prevent unexpected bleeding [11]. Zaaroor and colleagues [12] reported a successful clinical trial of intraoperative navigation system in neurosurgery based on three-axis miniature position sensor and a computer-controlled technique for real-time determination of orientation in the operating room. If the 3D-CTPA-navigation system with a position sensor is introduced in the operating room and used synchronously with a VATS monitor display in the future, it may also become a great help for VATS anatomic resection.
In conclusion the 3D-CTPA technique using MDCT is an easy, safe, and noninvasive investigation for patients and quickly provides important preoperative information to surgeons before anatomic pulmonary resection with or without a thoracoscope. 3D-CTPA navigation may increase the safety of surgical procedure and reduce surgical morbidity particularly in cases of dense interlobar adhesion or incomplete fissure.
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Abstract
Introduction
