Virtual Assisted Lung Mapping（VAL-MAP）
Although pre-operative CT-guided needle-mediated percutaneous marking techniques have been commonly used to identify and resect small lung nodules, major complications have been reported including bleeding, pneumothorax, and potentially fatal air embolism that may lead to myocardial infarction or cerebral infarction. CT-guided percutaneous marking techniques are also limited by the approachable locations (eg., lung apex, lung portions facing the mediastinum or the diaphragm, and interlobar fissure). As an alternative, the author (Sato M) developed Virtual Assisted Lung Mapping (VAL-MAP) in 2012 in Kyoto University. In this technique, we use virtual bronchoscopy that is developed from high-resolution CT as a guide of actual bronchoscopy and spray small amount of blue dye (indigo carmine) into the periphery of the lung. This “tattooing” is repeated for 2-6 points, which are clearly visible as a “map” on the lung surface during operation. These points provide “geometric information” to the lung; although the lung is so plastic, the relative relationship among the spots do not change even after deflation and manipulation of the lung, enabling satisfactory navigation for surgeons.
Figure 1 The map drawn by VAL-MAP (A) A ground glass lung nodule suspicious of lung cancer found on CT. (B) A planned lung map based on CT. (C) An intraoperative view showing the four spots identical to the planned 3D image in B. (cited from the reference 1 with permission)
In our hospital, bronchoscopic marking is conducted on the day before operation or in the morning of the day of operation. A patient undergo local anesthesia at his or her throat and mild sedation, which makes the procedure much less uncomfortable to the patient. The marking procedure usually takes 20-30 minutes. After insertion of a bronchoscope from the mouth into the bronchus, a thin metal-tip catheter with 1.8 mm in diameter is inserted into each target bronchus. A fluoroscoipy is used to confirm the tip of the catheter reaching the pleura (the very periphery of the lung). And then, 1 ml of indigocarmine (blue dye) is injected. This dye is commonly used for gastric endoscopy as well as in food. After completing the bronchoscopic procedure, another CT scan is taken to confirm the localization of the markings, which are further built into the final 3D images. Although we use a fluoroscope, the radiation exposure is minimum (approximately 45 seconds/mark; reference 1). A rare complication of VAL-MAP is minor pneumothorax, which usually does not need any further treatment. Please consult your doctor about other potential complications.
Figure 2. (A) Virtual bronchoscopy. (B) A metal-tip catheter used for VAL-MAP. (C) Actual bronchoscopic images. (D) A fluoroscopic image showing the catheter localization.
Figure 3. Two ground glass nodules accidentally found in the lung. Three markings were made to conduct wedge lung resection. The operation was completed in about 30 minutes. Both lesions were found to be early adenocarcinoma (lung cancer). (cited from the reference 3 with permission)
VAL-MAP has not been covered by medical insurance; although there is no extra charge for the procedure, a patient needs to register at a clinical study. VAL-MAP is considered to be especially useful to remove a tiny tumor and/or a tumor with ground glass opacity, which is hardly palpable during operation using thoracoscopy. VAL-MAP is also helpful to obtain sufficient resection margin. Thus, beyond the scope of conventional marking techniques, VAL-MAP is a novel intra-operative navigation that realizes precise thoracoscopic sublobar lung resection (wedge resection and segmentectomies). Indeed, I was invited for a lecture (clinical skills course – what future leaders need to know) at the annual meeting of American Association for Thoracic Surgeons (AATS, Seattle) in 2015. Currently, to examine the utility and reproducibility of VAL-MAP, Multi-Institutional Lung Mapping Study (MIL-MAP) Study is ongoing among nearly 20 centers in Japan. The interim result has been reported at the annual meeting of European Society for Thoracic Surgeons (ESTS, Lisbon) in June, 2015.
Contact information re: VAL-MAP：SATOM-SUR@h.u-tokyo.ac.jp
1) Sato M, Omasa M, Chen F, Sato T, Sonobe M, Bando T, Date H. Use of Virtual Assisted Lung Mapping (VAL-MAP), a bronchoscopic multi-spot dye-marking technique using virtual images, for precise navigation of thoracoscopic sublobar lung resection. J Thorac Cardiovasc Surg.2014;147(6):1813-9.
2) Sato M, Aoyama A, Yamada T, Menjyu T, Chen F, Sato T, Sonobe M, Omasa M, Date H. Thoracoscopic wedge lung resection using virtual-assisted lung mapping. Asian Cardiovasc Thorac Ann. 2015;23(1):46-54.
3) Sato M, Yamada T, Menju T, Aoyama A, Sato T, Chen F, Sonobe M, Omasa M, Date H. Virtual-assisted lung mapping: outcome of 100 consecutive cases in a single institute. Eur J Cardiothorac Surg. 2015;47(4):e131-9