video assisted thoracic surgery ( vats ) was introduced in the early 1990s [ 1 , 2 ] and is now widely considered to be the gold standard for suspected malignant lung nodule resection .
the technique might reduce patient discomfort , complications , the need for higher level of care , hospital stay , and cost compared to open thoracotomy . in 1999 , a review of vats lung nodule resection demonstrated that 54% of the cases required conversion to open thoracotomy to complete resection .
the study identified that nodule localization failure was the cause for the majority of conversions ( 46% ) .
the challenge increases further with small deeply placed lung nodules as the visceral pleura may not demonstrate any altered shape or colour , making these nodules even more difficult to locate thoracoscopically .
a number of differing methods of preoperative  marking  have been reported in the literature with varying degrees of success , complications , cost , specialised equipment , and required expertise .
we revisit a simple but safe technique using computed tomography ( ct ) guided marking using methylene blue injection prior to vats pulmonary metastasectomy described in both the adult and the paediatric populations dating back to the 1990s [ 5 , 6 ] but subsequently underutilized .
using our technique , nodules are identified on a  low dose  ct ( 120  kv , modulated ma and 6.0  mm acquisitions ) prior to marking .
a metallic skin marker is used to aid in localisation and to plan an appropriate cutaneous needle insertion point . to dilute the methylene blue safely , 5  ml of the patients ' venous blood is withdrawn and mixed with methylene blue aseptically in a ratio of 1 part methylene blue to 5 parts autologous blood .
then , under local anaesthesia and aseptic conditions , the nodule is then marked using ct fluoroscopy . in our institute
, we use manually controlled pulsed carevision ( siemens somatom ) ct fluoroscopic guidance ( 120  kv and a mas of 30 ) .
the nodule is approached with a 16/18 g spinal needle in a way akin to lung biopsy ( figure 1 ) .
on reaching the nodule , the methylene blue blood mixture is injected immediately adjacent to the nodule and along the needle tract right up to the pleural surface as the needle is retracted , leaving a methylene blue / blood tract ( figure 2 ) .
once in the operating department , the surgeon initially reviews the coronal reformatted images and can then locate the dye on the pleural surface under direct vision using the thoracoscope , guiding the approach to the parenchymal nodule . when the needle is placed slightly superior or inferior to the nodule due to technical difficulties , such as the approach being hindered by overlying ribs , the dye may not be immediately adjacent to the nodule . in this case , ct reconstructions and dialogue with the operating surgeon are essential .
the mean patient age was 68 ( 5181 ) , with a bmi of 25 ( 2228 ) and a mean fev1 98% of predicted ( 82115% ) .
the mean nodule size was 8  mm ( 418  mm ) located at a mean depth of 17  mm ( 642  mm ) , distributed through both lungs ( right = 17 ( upper = 5 , lower = 12 ) and left 13 ( upper = 8 , lower = 5 ) ) .
the mean volume of dye injected was 3  ml ( 24  ml ) .
dye was detected at the pleural surface in 97% ( 29/30 ) of the patients and at the nodule in 93% ( 28/30 ) .
there were no major complications , but two small pneumothoraces with no clinical significance , and one patient suffered discomfort ; this was resolved with secondary local anaesthetic injection .
there was no adverse effect on general anesthesia , and thoracoscopic resection was possible in 90% ( 27/30 ) of the cases .
one of the cases converted to open resection which was due to technical difficulties with the surgery rather than being related to the marking . in the other two cases in which thoracoscopic resection was not possible the location of the nodule made it difficult to ensure complete resection with vats resection , and this only became apparent during the surgery
computed tomography guided radiological marking techniques described include wire marking [ 7 , 8 ] , lipiodol marking , barium marking , and combinations of wire and lipiodol marking .
ct guided wire markings have been associated with uncontrollable pneumothorax and wire dislodgement , as well as high proportion of minor adverse events such as small pneumothorax and perifocal bleeding [ 7 , 8 , 11 , 12 ] .
the technique , using ct guided administered barium contrast balls to mark lung nodules , was found to cause local acute inflammations in all cases , and this can potentially hinder surgical resection . the use of stealthstation treon treatment guidance system ( medtronic ; louisville , ky ) has been described .
results have been successful with no reported major complications ; however , the equipment can be costly and requires training for use .
surgical techniques using methylene blue have been described with the surgeon palpating more superficial nodules with a finger through the port site incision and marking the palpated area before continuing with vats resection .
a technique using radiological guided methylene blue for marking prior to breast microdochectomy has also been shown to have equal diagnostic accuracy compared to wire marking .
the need for accurate localization particularly for deeper lung nodules is essential for the success of vats procedure for lung metastasectomy .
the technique described is a cost effective , safe , and reliable method in marking lung nodules prior to resection
. the method does not require expensive equipment described in other studies ; nor does it run the risk of wire dislodgement . as with the studies from lenglinger et al . in 1994   and mcconnell et al . in 2002 ,
no patients experienced any adverse effects of the methylene blue - autologous blood mixture and no major complications occurred .
small pneumothorax is a common minor complication in any procedure where a needle passes through the pleura and would usually resolve spontaneously without further management ; however , all these patients were undergoing immediate surgery . piercing the pleura multiple times
increases the risk of causing pneumothorax and therefore good planning prior to the procedure with a safe route for the needle to pass is essential .
one of the main risk factors for pneumothorax development is background chronic obstructive pulmonary disease and its associated complications , such as blebs and bullae .
other risk factors for the development of pneumothorax include increasing patient age , increased depth of lesion , increased time of needle across the pleura , and traversing a fissure [ 16 , 17 ] .
consideration also needs to be made of the motion of the lung with breathing and intermittent breath holds may be required during acquisition of images and advancement of the needle .
the incidence of pneumothorax is reported to range from 9% to 54% for lung nodule biopsy [ 16 , 17 ] , with an average of 20% , rising to 39% in patients with background emphysema .
our pneumothorax rate of 7% with this technique is less than the aforementioned 9 studies and none lead to any complication during subsequent induction of general anaesthesia .
none of the patients in this cohort had significant emphysema , bulla , or blebs .
an issue that we discovered is that even though only a small volume is injected , the dye can spread over a much larger area in the adjacent lung than simply the parenchyma surrounding the nodule to be marked ; thus , as the injection is started , this needs to be at a slow and steady rate while withdrawing the needle back to the visceral pleural surface .
clear communication with surgeons performing the subsequent metastasectomy is paramount and reconstructed multiplanar ct images of the nodule location aid their procedure planning .
this and the discussion with the surgeon when there is the slightest concern when the marking is not exact will inevitably reduce failure rates and complications .
 
 aim . we describe our experience of a simple , safe , and reproducible technique for lung nodule marking prethoracoscopic metastasectomy . 
 thoracoscopic lung nodule resection reduces patient discomfort , complications , higher level of care , hospital stay , and cost ; however , small deeply placed lung nodules are difficult to locate and resect thoracoscopically . materials and methods . 
 we describe and review the success of our novel technique , where nodules are identified on a low dose ct and marked with methylene blue using ct fluoroscopy guidance immediately prior to surgery . results . 
 30 nodules were marked with a mean size of 8  mm ( 418  mm ) located at a mean depth of 17  mm , distributed through both lungs . 
 dye was detected at the pleural surface in 97% of the patients and at the nodule in 93% . 
 there were no major complications . 
 thoracoscopic resection was possible in 90% . 
 conclusion . 
 this is a simple and safe method of lung nodule marking to facilitate thoracoscopic resection in cases where this may not be technically possible due to nodule location . 
1. Introduction
2. Method
3. Results
4. Discussion