non surgical treatments like rfa , litt are alternate methods of treatment in patients with medically or surgically inoperable lesions . even for operable lesions ,
image guided percutaneous ablative procedures are increasingly being used since they are relatively safer and equally effective .
it is preferred over the other ablative techniques in patients with larger lesions ( > 5 cm ) or closer to large vessels which are less likely to be ablated due to heat sink effect [ 5 , 6 ] .
the ibt consists of insertion of single or multiple percutaneous needles in the lesion under ultrasonography ( usg ) or ct scan guidance and connected to remote after loading brachytherapy machine for delivering a single hdr dose of about 12 - 20 gy . due to limited experience with large single doses of ibt in oncology , radiological response on usg / ct / mri scans
single large doses of hdr ibt may take longer time than the conventional fractionated radiation therapy techniques and may show persistent shadow without any tumor viability .
pet which is a functional imaging device , largely applicable in oncological practice , could provide better information for response assessment .
in april 2008 , a 67-year - old male patient was presented to our clinic as a diagnosed case of carcinoma of stomach for which he underwent radical gastrectomy in 1998 in a different hospital .
ct scan evaluation showed a metastatic lesion in segment v measuring 2.0  1.8 cm .
fine needle aspiration cytology ( fnac ) examination of this lesion revealed features suggestive of metastases from adenocarcinoma
1a , b ) showed an ill defined , solid , hypodense mass measuring 2.0 cm in segment v of liver with increased fdg uptake ( standard uptake value [ suv ] of 7.8 ) . since patient was declined for surgery , we decided to treat him with hdr ibt under ct guidance .
the procedure was carried out in ct scan room ( siemens medical system , erlanger , germany ) under local anesthesia ( 2% xylocaine ) . in the breath hold position ,
a single 16 gauze , blind end , stainless steel brachytherapy needle was inserted in the center of lesion through the percutaneous route .
the needle tip was advanced 1.0 cm beyond the lesion since the 0.8 cm of the needle tip was blind .
ct scan image ( a ) shows an ill defined , solid , hypodense mass measuring 2 cm in segment v of liver . pet scan image ( b ) shows increased fdg uptake with suv of 7.8 in the same region brachytherapy planning was performed using plato planning system , version 14.1 ( nucletron , veenandaal , netherlands ) with slice thickness of 2.5 mm .
treatment plan was generated for dose of 12 gy prescribed at periphery of the lesion .
the treatment was delivered in a single fraction on hdr remote afterloading unit ( microselectron ) and lasted for 20 minutes .
the ct image ( fig 2a ) did not show significant change in the size of the mass , however pet imaging ( fig .
2b ) showed no significant fdg uptake ( suv ; 2.3 ) , suggesting no viable tumor .
ct scan ( a ) shows no significant change in the size of the mass , however it had developed a necrotic area .
pet scan image ( b ) shows no significant fdg uptake in the lesion ( suv 2.3 )
the liver is one of the organs commonly involved with metastases from various primary malignancies .
surgical resection of lm is the only potentially curative modality , but it is possible in only 20 percent of patients .
ct guided hdr ibt is a new treatment technique for lm with only limited studies [ 7 , 8 ] in the literature reporting local control rates of 87 - 93% ; similar to other ablative therapies .
there is no clear consensus about which imaging technique is the most reliable in order to assess the response to ablative therapies . since the edema and necrosis caused by these therapies makes it difficult to assess the accurate response to these therapies on the basis of conventional ct / mri scans .
pet has recently been used for response assessment to rfa and sirt [ 9 , 10 ] and has been found very useful .
however , it has not been tried for ibt since this form of therapy is relatively rare in use .
ibt is advantageous over rfa because it is not affected by nearby blood vessel or size of the lesion .
compared to ebrt treatment methods , ibt dosimetry is not affected by respiratory movements since the implanted needle moves with target . therefore , it delivers the desired dose to the target lesion accurately and minimal dose to the surrounding liver parenchyma which has limited radiation tolerance .
so far , ibt for lm had been used in two studies both by ricke et al . [ 7 , 8 ] .
pet scan was used in none of these two studies . in their first study , 19 patients of lm were treated by ibt dose of 17 gy ( range 12 - 25 gy ) and assessed response by mri scan .
two patients ( 10% ) experienced severe side effects , one had obstructive jaundice due to irradiation edema and the other had intra - abdominal hemorrhage . in the second study by ricke et al .
, authors treated 37 patients with mean tumor size of 4.6 cm ( ranged 2.511 cm ) with either hdr ibt alone or in combination with thermal ablation .
a minimal dose of 17 gy inside the tumor margin was applied ( ranged , 10 - 20 gy ) .
the local control rate after 6 months was 87% and 73% for ibt alone and combined treatment respectively .
the decision of using ibt in our patient was based on the patient s refusal for surgery .
we used an hdr ibt dose of 12 gy in view of the small lesion size ( 2 cm ) and it is the first report in literature , where pet scan has been used for assessing response to hdr ibt for lm . on the basis of our case report and the only two studies available in the literature by ricke et al .
[ 7 , 8 ] , we conclude that ct guided hdr ibt is safe and effective alternative to ablative therapies for treating lm , and pet - ct scan , as compared to ct scan , provides better information for response assessment .
 for liver metastases ( lm ) , image guided percutaneous ablative procedures such as radiofrequency ablation ( rfa ) , laser induced thermal therapy ( litt ) and trans - arterial chemo - embolisation ( tace ) are increasingly being used because they are relatively safer , less invasive and equally effective . 
 ct scan guided interstitial brachytherapy ( ibt ) with a single large dose of radiation by high dose rate ( hdr ) brachytherapy is a novel technique of treating lm and has shown good results . 
 positron emission tomography ( pet ) scan may provide better information for assessing the response to ibt procedures . we hereby report a case of lm that was treated by hdr ibt and pet scan was done in addition to ct scan for assessing the response . 
Purpose
Case history
Discussion