Optimization of threshold method for volume and activity determinations by using SPECT Phantom for possible clinical use in predicting response to regeneration and targeted liver therapies. — ASN Events
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Optimization of threshold method for volume and activity determinations by using SPECT Phantom for possible clinical use in predicting response to regeneration and targeted liver therapies. (#112)

Amritjyot Kaur 1 , Virendra Singh 2 , Ajay Chitkara 1 , Anish Bhattacharya 1 , Ratti Ram Sharma 3 , Baljinder Singh 1
  1. Nuclear Medicine, PGIMER Chandigarh , INDIA, Chandigarh, India
  2. Hepatology, PGIMER Chandigarh , INDIA, Chandigarh, India
  3. Transfusion Medicine, PGIMER Chandigarh , INDIA, Chandigarh, India

Background: A threshold method for volume and activity determinations was developed through the use of a series of SPECT phantom studies.The estimated threshold values were used to calculate the liver volume and radioactivity measurements on baseline 99mTc-S Colloid SPECT/CT images in patients with cirrhosis who were planned for liver regeneration therapy subsequently.  

Materials and Methods:  A series of phantom measurements were performed using volumes 6-3200 mL and varying concentrations 0.4-10.27 µCi/mL. Images were acquired on dual headed gamma camera (Symbia- T16, SIEMENS, Germany) ;120 projections (20sec /projection); 128 x 128 matrix ; zoom 1. SPECT images were reconstructed by filtered back projection using butter worth filter (cut off  0.5 cycles/cm).Threshold was varied from 19 to 52 on attenuation and non attenuation corrected images. 99mTc-S Colloid SPECT/CT scan with standardised parameters were performed on  cirrhotic patients (n=6) planned for therapy. Liver volume(LV),Spleen volume(SV),Quantitative Liver uptake(QLU),Quantitative Spleen uptake(QSU),% Injected Dose/mL(%ID/mL) liver, %Injected Dose/mL (%ID/mL) spleen was calculated .

Results: Threshold was calculated using 3D volumetric analysis 8.5.10.1 Software. The best threshold value for both attenuation and non attenuation corrected images for 6-3800 mL is 38 and 37 (r=0.978;0.989). For concentration from 0.4-10.27 µCi/mL regression line equation was obtained for SPECT measured and phantom concentration (r=0.97). For patients of  Child Pugh Score Class A (n=3) and Class C  (n=3); LV (1469±247; 630±62),  SV (588±65; 444±15),  QLU (37.70±13.45; 9.36±1.37) , QSU (49.60±16.54; 57.20±2.78 ),  %ID/mL liver( 0.0286±0.009; 0.014±0.0007) %ID/mL spleen (0.06±0.02 ; 0 .104±0.011) were obtained respectively.

These parameters shall be assessed in follow up liver SPECT data to evaluate the extent of liver regeneration following regeneration therapy and these image findings shall be correlated with other parameters and clinical findings.

Conclusion: SPECT quantitation may be a useful tool for assessment of severity of liver disease and quantification of liver regeneration following appropriate therapies.