Ventilation scintigraphy with lipophilic cationic compounds.
OBJECTIVE
On the basis of our hypothesis that lipophilic cations may be more suitable for ventilation lung scintigraphy than the conventional technetium-99m diethylenetriamine penta-acetic acid (Tc-DTPA), comparative studies were carried out.


METHODS
The nebulization potential of nine routine radiopharmaceuticals was compared on medical and scintigraphy-specific nebulizers. This was followed by ventilation scintigraphy in 14 patients with chronic obstructive airway disease (n=13) or pulmonary embolism (n=1) where either 99mTc-methoxyisobutylisonitrile (n=10) or Tc-tetrofosmin (n=4) was used. Same-patient comparison with 99mTc-DTPA ventilation scan was available in six patients using the same acquisition protocol. Comparison with 99mTc-DTPA was made with respect to the nebulization rates, radioactivity delivered per unit of radioactivity available for inhalation, and regional distribution of inhaled counts.


RESULTS
Lipophilic cation solutions had a significantly higher nebulization rate compared with 99mTc-DTPA using the medical nebulizer (235%, P<0.01) and 370% on scintigraphy-specific nebulizer (P<0.01). More than three times the counts of 99mTc-methoxyisobutylisonitrile or 99mTc-tetrofosmin was deposited in the body compared with Tc-DTPA aerosol per megabecquerel activity inhaled (1.5 vs. 0.4 kcounts/MBq) (P<0.001), preferentially in the lungs (75.2 vs. 65.2%), at the expense of oropharynx and stomach. Within the lungs, about 50% more counts were deposited in the outer one-third lung with lipophilic cations. Overall, therefore, more than 12 times the radioactivity deposition was achieved in the peripheral one-third of the lungs with the lipophilic cations.


CONCLUSIONS
Ventilation lung scanning with lipophilic cations is a viable substitute of nanoparticle scintigraphy (technegas and pertechnegas, which are expensive and technically far more demanding).
Institute of Nuclear Medicine and Allied Sciences, Delhi, India. aseem_bhatnagar@indiatimes.com
Aseem
A
Bhatnagar
Krishan
K
Sawroop
Mahinder K
MK
Chopra
Neeraj
N
Kumar
Abhinav
A
Jaimini
Anuj
A
Bhatnagar
D000328:Adult; D006801:Humans; D008297:Male; D008875:Middle Aged; D009330:Nebulizers and Vaporizers; D009943:Organophosphorus Compounds / Q000008:administration & dosage; D015609:Organotechnetium Compounds / Q000008:administration & dosage; D029424:Pulmonary Disease, Chronic Obstructive / Q000000981:diagnostic imaging*; D011655:Pulmonary Embolism / Q000000981:diagnostic imaging*; D012123:Pulmonary Ventilation; D011877:Radionuclide Imaging; D019275:Radiopharmaceuticals / Q000008:administration & dosage; D016284:Technetium Tc 99m Pentetate / Q000008:administration & dosage; D017256:Technetium Tc 99m Sestamibi / Q000008:administration & dosage
D009943:Organophosphorus Compounds; D015609:Organotechnetium Compounds; D019275:Radiopharmaceuticals; C078700:technetium tc-99m tetrofosmin; D017256:Technetium Tc 99m Sestamibi; D016284:Technetium Tc 99m Pentetate