Department of Radiology, Brigham and Women's Hospital, Harvard Medical School, Boston, MA 02115, USA.
Nucl Med Biol. 2011 Apr;38(3):435-41. doi: 10.1016/j.nucmedbio.2010.10.001. Epub 2010 Dec 3.
Microwave reactors remain largely underutilized in the field of positron emission tomography (PET) chemistry. This is particularly unfortunate since microwave synthesis elegantly addresses two of the most critical issues of PET radiochemistry with short-lived radionuclides: reaction rate and side-product formation. In this study, we investigate the efficiency of synthesis of terminally [(18)F]fluorinated fatty acid analogs using a commercial microwave reactor in comparison with conventional heating (CH).
The labeling precursors were methyl esters of terminally substituted alkyl bromides and iodides. Duration and temperatures of the [(18)F]fluorination reaction were varied. Chemical and radiochemical purities, and radiochemical yields were investigated for conventional (CH) and microwave-assisted (MW) radiosyntheses.
The results demonstrate that microwave heating enhanced [(18)F]fluoride incorporation to >95% (up to 55% improvement), while reducing reaction times to 2 min (∼ 10-fold reduction) or temperatures to 55-60 °C (20 °C reduction). Overall decay-corrected radiochemical yields of purified [(18)F]fluoro fatty acids were higher (MW = 49.0 ± 4.5%, CH = 23.6 ± 3.5%, P < .05) with microwave heating and side-products were notably fewer.
For routine synthesis of [(18)F]fluoro fatty acid analogs, microwave heating is faster, milder, cleaner, less variable and higher yielding than CH and therefore the preferred reaction method.
微波反应堆在正电子发射断层扫描（PET）化学领域的应用仍未得到充分利用。这尤其不幸，因为微波合成巧妙地解决了放射性核素半衰期短的 PET 放射化学中最关键的两个问题：反应速率和副产物形成。在这项研究中，我们研究了使用商业微波反应堆合成末端[（18）F]氟化脂肪酸类似物的效率，与常规加热（CH）相比。
标记前体为末端取代的烷基溴化物和碘化物的甲酯。改变了[（18）F]氟化反应的持续时间和温度。研究了常规（CH）和微波辅助（MW）放射合成中化学和放射化学纯度以及放射化学产率。
结果表明，微波加热可将[（18）F]氟化物的掺入率提高到>95％（最高提高 55％），同时将反应时间缩短至 2 分钟（约减少 10 倍）或温度降低至 55-60°C（减少 20°C）。经纯化的[（18）F]氟代脂肪酸的总衰减校正放射化学产率更高（MW = 49.0±4.5％，CH = 23.6±3.5％，P<0.05），且副产物明显更少。
对于常规合成[（18）F]氟代脂肪酸类似物，微波加热比 CH 更快、更温和、更清洁、更稳定、产率更高，因此是首选的反应方法。
