背景：銦－111-DTPA-Octreotide（銦－111-DTPAOC）造影在診斷及追蹤神經內分泌腫瘤病患上，已被證實非常有價值。然而其昂貴價格與不普遍性限制了它在臨床上的運用。近來鎵－68-DOTATOC亦被報導適合用於神經內分泌腫瘤之診斷，但是鎵－68-DOTATOC需要昂貴的正子造影機與鍺－68/鎵－68發生器，並非所有醫院都有能力負擔。至於鎵－67則幾乎是每一個核醫部門的常備藥劑，雖然其造影品質不如銦－111和鎵－68理想，但其便宜且普遍之優點，仍然使其變成一個十分有吸引力的競爭者。本研究用鎵－67標幟DTPAOC，進行鎵－67-DTPAOC在正常老鼠之生物體分佈實驗。另外評估鎵－67-DTPAOC在長有胰臟癌老鼠之腫瘤攝取比率。並將結果與銦－111-DTPAOC比較。方法：本研究使用48隻健康老鼠，平均分為二組，第一組老鼠於注射0.1mCi銦－111-DTPAOC後的l、4、24及48小時將其犧牲（每個時間點6隻）。第二組老鼠則在注射0.1mCi鎵－67-DTPAOC之後於前述相同時間點犧牲。將體內不同器官取下約0.1公克樣本，小心秤重，再使用閃爍計數器測量放射活度，以計算組織放射濃度，以% injected dose/g表示之。此外，用8隻長有胰臟癌之老鼠，分成兩組，各於注射1mCi銦－111-DTPAOC或鎵－67-DTPAOC後的4、24及48小時，接受造影，以計算腫瘤攝取比率(T/N ratio)。結果：注射銦－111-DTPAOC後藥物放射活性於腎臟明顯較高，而其他組織藥物放射活性則相當低。注射鎵－67-DTPAOC後，鎵－67於腎臟之吸收亦非常明顯。然而鎵－67-DTPAOC除了在腎臟有明顯放射活性聚積外，其他組織如肝臟、脾臟以及骨骼也有相當之放射活性聚積。在帶有腫瘤之老鼠影像掃描中，兩種藥物於胰臟腫瘤均可見明顯積聚。鎵－67-DTPAOC在腫瘤之吸收劑量高於銦－111-DTPAOC。結論：鎵－67-DTPAOC與銦－111-DTPAOC同樣能有效的聚集在腫瘤內，然而鎵－67-DTPAOC組在腫瘤以外之組織中亦出現較高的放射濃度，可能是有部份鎵－67在體內游離出來，顯示標幟方法尚有進步的空間，但我們的結果仍可看出鎵－67-DTPAOC在偵測胰臟腫瘤的潛力。

Background: 111In-DTPA-octreotide (111In-DTPAOC) scintigraphy has become an invaluable tool in the diagnosis and monitor of patients with neuroendocrine tumors. However, the high price and poor availability of this isotope limits its clinical application. 68Ga-DOTA-Tyr3-octreotide (DOTATOC) has been proven to have high affinity to SSTR. However, the expensive cost of the PET scanner limits its clinical application in most hospitals. 67Ga is a common radiopharmaceutical in most nuclear medicine departments. Although the image quality of 67Ga is not as good as 111In and 68Ga, the worldwide availability and low cost of 67Ga scan still make it an attractive radioisotope. In this study, we labeled DTPAOC with 67Ga. We collected complete information of 67Ga-DTPAOC on pharmacokinetics and biodistribution in normal rats and compared the results with those of 111In- DTPAOC. Methods: Forty-eight healthy rats were divided into two groups. Group 1 (24 rats) were sacrificed at 1, 4, 24, and 48 h (6 in each) after injection of approximately 3.7 MBq of 111In-DTPAOC and another 24 rats were sacrificed at the same time period (6 in each) after injection of 3.7 MBq of 67Ga-DTPAOC. Samples of various organs were obtained and counted to calculate the tissue concentration. In addition, 8 rats (4 for 111In-DTPAOC and 4 for 67Ga-DTPAOC) bearing pancreatic tumor were scanned using a gamma camera at 4, 24, and 48h after injection of approximately 37 MBq of 111In-DTPAOC or 67Ga-DTPAOC. The tumor uptake ratios (T/N ratios) were calculated based on the images. Results: In the biodistribution study, the radioactivity was high in the kidney and quite low in other organs in the rats after injection with 111In-DTPAOC. After injection with 67Ga-DTPAOC, the rats also showed high radioactivity in the kidney, however, relatively high radioactivity in other organs such as liver, spleen and bone were also noted. In the images of the rats with pancreatic tumors, high radioactivity was noted in the tumor with injection of either 111In-DTPAOC or 67Ga-DTPAOC. The T/N ratios in the 67Ga-DTPAOC group were higher than those in the 111In-DTPAOC. Conclusion: Both 111In- and 67Ga-DTPAOC could be accumulated in the pancreatic tumor. However, other tissues besides the tumor also showed high radioactivity after injection with 67Ga-DTPAOC but not with 111In-DTPAOC. The existence of free form of 67Ga may be the cause and improvement of the labeling technique is needed. In general, our results still indicate the good potential of 67Ga-DTPAOC in the detection of a pancreatic tumor.