Biomedical subjects
Publications and source records attributed to J W Froelich.
With the availability of indium-labeled white blood cells, radionuclide imaging studies have a definite role in the diagnosis and staging of patients with inflammatory bowel disease. The In-111 white blood cell study is particularly helpful in evaluating recurrent disease in patients with severe intercurrent diseases and in screening patients without the need for barium examinations.
A Tc-99m blood cell study, performed on a patient with suspected gastrointestinal bleeding, demonstrated an unusual configuration of pelvic venous collaterals associated with idiopathic iliac vein occlusion. The cause of these findings subsequently was confirmed by intravenous digital subtraction angiography. This case demonstrates the importance of the dynamic phase of gastrointestinal bleeding studies in correctly identifying vascular abnormalities.
Hemangiomas are easily, quickly and relatively noninvasively detected using whole-body imaging with Tc-99m labeled RBCs. A case in which this method was used to confirm known lesions and detect additional unsuspected lesions is described. This method can also be useful in the detection and evaluation of other types of vascular malformations, such as arteriovenous communications. The lesions must be of sufficient size and flow to be seen. Applications include the examination of patients known to have one vascular malformation in a search for additional lesions and the screening of relatives of patients with familial conditions that include hemangiomas.
A 50-year-old man placed on peritoneal dialysis for end stage renal disease developed unilateral (left) scrotal edema following infusion of dialysis fluid into the peritoneum. The left side of the scrotum and left inguinal canal were surgically explored and a left hydrocele was removed. Following surgery, the patient again demonstrated left scrotal edema during peritoneal dialysis. Tc-99m MAA (5.0 mCi, 185 mBq) was injected into a 2-liter bag of dialysis fluid, which was subsequently infused into the peritoneum. The communication between the peritoneal cavity and the left inguinal canal was demonstrated.
The diagnosis of delayed rupture of the spleen is demonstrated and discussed by presenting a case in which the patient had significant thoracoabdominal trauma with an initially normal liver/spleen scintigram and benign hospital course. Twenty-three days after the trauma, the patient developed an acute abdominal crisis that brought him to the emergency room where an emergency ultrasound revealed hemoperitoneum and a subcapsular hematoma. At laparotomy, a splenic rupture was found. A splenectomy was not performed. Postoperative liver/spleen scintigram showed a persistent defect which was not present on the initial liver/spleen scintigram.
Whole-body thallium/technetium subtraction scintiscans, with thallium 201 chloride and technetium 99m pertechnetate, were obtained on 10 patients with medullary thyroid cancer with postoperative elevations of serum calcitonin values. Seven patients had the hereditary variant of medullary thyroid cancer (the multiple endocrine neoplasia, type II syndrome) while three patients had the sporadic form. Negative scans were obtained on five patients with basal calcitonin levels less than 3 ng/ml (normal less than 0.35 ng/ml). Five other patients with elevated calcitonin levels (range 3.6 to 69.2 ng/ml; mean 28.3 ng/ml) had positive scans that have guided further surgical approaches. Serum calcitonin appears to remain the most sensitive indicator of residual medullary thyroid cancer while localization of this residual tumor tissue frequently can be obtained through thallium/technetium subtraction imaging in both the hereditary and sporadic forms of the disease.
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Radionuclide techniques for localizing inflammatory processes had relied heavily upon 67Ga-citrate until McAfee and Thakur described the technique for the radiolabeling of leukocytes with 111In-oxine. Since their initial description in 1976 there has been continued development of the radiopharmaceutical, as well as clinical efficacy. At present 111In-labeled leukocytes continue to be handled as an investigational new drug but this has not greatly limited its clinical availability. Indium-111 leukocytes are the agent of choice for evaluation of patients with fever of unknown origin, osteomyelitis, and prosthetic graft infections; and preliminary data shows great promise in the area of detecting reoccurrence of inflammatory bowel disease. This article attempts to review currently accepted uses of 111In leukocytes as well as potential areas of application.
Twelve patients undergoing scintigraphy with Tc-99m-labeled red blood cells (RBC) exhibited abnormal small-bowel activity and were given glucagon to assess its role in detecting bleeding from the small bowel. Six demonstrated focal accumulation of activity which was not identified prior to glucagon. Endoscopy, barium studies, angiography, and colonoscopy located the small-bowel bleeding site in 4 patients; in the other 2, studies of the colon failed to show the bleeding site and the origin was presumed to be the small bowel. The authors suggest that intravenous glucagon can be beneficial as an adjuvant to Tc-99m-RBC when diagnosing bleeding from the small bowel.
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Ten patients had severe intercurrent illness and the gallbladder could not be seen on a hepatobiliary scan. In 4, surgery and pathological examination showed that the gallbladder was normal; 1 had chronic cholecystitis and 5 had acute acalculous cholecystitis. This study indicates that a positive hepatobiliary scan may not be indicative of acute gallbladder disease in the seriously ill patient.
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Recent experience with radionuclide imaging has provided the clinician with several techniques to noninvasively detect and locate sources of gastrointestinal hemorrhage. These tests can be rapidly performed and often in an ICU setting. One method used Tc-99m sulfur colloid which, in an animal model, has been shown to detect acute bleeding at rates as low as 0.1 ml/min. However, because the tracer remains in the blood for a short period of time, it may be suboptimal for identifying patients with intermittent bleeding. Tc-99m red cells is a tracer that remains within the blood and permits detection of both acute and intermittent bleeding. With tagged red cells, sites of bleeding from both the upper and lower gastrointestinal tract can be found. Both of these techniques can provide important information in the patient with suspected active gastrointestinal bleeding and aid the clinician in more effective management including the use of invasive diagnostic and therapeutic techniques.
Using a modified in vivo Tc-99M red cell labeling technique, gastrointestinal bleeding scintigraphy was performed in 100 patients with GI bleeding. Sixty-two patients with melena or bright red blood per rectum had positive scintiscans. In comparison to results of angiography, endoscopy, surgery and contrast radiography, radionuclide scintigraphy correctly located the site of bleeding in 83% of patients. The procedures could be performed over a 24 hr period which increased the sensitivity of the test since 85% of the scintiscans were positive at one hr or greater after the onset of imaging. The procedure was more sensitive than angiography in detecting sources of GI bleeding. We conclude that GI bleeding scintigraphy 99mTc-red cells in an accurate and effective method to detect upper and lower GI bleeding in patients with acute intermittent gastrointestinal bleeding.
A case is presented of a 17-month-old girl who underwent two Meckel's scans with Tc-99m pertechnetate. The initial study was interpreted as normal while a subsequent study five days later was definitely positive. Surgery immediately following the positive Meckel's scan demonstrated a Meckel's diverticulum containing gastric mucosa without evidence of active hemorrhage. This prompted a review of the literature in reference to false-negative Meckel's scans which revealed a wide variance in the reported incidence of false-negative examinations. Repeat scintigraphy in the face of a strong clinical suspicion after an initial normal study may decrease the indicence of false-negative imaging series.
In a prospective blind study of liver/spleen trauma, 32 consecutive patients were evaluated by radionuclide imaging (99mTc-sulfur colloid) and gray-scale ultrasound. Six patients (19%) had inadequate sonograms due to injuries and pain. Thirteen (41%) were normal, 13 (41%) were abnormal with one technique or the other, and there was a discrepancy in 2 (6%). Of the 13 abnormal patients, 1 had a lacerated spleen, 2 had angiographic confirmation of a subcapsular hematoma, and 10 showed resolution on follow-up. Two patients with left-sided trauma had abnormal radionuclide scans of the liver; sonograms were initially normal in one of them, but subsequent imaging confirmed the abnormality. The authors feel that imaging with 99mTc-sulfur colloid should be the primary screening examination for liver/spleen trauma.
The rate of incorporation of Tc-99m into red blood cells pretinned in vivo was measured by collecting blood samples in stannous DTPA solution, which served as a competing ligand for Tc-99m. This collection technique permitted a measurement of high-affinity red-cell labeling efficiency at the instant of sampling. At 0.5 min after injection only 62% of technetium is tightly bound to the red cell; this rises to 94.5% at 10 min. Based on the graded labeling of the red cells, the in vivo labeling procedure was modified by isolating pertechnetate and red blood cells tinned in vivo in a syringe during the first 10 min of labeling. The pertechnetate is thus prevented from distributing to extravascular compartments, and 90% of the injected Tc-99m is firmly bound to red blood cells at the time of injection. In a series of 23 patients, seven were tested with the in vivo method and seven with the modified in vivo method, and nine patients were tested with each method on separate occasions. A decrease in gastric activity and improved image quality were found with the modified method compared with the standard method of in vivo red-cell labeling.