Testicular scanning and other applications of radionuclide imaging of the genital tract.

The major application of nuclear imaging techniques to the genital tract is pertechnetate scintigraphy for evaluation of the acute hemiscrotum. Within a few years of the first descriptions of scrotal imaging, this technique achieved recognition as a valuable, even indispensable, emergency diagnostic procedure in this context; its validity has since been well confirmed in hundreds of reported cases. Because it is an established procedure with widely recognized applications, its discussion will occupy most of this article. Other nuclear procedures, less widely used either because they are investigative or applicable to smaller patient populations, will be more briefly described.

Disposal of low-level radioactive waste. Impact on the medical profession.

During 1985, low-level radioactive waste disposal has become a critical concern. The issue has been forced by the threatened closure of the three commercial disposal sites. The medical community has used radioactive isotopes for decades in nuclear medicine, radiation therapy, radioimmunoassay, and biomedical research. Loss of disposal capacity for radioactive wastes generated by these activities, by the suppliers of radioisotopes, and by pharmaceutical companies will have a profound impact on the medical profession.

Radionuclide imaging of the injured spleen and liver.

After the introduction of Tc-99m sulfur colloid and the gamma camera, radiocolloid liver-spleen imaging displaced angiography as the primary modality for diagnosing injury because of its sensitivity and non-invasiveness. A splenic defect may be nonspecific since it can be caused by a congenital variant. Specificity can be increased by awareness of common morphologic variations and judicious use of detector angulation to separate an overlapping left lobe. An increased incidence of overwhelming sepsis in postsplenectomy patients led to a more conservative approach to splenic injury, aided by sequential scintigraphy to demonstrate healing of traumatic defects. This decreased the significance of an initial false-positive scan that was caused by congenital variation, since the clinical "bottom line" was failure of a defect to enlarge or cause delayed rupture. Computed tomography (CT) is also a sensitive method of diagnosing injury or spleen and liver as well as other intraabdominal organs such as the kidneys. Its performance has not been compared to simultaneous multiorgan scintigraphy, an underutilized but very useful approach.

The fine points of scrotal scintigraphy.

The following discussion is intended to provide detailed technical assistance for the nuclear physician and technologist who are already familiar with the rationale and theory of scrotal scintigraphy but who may have very little practice with it. Scrotal exploration is a relatively benign surgical procedure with low morbidity and mortality, and it is nearly 100% definitive for the clinical question. Scintigraphy is less expensive and has no morbidity or mortality. To replace surgery, a diagnostic examination must be sensitive enough to allow no jeopardized testis to escape the surgeon, and specific enough to avoid most unnecessary operations. Performed properly, scrotal scintigraphy is such a test.

Radionuclide imaging in the nonsurgical treatment of liver and spleen trauma.

Twenty-nine patients had splenic or hepatic defects on 99mTc sulfur colloid scintigraphy performed after abdominal trauma. All were treated conservatively. One additional patient had a scan after a laceration was oversewn. Followup scans in 24 patients 1 to 13 months later showed resolution that was complete in nine, partial in 12, and unchanged in three. No defects enlarged. All but two patients were completely asymptomatic; two children with occasional unexplained upper abdominal pain had progressively resolving splenic defects. We conclude that surgery may not always be necessary for liver-spleen injury, that radionuclide imaging is useful in valuation of healing as well as in initial diagnosis, and that the risk of 'delayed' rupture is much smaller than heretofore feared.

Noninvasive methods for detection of valve vegetations in infective endocarditis.

To determine the optimal noninvasive method for the demonstration of endocarditic vegetations, 35 consecutive episodes of clinically diagnosed endocarditis in 33 patients were studied with M mode and two dimensional echocardiography, and with gallium-67 citrate and technetium-99m stannous pyrophosphate cardiac scanning. Clinical criteria for the diagnosis of endocarditis were: temperature higher than 38 degrees C; sustained bacteremia with at least three positive blood cultures; no extracardiac focus of bacteremia; and known underlying heart disease, a new or changing murmur or a history of intravenous drug abuse with radiologic evidence of septic pulmonary emboli. M mode echocardiography detected 18 vegetations in 17 of the 35 episodes of endocarditis studied (49 percent positive); two dimensional echocardiography detected 30 vegetations in 28 of the 35 episodes studied (80 percent positive). In contrast, no vegetations were detected with technetium-99m stannous pyrophosphate scanning,, and only two gallium-67 citrate scans were positive. The advantage of the two dimensional echocardiographic technique over all others tested was particularly notable for the identification of aortic and tricuspid valve vegetations.

The value of the negative radionuclide scrotal scan in the management of the acutely inflamed scrotum in children.

Torsion of the testis remains a clinical diagnosis and confirmatory testing is not required when the classic signs and symptoms are present. Conflicting laboratory data or adjunctive diagnostic studies should not dissuade the surgeon from exploration when the clinical index of suspicion is high. In those patients having equivocal clinical findings when the diagnosis of torsion is not clear-cut radionuclide scrotal imaging may be useful. In this series a negative scrotal scan at the time of acute scrotal pain did predict reliably the diagnosis of non-torsion, suggesting that in the appropriate clinical setting scrotal imaging is useful in avoiding surgical exploration.

Is the anterior bone scan necessary in the diagnosis of osseous metastases?

Bone imaging studies of 1650 patients with known or strongly suspected extraosseous malignancies were reviewed to determine whether a completely negative posterior view was sufficient to exclude metastatic disease. Of 708 negative posterior images, 27 (3.4%) were positive for metastasis on anterior views. All of the anterior lesions were in the sternium, sternoclavicular joints and first four ribs. When the posterior view is positive, further views may be unnecessary. Negative or equivocal posterior images necessitate anterior views of the thoracic cage.

The target sign: a new radiologic sign of septic pulmonary emboli.

A new radiographic sign consisting of a pulmonary density suspended in a thin-walled cystic area is described in five patients with hematogenously disseminated infection. A pathogenetic mechanism is suggested to account for this "target sign." The relationship of these findings to pulmonary pneumatoceles is also discussed.

Urine extravasation secondary to upper urinary tract obstruction.

To the best of our knowledge, this is the first reported case of renal salvage in a neonate with presumed spontaneous perirenal leakage of urine associated with ureteropelvic junction obstruction. Many instances of such extravasation in this age group have been described with lower urinary tract obstructions. As in the latter cases, the occurrence of extravasation secondary to upper tract obstruction need not preclude primary reconstruction.

Bone and marrow imaging in sickle cell disease: diagnosis of infarction.

Sickling of erythrocytes in patients with S-hemoglobin causes marrow and bone infarction. The former can be demonstrated as a lack of 99mTc-sulfur colloid uptake on marrow imaging examination. These defects may resolve or persist long after the acute episode. If the bone is involved in the acute episode, imaging within the first few days of onset of symptoms can show lack of 99mTc-labeled phosphate uptake, usually in a smaller area than that shown by marrow scanning. Follow-up bone imaging shows increased activity, particularly along the circumference of the bone where periosteal reaction can be demonstrated radiographically. Magnification by use of the pinhole collimator provides better definition of the uptake defect and the distribution of the increased reactive uptake. Timing of examination is important. If marrow imaging is performed in an asymptomatic period, the repeat examination during a painful crisis permits differentiation of old and acute marrow infarction. If 99mTc-phosphate imaging is performed after about 2 days of symptoms, acute infarction can be differentiated from osteomyelitis, which it may mimic clinically. Although osteomyelitis may cause no increased activity in the first 48 hr after onset of symptoms, it is characterized by intense focal activity thereafter (see article by Handmaker in this issue). To assist in differentiating bone infection in a site of marrow infarction demonstrated by marrow imaging, serial bone imaging with magnification may be useful. The uptake defect, followed in several days to 2 weeks, by circumferential increased activity, is a different pattern than the homogeneously intense activity of osteomyelitis, but the peripheral distribution may not be apparent on routine imaging. It is hoped that the utilization of these techniques can decrease the emotional and economic costs of prolonged hospitalization for suspected infection and can also expand our knowledge of the complex pathophysiologic changes of sickle cell bone disease.

Radioactive embolization from upper-extremity thrombophlebitis.

A lung scan in a patient with upper-extremity thrombophlebitis showed "hot spots" that apparently resulted from embolization of a propagative thrombus.