Regional alterations in lung ventilation in end-stage primary pulmonary hypertension: correlation between CT and scintigraphy.

OBJECTIVE: The purpose of this study was to correlate scintigraphic findings of regional alterations in lung ventilation and perfusion with regional variations in CT attenuation in patients with primary pulmonary hypertension. SUBJECTS AND METHODS: Chest CT scans and ventilation-perfusion scans obtained within 24 hr of each other in 18 patients with primary pulmonary hypertension referred for lung transplantation were reviewed. The lungs were divided into eight regions (left/right, superior/inferior relative to the carina, and anterior/posterior relative to the trachea). CT scans were evaluated and areas of parenchymal inhomogeneities were tabulated for the eight regions. Areas of reverse mismatch (perfusion without ventilation) were established by blinded analysis of planar scintigraphic studies in six projections using 99mTc-labeled DTPA-aerosol and macroaggregated albumin for the eight regions and then were correlated with the CT findings. RESULTS: Abnormal findings on ventilation scans and reverse ventilation-perfusion mismatches indicating an inadequate hypoxic vasoconstriction reflex were found in 91 regions in all 18 patients. Nonuniform parenchymal CT density was found in 12 patients. There was a significant correlation (p = .009) of scintigraphic reverse mismatches with abnormal CT density in 38 regions in 11 patients. In one patient, there was no scintigraphic correlation with abnormal CT attenuation. The specificity of abnormal CT density for scintigraphic reverse mismatches was 81%, with a sensitivity of 42%. CONCLUSION: Scintigraphic reverse mismatches indicate a high prevalence of significant pulmonary arterial shunting in patients with ventilatory defects. Increased relative CT attenuation in areas of impaired ventilation as shown on the ventilation scans is amplified in primary pulmonary hypertension by an inadequate hypoxic vasoconstriction reflex. This finding does not signify underlying infiltrative lung disease and correlates with regions with reverse mismatches.

Resting Tl-201 scintigraphy in the evaluation of coronary artery disease in children with Hurler syndrome.

Severe coronary artery disease may occur early in the course of mucopolysaccharidosis. The authors present radiologic, scintigraphic, and pathologic findings in five patients with Hurler syndrome. Thallium-201 myocardial scintigraphy and selective coronary angiography obtained within 2 days to 6 months were correlated in five patients. Postmortem examination of the coronary arteries was obtained in one patient within hours of angiography. Interobserver agreement on grading of scintigraphic abnormalities was poor. Nonspecific findings on Tl-201 studies included septal abnormalities in all five patients. Scintigraphic findings were corroborated by angiography and postmortem results in only 3 of 5 patients. Our findings suggest that resting Tl-201 scintigraphy has limited value in the detection of coronary artery disease in patients with Hurler syndrome.

Role of radiology in medical education: perspective of nonradiologists.

RATIONALE AND OBJECTIVES: We asked our nonradiologist colleagues to evaluate and comment on the most desirable format for radiology education. METHODS: Questionnaires were distributed to 631 nonradiologist physicians affiliated with the University of Minnesota and representing all medical specialties and academic ranks. Three hundred twenty-seven surveys were returned after one mailing. RESULTS: Residency was retrospectively noted to be indispensable for consolidating knowledge of radiology. The overwhelming majority of clinicians in all specialties believed that formal radiologic instruction should be mandatory for medical students (279 of 322; 87%). Film interpretation was believed to be an indispensable part of a medical student radiology rotation (226 of 321; 70%), but many clinicians indicated a need for additional training. A marked disparity in the perceived level of confidence in interpreting radiologic tests during medical school and residency between those who had and those who had not received formal radiologic instruction during medical school was evident. This difference in perceived level of confidence was present even among the most experienced clinicians. CONCLUSIONS: Collectively, the nonradiologist clinicians emphasized the need for a mandatory and clinically oriented radiology curriculum during medical school.

A comparison of single blood sample and multiple blood sample methods to measure GFR in a pediatric population.

Several single-sample, Cr-51 EDTA based methods of estimating glomerular filtration rate in children have been proposed. The authors retrospectively reviewed our experience in 467 pediatric patients using Tc-99m DTPA and 4 ultrafiltered serum samples drawn 2-4 hours postinjection. The authors used the 2-hour specimens for the single-sample method. Regression analysis of the 2 techniques revealed significant scatter. Mathematically, it was shown that the error of the single-sample method was minimized when the clearance t 1/2 equalled the sampling time x 0.693. This model predicted a 300% error when the t 1/2 was varied to its observed extremes. The observed error of the single-sample method fit this theoretical prediction very well. Analysis of a two-sample method versus the four-sample method showed no improvement in results. In a subset of 18 unfiltered plasma samples, the glomerular filtration rate was falsely low in 12 patients. The authors conclude that multiple blood samples and serum ultrafiltration are required to accurately measure glomerular filtration rate when using Tc-99m DTPA.

Postoperative diuresis renography and ultrasound in patients undergoing pyeloplasty. Predictors of surgical outcome.

The authors reviewed 50 pediatric patients (56 renal units) who underwent pyeloplasty and had serial preoperative and postoperative diuresis renogram and ultrasound studies. Of those patients that clinically improved with surgery, 73% and 91% showed improved renographic patterns in postoperative studies at 3 and 12 months, respectively. Ultrasound demonstrated more gradual improvement in grade and pelvic diameters over longer study intervals. Diuresis renography is an excellent predictor of surgical outcome within 3 months of pyeloplasty and showed change well in advance of that seen on ultrasound. Sonography is better suited to longer term evaluation of grade, pelvic diameter, and renal size.

Local reactions to radioiodine in the treatment of thyroid cancer.

PURPOSE: To compare the rate of local complications resulting from radioiodine ablation of thyroid cancer in patients with a residual intact thyroid lobe to that in patients who had more extensive surgical treatment prior to radioiodine administration. PATIENTS AND METHODS: We retrospectively studied 59 patients who had received 131I between 1979 and 1989. The patients were divided into two groups, depending on the extent of their previous surgical thyroid excision. Group 1 comprised 10 patients with a lobectomy or hemithyroidectomy before the ablative radioiodine dose, and Group 2 comprised 49 patients with more extensive thyroid excision (near-total or subtotal thyroidectomy) before the radioiodine treatment. RESULTS: Sixty percent of the 10 patients in Group 1 experienced some degree of neck pain or tenderness following radioiodine ablation of their residual thyroid. In one case, the local reaction was very severe and accompanied by the development of transient hyperthyroidism. There was only a 6% local complication rate in the patients who had undergone more extensive thyroid excision before ablative therapy (p less than 0.001), and none had a severe reaction. CONCLUSIONS: Patients with only unilateral surgical excision before radioiodine therapy have a higher rate of local complications than do patients treated with more extensive surgery prior to radioiodine ablation. If radioiodine is to be employed in such patients, they should be informed of this possible complication. Since evidence supports a dose effect in the pathogenesis of the complications, we recommend using a dose of less than 30 mCi for the initial ablation in these patients even though it may be necessary to repeat this dose to complete thyroid ablation.

Pancreas transplants: evaluation using perfusion scintigraphy.

To determine the value of scintigraphic perfusion studies in evaluating pancreas transplant patients, we reviewed 56 of these studies in 22 patients who had 27 transplants. Seventeen patients underwent two or more studies. The perfusion studies were performed with 20 mCi (740 MBq) of 99mTc-DTPA injected as a bolus followed by eight to 16 serial 2-sec images and a 500,000-count immediate static image. Images were evaluated for (1) the time and intensity of pancreatic peak radioactivity relative to the time and intensity of the iliac arterial peak; (2) relative pancreatic to iliac arterial intensity on the static image; and (3) size, homogeneity, and definition of the pancreas. Clinical diagnoses at the time of scintigraphy of normal function (n = 36), rejection (n = 13), pancreatitis (n = 6), or arterial thrombosis (n = 1) were based on insulin requirement, urine amylase, serum glucose, serum amylase, response to therapy, cultures, CT, MR, sonography, scintigraphy with 67Ga or 111In-WBCs, percutaneous drainage results, angiography, surgery, and pathologic examination of resected transplants. Three 99mTc-DTPA perfusion studies showed no pancreatic perfusion, four showed decreasing perfusion on serial studies, and five showed progressive loss of definition of the pancreas on serial studies. Of the three patients with no detectable perfusion, one had a normally functioning transplant, one had arterial thrombosis with transplant infarction, and one had severe rejection with minimal function. Decreasing perfusion was associated with rejection in three patients and pancreatitis in one. Decreasing definition was seen in four patients with rejection and one with pancreatitis. We conclude that perfusion scintigraphy is useful, primarily when performed serially, although nonspecific for evaluating pancreas transplants.

The significance of poor renal transplant concentrating ability as assessed by I-131 Hippuran imaging.

A pattern of very poor renal allograft concentration of I-131 Hippuran and good bladder activity has been observed by the authors. The kidneys are typically barely visualized and the renogram curve is flat. The significance of this particular finding has not been described in the literature. Accordingly, a retrospective review of all patients exhibiting this scan pattern was performed and the authors attempted to correlate it with clinical, laboratory, and pathological findings at the time of study. Of 11 patients exhibiting this scan pattern, three had very high urine outputs at the time of study. Of the remaining eight patients, five had chronic rejection. In the remaining three patients, the diagnosis was: one each, acute rejection, mixed acute and chronic rejection, and cyclosporine toxicity. The authors conclude that although this pattern is non-specific, if the patient is not in a high output state, it is usually related to chronic rejection.

Nonfunctional photomultiplier tubes can produce subtle total-body scan defects.

Nonfunctional photomultiplier tubes produce subtle total body scan defects. The resultant scan shows bands of reduced activity which are far less obvious than those seen on a standard image.

Improved prediction of thyroid lobar mass from parameters obtained by routine thyroid scintigraphy.

Estimation of thyroid mass both from parameters derived from thyroid scintigraphy and clinical palpation for purposes of therapeutic dosimetry has not been tested for accuracy. To more precisely determine thyroid mass 90 thyroid lobes from 45 autopsies without history of thyroid disease were studied. Specimens were dissected free of nonthyroidal tissue and assessed for volume, maximum depth (D), width (W), length (L) and mass (M). Using a linear regression model and applying known lobar depth, the most accurate formula to predict true lobar mass (in grams) was 4.9D + 0.07L2W-2.3 (in cms). Length and width would be obtainable in vivo from routine scintigraphic measurements (in cm) and depth would be most accurately determined by ultrasound. For most clinical circumstances where lobar depth is unknown we found the best formula for mass (g) to be 0.1L2W (in cm).