Miguel Gorenberg

Lower extremity scintigraphy: The foot and ankle

Disorders of the ankle and foot are common and may pose a significant clinical problem. Acute injuries of the ankle and foot are routinely evaluated by radiographs and, if inconclusive, by magnetic resonance imaging (MRI) or computed tomagraphy (CT). In subacute or chronic injuries, where prolonged pain is unexplained, bone scintigraphy may play a significant role. The bone scan may differentiate soft tissue from bone pathology, and, being a sensitive test, it may indicate the region that needs further specific radiologic examination. It may also indicate the clinical significance of a radiologic finding. Moreover, in some clinical settings bone scintigraphy can be specific in the diagnosis. Careful attention to the technique enhances the efficiency of bone scintigraphy and SPECT allows better investigation of the hindfoot. The importance of ankle and foot injuries in the orthopedic practice and the better understanding of subacute and chronic injuries in athletes and in the general population has led to an increased use of specific tests such as MRI, CT, and bone scintigraphy. With improved technique and instrumentation it is no longer sufficient to indicate a focal abnormality in the ankle or foot on bone scintigraphy. More precise information about perfusion, blood pool, and specific location of a lesion can be obtained by high resolution and tomographic images. The role of bone scintigraphy in the diagnosis of such disorders will be presented with a focus on subacute traumatic injuries and related disorders, as well as its role in systemic inflammatory disorders that often involve the ankle and foot.

Patterns of FDG uptake in post-thoracotomy surgical scars in patients with lung cancer.

Increased (18)F-fluorodeoxyglucose ((18)F-FDG) uptake can occur in surgical scars. This study assesses the incidence, patterns and natural history of (18)F-FDG uptake in post-thoracotomy scars of non-small cell lung cancer (NSCLC) patients. 73 (18)F-FDG-PET/CT studies performed after resection of NSCLC in 61 patients (49 men, 12 women; mean age, 66.7 years) were retrospectively reviewed for the presence, pattern and intensity (maximum standardized uptake value (SUV(max))) of (18)F-FDG uptake in sites of previous thoracotomy. Increased (18)F-FDG uptake in surgical scars was found in 61% of studies (43/70) (average SUV(max), 3.6); 3 patients with recurrence at the surgical scar were excluded from the analysis of the characteristics of physiological FDG uptake in scars over time. The average time from surgery was 14.4 months in patients with, and 43.8 months in patients without, scar uptake (p<0.0002). Increased uptake was seen in 14/14 studies (100%) at 1-3 months, in 12/13 studies (92%) at 3-12 months, and in 17/43 studies (40%) at more than 12 months after surgery in patients with no evidence of disease on follow-up. (18)F-FDG uptake was diffuse in 67% of studies (29/43). Tumour recurrence in the scar was found in three studies, showing focally increased uptake (average SUV(max), 9.1 ) at 3-8 months after thoracotomy. In conclusion, increased (18)F-FDG uptake in post-thoracotomy surgical scars is mainly diffuse, and decreases in incidence and intensity with time, with 60% of studies showing no scar uptake at more than 12 months after surgery. Focally intense scar uptake should be evaluated for suspected recurrence.

Endothelin release: a marker for the severity of exercise-induced ischemia

Elevated endothelin-1 levels were found in exercise-induced ischemia. To our knowledge, no attempt has been made to correlate the presence of the elevated endothelin levels with severity of ischemia. In the present study, we attempt to correlate the severity of ischemia, quantified using a bullseye visual display of scintigraphic ischemic score on SPECT technetium 99m sestamibi, with presence of endothelin at peak exercise. Twenty seven patients with documented effort angina were included in the study. All subjects underwent stress technetium 99m sestamibi and ischemic scores were evaluated on the polar map image divided into 13 segments. Endothelin levels were measured at baseline and at peak exercise. In 13 patients with elevated endothelin-1 levels, there were 88 ischemic segments, 26 of which showed severe ischemia. In the remaining 14 patients with no endothelin-1 elevation, there were 80 ischemic segments of which only four showed severe ischemia. The amount of severe ischemic segments per patient was 2+/-2.2 in the elevated endothelin positive group and 0.28+/-0.6 in the endothelin negative (P< or =0.011). When looking at ischemia as detected by sestamibi SPECT as a gold standard, we found that of 331 segments, 168 were without ischemia, 143 had mild to moderate ischemia, and 30 has severe ischemia. Endothelin levels were 1.2+/-0.6, 2.2+/-0.5, 6.2+/-0.7 pg/l (P<0.01), respectively. Thus, endothelin-1 is a marker of severity of ischemia rather than ischemia itself, and as such, may have prognostic value.

Ga-67 scintigraphy with a dual-head camera.

High quality images are necessary for correct interpretation of Ga-67 studies in lymphoma. The authors were interested if there is a significant change in the quality of the Ga-67 images using a newly introduced dual-head camera compared with a conventional single-head camera. The tomographic spatial resolution, full width at half maximum, was found to be 9.63 mm compared with 13.7 for a single-head camera. The volume sensitivity was 380 cps/μCi/ml per axial cm as compared with 333 cps/μCi/ml, and point source sensitivity was 5.6 cps/μCi compared with 3.8. There was a significant difference (P < 0.001), when using the threshold technique, in the number of counts per pixel over a wide range of volumes and concentrations in phantoms when the two cameras were compared. There was also a significant difference (P < 0.001) in Ga-67 uptake in lymphoma lesions in patients when the same parameters were used for both cameras when using SPECT. The average uptake in lymphoma lesions, using a dual-head camera, was 529 counts/pixel with a range of 112 to 1275 counts/pixel in different tumors. With a single-head camera, the average for the same tumor was 216 counts/pixel with a range of 59 to 469 counts/pixel. The high sensitivity of the dual-head camera enabled high-quality, whole body scintigraphy, including the limbs, in 20 minutes compared with the 35 minutes necessary for the single-head camera for images which did not include the legs. Whole body Ga-67 scintigraphy is shown to be important in patients with lymphoma of the upper and lower limbs. The high sensitivity of the dual-head camera enables the performance of SPECT studies at 7 days after injection and planar studies of satisfactory quality at 14 days, resulting in clearance of the colonic activity and better evaluation of the abdomen. The authors conclude that, at the present time, a dual-head camera appears to be the most appropriate equipment to use for Ga-67 scintigraphy.

A New Noninvasive Device for Measuring Central Ejection dP/dt Mathematical Foundation of Cardiac dP/dt Measurement Using a Model for a Collapsible Artery

We have developed a novel non-invasive device for the measurement of one of the most sensitive indices of myocardial contractility as represented by the rate of increase of intraventricular pressure (left ventricular dP/dt and arterial dP/dt performance index (dP/dtejc). Up till now, these parameters could be obtained only by invasive catheterization methods. The new technique is based on the concept of applying multiple successive occlusive pressures on the brachial artery from peak systole to diastole using a inflatable cuff and plotting the values against time intervals that leads to the reconstruction of the central aortic pressure noninvasively. The following describes the computer simulator developed for providing a mathematical foundation of the new sensor. At the core of the simulator lies a hemodynamic model of the blood flow on an artery under externally applied pressure. The purpose of the model is to reproduce the experimental results obtained in studies on patients (Gorenberg et al. in Cardiovasc Eng: 305–311, 2004; Gorenberg et al. in Emerg med J 22 (7): 486–489, 2005) and a animal model where ischemia resulted from balloon inflation during coronary catheterization (Gorenberg and Marmor in J Med Eng Technol, 2006) and to describe correlations between the dP/dtejc and other hemodynamic variables. The model has successfully reproduced the trends observed experimentally, providing a solid in-depth understanding of the hemodynamics involved in the new measurement. A high correlation between the dP/dtejc and the rate of pressure rise in the aorta during the ejection phase was observed. dP/dtejc dependence on other hemodynamic parameters was also investigated.

Renal scintigraphy in the diagnosis of aortic dissection affecting the renal arteries.

Aortic dissection type A in a patient with chronic renal failure is presented. The patient had acute deterioration of renal function, which was thought to be due to renal artery involvement by progression of the dissecting aneurysm. Abdominal CT without contrast enhancement was normal, but renal scintigraphy with Tc-99m DTPA showed aortic dissection with Involvement of the renal arteries. Early pharmacologic treatment is indicated in all patients with aortic dissection except for those with vital organ involvement who should be operated. Involvement of the renal arteries, shown on renal scintigraphy, was useful in the case presented to indicate the need for immediate surgery due to the dissection affecting the renal arteries.

Growing hepatic cavernous hemangioma demonstrated by Tc-99m red blood cell scintigraphy

Hepatic cavernous hemangiomas rarely grow. Although a few cases have been reported in the literature, none used Tc-99m red blood cell scintigraphy. The authors describe such a case here.

Hemangioma of the scrotum and penis in a child demonstrating a perfusion-blood pool mismatch on Tc-99m RBC imaging.

Tc-99m autologous labeled RBCs have been used to determine the blood flow and blood pool characteristics of a variety of lesions. In this report, the use of Tc-99m RBC scintigraphy in a hemangioma of the scrotum and penis showing the typical perfusion-blood pool mismatch is presented.

More Realistic Face Model Surface Improves Relevance of Pediatric In-Vitro Aerosol Studies

Background Various hard face models are commonly used to evaluate the efficiency of aerosol face masks. Softer more realistic “face” surface materials, like skin, deform upon mask application and should provide more relevant in-vitro tests. Studies that simultaneously take into consideration many of the factors characteristic of the in vivo face are lacking. These include airways, various application forces, comparison of various devices, comparison with a hard-surface model and use of a more representative model face based on large numbers of actual faces. Aim To compare mask to “face” seal and aerosol delivery of two pediatric masks using a soft vs. a hard, appropriately representative, pediatric face model under various applied forces. Methods Two identical face models and upper airways replicas were constructed, the only difference being the suppleness and compressibility of the surface layer of the “face.” Integrity of the seal and aerosol delivery of two different masks [AeroChamber (AC) and SootherMask (SM)] were compared using a breath simulator, filter collection and realistic applied forces. Results The soft “face” significantly increased the delivery efficiency and the sealing characteristics of both masks. Aerosol delivery with the soft “face” was significantly greater for the SM compared to the AC (p< 0.01). No statistically significant difference between the two masks was observed with the hard “face.” Conclusions The material and pliability of the model “face” surface has a significant influence on both the seal and delivery efficiency of face masks. This finding should be taken into account during in-vitro aerosol studies.

The Bnai Zion Planar Method: a simplified technique for the quantitation of the absolute renal uptake of (99m)Tc-DMSA in children.

Aim and purposeRadionuclide imaging of the kidneys using dimercaptosuccinic acid chelate labeled with technetium-99m (99mTc-DMSA) is a well-established method for evaluating the extent of kidney parenchymal involvement in the scenario of urinary tract infection and for the estimation of the functional renal mass. We have developed a simplified technique, Bnai Zion Planar Method (BZPM), to estimate absolute DMSA uptake by the kidneys, which uses a shorter time of acquisition and does not require cumbersome calculations of attenuation correction. The aim of this study was to validate this technique by comparing it with the Quantitative DMSA single-photon emission computed tomography (SPECT) (QDMSA) measurements as the reference method. MethodsSixty-one consecutive children (mean age 5.4±4.8 years) were included in the study. Absolute uptake of the radiopharmaceutical by the kidneys was measured using the QDMSA SPECT methods described earlier with data acquisition of 20 min. Kidney volumes and radioactivity concentration measurements were calculated on the reconstruction data using the threshold method. For the simplified technique (BZPM), a planar posterior view of the kidneys was acquired for 1 min at the end of the QDMSA SPECT study. ResultsIn both kidneys we observed a significant strong correlation between the two methods. BZPM measurements were very similar to those obtained using the validated QDMSA method, as determined by linear regression analysis (Pearsons r=0.924, P<0.001), r2=0.854. The uptake according to QDMSA can be predicted by the uptake measured by the BZPM method using the following regression equation: QDMSA=0.445+1.061 BZPM. ConclusionBZPM estimation in children using the newly proposed planar method was found to be nearly identical to the validated QDMSA SPECT method.