John V. Crues

Alterations in body and skin temperatures caused by magnetic resonance imaging: is the recommended exposure for radiofrequency radiation too conservative?

Abstract Increases in tissue temperature caused by exposure to radiofrequency (RF) radiation are a primary safety concern of magnetic resonance imaging (MRI). Therefore, body and skin temperatures were measured in six subjects before (20 min), during (30min) and after (20 min) MRI procedures performed at specific absorption rates (SARs) six to 10 times higher than the limit recommended by the UK National Radiological Protection Board. Body temperature was unchanged throughout the experiment. Abdominal skin temperature increased significantly (p<0.05) during MRI, decreased significantly post-MRI, but was still significantly (p<0.05) higher than baseline. The highest abdominal skin temperature recorded was 36°C. Upper arm, forearm and chest skin temperatures increased significantly (p<0.05) during MRI and remained elevated post-MRI. The highest skin temperatures recorded on the upper arm, forearm and chest were 38.1, 36.0 and 34.5°C, respectively. Thigh and calf skin temperatures were not significantly chan...

Atrial emptying with orthotopic heart transplantation using bicaval and pulmonary venous anastomoses: A magnetic resonance imaging study

OBJECTIVES We hypothesized that orthotopic heart transplantation with bicaval and pulmonary venous anastomoses preserves atrial contractility. BACKGROUND The standard biatrial anastomotic technique of orthotopic heart transplantation causes impaired function and enlargement of the atria. Cine magnetic resonance imaging (MRI) allows assessment of atrial size and function. METHODS We studied 16 patients who had undergone bicaval (n = 8) or biatrial (n = 8) orthotopic heart transplantation without evidence of rejection and a control group of 6 healthy volunteers. For all three groups, cine MRI was performed by combining coronal and axial gated spin echo and gradient echo cine sequences. Intracardiac volumes were calculated with the Simpson rule. Atrial emptying fraction was defined as the difference between atrial diastolic and systolic volumes, divided by atrial diastolic volume, expressed in percent. All patients had right heart catheterization. RESULTS Right atrial emptying fraction was significantly higher in the bicaval (mean [+/- SD] 37 +/- 9%) than in the biatrial group (22 +/- 11%, p < 0.05) and similar to that in the control group (48 +/- 4%). Left atrial emptying fraction was significantly higher in the bicaval (30 +/- 5%) than in the biatrial group (15 +/- 4%, p < 0.05) and significantly lower in both transplant groups than in the control group (47 +/- 5%, p < 0.05). The left atrium was larger in the biatrial than in the control group (p < 0.05). Cardiac index, stroke index, heart rate and blood pressure were similar in the transplant groups. CONCLUSIONS Left and right atrial emptying fractions are significantly depressed with the biatrial technique and markedly improved with the bicaval technique of orthotopic heart transplantation. The beneficial effects of the latter technique on atrial function could improve allograft exercise performance.

MRI of the knee in diffuse pigmented villonodular synovitis

Magnetic resonance imaging (MRI) was performed on 11 patients with surgically proven pigmented villonodular synovitis (PVNS) of the knee. PVNS was diagnosed on the basis of presence of hemosiderin, joint effusion, and hyperplastic synovium without significant joint destruction. MRI provided a detailed map of the distribution of the disease within the joint, emphasizing the common occurrence of the disease behind the cruciate ligaments and in synovial cysts in the popliteal fossa. MRI aided in preoperative planning and postoperative follow-up for residual and recurrent disease. Nine additional cases of joint hemorrhage, hemophilia, desmoplastic tumors, and synovial chondromatosis were included to delineate differential diagnostic criteria.

Osteochondral grafting for failed knee osteochondritis dissecans repairs

BACKGROUND Revision of failed surgical treatments of osteochondritis dissecans (OCD) lesions remains a challenge without an obvious solution. The aim of this study was to evaluate seven consecutive patients undergoing osteochondral grafting of a failed OCD repair. METHODS The mean time from surgery to the latest evaluation was 7.0 years. IKDC, WOMAC, Tegner, and MRI studies were collected both preoperatively and during follow-up. Evaluation of the graft was assessed using the magnetic resonance observation of cartilage repair tissue (MOCART) grading system. RESULTS Over the course of the study period, five patients required additional surgery with a study median of one additional surgery (range, zero to 3). At most recent follow-up, there was significant improvement from preoperative values in median IKDC (p=0.004), WOMAC (p=0.030), and Tegner (p=0.012). Complete cartilage fill and adjacent tissue integration of the paste graft were observed by MRI evaluation in five of the seven (71.4%) patients. Definitive correlation between clinical outcomes and MRI scores was not observed. CONCLUSIONS This study shows promising results of osteochondral grafting as a viable option for the revision of failed OCD lesion repairs; however, more patients are needed to fully support its efficacy in these challenging failed revision cases.

Alterations in body and skin temperatures caused by magnetic resonance imaging; is the recommended exposure for radiofrequency radiation too conservative?

Increases in tissue temperature caused by exposure to radiofrequency (RF) radiation are a primary safety concern of magnetic resonance imaging (MRI). Therefore, body and skin temperatures were measured in six subjects before (20 min), during (30 min) and after (20 min) MRI procedures performed at specific absorption rates (SARs) six to 10 times higher than the limit recommended by the UK National Radiological Protection Board. Body temperature was unchanged throughout the experiment. Abdominal skin temperature increased significantly (p less than 0.05) during MRI, decreased significantly post-MRI, but was still significantly (p less than 0.05) higher than baseline. The highest abdominal skin temperature recorded was 36 degrees C. Upper arm, forearm and chest skin temperatures increased significantly (p less than 0.05) during MRI and remained elevated post-MRI. The highest skin temperatures recorded on the upper arm, forearm and chest were 38.1, 36.0 and 34.5 degrees C, respectively. Thigh and calf skin temperatures were not significantly changed during MRI. These alterations in tissue temperatures were physiologically trivial and easily tolerated by the subjects, suggesting that the recommended exposure to RF radiation during MRI of the body for patients with normal thermoregulatory function may be too conservative.